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UNIT - 6DETERIORATION AND REPAIR IN CONCRETEQ1) Explain durability and factors affecting durability A1)Durability is the capacity to remaining a long term without massive deterioration. A long lasting cloth allows the surroundings with the aid of using keeping sources and lowering wastes and the environmental affect of restore and substitute. The manufacturing of substitute constructing substances depletes herbal sources and may produce air and water pollution. Concrete resists weathering action, chemical attack, and abrasion even as retaining its favored engineering houses. Different concretes require extraordinary levels of sturdiness relying at the publicity surroundings and the houses favored. Concrete ingredients, their proportioning, interactions among them, setting and curing practices, and the provider surroundings decide the remaining sturdiness and lifestyles of the concrete. The layout provider lifestyles of maximum homes regularly 30 years, despite the fact that homes regularly remaining 50 to one hundred years or longer. Because in their sturdiness, maximum concrete and masonry homes are demolished because of useful obsolescence in place of deterioration. However, a concrete shell or shape may be repurposed if a constructing use or characteristic adjustments or whilst a constructing indoors is renovated. Concrete, as a structural cloth and because the constructing outside skin, has the capacity to face up to nature’s ordinary deteriorating mechanisms in addition to herbal disasters. Durability of concrete can be described because the capacity of concrete to withstand weathering action, chemical attack, and abrasion even as retaining its favored engineering houses. Different concretes require extraordinary levels of sturdiness relying at the publicity surroundings and houses favored. For example, concrete uncovered to tidal seawater could have extraordinary necessities than an indoor concrete floor. FACTOR AFFECTING THE DURABILITY OF CONCRETEThe following are the factors that affect the strength of concrete.Cement content Aggregate quality Water Quality Concrete compaction Curing period Permeability Moisture Temperature Abrasion Carbonation 01. Cement contentThe amount of cement used in concrete mixing is a major factor affecting the durability of concrete. If the cement content used is less than required, the cement water level Decreases and the performance of concrete also decreases. Adding too much water to this concrete mix causes the formation of capillary voids that will make the concrete a resilient one inviting decay. Adding excess cement can cause problems such as stopping the shrinkage. Alkali-silica reactions may also eventually affect the strength of the concrete. 02. Aggregate QualityApplying a good quality mix to the concrete mix will definitely increase the strength of the concrete. The shape of the composite particles should be small and circular. Flaky and compact assembly can affect the performance of the new concrete making it easier to enter where it can open and will work with less power. Bad angular compilation is recommended but requires a lot of cement content to get a good binding. Yes, structural composites should be used to achieve greater concrete mixing. Determination of the combined moisture content should be done beforehand, otherwise, it can create a more usable concrete mix and make it worse. 03. Water QualityThe water used in the concrete mix also affects the strength of the concrete. Usually, drinking water is recommended to make concrete. the pH of the water used will be in grades 7 to 8 only. Water should be free and clean from fats, acids, alkalis, sugar, organic salts etc. Contamination in the water can lead to metal corrosion or corrosion due to different chemical attacks of concrete. 04. Concrete compactionCare should be taken during the installation of the concrete. It is important to glue the local concrete without splitting. Adequately compacted concrete contains a number of air gaps in it that reduce the strength of the concrete and its strength and will make it stronger. 05. Curing periodProper treatment should be done in the early stages of concrete reinforcement as it will lead to the reinforcement of the concrete. Adequate treatment can lead to the formation of cracks due to plastic shrinkage, dehydration, heat effects etc. due to reduced stiffness. 06. PermeabilityDue to the overcrowding of the concrete, it expands and leads to the formation of cracks and eventually, the deterioration of the concrete occurs. Concrete usually consists of small gel pores and capillary cavities. However, gel pores prevent water ingress because they are too small. Capillary holes in concrete are facing, which are formed due to the high water content of concrete To prevent intrusion, a very small amount of cement water should be used. Using a small amount of pozzolanic material also helps to reduce penetration 07. MoistureThe moisture found in the atmosphere will also affect the strength of concrete structures. Concrete moisture is responsible for Efflorescence, which will convert salt into soluble solutions and when evaporated salt becomes brighter and appears on the concrete surface. This will definitely damage the concrete structure and the durability will decrease. 08. TemperatureWhen new concrete is exposed to high temperatures, the hydration level is affected and strength and durability are reduced. Concrete materials have different temperature coefficients, so at higher temperatures, spelling and damage to concrete are possible. 09. AbrasionConcrete damage also occurs due to severe facial injuries. When concrete is exposed to fast-moving water, steel tires, floating ice that wears continuously on the surface occur and stiffness is affected. The higher the pressure of the concrete pressure the higher it will be to resist the abrasion 10. CarbonationWhen wet concrete is exposed to the atmosphere, carbon dioxide in the atmosphere reacts with concrete and reduces the pH of the concrete by reacting with CaO in concrete. When the pH value of concrete is reduced to 10 or 9 or more, it releases its alkali. Because it will not be able to protect the metal bars beneath it. Due to rust, rust will build up around the bar which has led to an increase in the volume of the bar. This will create cracks in the concrete. Cracking will continue to promote moisture and CO2 which will lead to the loss of alkali. So bad cycles occur, eventually causing the concrete to crack with delamination and spraying of the concrete if not done in time, the bars will start to lose their place and thus become stronger. Most of the building in modern times, suffers from this, and buildings that were supposed to be 100 years old have been extensively renovated at some point within ten years. The process of rust therefore places on the existing strength of the concrete. The rust of the reinforcement causes cracks in the solid concrete and deterioration occurs. Q2) Explain permeability and sulphate attack A2)Definition: the capacity of a given concrete to allow drinks or gases to by skip through.- ACI Concrete Terminology Permeability is a degree of the quantity of water, air, and different materials which could input the concrete matrix. Concrete consists of pores which could permit those materials to go into or depart. Permeability of concrete may be a number one motive for concrete deterioration because of reinforcing metal corrosion and different deterioration mechanisms. On a macro scale, permeability additionally refers to “porous” slabs used to empty pavements, sidewalks, and parking regions of water, putting off the want for drainage slope, systems, and piping. This technology—every now and then called “no-fines concrete”—is gaining reputation once more with the preference to lessen floor run-off from pavements, sidewalks, and parking regions. Permeability of cement mortar or concrete is of unique importance in systems which might be meant to hold water or which come into touch with water. Besides useful considerations, permeability is likewise in detail associated with the sturdiness of concrete, mainly its resistance, towards revolutionary deterioration below publicity to extreme climate, and leaching because of extended seepage of water, specially whilst it consists of competitive gases or minerals in solution. The willpower of the permeability traits of mortar and concrete, therefore, assumes widespread importance.
Fig no 1Concrete permeability apparatusThe permeability mobileular shall encompass a steel cylinder for containing the specimen. A rubber or neoprene O-ring or different appropriate gasket, seated in matching grooves will be used among the mobileular and the quilt plate to render the joint water-tight.
Fig no 2 Water Reservoir in Permeability ApparatusA appropriate reservoir may also encompass a duration of steel pipe, 50 to a hundred mm in diameter and approximately 500 mm long. The reservoir will be equipped with a graduated facet arm gauge-glass, and the vital fittings and valves for admitting water and compressed air and for draining, bleeding and connection to the permeability mobileular. Procedure:Preparation of Test SpecimenTest specimen of 2 hundred mm diameter and a hundred and twenty mm thick will be used. After 24 hrs of casting of specimen, crucial round place of a hundred mm diameter will be roughened with a twine brush at the facet on which the water stress is to be carried out. The un roughened a part of the facet of the check specimen that's subjected to water stress is to be sealed with coats of cement water paste (W/C = 0.4). Test ProcedureAfter 28 days curing, check specimen is equipped right into a check equipment in which the water stress acts on the specified face and final faces may be observed. At first, a stress of one Bar is carried out for forty eight hours, then three bar for twenty-four hours and seven Bar for twenty-four hours. After the check, the specimen is break up with inside the center with the aid of using the compression carried out on spherical metal bars mendacity on contrary sides, above and below. The facet after the check specimen uncovered to the water stress ought to face downwards. Observation:The finest water penetration depth, is taken because the common cost of the finest penetration depths on 3 check specimen. SULPHATE ATTACKCement is composed of two minerals: tri-calcium silicate (C3S), and di-calcium silicate (C2S). In addition to hydration, the main reaction products are calcium silicate gel (C-SH) and calcium hydroxide Ca (OH) 2, labeled as CH in chemistry notation. Moisture is required in this reaction which can cause serious damage to the construction of both the walls and the walls of buildings in buildings. Sulfate attacks occur on the lower slabs. This problem usually affects buildings from the 1950s to the 1960s but can also affect previous buildings where the concrete floor slab is installed. It occurs when the filler material under the slide contains sulphates and this is considered to be a solution with soil moisture entering the concrete that forms the slab on the floor. Attacks can occur from MgSO4 salts, NaSO4 salts, and other salts containing SO3-ions. The interaction of Ca2 + ions with SO4 present in the solution will produce CaSO4 or gypsum. The effect of gypsum on C-S-H gel, which is the main component of reinforced cement, is an irreversible topic. Some substances present in cement, such as tri-calcium aluminate, also interact with sulphate ions. This reaction is well established in the literature. Q3) Explain acid attack and chloride attack A3)Acid attack is the dissolution and leaching of acid-prone elements, particularly calcium hydroxide, from the cement paste of hardened concrete. This movement outcome in an boom in capillary porosity, lack of cohesiveness and subsequently lack of power. In said instances, acid assault can be observed with the aid of using crack formation and subsequently disintegration, in particular whilst the shape is subjected at one facet to water pressure. Unlike sulfate assault (see beneath), the goods fashioned from acid assault aren't expansive, and leaching will handiest arise in systems which are tremendously permeable. In excessive overall performance concrete structures containing cement pastes with a low content material of calcium hydroxide, acid assault is relative gradual and can contain handiest the finely divided calcium hydroxide crystals included with inside the interstices of the calcium silicate hydrates, C-S-H. The micrographs received from PFM analysis, supplemented with SEM–EDS studies, monitor that handiest the top, floor part of the concrete has been attacked with the aid of using acidic answer. The relaxation of the concrete suggests no shape of degradation. In the attacked zone, there's clean proof of leaching of the cement paste matrix, main to accelerated capillary porosity and lack of brotherly love of the matrix. Locally, there's lack of bonding of the cement paste to aggregate, however at the whole, those elements have now no longer adversely affected the microstructure and nice of the concrete. In this instance, long-time period sturdiness of the concrete isn't always probably to be compromised.
Fig no 3 Acid Attack on Concrete blockAcid assault of concrete takes 3 forms. First, hydration merchandise react with the acid to shape dissolved ions, main to lack of strong material—acidolysis. Second, withinside the case of a few acids, insoluble salts shape, a number of which precipitate to purpose growth and cracking. Finally, a few acids supply complexes with calcium, aluminium, iron and silicate ions which produce an awful lot better concentrations of those ions in answer than could in any other case be the case, once more main to dissolution. This can probably arise at pH situations beneath which cement could usually be tremendously stable (complexolysis). Depending at the acid present, extra than this sort of deterioration mechanisms can be powerful. Where acidolysis is the main mechanism, an acid answer penetrating the pores of concrete will begin to purpose a number of the elements to dissolve. Calcium is generally the primary cation to be dissolved, considering that port land will become soluble beneath tremendously excessive pH values. A F m and A F t stages commonly dissolve at barely decrease pH values, even though strong aluminium and iron hydroxides are precipitated, which persist till the answer is tremendously acidic. Exposure to acidic answer additionally reasons lack of calcium—decalcification—of C-S-H gel, leaving tremendously vulnerable silica gel behind. The importance of calcium on this shape of degradation approach that adjusting the composition of the cement matrix of concrete to attain a decrease calcium content material will probably impart extra resistance. Thus, pozzolanic substances can be powerful in improving resistance to this form of acid assault, considering that their aggregate with PC will produce such an adjustment. However, decreased quotes of mass shipping and more desirable power done thru the usage of pozzolanic substances also are probably to be motives for progressed resistance. CHLORIDE ATTACKChloride Attack Chloride attack is one of the most important factors when working with concrete strength. It mainly causes corrosion corrosion. Statistics have shown that more than 40% of structural failures are due to metal corrosion. Concrete and the penetration layer with a strong alkaline Ca (OH) 2 (pH approximately 13) prevents metal corrosion by forming a thin film to protect the iron oxide on the surface of the metal. This protection is known as inaction. If concrete can penetrate in such a way that the dissolved chloride enters until it hardens and water and oxygen are also present, then corrosion of the metal will occur. This layer can also be lost due to carbonation. Chloride enters the concrete from cement, water, and is sometimes mixed from tips. This can come in increments from nature when the concrete is filled. The Bureau of Indian Standard specified the high chloride content in cement as 0.1%. The amount of chloride needed to start corrosion depends on the pH value of the pore water in the concrete. A pH value below11.5 corrosion is possible without the presence of chloride. Q4) Explain corrosion of reinforcement, carbonation of concrete A4)CORROSION OF REINFORCEMENTConcrete, in itself, has a low strength. To increase the strength of the concrete, the steel hardens. Steel bars are inserted inside the weight of the concrete. These steel bearings carry a high load-bearing capacity applied to concrete. Concrete makes metal bars obsolete due to the alkaline environment, thus preventing them from cracking. However, for a variety of reasons, metal bars can be pulled longer. And as a result of the rust of the steel bars, various weaknesses appear in the concrete structure, which could eventually collapse if not properly maintained. The rust of steel reinforcement bars is actually a way of responding to electricity. Small anodes and cathodes are formed and the flow of ions between these two electrodes leads to the breakdown of metal bars. There are two types of corrosion detected in steel reinforcement bars: Metal Rust - In small cracks in a concrete structure, solutions may remain. Anodes and cathodes can be formed within solutions due to the uneven reaction of solute ions over the volume of the solution. The flow of ions is caused by these electrodes, thus causing a gradual corrosion. Rust corrosion - Related to the removal of small areas in the steel bars of the reinforcement. This type of rust is extremely well-formed and small holes or holes are made in the metal. Causes of Stainless Steel RustCorruption of steel reinforcement barriers may be due to the local failure of the metal film of chloride ions or the general failure of the concrete to malfunction due to the carbon dioxide reaction from the atmosphere. The main factors facing corrosion of reinforcement barriers are: Loss of alkalinity due to carbonation - When a metal surface is left unprotected in the atmosphere, corrosion begins to form on the surface of the metal and then slowly moves away. Loss of alkalinity due to chlorides - Chloride ions tend to remove metal energy by destroying concrete. Cracking of Concrete - Cracking can expose metal bars in the atmosphere and increase liquidity. Moisture Methods - Regular wetting of concrete can lead to water reaching the metal bars by dispersing through the pore structure of the concrete or existing cracks in the concrete. Rust of steel bars follows after that. Insufficient cover: Insufficient size of concrete cover. Metal Rust due to Improper Cover Damaged steel reinforcement may occur due to insufficient concrete cover Effects of Stainless Steel RustWhen steel bars begin to break, reinforced concrete joints begin to break down through the following stages:White spot formation - Atmospheric carbon dioxide reacts with calcium hydroxide present in the reduction of cement forming calcium carbonate. This calcium carbonate is treated with moisture and deposited on the surface of the white-formed concrete. Dirty stains by reinforcement - When the metal bars begin to deteriorate, a layer of iron oxide forms in it. This metal oxide is also transferred to the surface of the concrete with moisture. Formations of cracks - Rust products take on a larger volume than the original. So they put pressure on the concrete and it cracks. In the event of a lot of rust, many wide cracks are formed. Disintegration of concrete cover - Due to the loss of bond between concrete and steel, concrete begins to form many layers of scales and then peels off. Metal bars are also reduced in size. Cracking of bars - Due to the decrease in the size of the steel bars, they eventually break. Also, there is a significant reduction in the size of the main bars. Piercing of bars - The collapse of the concrete cover and the cracking of the bars resulted in the collapse of the main bars. This floods the concrete area and eventually the entire building collapses. How to Avoid Rusting Metal RustThe rust of steel reinforcement bars can be prevented or at least delayed by good measures. Also, damaged steel bars can be repaired and the concrete structure can be properly restored. Some steps are given below: Providing Sufficient Concrete Cover: A good amount of concrete cover should be provided in addition to the reinforcing steel bars. This ensures proper care of the alkaline type inside the concrete and the passage of the steel bars. Metal bars should be placed precisely in place Use of Quality Concrete: High quality concrete should be used. It helps to maintain an alkaline environment. In concrete, a water level of 0.4 or less should be maintained. Too much water can damage metal bars Compact Compaction fo Concrete: Concrete must be thoroughly mixed so that no air gaps or pockets are present. Use of FBE Bonds: Fusion Bonded Epoxy Coating (FBEC) can be used on metal bales to prevent corrosion. Epoxy powder is still electrically distributed in metal barns. The powder melts and flows over the bars as it heats up, forming a protective coating. It is a thermoset polymer coating because the use of heat will not melt the wear. Apart from the rebar it also has extensive function in pipeline construction Use of Cement-Based Polymers: Cement-based polymers can be used in concrete to increase their protection against corrosion. Cement-based polymers act as a bond in concrete. They also increase the strength, durability and melting of concrete CARBONATION OF CONCRETECarbonation of concrete is associated with corrosion of steel reinforcement and shrinkage. However, it also increases both the compression strength and the strength of the concrete, so not all of its effects on concrete are bad. Carbonation is the result of the decomposition of CO2 in pore fluid in concrete and this reacts with calcium from calcium hydroxide and calcium silicate hydrate to form calcite (CaCO3). Aragonite can form in hot climates. Within a few hours, or a day or two in total, the new concrete will be processed by CO2 in the air. Gradually, the process penetrates deeper into the concrete at a rate equal to the square root of time. After a year or more it is likely to reach a depth of about 1 mm with dense low-penetration concrete made of low water / cement, or up to 5 mm or more of high-density and permitted concrete using high water / cement scale. Carbonation determinationThe affected depth from the concrete surface can be easily indicated by the use of a phenolphthalein indicator solution. This is available from chemical suppliers. Phenolphthalein is a white or pale yellow with a crystal. Use as a solvent dissolves in a suitable solution such as isopropyl alcohol (isopropanol) by 1%. The indicator has not changed color near the upper and lower extremities, suggesting that these regions near the surface be carbonated at a depth of at least 4 mm from the top to the top and 6 mm from the bottom. When the index turns purple - in the middle of the slide - the pH of the pore fluid anchor remains high (above 8.6, about 10). Whether you are pasting the cement here is not completely illuminated, despite the strong purple color; a complete test will require very little testing. The index was not applied to the concrete to the right of this image so the concrete here retains its original color. The depth of carbonation is about the same as the square root of time. For example, if the depth of carbon is 1mm in one-year-old concrete, it will be about 3mm after 9, 5mm after 25 years and 10mm after 100 years. Q5) Explain symptoms and diagnosis of distressA5)The rapid industrialization of India after independence required the transportation of goods and services and led to the construction of a network of wide roads with built-in bridges and flyovers. Many of the existing bridges show signs of stress within their work life built in many cases in the 10-20 years of construction in India and many other countries. The collapse of the I-35W bridge over the Mississippi River in the United States of America in August 2007 has attracted the attention of international media. In India, the collapse of the Mandovi Bridge in Goa in 1986 (after 16 years of service) and the great tribulation at the Zuari bridge (rebuilt in 2000 by an international consultant) in Goa and many other bridges such as Khalghat and Borad Bridge on NH3 (Route) Agra to Mumbai) due to environmental constraints is attracting the attention of transport authorities and the scientific community to transform the operational bridge management system. The cause of the distress, the level of grief and the reduction in the capacity of the bridge can be ensured in order to further the necessary adjustments to ensure the safety of the bridge during their operation. An assessment of the pressure and load capacity of existing bridges and to improve the load capacity is required while upgrading highways. India has already implemented the consolidation and use of four 7000 Km of highways under the Golden Quadrilateral program where the strengthening / replacement of many existing bridges was required. Various causes of damage to reinforced concrete bridges are low construction standards, rust of steel on reinforced concrete bridges and pre-reinforced concrete bridges, improper shape and details of normal loads and seismic forces, improper operation of bearings etc. a number of case studies have been reported in the literature on reinforced concrete damage and compacted concrete bridges during earthquakes and the reinforcement of reinforced and compressed concrete bridges due to nature and other loads. A concerted effort has been made to review critical documentation of reinforced concrete damage and pre-pressure concrete bridges and repair / rehabilitation strategies based on information from bridge reconstruction projects in which the authors were involved. Causes of distressRelationship problems such as conflicts, illness / death of a loved one, divorce, abuse, partner, etc. Financial difficulties Environmental remediation Educational difficulties Time management and organizational complexity Anxiety Depression An abusive event Drug abuse Diagnosis of distressSometimes the cause of grief is known e.g. suffering during an earthquake, impact and explosion is known perhaps the active load exceeds the intended load but it is often difficult to find the real cause of grief where many variables are affected e.g. poor construction quality (faulty details, faults and performance), shrinkage, penetration, rust consolidation etc. Following a test may be necessary to determine the cause and degree of grief.Determination of compression strength from NDT and cores of concrete Strategies for detecting explosions Signature / Vibration Analysis Download tests to find deviations / issues and distribute the load Rust studies (pH, depth of carbon, chloride) Deviation / disposal slopes from Instrumented Bridge Q6) Explain evaluation of crack A6)When inspecting a slab or conducting a crack crack, always measure the width of the crack and determine whether the metal reinforcement passes through it and whether the crack is active or asleep. This information, especially the details of the reinforcement and cracking function, is very important when choosing the best repair option.Crack widthThe extent of the crack is usually measured using a crack comparison card. Measuring the width of the crack helps to separate the stiffness of the cracks and to evaluate the performance of the joint joints across the fracture of the direct direction of the fracture and the transmission of the load. Also, many repair options depend on the width of the crack. Unless the steel reinforcement passes through a crack, the alignment of the vertical tube and the transmission of the broken load depends on the joint bonding. If the diameter of the fracture is less than 0.035 inches, the composite particles that come from the other side of the fracture to the other side will normally provide adequate load transfer and maintain vertical alignment throughout the split. For larger screens, maintaining a straight slide alignment can be a challenge. The success of the remediation approach will depend on the slide loading and the quality of the base material and the ground cover. Steel ReinforcementAlthough steel reinforcement does not prevent cracking, it limits the width of the crack so that the joint joints are maintained. Strengthening itself also provides load transfer and helps maintain vertical alignment in the cracks. When the reinforcement passes through a split, both the width split and the future width increase are controlled. The new cracks of the non-reinforced concrete will continue to grow and the diameter can double before the increase in crack-width. With the cracks caused by the drying shrink, the cracks will stabilize at the end. Splits due to other causes, however, such as soil erosion or height, may not be stable and may continue to increase unless a significant amount of reinforcement passes through space. Determining the amount of reinforcement that goes beyond cracking is important in predicting the performance of future cracks and choosing the best repair option. Dormant and active crackCracks that fall through steel reinforcement are generally stable and are often considered sleepy. Of course, the stability of the cracks depends on the source and the degree of reinforcement of the cracks. The lying cracks have a fixed width and can be repaired with solid or flexible materials. Functional cracks should only be repaired using a flexible object that can accommodate future cracked movements. Generally, the active cracks in the slabs actually belong to the active members and should be treated in the same way as the joints. After all, random or non-joining cracks in flatwork are self-assembling joints. Q7) Explain selection of repair procedure A7)StructureStructural repairs include using epoxy frames to bind or bond concrete together. Epoxy repair not only repairs the sealing cracks but also restores the strength and durability of the concrete. Use epoxy to repair dormant cracks only. Fixing functional cracks with epoxy often leads to a new formation near the original, epoxied fragment. Epoxy injection is a common way to inject epoxy into cracks, especially in direct and indirect areas. But gravity filling works well and is a common way to apply epoxy to flatwork cracks or to direct surfaces. The filling of gravity consists of pouring low-viscosity epoxy into the cracks that have been signed or distributed and allowed the gravitational force to pull the epoxy down the cracks. Viscosity resistance to fluid flow is measured in centipoises (cps). Decreased viscosity value, less (runnier) significant. Grade I and II epoxies have viscosities of less than 20 cps and between 20 and 100 cps, respectively. For comparison, the viscosities of other common beverages are: water - 1 cps, milk - 3 cps, anti-freeze - 15 cps, maple syrup - 150 to 200 cps, and honey -3000 cps. Low viscosities are required for solid cracks. Otherwise, the repair material will be too large to penetrate and flow into the crack. Epoxies were cured or hardened due to the chemical reaction between the frame and the hardener. Chemical reactions are rapid at high temperatures. Epoxies are obtained by different injections or by temperature treatments so chemical reactions are less rapid or slow (Type A, less than 40º F; Type B, 40º F to 60º F; and type C, more than 60º F). With the adjustment of gravity filling culture, consider the depth and depth, epoxy viscosity, and temperature input when choosing the distance and type of epoxy. Otherwise, the epoxy can be very strong or very hard to penetrate or it can just run between the river and the pool under the slide. Sealing and fillingSealing and filling of non-construction repairs. However, some repair materials include cracked surfaces and can have a strong impact that can cause cracking of the material and concrete in the event of a major crack movement. Typical sealants and internal fixing fillers include semi-rigid epoxies, hybrid polyurethanes and polyureas, and polymer mortar. Polyurethanes and silicones are common labels used for exterior repairs. Usually, sealants are flexible or elastomeric materials; and the fillers are very hard so the fixing materials support the edges of the cracks to avoid collapse or damage under load. When heavy traffic is exposed to heavy wheels, composite fillers or special cracks with about 80 Shore A Hardness should be used. Unfortunately, there is a tradeoff to increase the complexity of explosive repair materials. As the repair material gets harder, it becomes much thinner and does not tolerate cracked movement. For example, semi-rigid epoxies usually have a hardness of about 90 and an extension value of 50%; whereas, silicone sealants have a hardness of about 5 and an extension value of 1400%. Therefore, when choosing a fix, consider the expected movement of the comparison and the need to support the edges of the cracks. For effective cracking with the expected cracking motion, use elastomeric sealants or sealants with sufficient elastic properties, to see that the tradeoff will be a little support for the fracture edges. For cracks exposed to heavy-duty traffic, use hard materials that support the edges of the cracks. But understand that these things do not tolerate the movement of cracks. If you are using elastomeric sealants in active cracks, always seal the sealant with a saw or by moving the track as recommended by the repairman. Without a dam, there would not be enough to tolerate future fracture movements. Expansion structures reported by manufacturers are based on the size of the recommended lakes or, in particular, the width and depth of the dam. Of course, cutting or scraping increases the width of the crack and makes crack repairs more noticeable. For cosmetic repairs in colored or decorative flats where cracks lie or are well established, do not see or move the sealant or filler dam. Instead, choose a low viscosity cracker (less than 100 cps) and small injection tips for cracks to fill gravity. Dams are not required. But in the event of a fracture movement, the cracking of the repair material or concrete may occur due to the small diameter of the depth of the material. Also, manufacturers now offer many of these low viscosity fixes in a variety of colors or offer color production recommendations and textures similar to concrete concrete surfaces. Before fixing your next explosion, do a crack test and establish repair targets. Decide what kind of adjustment is needed. Options include structural repairs using epoxy, route fixes and seal applications using flexible sealant to hold future cracks, and solid or durable repairs that fill the edges of cracks, with or without. Also, set cosmetic requirements. After selecting the fix and procedure, follow the manufacturer's recommendations. Q8) Explain shortcrete and grouting A8)SHORTCRETEShotcrete or sprayed concrete is concrete or mortar conveyed thru a hose and pneumatically projected at excessive pace onto a floor, as a production method, first utilized in 1914. It is usually strengthened with the aid of using traditional metallic rods, metallic mesh, or fibers. Properly carried out shotcrete is a structurally sound and sturdy production cloth which well-known shows terrific bonding traits to present concrete, rock, metallic, and plenty of different materials. It may have excessive strength, low absorption, correct resistance to weathering, and resistance to a few varieties of chemical attack. Many of the bodily residences of sound shotcrete are similar or advanced to the ones of traditional concrete or mortar having the equal composition. Improperly carried out shotcrete can also additionally create situations a lot worse than the untreated condition. Advantages of shotcrete:Shotcrete is utilized in lieu of traditional concrete, in maximum instances, for motives of fee or convenience. Shotcrete is fine in conditions whilst formwork is fee prohibitive or impractical and wherein paperwork may be decreased or eliminated, get entry to to the paintings place is difficult, skinny layers or variable thicknesses are required, or ordinary casting strategies cannot be employed. Additional financial savings are feasible due to the fact shotcrete calls for handiest a small, transportable plant for manufacture and placement. Shotcreting operations can regularly be executed in regions of restrained get entry to to make upkeep to structures. GROUTINGGrout is usually a mixture of cement, sand, and water or chemicals used to fill gaps. They are used to repair concrete cracks, to fill gaps and gaps in tiles, to fill gaps and waterproofing, and to strengthen the soil. It is also used to provide additional power to load-bearing structures. It basically involves the process of injecting something that can be pumped into a building to change its body structures. There are different types of grinding, cement grinding, chemical grinding, and bituminous grating, depending on the material used. Frames are also sometimes used as grout materials. A mortar is often used to fill cracks and gaps in soil or rock. What is GroutingAlso, it is used to stabilize the soil and keep it out. Cracking is used for a variety of purposes such as water repair, standing on immersed structures such as ditches, tunnels, etc., filling in the gaps between tiles and stabilizing the soil. Here we have provided details on the type of grouts used to repair cracks. Advantage of Grouting Includes:This can be done in almost any soil condition It does not vibrate and can be controlled to avoid structural damage Development of underground structures can be measured It is very useful for limited space and low head items It is used to install slab jacking that lifts or measures the crippled foundation It can be installed near existing walls It can be used to control the flow of water, groundwater flow, and hazardous waste materials. Many Different Types of Grouting Materials:Stopping cement Chemical Grouting Bentonite grouting The amber is growing Bituminous Grouting Q9) Explain introduction of retrofitting of concrete structure by FPP and polymer impregnated concrete A9)FIBER REINFORCED POLYMERFiber-reinforced polymer (FRP), also fiber-reinforced plastic, is a composite made of polymer matrix reinforced with fibers. Threads are usually glass, carbon, or aramid, although other fibers such as paper or wood or asbestos have sometimes been used. The polymer is usually epoxy, vinylester or polyester thermosetting plastic, and phenol formaldehyde frames are still active. FRPs are widely used in the aerospace, automotive, marine and construction industries. Composite materials are made of building materials or naturally made from two or more materials that have a structure with very different physical or chemical properties that are always different and distinct from the finished structure. Most compounds have strong, strong fibers in a weak and strong matrix. The goal is usually to make the part stronger and stronger, usually with a lower volume. Commercial materials usually contain glass or carbon fibers in a matrix based on thermosetting polymers, such as epoxy or polyester resins. In some cases, thermoplastic polymers may be preferred, as they form after the first production. There are additional stages of integration where the matrix is metal or ceramic. For the most part, these are still in the development phase, and the problems of high production costs have yet to be overcome [1]. Moreover, in these compounds the reasons for adding fibers (or, in some cases, particles) are often complex; for example, improvements may be required in penetration, wear, cracking, heat stabilization, etc. Fiber-reinforced polymer (FRP) is a compound used in almost every type of high-tech engineering facility, with its use from aircraft, helicopters and spacecraft to boats, ships and marine systems as well as automobiles, sports equipment, repair equipment chemicals and public infrastructure such as bridges and buildings. The use of FRP compounds continues to grow at an impressive rate as these materials are widely used in their existing markets and are being developed in brand new markets such as biomedical devices and social structures. An important factor contributing to the increased use of compounds over the years has been the development of new types of FRP materials. This includes the development of high-resin applications and new reinforcement styles, such as carbon nanotubes and nanoparticles. The book provides a timely account of fiction, mechanical properties, delamination resistance, impact tolerance and the use of 3D FRP compounds. Polymers reinforced polymer composites (FRPs) are increasingly being considered for the development and / or replacement of structural components or systems consisting of traditional engineering materials, namely concrete and steel. FRP compounds are simple, non-destructive, show a certain high strength and direct durability, are easily constructed, and can be customized to meet operational requirements. Because of these beneficial features, FRP compounds have been incorporated into the construction and renovation of buildings using their reinforcement in concrete, blocks, modular structures, formwork, and external reinforcement for seismic reinforcement and development. The effectiveness of Fiber Reinforced Polymer (FRP) reinforcement in concrete structures such as replacement of steel bars or pre-pressurized muscles has been extensively studied in many research laboratories and professional organizations around the world. FRP reinforcement offers many benefits such as corrosion resistance, non-magnetic properties, very strong, lightweight and easy to handle. However, they usually have a direct response to stiffness to the point of failure (defined as damaging failure) and poor resistance to friction or shear. They are also less resistant to fire and when exposed to high temperatures. They release vital energy as they bend, and they are sensitive to the effects of pressure fractures. In addition, their cost, whether considered for each weight or on the basis of strength-bearing capacity, is relatively high compared with conventional steel reinforcement bars or pressure straps. From a structural engineering perspective, the most serious problems with FRP reinforcement are the lack of plastic conduct and very low shear strength on the short side. Such features can lead to premature tender fragmentation, especially if mixed results are obtained, such as in shear-breaking planes on reinforced concrete pillars where there is a delow action. The downtime action reduces the remaining resistance to stiffness and shear tenderness. Solutions and limitations for use are provided and further improvements are expected in the future. The cost of FRP consolidation unit is expected to decrease significantly with increasing market share and demand. However, even today, there are applications where FRP consolidation is less expensive and justified. Such cases include the use of FRP sheets or bonded plates in repairing and strengthening concrete structures, as well as the use of FRP meshes or fabrics or fabrics in small cement products. The cost of renovating and renovating a building remains, in certain terms, much higher than the cost of the original building. Repairs usually require a small amount of repair materials but a high commitment from staff. In addition, labor costs in developed countries are so high that the cost of materials is secondary. So the performance and performance that lasts the longest, the repair is very expensive. This means that the cost of materials is not a problem to be rectified and the fact that FRP materials are expensive is not a particular problem [5]. Given only the physical strength and resources, at the top, the controversy over FRP compounds in a sustainable built environment is questionable. However, such a conclusion needs to be evaluated in terms of the potential benefits of using FRP compounds related to assumptions such as: High powerLight weightHigh performanceIt lasts a long timeRenovating existing buildings and extending their lifeSeismic developmentSecurity systemsSpace programsOcean areasIn the case of FRP compounds, environmental concerns appear to be a barrier to its functioning as a viable alternative especially in terms of fuel depletion, air pollution, fog, and acidification associated with its production. In addition, the ability to reuse FRP compounds is limited and, unlike steel and wood, structural components cannot be reused to perform the same function in another structure. However, examining the environmental impact of FRP compounds on infrastructure use, especially through life cycle analysis, may reveal more direct and indirect benefits that compete more than conventional ones. The composite material has greatly improved since its inception. However, before composite materials can be used as an alternative to conventional materials as part of a sustainable environment a few needs remain. Availability of durability data for FRP building materials. Integration of robust data and service life prediction methods for building members using FRP combinations. Development of selection methods according to the life cycle cycle of materials and systems. Finally, in order for the mixtures to be considered a viable option, they must be structurally and economically viable. Many studies on the structure of the composite material are widely available in the literature. However, limited studies are available on the economic and environmental availability of these items from the perspective of the life cycle, because short-term data are available or only economic costs are considered in comparison. In addition, the long-term impact of using composite materials needs to be determined. The products produced, the sustainability of the materials, and the capacity to recycle the materials need to be tested to determine if the composite materials can be part of a sustainable environment. So in this chapter describe the physicochemical properties of polymers and compounds most commonly used in Civil Engineering. The theme will be presented in a simple and basic way for better understanding. POLYMER IMPREGNATED CONCRETEIn the case of pregnant polymer concrete, prepolymers or lower liquid monomers are partially or partially impregnated with a pore system of a composite cement framework. After this process, the entire treated structure is allowed to polish. The general process of treatment of reinforced concrete leads to the acquisition of a large amount of free water in its spaces. These water-filled voids form a significant amount of total volume. From 5% in the case of dense concrete and 15% in the case of gaped concrete. In the case of pregnant polymer concrete, it is these voids (holes filled with water) that should be filled with the selected polymer. So the main thing that affects the loading of the monomer is this: the moisture content in the solid concrete and the air loses energy in the concrete. Procedure for polymer impregnated concrete manufacturingThe activities involved in the pregnancy process to improve pregnant polymer concrete are:1. Well-constructed concrete is available. They need to get better and get stronger.2. Moisture is removed by drying the concrete. Drying is done by heating the structure element at temperatures above the order of 120 to 150 degrees Celsius. An air oven can be used to dry small specimens.If the element has a large surface, a thick cloth, say, 10mm thick, can be used to protect it from any hot gradient. Another complex application is the use of infrared heaters.Complete removal of moisture from concrete, requires 6 to 8 hours of heat.3. After complete removal, the concrete area has cooled to a safer level. This can go up to a temperature of 35 degrees Celsius. This heat will avoid overheating.4. The concrete is now transferred to a vacuum cleaner, where all the air inside the concrete structure is removed. The amount of monomer installed will determine the time and level of use of the machine.5. Concrete after sufficient ventilation is placed in a monomer solution. Wet for a long time until the desired depth of monomer penetration is obtained.Filling time depends on the viscosity of the monomer, the adjustment of the template and the advanced characteristics of the concrete.To reduce the time taken to get the desired input, it is preferable to use external pressure such as air or nitrogen gas. This helps to get in faster.6. After the above procedure, the surface is covered with plastic paper. This helps prevent the evaporation of the monomer.7. A high-temperature polymerization method is performed. This method involves polymerization by heating the deformed monomer to the required temperature. This will start from 60 degrees to 150 degrees Celsius. The selected temperature range depends on the type of monomer.Heating can be done under water or with a low pressure steam injection, or with infrared heaters or an air oven. The heat decomposes the catalyst and thus initiates the polymerization reaction.Once the monomer has penetrated the concrete, polymerization can also be initiated using ionization radiation similar to gamma rays. Polymers when they are completely polymer or when connected on the other side, act as solids that reside in the voids they are embedded in.8. The concrete structure is then allowed to cool.Every process from 1 to 8 can only be done in a precast factory. Monomers such as acrylate, styrene and vinyl chloride etc. are widely used for concrete installations. Another widely used material is Methyl Methacrylate (MMA).Properties of polymer impregnated concrete1. The polymer concrete gains the strength of the cube to strengthen more than 100N / mm2. This strength does not depend on the strength of the standard concrete.2. The flexibility of a pregnant polymer concrete is approximately 15N / mm2. This is slightly higher than high-grade clear concrete made from common ingredients.3. The elastic modulus lies in the range from 30 to 60N / mm2. This value is the same as the value obtained from high-strength concrete (e.g. approximately 45N / mm2)4. Pregnant polymer concrete has less movement problems and shrinkage due to the small number of pores.5. Pregnant polymer concrete is more resistant to acid attacks, sulfate attacks and chloride attacks compared to PCC.Application of polymer impregnated concreteThe use of pregnant polymer concrete in various construction sites is described below:1. Surface Impregnation of Bridge Decks: Bridge decks are allowed to be installed to avoid the ingress of moisture, chemicals and chloride ions.Bridge floors built in areas with high salt water and moisture exposure can be protected in this way.2. Structural repairs: Damaged structures can be developed in the form of a polymer abstract. The life span of undeveloped buildings can be extended in this way.This method is why it helps in the restoration and preservation of stone monuments.3. Underwater and Marine Applications: Polymer impregnation capabilities help to improve structures, water absorption, and non-concrete structures. This makes them widely used in water and sea construction.Buildings built on desalination plants and underwater structures use this method of building concrete. It has been shown that the small absorption of concrete masses from seawater reduces the corrosion of the steel by 24 times.4. Use in Irrigation Systems: The use of standard methods for the repair and rehabilitation of dams and other important water structures appears to be inefficient and incomplete.This is later found to cause significant losses in profits from irrigation, energy production, flood control etc. But the method of pregnancy works very well.Concrete from the damaged area is removed, glued and dried. This area is later treated using polymer emissions.5. Composite Joints: Pregnant polymer concrete is as strong as building materials. PIC also shows the amazing development of standard concrete.Internal and empty cracks are the basic foundation for all the issues in common concrete structures. Since the suspension of the polymer determines the cause, it is best used for construction members. Q10) Explain corrosion monitoring and preventive measure A10)The rust measuring, control, and prevention field covers a wide range of technical tasks. Within the field of corrosion control and prevention, there are technical options such as cathodic and anodic protection, material selection, chemical insertion and use of indoor and outdoor clothing. The rust scale uses a variety of techniques to determine how much damage the environment consumes and how much iron loss is experienced. Rust rating is a measure of how rust management performance and prevention strategies can be implemented and provides feedback to enable rust control and preventative measures to be improved. Some rust measurement techniques can be used online, regularly displayed in process broadcasts, while others provide external measurement, such as those determined in laboratory analysis. Some techniques provide a precise measure of metal loss or rust ratio, while others are used to indicate the possibility of corrosion. Rust monitoring is the practice of measuring the deterioration of process dissemination conditions by using probes that are incorporated into process dissemination and that are continuously expressed in the process dissemination process. Rust monitoring probes can be mechanical, electrical or electrical devices. Rust monitoring alone provides accurate and online measurement of metal loss / corrosion rate in industrial process systems. Typically, the rust measuring system, testing and adjustment used in any industrial area will include measuring instruments provided by four combinations of on-line / offline, direct / indirect measurements. Corrosion Monitoring Direct, On-line Direct, Offline Non-Destructive Testing Indirect Analytical Chemistry, Off-line Indirect, online Operational Data In a well-managed and integrated system, data from each source will be used to draw reasonable conclusions about the levels of active corrosion by the process process and how they are effectively reduced. The Need of corrosion monitoringThe level of rust determines which process plant can be used efficiently and safely for how long. The rust scale and the action of adjusting the high levels of rust allow for the efficient operation of plants that must be achieved while minimizing the life cycle costs associated with the work.Rust monitoring techniques can help in a number of ways:by giving an early warning that harmful procedural conditions exist that could lead to failures caused by rust. by studying the integration of changes in process parameters and their effect on system corrosivity. by identifying a specific rust problem, identifying its cause and the parameters that control the level, such as pressure, temperature, pH, flow rate, etc. by evaluating the effectiveness of the corrosion / prevention control method such as chemical prevention and good use. by providing management information relating to conservation needs and the ongoing condition of the plant. Corrosion monitoring techniquesA large number of rust monitoring strategies are available. The following list describes the most common strategies used in industrial applications:Rust Coupons (Weight Loss Rate) Electrical Resistance (ER) Linear Separation Resistance (LPR) Galvanic (ZRA) / Possible Hydrogen Ingestion Bacteria Sand / Soil erosion Other strategies are available, but almost all require professional work, otherwise they are not enough or flexible to apply.In the above-mentioned strategies, corrosion coupons, ER, and LPR form the core of industrial corrosion monitoring systems. The other four strategies are usually found in special programs that are discussed over time.These rust monitoring methods have been used successfully and are being used by a growing number of applications because:The techniques are easy to understand and apply. The reliability of the equipment has been demonstrated in the field field for many years of application operation. The results are easy to explain. Measurement equipment can be made internally safe from hazardous environmental performance. Consumers have gained significant economic benefits by reducing planting time and extending plant life. PREVENTIVE MEASURESMetal corrosion is a natural process that requires three conditions: moisture, metal surface, and an oxidizing agent called an electron acceptor. Rust converts the active metal into a separate form of oxide, hydroxide, or sulphide. The most common type of rust is rust. Metallic metal not only affects the structure of the metal, but it can also affect the people who use the material or objects close to the metal. In extreme cases, rotten metal can lead to the construction of buildings and bridges, leaking pipes, and medical implants that infect human blood. While all metals are in danger of corrosion, some metals, such as pure metal, deteriorate much faster than others. However, iron can be combined with other alloys to form a stainless steel that is more resistant to corrosion. It is estimated that approximately 25-30% of rust can be prevented using appropriate protective measures. In general, you can prevent rust by choosing the right type of metal, Protective Fabrics, Environmental Measures, Self-Sacrifice Items, Rust Stumbling Stuff, Metal Installation and Repairs for Your Project. Choose the right metal typeOne of the easiest ways to prevent rust is to use rust-resistant metal such as stainless steel, duplex, super duplex, nickel alloy or 6% Moly. These devices are so well made that they have a high resistance to corrosion and use them to reduce the need for alternative corrosion protection. For Special Drawing Materials, we offer products made of the highest quality synthetic materials available - stainless steel, duplex, super duplex, 6% Moly and Nickel Alloy. A variety of materials are selected by our clients in a variety of areas, with one of the factors considered for possible corrosion. Protective coatingAnother way to prevent rust is to cover it with a special protective paint. Paint coating can act as a barrier that works by preventing electrochemical charging that transmits to the destructive and metal solution below. One way to do this is to put a powder coating in a clean metal place. The metal is heated to turn the flour into a smooth, non-abrasive film that acts as a barrier to rust. Many different powder compositions can be used, such as acrylic, polyester, epoxy, nylon, and urethane. Environmental MeasuresRust is certainly due to the nature of the metal in it as the chemical reactions that occur are due to metal reacting with liquids and gases in the surrounding environment. Controlling the environment can therefore help reduce this response. This could be as simple as reducing exposure to rain or seawater or it could be steps taken to reduce the amount of sulfur, chlorine, or oxygen in the area. For example, carrying water in water boilers to adjust hardness, alkalinity, or oxygen content, before placing the metal in that water can be very helpful in preventing corrosion. Sacrificial coatingSacrifice cover to prevent corrosion means covering the metal with a type of metal that may have oxidise - you sacrifice this top layer to protect the lower metal.There are two main ways to accomplish the sacrificial attire:Cathodic Protection: Cathodic protection works by making the metal cathode of an electrochemical cell. The most common example of cathodic protection is the coating of iron ore and zinc - this process is known as galvanizing. Zinc is more than an active metal so rust prevents metal rot. Cathodic protection is frequently used for steel or petrol pipelines, heat tanks, ports, and overseas oil platforms. Anodic Protection: Anodic protection is opposed to cathodic protection and works by making the metal anode of an electrochemical cell. A common way to do this is to cover a thin layer of stainless steel, such as tin. The tin will not corrode, so the metal will be protected as long as the tin coating is in place. Anodic protection is often used for carbon storage tanks used to store sulfuric acid and 50% caustic soda. Corrosion InhibitorsChemical corrosion inhibitors are selected to react to metal surfaces or surrounding gases and therefore suppress electrochemical reactions that can lead to decay. When applied to a metal surface, they form a protective film. Inhibitors can be used as a solution or as a protective cover using distribution methods. Corrosion inhibitors are often used in a process known as passivation. An example of passivation is the Statement of Freedom where a blue and green metal signature is actually present to protect the copper underneath. Metal PlatingThe installation is very similar to the cover as a thin layer of metal is inserted into the metal you want to protect. As well as preventing corrosion, the metal layer provides a good finish of beauty. There are four types of metal wraps:Electroplating: The application of a thin layer of metal such as chromium or nickel to the underground metal by means of an electrolyte bath. Mechanical Plating: this involves cold welding powder metal metal substrate. Electro less: Coating such as nickel or cobalt is placed on a metal substrate using non-electrical chemical reactions. Hot dipping: A simple covering method that involves placing the substrate in a molten metal protective tub. Design ModificationChanging the structure of the project can have a significant impact on rust protection as it works by eliminating the causes of rust.
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UNIT - 6DETERIORATION AND REPAIR IN CONCRETEQ1) Explain durability and factors affecting durability A1)Durability is the capacity to remaining a long term without massive deterioration. A long lasting cloth allows the surroundings with the aid of using keeping sources and lowering wastes and the environmental affect of restore and substitute. The manufacturing of substitute constructing substances depletes herbal sources and may produce air and water pollution. Concrete resists weathering action, chemical attack, and abrasion even as retaining its favored engineering houses. Different concretes require extraordinary levels of sturdiness relying at the publicity surroundings and the houses favored. Concrete ingredients, their proportioning, interactions among them, setting and curing practices, and the provider surroundings decide the remaining sturdiness and lifestyles of the concrete. The layout provider lifestyles of maximum homes regularly 30 years, despite the fact that homes regularly remaining 50 to one hundred years or longer. Because in their sturdiness, maximum concrete and masonry homes are demolished because of useful obsolescence in place of deterioration. However, a concrete shell or shape may be repurposed if a constructing use or characteristic adjustments or whilst a constructing indoors is renovated. Concrete, as a structural cloth and because the constructing outside skin, has the capacity to face up to nature’s ordinary deteriorating mechanisms in addition to herbal disasters. Durability of concrete can be described because the capacity of concrete to withstand weathering action, chemical attack, and abrasion even as retaining its favored engineering houses. Different concretes require extraordinary levels of sturdiness relying at the publicity surroundings and houses favored. For example, concrete uncovered to tidal seawater could have extraordinary necessities than an indoor concrete floor. FACTOR AFFECTING THE DURABILITY OF CONCRETEThe following are the factors that affect the strength of concrete.Cement content Aggregate quality Water Quality Concrete compaction Curing period Permeability Moisture Temperature Abrasion Carbonation 01. Cement contentThe amount of cement used in concrete mixing is a major factor affecting the durability of concrete. If the cement content used is less than required, the cement water level Decreases and the performance of concrete also decreases. Adding too much water to this concrete mix causes the formation of capillary voids that will make the concrete a resilient one inviting decay. Adding excess cement can cause problems such as stopping the shrinkage. Alkali-silica reactions may also eventually affect the strength of the concrete. 02. Aggregate QualityApplying a good quality mix to the concrete mix will definitely increase the strength of the concrete. The shape of the composite particles should be small and circular. Flaky and compact assembly can affect the performance of the new concrete making it easier to enter where it can open and will work with less power. Bad angular compilation is recommended but requires a lot of cement content to get a good binding. Yes, structural composites should be used to achieve greater concrete mixing. Determination of the combined moisture content should be done beforehand, otherwise, it can create a more usable concrete mix and make it worse. 03. Water QualityThe water used in the concrete mix also affects the strength of the concrete. Usually, drinking water is recommended to make concrete. the pH of the water used will be in grades 7 to 8 only. Water should be free and clean from fats, acids, alkalis, sugar, organic salts etc. Contamination in the water can lead to metal corrosion or corrosion due to different chemical attacks of concrete. 04. Concrete compactionCare should be taken during the installation of the concrete. It is important to glue the local concrete without splitting. Adequately compacted concrete contains a number of air gaps in it that reduce the strength of the concrete and its strength and will make it stronger. 05. Curing periodProper treatment should be done in the early stages of concrete reinforcement as it will lead to the reinforcement of the concrete. Adequate treatment can lead to the formation of cracks due to plastic shrinkage, dehydration, heat effects etc. due to reduced stiffness. 06. PermeabilityDue to the overcrowding of the concrete, it expands and leads to the formation of cracks and eventually, the deterioration of the concrete occurs. Concrete usually consists of small gel pores and capillary cavities. However, gel pores prevent water ingress because they are too small. Capillary holes in concrete are facing, which are formed due to the high water content of concrete To prevent intrusion, a very small amount of cement water should be used. Using a small amount of pozzolanic material also helps to reduce penetration 07. MoistureThe moisture found in the atmosphere will also affect the strength of concrete structures. Concrete moisture is responsible for Efflorescence, which will convert salt into soluble solutions and when evaporated salt becomes brighter and appears on the concrete surface. This will definitely damage the concrete structure and the durability will decrease. 08. TemperatureWhen new concrete is exposed to high temperatures, the hydration level is affected and strength and durability are reduced. Concrete materials have different temperature coefficients, so at higher temperatures, spelling and damage to concrete are possible. 09. AbrasionConcrete damage also occurs due to severe facial injuries. When concrete is exposed to fast-moving water, steel tires, floating ice that wears continuously on the surface occur and stiffness is affected. The higher the pressure of the concrete pressure the higher it will be to resist the abrasion 10. CarbonationWhen wet concrete is exposed to the atmosphere, carbon dioxide in the atmosphere reacts with concrete and reduces the pH of the concrete by reacting with CaO in concrete. When the pH value of concrete is reduced to 10 or 9 or more, it releases its alkali. Because it will not be able to protect the metal bars beneath it. Due to rust, rust will build up around the bar which has led to an increase in the volume of the bar. This will create cracks in the concrete. Cracking will continue to promote moisture and CO2 which will lead to the loss of alkali. So bad cycles occur, eventually causing the concrete to crack with delamination and spraying of the concrete if not done in time, the bars will start to lose their place and thus become stronger. Most of the building in modern times, suffers from this, and buildings that were supposed to be 100 years old have been extensively renovated at some point within ten years. The process of rust therefore places on the existing strength of the concrete. The rust of the reinforcement causes cracks in the solid concrete and deterioration occurs. Q2) Explain permeability and sulphate attack A2)Definition: the capacity of a given concrete to allow drinks or gases to by skip through.- ACI Concrete Terminology Permeability is a degree of the quantity of water, air, and different materials which could input the concrete matrix. Concrete consists of pores which could permit those materials to go into or depart. Permeability of concrete may be a number one motive for concrete deterioration because of reinforcing metal corrosion and different deterioration mechanisms. On a macro scale, permeability additionally refers to “porous” slabs used to empty pavements, sidewalks, and parking regions of water, putting off the want for drainage slope, systems, and piping. This technology—every now and then called “no-fines concrete”—is gaining reputation once more with the preference to lessen floor run-off from pavements, sidewalks, and parking regions. Permeability of cement mortar or concrete is of unique importance in systems which might be meant to hold water or which come into touch with water. Besides useful considerations, permeability is likewise in detail associated with the sturdiness of concrete, mainly its resistance, towards revolutionary deterioration below publicity to extreme climate, and leaching because of extended seepage of water, specially whilst it consists of competitive gases or minerals in solution. The willpower of the permeability traits of mortar and concrete, therefore, assumes widespread importance.
Fig no 1Concrete permeability apparatusThe permeability mobileular shall encompass a steel cylinder for containing the specimen. A rubber or neoprene O-ring or different appropriate gasket, seated in matching grooves will be used among the mobileular and the quilt plate to render the joint water-tight.
Fig no 2 Water Reservoir in Permeability ApparatusA appropriate reservoir may also encompass a duration of steel pipe, 50 to a hundred mm in diameter and approximately 500 mm long. The reservoir will be equipped with a graduated facet arm gauge-glass, and the vital fittings and valves for admitting water and compressed air and for draining, bleeding and connection to the permeability mobileular. Procedure:Preparation of Test SpecimenTest specimen of 2 hundred mm diameter and a hundred and twenty mm thick will be used. After 24 hrs of casting of specimen, crucial round place of a hundred mm diameter will be roughened with a twine brush at the facet on which the water stress is to be carried out. The un roughened a part of the facet of the check specimen that's subjected to water stress is to be sealed with coats of cement water paste (W/C = 0.4). Test ProcedureAfter 28 days curing, check specimen is equipped right into a check equipment in which the water stress acts on the specified face and final faces may be observed. At first, a stress of one Bar is carried out for forty eight hours, then three bar for twenty-four hours and seven Bar for twenty-four hours. After the check, the specimen is break up with inside the center with the aid of using the compression carried out on spherical metal bars mendacity on contrary sides, above and below. The facet after the check specimen uncovered to the water stress ought to face downwards. Observation:The finest water penetration depth, is taken because the common cost of the finest penetration depths on 3 check specimen. SULPHATE ATTACKCement is composed of two minerals: tri-calcium silicate (C3S), and di-calcium silicate (C2S). In addition to hydration, the main reaction products are calcium silicate gel (C-SH) and calcium hydroxide Ca (OH) 2, labeled as CH in chemistry notation. Moisture is required in this reaction which can cause serious damage to the construction of both the walls and the walls of buildings in buildings. Sulfate attacks occur on the lower slabs. This problem usually affects buildings from the 1950s to the 1960s but can also affect previous buildings where the concrete floor slab is installed. It occurs when the filler material under the slide contains sulphates and this is considered to be a solution with soil moisture entering the concrete that forms the slab on the floor. Attacks can occur from MgSO4 salts, NaSO4 salts, and other salts containing SO3-ions. The interaction of Ca2 + ions with SO4 present in the solution will produce CaSO4 or gypsum. The effect of gypsum on C-S-H gel, which is the main component of reinforced cement, is an irreversible topic. Some substances present in cement, such as tri-calcium aluminate, also interact with sulphate ions. This reaction is well established in the literature. Q3) Explain acid attack and chloride attack A3)Acid attack is the dissolution and leaching of acid-prone elements, particularly calcium hydroxide, from the cement paste of hardened concrete. This movement outcome in an boom in capillary porosity, lack of cohesiveness and subsequently lack of power. In said instances, acid assault can be observed with the aid of using crack formation and subsequently disintegration, in particular whilst the shape is subjected at one facet to water pressure. Unlike sulfate assault (see beneath), the goods fashioned from acid assault aren't expansive, and leaching will handiest arise in systems which are tremendously permeable. In excessive overall performance concrete structures containing cement pastes with a low content material of calcium hydroxide, acid assault is relative gradual and can contain handiest the finely divided calcium hydroxide crystals included with inside the interstices of the calcium silicate hydrates, C-S-H. The micrographs received from PFM analysis, supplemented with SEM–EDS studies, monitor that handiest the top, floor part of the concrete has been attacked with the aid of using acidic answer. The relaxation of the concrete suggests no shape of degradation. In the attacked zone, there's clean proof of leaching of the cement paste matrix, main to accelerated capillary porosity and lack of brotherly love of the matrix. Locally, there's lack of bonding of the cement paste to aggregate, however at the whole, those elements have now no longer adversely affected the microstructure and nice of the concrete. In this instance, long-time period sturdiness of the concrete isn't always probably to be compromised.
Fig no 3 Acid Attack on Concrete blockAcid assault of concrete takes 3 forms. First, hydration merchandise react with the acid to shape dissolved ions, main to lack of strong material—acidolysis. Second, withinside the case of a few acids, insoluble salts shape, a number of which precipitate to purpose growth and cracking. Finally, a few acids supply complexes with calcium, aluminium, iron and silicate ions which produce an awful lot better concentrations of those ions in answer than could in any other case be the case, once more main to dissolution. This can probably arise at pH situations beneath which cement could usually be tremendously stable (complexolysis). Depending at the acid present, extra than this sort of deterioration mechanisms can be powerful. Where acidolysis is the main mechanism, an acid answer penetrating the pores of concrete will begin to purpose a number of the elements to dissolve. Calcium is generally the primary cation to be dissolved, considering that port land will become soluble beneath tremendously excessive pH values. A F m and A F t stages commonly dissolve at barely decrease pH values, even though strong aluminium and iron hydroxides are precipitated, which persist till the answer is tremendously acidic. Exposure to acidic answer additionally reasons lack of calcium—decalcification—of C-S-H gel, leaving tremendously vulnerable silica gel behind. The importance of calcium on this shape of degradation approach that adjusting the composition of the cement matrix of concrete to attain a decrease calcium content material will probably impart extra resistance. Thus, pozzolanic substances can be powerful in improving resistance to this form of acid assault, considering that their aggregate with PC will produce such an adjustment. However, decreased quotes of mass shipping and more desirable power done thru the usage of pozzolanic substances also are probably to be motives for progressed resistance. CHLORIDE ATTACKChloride Attack Chloride attack is one of the most important factors when working with concrete strength. It mainly causes corrosion corrosion. Statistics have shown that more than 40% of structural failures are due to metal corrosion. Concrete and the penetration layer with a strong alkaline Ca (OH) 2 (pH approximately 13) prevents metal corrosion by forming a thin film to protect the iron oxide on the surface of the metal. This protection is known as inaction. If concrete can penetrate in such a way that the dissolved chloride enters until it hardens and water and oxygen are also present, then corrosion of the metal will occur. This layer can also be lost due to carbonation. Chloride enters the concrete from cement, water, and is sometimes mixed from tips. This can come in increments from nature when the concrete is filled. The Bureau of Indian Standard specified the high chloride content in cement as 0.1%. The amount of chloride needed to start corrosion depends on the pH value of the pore water in the concrete. A pH value below11.5 corrosion is possible without the presence of chloride. Q4) Explain corrosion of reinforcement, carbonation of concrete A4)CORROSION OF REINFORCEMENTConcrete, in itself, has a low strength. To increase the strength of the concrete, the steel hardens. Steel bars are inserted inside the weight of the concrete. These steel bearings carry a high load-bearing capacity applied to concrete. Concrete makes metal bars obsolete due to the alkaline environment, thus preventing them from cracking. However, for a variety of reasons, metal bars can be pulled longer. And as a result of the rust of the steel bars, various weaknesses appear in the concrete structure, which could eventually collapse if not properly maintained. The rust of steel reinforcement bars is actually a way of responding to electricity. Small anodes and cathodes are formed and the flow of ions between these two electrodes leads to the breakdown of metal bars. There are two types of corrosion detected in steel reinforcement bars: Metal Rust - In small cracks in a concrete structure, solutions may remain. Anodes and cathodes can be formed within solutions due to the uneven reaction of solute ions over the volume of the solution. The flow of ions is caused by these electrodes, thus causing a gradual corrosion. Rust corrosion - Related to the removal of small areas in the steel bars of the reinforcement. This type of rust is extremely well-formed and small holes or holes are made in the metal. Causes of Stainless Steel RustCorruption of steel reinforcement barriers may be due to the local failure of the metal film of chloride ions or the general failure of the concrete to malfunction due to the carbon dioxide reaction from the atmosphere. The main factors facing corrosion of reinforcement barriers are: Loss of alkalinity due to carbonation - When a metal surface is left unprotected in the atmosphere, corrosion begins to form on the surface of the metal and then slowly moves away. Loss of alkalinity due to chlorides - Chloride ions tend to remove metal energy by destroying concrete. Cracking of Concrete - Cracking can expose metal bars in the atmosphere and increase liquidity. Moisture Methods - Regular wetting of concrete can lead to water reaching the metal bars by dispersing through the pore structure of the concrete or existing cracks in the concrete. Rust of steel bars follows after that. Insufficient cover: Insufficient size of concrete cover. Metal Rust due to Improper Cover Damaged steel reinforcement may occur due to insufficient concrete cover Effects of Stainless Steel RustWhen steel bars begin to break, reinforced concrete joints begin to break down through the following stages:White spot formation - Atmospheric carbon dioxide reacts with calcium hydroxide present in the reduction of cement forming calcium carbonate. This calcium carbonate is treated with moisture and deposited on the surface of the white-formed concrete. Dirty stains by reinforcement - When the metal bars begin to deteriorate, a layer of iron oxide forms in it. This metal oxide is also transferred to the surface of the concrete with moisture. Formations of cracks - Rust products take on a larger volume than the original. So they put pressure on the concrete and it cracks. In the event of a lot of rust, many wide cracks are formed. Disintegration of concrete cover - Due to the loss of bond between concrete and steel, concrete begins to form many layers of scales and then peels off. Metal bars are also reduced in size. Cracking of bars - Due to the decrease in the size of the steel bars, they eventually break. Also, there is a significant reduction in the size of the main bars. Piercing of bars - The collapse of the concrete cover and the cracking of the bars resulted in the collapse of the main bars. This floods the concrete area and eventually the entire building collapses. How to Avoid Rusting Metal RustThe rust of steel reinforcement bars can be prevented or at least delayed by good measures. Also, damaged steel bars can be repaired and the concrete structure can be properly restored. Some steps are given below: Providing Sufficient Concrete Cover: A good amount of concrete cover should be provided in addition to the reinforcing steel bars. This ensures proper care of the alkaline type inside the concrete and the passage of the steel bars. Metal bars should be placed precisely in place Use of Quality Concrete: High quality concrete should be used. It helps to maintain an alkaline environment. In concrete, a water level of 0.4 or less should be maintained. Too much water can damage metal bars Compact Compaction fo Concrete: Concrete must be thoroughly mixed so that no air gaps or pockets are present. Use of FBE Bonds: Fusion Bonded Epoxy Coating (FBEC) can be used on metal bales to prevent corrosion. Epoxy powder is still electrically distributed in metal barns. The powder melts and flows over the bars as it heats up, forming a protective coating. It is a thermoset polymer coating because the use of heat will not melt the wear. Apart from the rebar it also has extensive function in pipeline construction Use of Cement-Based Polymers: Cement-based polymers can be used in concrete to increase their protection against corrosion. Cement-based polymers act as a bond in concrete. They also increase the strength, durability and melting of concrete CARBONATION OF CONCRETECarbonation of concrete is associated with corrosion of steel reinforcement and shrinkage. However, it also increases both the compression strength and the strength of the concrete, so not all of its effects on concrete are bad. Carbonation is the result of the decomposition of CO2 in pore fluid in concrete and this reacts with calcium from calcium hydroxide and calcium silicate hydrate to form calcite (CaCO3). Aragonite can form in hot climates. Within a few hours, or a day or two in total, the new concrete will be processed by CO2 in the air. Gradually, the process penetrates deeper into the concrete at a rate equal to the square root of time. After a year or more it is likely to reach a depth of about 1 mm with dense low-penetration concrete made of low water / cement, or up to 5 mm or more of high-density and permitted concrete using high water / cement scale. Carbonation determinationThe affected depth from the concrete surface can be easily indicated by the use of a phenolphthalein indicator solution. This is available from chemical suppliers. Phenolphthalein is a white or pale yellow with a crystal. Use as a solvent dissolves in a suitable solution such as isopropyl alcohol (isopropanol) by 1%. The indicator has not changed color near the upper and lower extremities, suggesting that these regions near the surface be carbonated at a depth of at least 4 mm from the top to the top and 6 mm from the bottom. When the index turns purple - in the middle of the slide - the pH of the pore fluid anchor remains high (above 8.6, about 10). Whether you are pasting the cement here is not completely illuminated, despite the strong purple color; a complete test will require very little testing. The index was not applied to the concrete to the right of this image so the concrete here retains its original color. The depth of carbonation is about the same as the square root of time. For example, if the depth of carbon is 1mm in one-year-old concrete, it will be about 3mm after 9, 5mm after 25 years and 10mm after 100 years. Q5) Explain symptoms and diagnosis of distressA5)The rapid industrialization of India after independence required the transportation of goods and services and led to the construction of a network of wide roads with built-in bridges and flyovers. Many of the existing bridges show signs of stress within their work life built in many cases in the 10-20 years of construction in India and many other countries. The collapse of the I-35W bridge over the Mississippi River in the United States of America in August 2007 has attracted the attention of international media. In India, the collapse of the Mandovi Bridge in Goa in 1986 (after 16 years of service) and the great tribulation at the Zuari bridge (rebuilt in 2000 by an international consultant) in Goa and many other bridges such as Khalghat and Borad Bridge on NH3 (Route) Agra to Mumbai) due to environmental constraints is attracting the attention of transport authorities and the scientific community to transform the operational bridge management system. The cause of the distress, the level of grief and the reduction in the capacity of the bridge can be ensured in order to further the necessary adjustments to ensure the safety of the bridge during their operation. An assessment of the pressure and load capacity of existing bridges and to improve the load capacity is required while upgrading highways. India has already implemented the consolidation and use of four 7000 Km of highways under the Golden Quadrilateral program where the strengthening / replacement of many existing bridges was required. Various causes of damage to reinforced concrete bridges are low construction standards, rust of steel on reinforced concrete bridges and pre-reinforced concrete bridges, improper shape and details of normal loads and seismic forces, improper operation of bearings etc. a number of case studies have been reported in the literature on reinforced concrete damage and compacted concrete bridges during earthquakes and the reinforcement of reinforced and compressed concrete bridges due to nature and other loads. A concerted effort has been made to review critical documentation of reinforced concrete damage and pre-pressure concrete bridges and repair / rehabilitation strategies based on information from bridge reconstruction projects in which the authors were involved. Causes of distressRelationship problems such as conflicts, illness / death of a loved one, divorce, abuse, partner, etc. Financial difficulties Environmental remediation Educational difficulties Time management and organizational complexity Anxiety Depression An abusive event Drug abuse Diagnosis of distressSometimes the cause of grief is known e.g. suffering during an earthquake, impact and explosion is known perhaps the active load exceeds the intended load but it is often difficult to find the real cause of grief where many variables are affected e.g. poor construction quality (faulty details, faults and performance), shrinkage, penetration, rust consolidation etc. Following a test may be necessary to determine the cause and degree of grief.Determination of compression strength from NDT and cores of concrete Strategies for detecting explosions Signature / Vibration Analysis Download tests to find deviations / issues and distribute the load Rust studies (pH, depth of carbon, chloride) Deviation / disposal slopes from Instrumented Bridge Q6) Explain evaluation of crack A6)When inspecting a slab or conducting a crack crack, always measure the width of the crack and determine whether the metal reinforcement passes through it and whether the crack is active or asleep. This information, especially the details of the reinforcement and cracking function, is very important when choosing the best repair option.Crack widthThe extent of the crack is usually measured using a crack comparison card. Measuring the width of the crack helps to separate the stiffness of the cracks and to evaluate the performance of the joint joints across the fracture of the direct direction of the fracture and the transmission of the load. Also, many repair options depend on the width of the crack. Unless the steel reinforcement passes through a crack, the alignment of the vertical tube and the transmission of the broken load depends on the joint bonding. If the diameter of the fracture is less than 0.035 inches, the composite particles that come from the other side of the fracture to the other side will normally provide adequate load transfer and maintain vertical alignment throughout the split. For larger screens, maintaining a straight slide alignment can be a challenge. The success of the remediation approach will depend on the slide loading and the quality of the base material and the ground cover. Steel ReinforcementAlthough steel reinforcement does not prevent cracking, it limits the width of the crack so that the joint joints are maintained. Strengthening itself also provides load transfer and helps maintain vertical alignment in the cracks. When the reinforcement passes through a split, both the width split and the future width increase are controlled. The new cracks of the non-reinforced concrete will continue to grow and the diameter can double before the increase in crack-width. With the cracks caused by the drying shrink, the cracks will stabilize at the end. Splits due to other causes, however, such as soil erosion or height, may not be stable and may continue to increase unless a significant amount of reinforcement passes through space. Determining the amount of reinforcement that goes beyond cracking is important in predicting the performance of future cracks and choosing the best repair option. Dormant and active crackCracks that fall through steel reinforcement are generally stable and are often considered sleepy. Of course, the stability of the cracks depends on the source and the degree of reinforcement of the cracks. The lying cracks have a fixed width and can be repaired with solid or flexible materials. Functional cracks should only be repaired using a flexible object that can accommodate future cracked movements. Generally, the active cracks in the slabs actually belong to the active members and should be treated in the same way as the joints. After all, random or non-joining cracks in flatwork are self-assembling joints. Q7) Explain selection of repair procedure A7)StructureStructural repairs include using epoxy frames to bind or bond concrete together. Epoxy repair not only repairs the sealing cracks but also restores the strength and durability of the concrete. Use epoxy to repair dormant cracks only. Fixing functional cracks with epoxy often leads to a new formation near the original, epoxied fragment. Epoxy injection is a common way to inject epoxy into cracks, especially in direct and indirect areas. But gravity filling works well and is a common way to apply epoxy to flatwork cracks or to direct surfaces. The filling of gravity consists of pouring low-viscosity epoxy into the cracks that have been signed or distributed and allowed the gravitational force to pull the epoxy down the cracks. Viscosity resistance to fluid flow is measured in centipoises (cps). Decreased viscosity value, less (runnier) significant. Grade I and II epoxies have viscosities of less than 20 cps and between 20 and 100 cps, respectively. For comparison, the viscosities of other common beverages are: water - 1 cps, milk - 3 cps, anti-freeze - 15 cps, maple syrup - 150 to 200 cps, and honey -3000 cps. Low viscosities are required for solid cracks. Otherwise, the repair material will be too large to penetrate and flow into the crack. Epoxies were cured or hardened due to the chemical reaction between the frame and the hardener. Chemical reactions are rapid at high temperatures. Epoxies are obtained by different injections or by temperature treatments so chemical reactions are less rapid or slow (Type A, less than 40º F; Type B, 40º F to 60º F; and type C, more than 60º F). With the adjustment of gravity filling culture, consider the depth and depth, epoxy viscosity, and temperature input when choosing the distance and type of epoxy. Otherwise, the epoxy can be very strong or very hard to penetrate or it can just run between the river and the pool under the slide. Sealing and fillingSealing and filling of non-construction repairs. However, some repair materials include cracked surfaces and can have a strong impact that can cause cracking of the material and concrete in the event of a major crack movement. Typical sealants and internal fixing fillers include semi-rigid epoxies, hybrid polyurethanes and polyureas, and polymer mortar. Polyurethanes and silicones are common labels used for exterior repairs. Usually, sealants are flexible or elastomeric materials; and the fillers are very hard so the fixing materials support the edges of the cracks to avoid collapse or damage under load. When heavy traffic is exposed to heavy wheels, composite fillers or special cracks with about 80 Shore A Hardness should be used. Unfortunately, there is a tradeoff to increase the complexity of explosive repair materials. As the repair material gets harder, it becomes much thinner and does not tolerate cracked movement. For example, semi-rigid epoxies usually have a hardness of about 90 and an extension value of 50%; whereas, silicone sealants have a hardness of about 5 and an extension value of 1400%. Therefore, when choosing a fix, consider the expected movement of the comparison and the need to support the edges of the cracks. For effective cracking with the expected cracking motion, use elastomeric sealants or sealants with sufficient elastic properties, to see that the tradeoff will be a little support for the fracture edges. For cracks exposed to heavy-duty traffic, use hard materials that support the edges of the cracks. But understand that these things do not tolerate the movement of cracks. If you are using elastomeric sealants in active cracks, always seal the sealant with a saw or by moving the track as recommended by the repairman. Without a dam, there would not be enough to tolerate future fracture movements. Expansion structures reported by manufacturers are based on the size of the recommended lakes or, in particular, the width and depth of the dam. Of course, cutting or scraping increases the width of the crack and makes crack repairs more noticeable. For cosmetic repairs in colored or decorative flats where cracks lie or are well established, do not see or move the sealant or filler dam. Instead, choose a low viscosity cracker (less than 100 cps) and small injection tips for cracks to fill gravity. Dams are not required. But in the event of a fracture movement, the cracking of the repair material or concrete may occur due to the small diameter of the depth of the material. Also, manufacturers now offer many of these low viscosity fixes in a variety of colors or offer color production recommendations and textures similar to concrete concrete surfaces. Before fixing your next explosion, do a crack test and establish repair targets. Decide what kind of adjustment is needed. Options include structural repairs using epoxy, route fixes and seal applications using flexible sealant to hold future cracks, and solid or durable repairs that fill the edges of cracks, with or without. Also, set cosmetic requirements. After selecting the fix and procedure, follow the manufacturer's recommendations. Q8) Explain shortcrete and grouting A8)SHORTCRETEShotcrete or sprayed concrete is concrete or mortar conveyed thru a hose and pneumatically projected at excessive pace onto a floor, as a production method, first utilized in 1914. It is usually strengthened with the aid of using traditional metallic rods, metallic mesh, or fibers. Properly carried out shotcrete is a structurally sound and sturdy production cloth which well-known shows terrific bonding traits to present concrete, rock, metallic, and plenty of different materials. It may have excessive strength, low absorption, correct resistance to weathering, and resistance to a few varieties of chemical attack. Many of the bodily residences of sound shotcrete are similar or advanced to the ones of traditional concrete or mortar having the equal composition. Improperly carried out shotcrete can also additionally create situations a lot worse than the untreated condition. Advantages of shotcrete:Shotcrete is utilized in lieu of traditional concrete, in maximum instances, for motives of fee or convenience. Shotcrete is fine in conditions whilst formwork is fee prohibitive or impractical and wherein paperwork may be decreased or eliminated, get entry to to the paintings place is difficult, skinny layers or variable thicknesses are required, or ordinary casting strategies cannot be employed. Additional financial savings are feasible due to the fact shotcrete calls for handiest a small, transportable plant for manufacture and placement. Shotcreting operations can regularly be executed in regions of restrained get entry to to make upkeep to structures. GROUTINGGrout is usually a mixture of cement, sand, and water or chemicals used to fill gaps. They are used to repair concrete cracks, to fill gaps and gaps in tiles, to fill gaps and waterproofing, and to strengthen the soil. It is also used to provide additional power to load-bearing structures. It basically involves the process of injecting something that can be pumped into a building to change its body structures. There are different types of grinding, cement grinding, chemical grinding, and bituminous grating, depending on the material used. Frames are also sometimes used as grout materials. A mortar is often used to fill cracks and gaps in soil or rock. What is GroutingAlso, it is used to stabilize the soil and keep it out. Cracking is used for a variety of purposes such as water repair, standing on immersed structures such as ditches, tunnels, etc., filling in the gaps between tiles and stabilizing the soil. Here we have provided details on the type of grouts used to repair cracks. Advantage of Grouting Includes:This can be done in almost any soil condition It does not vibrate and can be controlled to avoid structural damage Development of underground structures can be measured It is very useful for limited space and low head items It is used to install slab jacking that lifts or measures the crippled foundation It can be installed near existing walls It can be used to control the flow of water, groundwater flow, and hazardous waste materials. Many Different Types of Grouting Materials:Stopping cement Chemical Grouting Bentonite grouting The amber is growing Bituminous Grouting Q9) Explain introduction of retrofitting of concrete structure by FPP and polymer impregnated concrete A9)FIBER REINFORCED POLYMERFiber-reinforced polymer (FRP), also fiber-reinforced plastic, is a composite made of polymer matrix reinforced with fibers. Threads are usually glass, carbon, or aramid, although other fibers such as paper or wood or asbestos have sometimes been used. The polymer is usually epoxy, vinylester or polyester thermosetting plastic, and phenol formaldehyde frames are still active. FRPs are widely used in the aerospace, automotive, marine and construction industries. Composite materials are made of building materials or naturally made from two or more materials that have a structure with very different physical or chemical properties that are always different and distinct from the finished structure. Most compounds have strong, strong fibers in a weak and strong matrix. The goal is usually to make the part stronger and stronger, usually with a lower volume. Commercial materials usually contain glass or carbon fibers in a matrix based on thermosetting polymers, such as epoxy or polyester resins. In some cases, thermoplastic polymers may be preferred, as they form after the first production. There are additional stages of integration where the matrix is metal or ceramic. For the most part, these are still in the development phase, and the problems of high production costs have yet to be overcome [1]. Moreover, in these compounds the reasons for adding fibers (or, in some cases, particles) are often complex; for example, improvements may be required in penetration, wear, cracking, heat stabilization, etc. Fiber-reinforced polymer (FRP) is a compound used in almost every type of high-tech engineering facility, with its use from aircraft, helicopters and spacecraft to boats, ships and marine systems as well as automobiles, sports equipment, repair equipment chemicals and public infrastructure such as bridges and buildings. The use of FRP compounds continues to grow at an impressive rate as these materials are widely used in their existing markets and are being developed in brand new markets such as biomedical devices and social structures. An important factor contributing to the increased use of compounds over the years has been the development of new types of FRP materials. This includes the development of high-resin applications and new reinforcement styles, such as carbon nanotubes and nanoparticles. The book provides a timely account of fiction, mechanical properties, delamination resistance, impact tolerance and the use of 3D FRP compounds. Polymers reinforced polymer composites (FRPs) are increasingly being considered for the development and / or replacement of structural components or systems consisting of traditional engineering materials, namely concrete and steel. FRP compounds are simple, non-destructive, show a certain high strength and direct durability, are easily constructed, and can be customized to meet operational requirements. Because of these beneficial features, FRP compounds have been incorporated into the construction and renovation of buildings using their reinforcement in concrete, blocks, modular structures, formwork, and external reinforcement for seismic reinforcement and development. The effectiveness of Fiber Reinforced Polymer (FRP) reinforcement in concrete structures such as replacement of steel bars or pre-pressurized muscles has been extensively studied in many research laboratories and professional organizations around the world. FRP reinforcement offers many benefits such as corrosion resistance, non-magnetic properties, very strong, lightweight and easy to handle. However, they usually have a direct response to stiffness to the point of failure (defined as damaging failure) and poor resistance to friction or shear. They are also less resistant to fire and when exposed to high temperatures. They release vital energy as they bend, and they are sensitive to the effects of pressure fractures. In addition, their cost, whether considered for each weight or on the basis of strength-bearing capacity, is relatively high compared with conventional steel reinforcement bars or pressure straps. From a structural engineering perspective, the most serious problems with FRP reinforcement are the lack of plastic conduct and very low shear strength on the short side. Such features can lead to premature tender fragmentation, especially if mixed results are obtained, such as in shear-breaking planes on reinforced concrete pillars where there is a delow action. The downtime action reduces the remaining resistance to stiffness and shear tenderness. Solutions and limitations for use are provided and further improvements are expected in the future. The cost of FRP consolidation unit is expected to decrease significantly with increasing market share and demand. However, even today, there are applications where FRP consolidation is less expensive and justified. Such cases include the use of FRP sheets or bonded plates in repairing and strengthening concrete structures, as well as the use of FRP meshes or fabrics or fabrics in small cement products. The cost of renovating and renovating a building remains, in certain terms, much higher than the cost of the original building. Repairs usually require a small amount of repair materials but a high commitment from staff. In addition, labor costs in developed countries are so high that the cost of materials is secondary. So the performance and performance that lasts the longest, the repair is very expensive. This means that the cost of materials is not a problem to be rectified and the fact that FRP materials are expensive is not a particular problem [5]. Given only the physical strength and resources, at the top, the controversy over FRP compounds in a sustainable built environment is questionable. However, such a conclusion needs to be evaluated in terms of the potential benefits of using FRP compounds related to assumptions such as: High powerLight weightHigh performanceIt lasts a long timeRenovating existing buildings and extending their lifeSeismic developmentSecurity systemsSpace programsOcean areasIn the case of FRP compounds, environmental concerns appear to be a barrier to its functioning as a viable alternative especially in terms of fuel depletion, air pollution, fog, and acidification associated with its production. In addition, the ability to reuse FRP compounds is limited and, unlike steel and wood, structural components cannot be reused to perform the same function in another structure. However, examining the environmental impact of FRP compounds on infrastructure use, especially through life cycle analysis, may reveal more direct and indirect benefits that compete more than conventional ones. The composite material has greatly improved since its inception. However, before composite materials can be used as an alternative to conventional materials as part of a sustainable environment a few needs remain. Availability of durability data for FRP building materials. Integration of robust data and service life prediction methods for building members using FRP combinations. Development of selection methods according to the life cycle cycle of materials and systems. Finally, in order for the mixtures to be considered a viable option, they must be structurally and economically viable. Many studies on the structure of the composite material are widely available in the literature. However, limited studies are available on the economic and environmental availability of these items from the perspective of the life cycle, because short-term data are available or only economic costs are considered in comparison. In addition, the long-term impact of using composite materials needs to be determined. The products produced, the sustainability of the materials, and the capacity to recycle the materials need to be tested to determine if the composite materials can be part of a sustainable environment. So in this chapter describe the physicochemical properties of polymers and compounds most commonly used in Civil Engineering. The theme will be presented in a simple and basic way for better understanding. POLYMER IMPREGNATED CONCRETEIn the case of pregnant polymer concrete, prepolymers or lower liquid monomers are partially or partially impregnated with a pore system of a composite cement framework. After this process, the entire treated structure is allowed to polish. The general process of treatment of reinforced concrete leads to the acquisition of a large amount of free water in its spaces. These water-filled voids form a significant amount of total volume. From 5% in the case of dense concrete and 15% in the case of gaped concrete. In the case of pregnant polymer concrete, it is these voids (holes filled with water) that should be filled with the selected polymer. So the main thing that affects the loading of the monomer is this: the moisture content in the solid concrete and the air loses energy in the concrete. Procedure for polymer impregnated concrete manufacturingThe activities involved in the pregnancy process to improve pregnant polymer concrete are:1. Well-constructed concrete is available. They need to get better and get stronger.2. Moisture is removed by drying the concrete. Drying is done by heating the structure element at temperatures above the order of 120 to 150 degrees Celsius. An air oven can be used to dry small specimens.If the element has a large surface, a thick cloth, say, 10mm thick, can be used to protect it from any hot gradient. Another complex application is the use of infrared heaters.Complete removal of moisture from concrete, requires 6 to 8 hours of heat.3. After complete removal, the concrete area has cooled to a safer level. This can go up to a temperature of 35 degrees Celsius. This heat will avoid overheating.4. The concrete is now transferred to a vacuum cleaner, where all the air inside the concrete structure is removed. The amount of monomer installed will determine the time and level of use of the machine.5. Concrete after sufficient ventilation is placed in a monomer solution. Wet for a long time until the desired depth of monomer penetration is obtained.Filling time depends on the viscosity of the monomer, the adjustment of the template and the advanced characteristics of the concrete.To reduce the time taken to get the desired input, it is preferable to use external pressure such as air or nitrogen gas. This helps to get in faster.6. After the above procedure, the surface is covered with plastic paper. This helps prevent the evaporation of the monomer.7. A high-temperature polymerization method is performed. This method involves polymerization by heating the deformed monomer to the required temperature. This will start from 60 degrees to 150 degrees Celsius. The selected temperature range depends on the type of monomer.Heating can be done under water or with a low pressure steam injection, or with infrared heaters or an air oven. The heat decomposes the catalyst and thus initiates the polymerization reaction.Once the monomer has penetrated the concrete, polymerization can also be initiated using ionization radiation similar to gamma rays. Polymers when they are completely polymer or when connected on the other side, act as solids that reside in the voids they are embedded in.8. The concrete structure is then allowed to cool.Every process from 1 to 8 can only be done in a precast factory. Monomers such as acrylate, styrene and vinyl chloride etc. are widely used for concrete installations. Another widely used material is Methyl Methacrylate (MMA).Properties of polymer impregnated concrete1. The polymer concrete gains the strength of the cube to strengthen more than 100N / mm2. This strength does not depend on the strength of the standard concrete.2. The flexibility of a pregnant polymer concrete is approximately 15N / mm2. This is slightly higher than high-grade clear concrete made from common ingredients.3. The elastic modulus lies in the range from 30 to 60N / mm2. This value is the same as the value obtained from high-strength concrete (e.g. approximately 45N / mm2)4. Pregnant polymer concrete has less movement problems and shrinkage due to the small number of pores.5. Pregnant polymer concrete is more resistant to acid attacks, sulfate attacks and chloride attacks compared to PCC.Application of polymer impregnated concreteThe use of pregnant polymer concrete in various construction sites is described below:1. Surface Impregnation of Bridge Decks: Bridge decks are allowed to be installed to avoid the ingress of moisture, chemicals and chloride ions.Bridge floors built in areas with high salt water and moisture exposure can be protected in this way.2. Structural repairs: Damaged structures can be developed in the form of a polymer abstract. The life span of undeveloped buildings can be extended in this way.This method is why it helps in the restoration and preservation of stone monuments.3. Underwater and Marine Applications: Polymer impregnation capabilities help to improve structures, water absorption, and non-concrete structures. This makes them widely used in water and sea construction.Buildings built on desalination plants and underwater structures use this method of building concrete. It has been shown that the small absorption of concrete masses from seawater reduces the corrosion of the steel by 24 times.4. Use in Irrigation Systems: The use of standard methods for the repair and rehabilitation of dams and other important water structures appears to be inefficient and incomplete.This is later found to cause significant losses in profits from irrigation, energy production, flood control etc. But the method of pregnancy works very well.Concrete from the damaged area is removed, glued and dried. This area is later treated using polymer emissions.5. Composite Joints: Pregnant polymer concrete is as strong as building materials. PIC also shows the amazing development of standard concrete.Internal and empty cracks are the basic foundation for all the issues in common concrete structures. Since the suspension of the polymer determines the cause, it is best used for construction members. Q10) Explain corrosion monitoring and preventive measure A10)The rust measuring, control, and prevention field covers a wide range of technical tasks. Within the field of corrosion control and prevention, there are technical options such as cathodic and anodic protection, material selection, chemical insertion and use of indoor and outdoor clothing. The rust scale uses a variety of techniques to determine how much damage the environment consumes and how much iron loss is experienced. Rust rating is a measure of how rust management performance and prevention strategies can be implemented and provides feedback to enable rust control and preventative measures to be improved. Some rust measurement techniques can be used online, regularly displayed in process broadcasts, while others provide external measurement, such as those determined in laboratory analysis. Some techniques provide a precise measure of metal loss or rust ratio, while others are used to indicate the possibility of corrosion. Rust monitoring is the practice of measuring the deterioration of process dissemination conditions by using probes that are incorporated into process dissemination and that are continuously expressed in the process dissemination process. Rust monitoring probes can be mechanical, electrical or electrical devices. Rust monitoring alone provides accurate and online measurement of metal loss / corrosion rate in industrial process systems. Typically, the rust measuring system, testing and adjustment used in any industrial area will include measuring instruments provided by four combinations of on-line / offline, direct / indirect measurements. Corrosion Monitoring Direct, On-line Direct, Offline Non-Destructive Testing Indirect Analytical Chemistry, Off-line Indirect, online Operational Data In a well-managed and integrated system, data from each source will be used to draw reasonable conclusions about the levels of active corrosion by the process process and how they are effectively reduced. The Need of corrosion monitoringThe level of rust determines which process plant can be used efficiently and safely for how long. The rust scale and the action of adjusting the high levels of rust allow for the efficient operation of plants that must be achieved while minimizing the life cycle costs associated with the work.Rust monitoring techniques can help in a number of ways:by giving an early warning that harmful procedural conditions exist that could lead to failures caused by rust. by studying the integration of changes in process parameters and their effect on system corrosivity. by identifying a specific rust problem, identifying its cause and the parameters that control the level, such as pressure, temperature, pH, flow rate, etc. by evaluating the effectiveness of the corrosion / prevention control method such as chemical prevention and good use. by providing management information relating to conservation needs and the ongoing condition of the plant. Corrosion monitoring techniquesA large number of rust monitoring strategies are available. The following list describes the most common strategies used in industrial applications:Rust Coupons (Weight Loss Rate) Electrical Resistance (ER) Linear Separation Resistance (LPR) Galvanic (ZRA) / Possible Hydrogen Ingestion Bacteria Sand / Soil erosion Other strategies are available, but almost all require professional work, otherwise they are not enough or flexible to apply.In the above-mentioned strategies, corrosion coupons, ER, and LPR form the core of industrial corrosion monitoring systems. The other four strategies are usually found in special programs that are discussed over time.These rust monitoring methods have been used successfully and are being used by a growing number of applications because:The techniques are easy to understand and apply. The reliability of the equipment has been demonstrated in the field field for many years of application operation. The results are easy to explain. Measurement equipment can be made internally safe from hazardous environmental performance. Consumers have gained significant economic benefits by reducing planting time and extending plant life. PREVENTIVE MEASURESMetal corrosion is a natural process that requires three conditions: moisture, metal surface, and an oxidizing agent called an electron acceptor. Rust converts the active metal into a separate form of oxide, hydroxide, or sulphide. The most common type of rust is rust. Metallic metal not only affects the structure of the metal, but it can also affect the people who use the material or objects close to the metal. In extreme cases, rotten metal can lead to the construction of buildings and bridges, leaking pipes, and medical implants that infect human blood. While all metals are in danger of corrosion, some metals, such as pure metal, deteriorate much faster than others. However, iron can be combined with other alloys to form a stainless steel that is more resistant to corrosion. It is estimated that approximately 25-30% of rust can be prevented using appropriate protective measures. In general, you can prevent rust by choosing the right type of metal, Protective Fabrics, Environmental Measures, Self-Sacrifice Items, Rust Stumbling Stuff, Metal Installation and Repairs for Your Project. Choose the right metal typeOne of the easiest ways to prevent rust is to use rust-resistant metal such as stainless steel, duplex, super duplex, nickel alloy or 6% Moly. These devices are so well made that they have a high resistance to corrosion and use them to reduce the need for alternative corrosion protection. For Special Drawing Materials, we offer products made of the highest quality synthetic materials available - stainless steel, duplex, super duplex, 6% Moly and Nickel Alloy. A variety of materials are selected by our clients in a variety of areas, with one of the factors considered for possible corrosion. Protective coatingAnother way to prevent rust is to cover it with a special protective paint. Paint coating can act as a barrier that works by preventing electrochemical charging that transmits to the destructive and metal solution below. One way to do this is to put a powder coating in a clean metal place. The metal is heated to turn the flour into a smooth, non-abrasive film that acts as a barrier to rust. Many different powder compositions can be used, such as acrylic, polyester, epoxy, nylon, and urethane. Environmental MeasuresRust is certainly due to the nature of the metal in it as the chemical reactions that occur are due to metal reacting with liquids and gases in the surrounding environment. Controlling the environment can therefore help reduce this response. This could be as simple as reducing exposure to rain or seawater or it could be steps taken to reduce the amount of sulfur, chlorine, or oxygen in the area. For example, carrying water in water boilers to adjust hardness, alkalinity, or oxygen content, before placing the metal in that water can be very helpful in preventing corrosion. Sacrificial coatingSacrifice cover to prevent corrosion means covering the metal with a type of metal that may have oxidise - you sacrifice this top layer to protect the lower metal.There are two main ways to accomplish the sacrificial attire:Cathodic Protection: Cathodic protection works by making the metal cathode of an electrochemical cell. The most common example of cathodic protection is the coating of iron ore and zinc - this process is known as galvanizing. Zinc is more than an active metal so rust prevents metal rot. Cathodic protection is frequently used for steel or petrol pipelines, heat tanks, ports, and overseas oil platforms. Anodic Protection: Anodic protection is opposed to cathodic protection and works by making the metal anode of an electrochemical cell. A common way to do this is to cover a thin layer of stainless steel, such as tin. The tin will not corrode, so the metal will be protected as long as the tin coating is in place. Anodic protection is often used for carbon storage tanks used to store sulfuric acid and 50% caustic soda. Corrosion InhibitorsChemical corrosion inhibitors are selected to react to metal surfaces or surrounding gases and therefore suppress electrochemical reactions that can lead to decay. When applied to a metal surface, they form a protective film. Inhibitors can be used as a solution or as a protective cover using distribution methods. Corrosion inhibitors are often used in a process known as passivation. An example of passivation is the Statement of Freedom where a blue and green metal signature is actually present to protect the copper underneath. Metal PlatingThe installation is very similar to the cover as a thin layer of metal is inserted into the metal you want to protect. As well as preventing corrosion, the metal layer provides a good finish of beauty. There are four types of metal wraps:Electroplating: The application of a thin layer of metal such as chromium or nickel to the underground metal by means of an electrolyte bath. Mechanical Plating: this involves cold welding powder metal metal substrate. Electro less: Coating such as nickel or cobalt is placed on a metal substrate using non-electrical chemical reactions. Hot dipping: A simple covering method that involves placing the substrate in a molten metal protective tub. Design ModificationChanging the structure of the project can have a significant impact on rust protection as it works by eliminating the causes of rust.
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