Unit – 1

Introduction to Civil Engineering

1. What are the Role of Civil Engineers in various construction activities?

Civil engineer has very important role in the development of the following infrastructure:

• Measure and map the earth’s surface.
• Plan new townships and extension of existing towns
• Build the suitable structures for the rural and urban areas for various utilities
• Build tanks and dams to exploit water resources.
• Build river navigation and flood control projects.
• Provide and maintain communication systems like roads, railways, harbours and airports
• Purify and supply water to the needy areas like houses, schools, offices etc.
• Build canals and distributaries to take water to agricultural fields
• Devise systems for control and efficient flow of traffic
• Provide and maintain solid and waste water disposal system
• Monitor land, water and air pollution and take measures to control them

Fast growing industrialization has put heavy responsibilities on civil engineers to preserve and protect environment.

2.    What are the Basic engineering properties and uses of materials BRICKS?

Constituents of good brick earth: Bricks are the most commonly used construction material. Bricks are prepared by moulding clay in rectangular blocks of uniform size and then drying and burning these blocks. In order to get a good quality brick, the brick earth should contain the following constituents.

• Silica
• Alumina
• Lime
• Iron oxide
• Magnesia

Brick plays very important role in the field of civil engineering construction. Bricks are used as an alternative of stones in construction purpose.

• USES OF CEMENT

1. Construction of walls of any size
2. Construction of floors
3. Construction of arches and cornices
4. Construction of brick retaining wall
5. Making Khoa (Broken bricks of required size) to use as an aggregate in concrete
6. Manufacture of surki (powdered bricks) to be used in lime plaster and lime concrete

Classification of Bricks as per constituent materials

There are various types of bricks used in masonry

• Common Burnt Clay Bricks
• Sand Lime Bricks (Calcium Silicate Bricks)
• Engineering Bricks
• Concrete Bricks
• Fly ash Clay Bricks 

Common Burnt Clay Bricks

Common burnt clay bricks are formed by pressing in moulds. Then these bricks are dried and fired in a kiln. Common burnt clay bricks are used in general work with no special attractive appearances. When these bricks are used in walls, they require plastering or rendering.

Sand Lime Bricks

Sand lime bricks are made by mixing sand, fly ash and lime followed by a chemical process during wet mixing. The mix is then moulded under pressure forming the brick. These bricks can offer advantages over clay bricks such as: their colour appearance is grey instead of the regular reddish colour. Their shape is uniform and presents a smoother finish that doesn’t require plastering. These bricks offer excellent strength as a load-bearing member.

Engineering Bricks

Engineering bricks are bricks manufactured at extremely high temperatures, forming a dense and strong brick, allowing the brick to limit strength and water absorption. Engineering bricks offer excellent load bearing capacity damp-proof characteristics and chemical resisting properties. Concrete Bricks Concrete bricks are made from solid concrete. Concrete bricks are usually placed in facades, fences, and provide an excellent aesthetic presence. These bricks can be manufactured to provide different colours as pigmented during its production.

Fly Ash Clay Bricks

Fly ash clay bricks are manufactured with clay and fly ash, at about 1,000 degrees C. Some studies have shown that these bricks tend to fail poor produce pop-outs, when bricks come into contact with moisture and water, causing the bricks to expand.

• ENGINEERING PROPERTIES OF CEMENT

To know the quality of bricks following 7 tests can be performed. In these tests some are performed in laboratory and the rest are on field.

• Compressive strength test
• Water Absorption test
• Efflorescence test
• Hardness test
• Size, Shape and Colour test
• Soundness test

Structure test Compressive strength test

This test is done to know the compressive strength of brick. It is also called crushing strength of brick. Generally 5 specimens of bricks are taken to laboratory for testing and tested one by one. In this test a brick specimen is put on crushing machine and applied pressure till it breaks. The ultimate pressure at which brick is crushed is taken into account. All five brick specimens are tested one by one and average result is taken as brick’s compressive/crushing strength.

Water Absorption test In this test bricks are weighed in dry condition and let them immersed in fresh water for 24 hours. After 24 hours of immersion those are taken out from water and wipe out with cloth. Then brick is weighed in wet condition. The difference between weights is the water absorbed by brick. The percentage of water absorption is then calculated. The less water absorbed by brick the greater its quality. Good quality brick doesn’t absorb more than 20% water of its own weight.

Efflorescence test The presence of alkalies in bricks is harmful and they form a grey or white layer on brick surface by absorbing moisture. To find out the presence of alkalis in bricks this test is performed. In this test a brick is immersed in fresh water for 24 hours and then it’s taken out from water and allowed to dry in shade. If the whitish layer is not visible on surface it proofs that absence of alkalis in brick. If the whitish layer visible about 10% of brick surface then the presence of alkalis is inacceptable range. If that is about 50% of surface then it is moderate. If the alkalies’ presence is over 50% then the brick is severely affected by alkalies.

Hardness test

In this test a scratch is made on brick surface with a hard thing. If that doesn’t left any impression on brick then that is good quality brick.

Size, shape and colour test

In this test randomly collected 20 bricks are staked along lengthwise, width wise and height wise and then those are measured to know the variation of sizes as per standard. Bricks are closely viewed to check if its edges are sharp and straight and uniform in shape. A good quality brick should have bright and uniform colour throughout.

Soundness test

In this test two bricks are held by both hands and struck with one another. If the bricks give clear metallic ringing sound and don’t break then those are good quality bricks.

Structure test In this test a brick is broken or a broken brick is collected and closely observed. If there are any flows, cracks or holes present on that broken face then that isn’t good quality brick.

3.    Explain Basic engineering properties and uses of materials TIMBER?

TIMBER is the oldest material used by humans for construction after stone. Despite its complex chemical nature, wood has excellent properties which lend themselves to human use. It is readily and economically available; easily machinable ; amenable to fabrication into an infinite variety of sizes and shapes using simple on-site building techniques;

• Exceptionally strong relative to its weight
• A good heat and electrical insulator
• It is a renewable and biodegradable resource

A tree basically consists of three parts namely, trunk, crown and roots. The function of the trunk is to support the crown and to supply water and nutrients from the roots to the leaves through branches and from the leaves back to the roots .The roots are meant to implant the trees in the soil ,to absorb moisture and the mineral substances it contains and to supply them to the trunk.

The quality of timber must be ensured before using it for a purpose. The quality can be ensured by investigating the properties of timber. Here we have discussed both physical and mechanical properties of timber which affects timber quality.

Followings are the physical and mechanical properties of Timber

• Colour
• Appearance
• Hardness
• Specific Gravity
• Moisture Content
• Grain
• Shrinkage and Swelling
• Strength
• Density
• Toughness
• Elasticity
• Warping
• Durability
• Defectless
• Workability
• Soundness
• Free of abrasion

Colour

Color is a uniform property by which most trees are characterized as they show variation from tree to tree. Light color indicates weak timber. For example, freshly cut teak, Deodar, and Walnut have a golden yellow, whitish and dark brown shades respectively.

Appearance

Smell is a good property as timbers for few plants as they can be identified by their characteristic aroma. Fresh cut timbers have a good smell. For example resinous smell from pine.

Hardness

For the resistance of any kind of damage, hardness is an obvious property.

Specific Gravity

Variation of timber in specific gravity (0.3-0.9) is found. It depends on pores present inside timber. The specific gravity of this light material is less than that of water (<1). But in case of compact wood where pores are almost absent and become heavier, their specific gravity increases up to 1.5.

Moisture Content

Timbers are hygroscopic and gain water from nature (atmosphere). The absorption of water or dehydration depends on atmospheric humidity. If timbers moisture content is high that means the timber quality is low. Water content is the risk of fungal attack.

Grain

Several types of grain arrangement found. On the grain structure quality of timber varies. Grains remain closely related.

1. Straight grain: Arrangement of vascular tissue (xylem and phloem) is important which grow parallel to the length of the timber that is termed as straight grain.
2. Coarse grain: vascular tissue and fibre arranged broadly and widely.
3. Interlocked grain: Instead of parallel arrangement twisted, a spiral arrangement may be found.

Shrinkage and Swelling

The percentage of shrinkage and swelling varies from plant to plant. Some give higher percentage after drying. Shrinkage starts when cell walls of timber start to release water. In moisture atmosphere timber swells when cell walls absorb water. Good quality timbers swell less. Timbers having thicker wall swell more than a thinner one.

Strength

Best quality timbers have the highest strength. Strength means capable to bear loads. Anisotropic material like timber has different structure at the different portion. So, the strength of timber is different at different points. Grain structure determines the strength of the timber. Some types of strength are

1. Compressive strength: 500 kg/cm2 to 700 kg/cm2 load is enough to test timbers strength.
2. Tensile strength: When timber is enough strong to the tensile force. If perpendicular force is made then timber is weaker. 500-2000 kg/cm2 is the range of tensile strength load.
3. Transverse strength: Enough bending strength indicates good quality timber.

Density

Timber having higher density have a thicker wall. An important property that quality of timber. Moisture content: Presence of defects: There may be some of the natural and artificial defects in timber such as cross-grain, knots, and shakes, etc. All of them cause a decrease in the strength of the timber.

Toughness

Timber has to have the capability to bear shocks, jerk. Anti-bending and ant splitting characteristic is needed. Old timbers have annual rings which indicate their age is a good indicator.

Elasticity

Another property elasticity means timber should attain its own shape after use. Because of this quality, it is used in sports bat.

Warping

Environmental change with season can’t effect good quality timber.

Durability

A good quality timber has the property to resist the attack the infection of fungus or other insects. This resistance quality makes timber better.

Defectless

This property is gained if the timber is from a sound tree. A defectless tree is free from sap, shakes, and dead knots.

Workability

A good timber is always easy to work on it. Easy to drag using saw on good timber. The finishing can be done well.

Soundness

A good quality timber gives good sound.

Texture

The texture of good timber is fine and even.

Free of Abrasion

Timber should not be damaged by the external environment. It has to gain the ability to protect its skin.

Wood is a plant part having multipurpose uses those are impossible to deny and difficult to note all in our daily life. From the ancient time wood is used by human and this continuation still remains in the modern civilization. A few of many uses of wood are mentioned below:

1. Construction and Fencing

• Home Construction:

During the early periods, use of wood in domestic construction was a common scene and this is still followed in this twenty-first century. In different parts of the world in the making of houses, wood is used commonly like the flooring, frames of doors and windows for its strength and internment quality. e.g. Deodar, walnut wood is used in Pakistan widely, teak in South Asia and all over the world, Chir pine etc. In Bangladesh during construction of buildings woods from mango,bur flower tree are used for casting and piling.  

• Fencing and Decorating Gardens:

In modern decoration system woods are also used for building the fencing and simple decoration for artificial gardening inside a home or on roofs.
e.g. Cedar, redwood, Shorea sp, Acacia sp.

2. Household Uses

• Utensils:

Utensils made up of wood instead of plastic and steel are a symbol of elegance which increases the charm and loveliness of the home corners.
e.g. Black walnut wood is used in the west for home utensils.  

• Hand Tools:

The handles of most common hand tools made of wood help as heat resistant when they are kitchenware used in an oven and closes the chance to shock while used on electricity.

3. Art Industry

• Artworks:

For artworks such as statues, sculptures, carvings and making decorative objects woods are widely used. The frames of art board, color plate are also made from wood in many cases. e.g. Pine, maple, cherry wood for framing work.  

• Musical instrument:

The musical instruments such as Piano, violin, cello, drums, flute, guitar, double bass and a number of other music instruments material requires wood for making a perfect tune. e.g. Mahogany , maple, ash wood for guitars.

4. Sports Equipment

• Wooden Toys:

These are preferred to plastic towards the health conscious people which were supposed as a fashion before. Plastic is nothing but the combination of chemicals which is hazardous to children's health. Cricket, hockey, billiard, table tennis etc. Toys and sports equipment have long made use of wood for handles and main parts. e.g. Willow wood for cricket, tennis bat; Mulberry  wood for hockey sticks.

5. Commercial Uses

• Furniture:

At present, the market for wooden furniture is very profitable. No one can deny the demand for wooden furniture as it is a sign of aristocracy since ancient time.
e.g. Teak  wood is the best for making furniture. Some other woods from Mahogany , Shimul , Sundari, Jackfruit, Mango trees are used in south Asia for making different types of furniture.

• Ship building

Ships and rural fishing boats were made from wood. For constructing boats and ships wood is one of the most important construction material. Hardwood and softwood were used in the past for ship industry.
e.g. Teak, shal , mango, Arjun were frequently used in the past. Now Cypress ,redwood ,white, oak are water resistant and used for shipbuilding and boat building. Woods like kauri  is used for making the frames of ships.  

• Fuel

Wood is an age-old source of energy all over the world. Before the exploration of gas, fuel was the main source we can also define as only one source of energy that people used by burning as woods were available in the forest easily. Generally, sticks, pellets, sawdust, and charcoal are used as an energy source from wood. Usually, woods from cheap plants are used in this sector.  

• Stationary

Some stationeries like paper pencil are made of wood. Wood pulp is used for making paper. Wood is used for making pencils too.
e.g. In the past Cyper papyrus trees were used to make paper.

4.    Explain Basic engineering properties and uses of materials STONES?

• USES OF STONES

1. Stone masonry is used for the construction of foundations, walls, columns and arches.
2. Stones are used for flooring.
3. Stone slabs are used as damp proof courses, lintels and even as roofing materials.
4. Stones with good appearance are used for the face works of buildings. Polished marbles and granite are commonly used for face works.
5. Stones are used for paving of roads, footpaths and open spaces round the buildings.
6. Stones are also used in the constructions of piers and abutments of bridges, dams and retaining walls.
7. Crushed stones with graved are used to provide base course for roads. When mixed with tar they form finishing coat.

Crushed stones are used in the following works also:

1. As a basic inert material in concrete.
2. For making artificial stones and building blocks.
3. As railway ballast.

• ENGINEERING PROPERTIES OF STONES

1. STRUCTURE

The structure of the stone may be stratified (layered) or unstratified. Structured stones should be easily dressed and suitable for super structure. Unstratified stones are hard and difficult to dress. They are preferred for the foundation works.

2. TEXTURE

Fine grained stones with homogeneous distribution look attractive and hence they are used for carving. Such stones are usually strong and durable.

3. DENSITY

Denser stones are stronger. Light weight stones are weak. Hence stones with specific gravity less than 2.4 are considered unsuitable for buildings.

4. APPEARANCE

A stone with uniform and attractive colour is durable, if grains are compact. Marble and granite get very good appearance, when polished. Hence they are used for face works in buildings.

5. STRENGTH

Strength is an important property to be looked into before selecting stone as building block. Indian standard code recommends, a minimum crushing strength of 3.5 N/mm2 for any building block

6. HARDNESS

It is an important property to be considered when stone is used for flooring and pavement. Coefficient of hardness is to be found by conducting test on standard specimen in Dory’s testing machine. For road works coefficient of hardness should be at least 17. For building works stones with coefficient of hardness less than 14 should not be used.

7. PERCENTAGE WEAR

It is measured by attrition test. It is an important property to be considered in selecting aggregate for road works and railway ballast. A good stone should not show wear of more than 2%.

8. POROSITY AND ABSORPTION

All stones have pores and hence absorb water. The reaction of water with stone causes disintegration. Absorption test is specified as percentage of water absorbed by the stone when it is immersed under water for 24 hours. For a good stone it should be as small as possible and in no case more than 5.

9. WEATHERING

Rain and wind cause loss of good appearance of stones. Hence stones with good weather resistance should be used for face works.

10. TOUGHNESS

The resistance to impact is called toughness. It is determined by impact test. Stones with toughness index more than 19 are preferred for road works. Toughness index 13 to 19 is considered as medium tough and stones with toughness index less than 13 are poor stones.

11. RESISTANCE TO FIRE

Sand stones resist fire better. Argillaceous materials, though poor in strength, are good in resisting fire.

12. EASE IN DRESSING

Cost of dressing contributes to cost of stone masonry to a great extent. Dressing is easy in stones with lesser strength. Hence an engineer should look into sufficient strength rather than high strength while selecting stones for building works.

13. SEASONING

The stones obtained from quarry contain moisture in the pores. The strength of the stone improves if this moisture is removed before using the stone. The process of removing moisture from pores is called seasoning. The best way of seasoning is to allow it to the action of nature for 6 to 12 months. This is very much required in the case of laterite stones.

5.    Write basic engineering properties and uses of materials SAND?

Sand is a mixture of small grains of rock and granular materials which is mainly defined by size, being finer than gravel and coarser than silt. And ranging in size from 0.06 mm to 2 mm. Particles which are larger than 0.0078125 mm but smaller than 0.0625 mm are termed silt.

Sand is made by erosion or broken pebbles and weathering of rocks, which is carried by seas or rivers. And freezing and thawing during the winter break rock up the sand will be made. Sometimes Sand on beaches can also be made by small broken-up pieces of coral, bone, and shell, which are broken up by predators and then battered by the sea, and even tiny pieces of glass from bottles discarded in the sea and other mineral materials or the bones of fishes or other oceanic animals. Sand can be also considered as a textural class of soil or soil type.

In the real world, there are a lot of situations where we can find uses of sand. Followings are the common sand uses.

1. We can use sand to filter water; it works like an abrasive.
2. We can use sand to give a grip to our painting or wall art by combining 2 cups of paint with a ¾ cup of sand.
3. People make sandpaper by gluing sand to a paper.
4. While bunging metal, we can mix sand with clay binder for frameworks used in the foundries.
5. Sand can be used for cleaning up oil leak or any spill by dredging sand on that spill. The material will form clumps by soaking up, and we can quickly clean the mess.
6. Sand can be used as a road base which is a protective layer underneath all roads
7. Industrial sand is used to make glass, as foundry sand and as abrasive sand.
8. One creative usage of sand is serving as a candle holder. We can try putting some sand before pouring tea light or any candle in a glass. It holds the candle still and refrain the candle from rolling by giving it an excellent decoration.
9. Adds texture and aesthetic appeal to space.
10. Sand is mostly pure to handle, promptly available and economically wise.
11. We can make children’s sandpit to keep the play areas safer. It is quite inexpensive as well.
12. We use sand in aquariums, fabricating artificial fringing reefs, and in human-made beaches
13. Sandy soils are ideal for growing crops, fruits and vegetables like watermelon, peaches, peanuts, etc.
14. Sand can light a path by filling mason jars with sand and tea light which is another inexpensive way to make a walkway glow.
15. Sand can be used for cleaning narrow neck receptacle by putting a little sand and warm soapy water in the container.
16. We can keep an item steady which needs repairing by using sand. Burying the broken pieces under sand grains helps to hold the elements together while gluing.
17. Sand helps to improve resistance (and thus traffic safety) in icy or snowy conditions.
18. We need sand in the beaches where tides, storms or any form of preconceived changes to the shoreline crumble the first sand.
19. Sand containing silica is used for making glass in the automobile and food industry- even household products for the kitchen.
20. Sand is a strong strand which is used for plaster, mortar, concrete and asphalt.
21. The usual bricks formulated of clay only is way weaker and lesser in weight than blocks made of clay mixed with sand

Followings are the desirable properties of sand: 

• Should be completely inert. (i.e., should not have any chemical activity).
• Grains should be sharp, strong & angular.
• Should not contain any hygroscopic salts (i.e., CaCl2, MgCl2, etc.).
• Should not contain clay & silt; usually 3-4% clay & silt is ordinarily permitted for practical reasons.
• There should be no organic matter.

6.    Write Basic engineering properties and uses of materials AGGREGATES?

Aggregate is an aggregation of non-metallic minerals obtained in particulate form and can be processed and used for civil and highway engineering construction.

Aggregates are mainly classified into two categories:

1. Fine Aggregate
2. Coarse Aggregate

Aggregates are used in concrete to provide economy in the cost of concrete. Aggregates act as filler only. These do not react with cement and water. But there are properties or characteristics of aggregate which influence the properties of resulting concrete mix. These are as follow.

1. Composition
2. Size & Shape
3. Surface Texture
4. Specific Gravity
5. Bulk Density
6. Voids
7. Porosity & Absorption
8. Bulking of Sand
9. Fineness Modulus of Aggregate
10. Surface Index of Aggregate
11. Deleterious Material
12. Crushing Value of Aggregate
13. Impact Value of Aggregate
14. Abrasion Value of Aggregate

1. COMPOSITION

Aggregates consisting of materials that can react with alkalies in cement and cause excessive expansion, cracking and deterioration of concrete mix should never be used. Therefore it is required to test aggregates to know whether there is presence of any such constituents in aggregate or not.

2. SIZE & SHAPE

The size and shape of the aggregate particles greatly influence the quantity of cement required in concrete mix and hence ultimately economy of concrete. For the preparation of economical concrete mix on should use largest coarse aggregates feasible for the structure. IS-456 suggests following recommendation to decide the maximum size of coarse aggregate to be used in P.C.C & R.C.C mix.

Maximum size of aggregate should be less than

• One-fourth of the minimum dimension of the concrete member.
• One-fifth of the minimum dimension of the reinforced concrete member.
• The minimum clear spacing between reinforced bars or 5 mm less than the minimum cover between the reinforced bars and form, whichever is smaller for heavily reinforced concrete members such as the ribs of the main bars.

3. SURFACE TEXTURE

The development of hard bond strength between aggregate particles and cement paste depends upon the surface texture, surface roughness and surface porosity of the aggregate particles.If the surface is rough but porous, maximum bond strength develops. In porous surface aggregates, the bond strength increases due to setting of cement paste in the pores.

4. SPECIFIC GRAVITY

The ratio of weight of oven dried aggregates maintained for 24 hours at a temperature of 100 to 1100C, to the weight of equal volume of water displaced by saturated dry surface aggregate is known as specific gravity of aggregates.

5. BULK DENSITY

It is defined as the weight of the aggregate required to fill a container of unit volume. It is generally expressed in kg/litre.

Bulk density of aggregates depends upon the following 3 factors.

• Degree of compaction
• Grading of aggregates
• Shape of aggregate particles

6. VOIDS

The empty spaces between the aggregate particles are known as voids. The volume of void equals the difference between the gross volume of the aggregate mass and the volume occupied by the particles alone.

7. POROSITY & ABSORPTION

The minute holes formed in rocks during solidification of the molten magma, due to air bubbles, are known as pores. Rocks containing pores are called porous rocks. Water absorption may be defined as the difference between the weight of very dry aggregates and the weight of the saturated aggregates with surface dry conditions.

Depending upon the amount of moisture content in aggregates, it can exist in any of the 4 conditions.

• Very dry aggregate ( having no moisture)
• Dry aggregate (contain some moisture in its pores)
• Saturated surface dry aggregate (pores completely filled with moisture but no moisture on surface)
• Moist or wet aggregates (pores are filled with moisture and also having moisture on surface)

8. BULKING OF SAND

It can be defined as in increase in the bulk volume of the quantity of sand (i.e. fine aggregate) in a moist condition over the volume of the same quantity of dry or completely saturated sand. The ratio of the volume of moist sand due to the volume of sand when dry, is called bulking factor.

9. FINENESS MODULUS

Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 80 mm to 150 micron and dividing this sum by 100.

Fineness modulus is generally used to get an idea of how coarse or fine the aggregate is. More fineness modulus value indicates that the aggregate is coarser and small value of fineness modulus indicates that the aggregate is finer.

10. SPECIFIC SURFACE OF AGGREGATE

The surface area per unit weight of the material is termed as specific surface. This is an indirect measure of the aggregate grading. Specific surface increases with the reduction in the size of aggregate particle. The specific surface area of the fine aggregate is very much more than that of coarse aggregate.

11. DELETERIOUS MATERIALS

Aggregates should not contain any harmful material in such a quantity so as to affect the strength and durability of the concrete. Such harmful materials are called deleterious materials. Deleterious materials may cause one of the following effects

• To interfere hydration of cement
• To prevent development of proper bond
• To reduce strength and durability
• To modify setting times

12. CRUSHING VALUE

The aggregates crushing value gives a relative measure of resistance of an aggregate to crushing under gradually applied compressive load. The aggregate crushing strength value is a useful factor to know the behavior of aggregates when subjected to compressive loads.

13. IMPACT VALUE

The aggregate impact value gives a relative measure of the resistance of an aggregate to sudden shock or impact. The impact value of an aggregate is sometime used as an alternative to its crushing value.

14. ABRASION VALUE OF AGGREGATES

The abrasion value gives a relative measure of resistance of an aggregate to wear when it is rotated in a cylinder along with some abrasive charge.

7.    Basic engineering properties and uses of materials CEMENT?

Cement is a binder, a substance that sets and hardens and can bind other materials together. Cements used in construction can be characterized as being either hydraulic or non-hydraulic, depending upon the ability of the cement to be used in the presence of water. Non-hydraulic cement will not set in wet conditions or underwater, rather it sets as it dries and reacts with carbon dioxide in the air. It can be attacked by some aggressive chemicals after setting. Hydraulic cement is made by replacing some of the cement in a mix with activated aluminium silicates, pozzolan as, such as fly ash. The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water and safe from chemical attack. This allows setting in wet condition or underwater and further protects the hardened material from chemical attack (e.g., Portland cement).

• USE OF CEMENT

• Cement mortar for Masonry work, plaster and pointing etc.
• Concrete for laying floors, roofs and constructing lintels, beams, weather shed, stairs, pillars etc.
• Construction for important engineering structures such as bridge, culverts, dams, tunnels, light house, clocks, etc.
• Construction of water ,wells, tennis courts, septic tanks, lamp posts, telephone cabins etc.
• Making joint for joints, pipes , etc.
• Manufacturing of precast pipes, garden seats, artistically designed wens, flower posts, etc.
• Preparation of foundation, water tight floors, footpaths, etc.

• ENGINEERING PROPERTIES OF CEMENT

Fineness

• This test is carried out to check proper grinding of cement.  The fineness of cement particles may be determined either by sieve test or permeability apparatus test.
• In sieve test ,the cement weighing 100 gm is taken and it is continuously passed for 15 minutes through standard BIS sieve no. 9.The residue is then weighed and this weight should not be more than 10% of original weight.
• In permeability apparatus test, specific area of cement particles is calculated. This test is better than sieve test. The specific surface acts as a measure of the frequency of particles of average size.

Compressive strength

• This test is carried out to determine the compressive strength of cement.
• The mortar of cement and sand is prepared in ratio 1:3.
• Water is added to mortar in water cement ratio 0.4.
• The mortar is placed in moulds. The test specimens are in the form of cubes and the moulds are of metals. For 70.6 mm and 76 mm cubes ,the cement required is 185gm and 235 gm respectively.
• Then the mortar is compacted in vibrating machine for 2 minutes and the moulds are placed in a damp cabin for 24 hours.
• The specimens are removed from the moulds and they are submerged in clean water for curing.
• The cubes are then tested in compression testing machine at the end of 3days and 7 days. Thus compressive strength was found out.

Consistency

• The purpose of this test is to determine the percentage of water required for preparing cement pastes for other tests.
• Take 300 gm of cement and add 30 percent by weight or 90 gm of water to it.
• Mix water and cement thoroughly.
• Fill the mould of Vicat apparatus and the gauging time should be 3.75 to 4.25 minutes.
• Vicat apparatus consists of aneedle is attached a movable rod with an indicator attached to it.
• There are three attachments: square needle, plunger and needle with annular collar.
• The plunger is attached to the movable rod. The plunger is gently lowered on the paste in the mould.
• The settlement of plunger is noted. If the penetration is between 5 mm to 7 mm from the bottom of mould, the water added is correct. If not process is repeated with different percentages of water till the desired penetration is obtained.

Setting time

• This test is used to detect the deterioration of cement due to storage. The test is performed to find out initial setting time and final setting time.
• Cement mixed with water and cement paste is filled in the Vicat mould.
• Square needle is attached to moving rod of vicat apparatus.
• The needle is quickly released and it is allowed to penetrate the cement paste. In the beginning the needle penetrates completely. The procedure is repeated at regular intervals till the needle does not penetrate completely. (up to 5mm from bottom)
• Initial setting time equal to or less than 30min for ordinary Portland cement and 60 min for low heat cement.
• The cement paste is prepared as above and it is filled in the Vicat mould.
• The needle with annular collar is attached to the moving rod of the Vicat apparatus.
• The needle is gently released. The time at which the needle makes an impression on test block and the collar fails to do so is noted.
• Final setting time is the difference between the time at which water was added to cement and time as recorded in previous step ,and it is equal to or less than 10hours.

Soundness

• The purpose of this test is to detect the presence of un combined lime in the cement.
• The cement paste is prepared.
• The mould is placed and it is filled by cement paste.
• It is covered at top by another glass plate.A small weight is placed at top and the whole assembly is submerged in water for 24 hours.
• The distance between the points of indicator is noted. The mould is again placed in water and heat is applied in such a way that boiling point of water is reached in about 30 minutes. The boiling of water is continued for one hour.
• The mould is removed from water and it is allowed to cool down.
• The distance between the points of indicator is again measured. The difference between the two readings indicates the expansion of cement and it should not exceed 10 mm.

Tensile strength

• This test was formerly used to have an indirect indication of compressive strength of cement.
• The mortar of sand and cement is prepared.
• The water is added to the mortar.
• The mortar is placed in briquette moulds. The mould is filled with mortar and then a small heap of mortar is formed at its top . It is beaten down by a standard spatula till water appears on the surface. Same procedure is repeated for the other face of briquette.
• The briquettes are kept in a damp for 24 hours and carefully removed from the moulds.
• The briquettes are tested in a testing machine at the end of 3 and 7 days and average is found out

Strength

Strength of concrete are of the following types:

1. Compressive strength
2. Tensile strength
3. Flexural strength
4. Shear strength

Concrete is very weak in tension. The tensile strength of ordinary concrete ranges from about 7 to 10 percent of the compressive strength.

The flexural strength of plain concrete is almost wholly dependent upon the tensile strength. However, experiments show that the modulus of rupture is considerably greater than the strength in tension.

It is the real determining factor in the compressive strength of short columns. The average strength of concrete in direct shear varies from about half of the compressive strength for rich mixtures to about 0.8 of the compressive strength for lean mixtures.

Workability

The strength of concrete of a given mix proportion is very seriously affected by the degree of its compaction. It is therefore vital that the consistency of the mix be such that the concrete can be transported, placed and finished sufficiently easily and without segregation. A concrete satisfying these conditions is said to be workable.

Factors affecting the workability of concrete are:

• Water Content
• Mix Proportions
• Size of Aggregates
• Shape of Aggregates
• Grading of Aggregates
• Surface Texture of Aggregates
• Use of Admixtures
• Use of Supplementary Cementitious Materials
• Time
• Temperature

Elastic Properties

Concrete is not perfectly elastic for any range of loading, an appreciable permanent setting taking place for even low loads. The deformation is not proportional to the stress at any stage of loading. The elastic properties of concrete vary with the richness of the mixture and with the intensity of the stress. They also vary with the age of concrete.

Durability

Durability is the property of concrete to withstand the condition for which it has been designed, without deterioration over a period of years. Lack of durability can be caused by external agents arising from the environment or by internal agents within the concrete.

Impermeability

Penetration of concrete by materials in solution may adversely affect its durability, for instance, when Ca(OH)2 is being leached out or an attack by aggressive liquids (acids) takes place. Permeability has an important bearing on the vulnerability of concrete to water and frost. In the case of reinforced cement concrete, the penetration of moisture and air will result in the corrosion of steel. This leads to an increase in the volume of the steel, resulting in cracking and spalling of the concrete. Permeability of concrete is also of importance for liquid retaining and hydraulic structures

Segregation

The tendency of separation of coarse aggregate grains from the concrete mass is called segregation. It increases when the concrete mixture is lean and too wet. It also increases when rather large and rough-textured aggregate is used. The phenomenon of segregation can be avoided as follows.

1. Addition of little air-entraining agents in the mix.
2. Restricting the amount of water to the smallest possible amount.
3. All the operations like handling, placing and consolidation must be carefully conducted.
4. Concrete should not be allowed to fall from large heights.

Bleeding

The tendency of water to rise to the surface of freshly laid concrete is known as bleeding. The water rising to the surface carries with it, particles of sand and cement, which on hardening form a scum layer is popularly known as laitance. Concrete bleeding can be checked by adopting the following measures.

1. By adding more cement
2. By using more finely ground cement
3. By properly designing the mix and using the minimum quantity of water
4. By using little air entraining agent
5. By increasing the finer part of fine aggregate

Fatigue

Plain concrete when subjected to flexure, exhibits fatigue. The flexure resisting ability of concrete of a given quality is indicated by an endurance limit whose value depends upon the number of repetitions of stress. In concrete pavement design, the allowable flexural working stress is limited to 55% of the modulus of rupture.

9.    What are the uses of STEEL?

Some vital utilization of steels are given below:

1. Steel is environment-friendly & sustainable. It posses great durability.
2. Compared to other materials, steel requires a low amount of energy to produce lightweight steel construction. 
3. Steel is the world’s most recycled material which can be recycled very easily. Its unique magnetic properties make it an easy material to recover from stream to be recycled.
4. Steel can be designed into various forms. It gives better shape and edge than iron which is used to make weapons.  
5. Engineering steels are used for general engineering and manufacturing sectors.  
6. Steel is highly used in the automobile industry. Different types of steels are used in a car body, doors, engine, suspension, and interior. The average 50% of a car is made of steel. 
7. Steel reduces CO2 emissions. 
8. All types of energy sectors demand steel for infrastructure and resource extraction.  
9. Stainless steels are used to produce offshore platforms and pipelines.  
10. Steels are used for packaging and protecting goods from water, air and light exposure.  
11. Most of the household appliances like fridge, TV, oven, sinks, etc are made of steel.  
12. Steels are used for producing industrial goodies like farm vehicles and machines. 
13. Stainless steel is used as a cutlery material. 
14. Because of its easily welding capability and attractive finishing, steel has become a prominent feature in modern architecture. 
15. Stainless steel gives a hygienic environment. That’s why it is used for surgical implants. 
16. Steel has a wider range of temperature which is used to make large sheets.  
17. Renewable energy resources like solar, hydro and wind power use the stainless steel components.  
18. Mild steel is used for building construction. It is also a highly favored building frame material.

1. Tensile strength

The stress-strain curve for the steel is generally obtained by conducting tensile test on any standard steel specimen. Tensile strength of the steel can be defined in terms of yield strength and ultimate strength.

Hardness is regarded as the resistance of any material to identification and scratching. This is generally determined by forcing an indenter on to the surface. The resultant deformation steel is both elastic and plastic. The different methods to find out the hardness of metal which includes Brinell hardness test, Vicker’s hardness test, and Rockwell hardness test.

There is the possibility of microscopic cracks in a material or the material may develop such cracks as a result of several cycles of loading. These cracks may result in sudden collapse of the structure and it is very dangerous. Therefore to ensure that this should not happen, materials in which the cracks grow slowly are preferred. These types of steel are known as notch-tough steels and the amount of energy it absorb is measure by impacting the notch specimen.

A component of structure, which is designed to carry a single monotonically static load, may fail if the same load is applied cyclically a large number of times. If the example of a thin rod is considered, it bent back and forth beyond yielding fails after few cycles of such repeated bending. This type of failure is termed as fatigue failure. Examples: bridges, cranes, offshore structure, slender tower, etc.

Corrosion is the procedure in which oxidation of a metal in a normal atmospheric condition owing to the excessive presence of moisture and oxygen in the air. Corrosion of the metal is a very natural and rapid phenomenon in the areas of high humidity and places closer to saline water. Therefore the efforts to be made to control the corrosion by using galvanize and epoxy coated reinforcement bars but failed in practical usage due to the risk of disbanding, causing accelerated corrosion. Corrosion resistance elements such as copper, phosphorus and chromium are added in appropriate measure to the metal which results in corrosion resistance steel.