UNIT - 4

CONCRETE MIX DESIGN AND METHODS OF MIX DESIGN

4.1 A) CONCRETE MIX DESIGN - CONCEPT AND OBJECTIVE OF CONCRETE MIX DESIGN

Introduction

• A concrete blend is a mixture of 5 primary factor numerous proportions: cement, water, coarse aggregates, quality aggregates (i.e. sand), And air.

• Additional factors including pozzolana substances and chemical admixtures also can be integrated into the combination positive ideal properties.

• While a concrete blend layout is a system of choosing substances for a concrete aggregate and choosing their proportions.

• When designing a blend, you don't forget the favored power, durability, and workability of the concrete for the venture in question.

• Needless to say, Already-blend manufacturers attempt to locate the suitable proportions of those substances to optimize the concrete mixes and provide their concrete power, durability, workability, and different ideal properties.

• It’s crucial to optimize concrete to make sure the bottom keeping the very best power of your aggregate.

• Concrete blend layout is frequently mistake analysis “cement blend layout.” However, cement is since rely one of the substances of concrete.

• It is a binding substance that let sin concrete to set, harden, and cling to different substances.

• Therefore, it can't and ought to now no longer be used interchangeably with concrete blend layout.

Objective

The following are the objectives of the concrete mix design:

a. Finding the pressure force at a certain distance.

b. Maintain concrete mixing performance throughout the work.

c. By gaining strength.

d. Achieve economy by choosing the right concrete ingredients.

e. Getting the highest yield in a cement bag.

f. Avoid bee contact and bleeding.

g. Compliance with various levels.

h. Reduce concrete damage by proper measurement.

DIFFERENT METHODS OF MIX DESIGN

The following points highlight five methods of concrete construction. The methods are:

1. American Method of Mix Design

2. Graphic Method of Mix Design

3. Mix Design by Indian Standard Method

4. American Concrete Institute Method of Mix Design

5. Quick Method of Mix Design.

1. The American Way of Mixing Designs:

• The American Concrete Institute (ACI) approach is based on the fact that the given size of a mixture of water content per kilogram of concrete determines the performance of a concrete mix, usually independent of the equilibrium. It is therefore possible to start the mixing formation by selecting the water content in these tables.
• In addition it is also assumed that the maximum volume of the estimated quantity of the total value of the concrete depends only on the maximum size and the combination of good composites.

2. Graphic Method of Mix Design

• This approach was developed by the Road Research Laboratory, London and its detailed procedure is described. Combined composites are supplied and their percentage above the normal working fine collection is 4.75 mm, 2.36 mm, 1.18 mm. 600 microns, 300 microns and 150 microns are used. For the maximum combined size of the allowable size, it says 38 mm, 19 mm, 9.5 mm 4.75 mm, 2.36 mm is used.

3. Assemble Design in a Traditional Indian Way:

• The Indian Bureau of Standards has recommended the concrete construction process in conjunction with the experimental work carried out in national laboratories. The mixing process is provided by IS-10262- 1982. Subsequently no updates have been made to this process , and IS 456-1968 has been updated in 2000. That is why IS 10262-1982 needs to be reviewed as the cement power available to a highly developed country.

Therefore the following changes need to be made:

1. The 28-day capacity for phase A, B, C, D, E & F renewal needs to be reviewed.

2. The relationship between the different strengths of cement and the size of w / c should be re-established.

3. The relationship between 28 days of pressure and w / c ratio should reach a pressure of 80 MPa (800 kg / cm2), if the graph is to be used for high strength concrete.

4. According to the revised IS 456-2000 the usability level is expressed in degradation instead of compacting factor. This change requires new amounts of sand and water content for the use of standard concrete up to 35 M Pa and high strength Concrete over 35 M Pa.

• However in the absence of a review on IS 10262-1982, the existing IS 10262 process is described below as a smart move.
• The IS recommendations for mixing design include the composition of the mixing of self-contained (non-ventilated) concrete of medium and high strength concrete.

The integration method consists of the following:

(a) Water content

(b) Percentage of penalty collections corresponding to the maximum aggregate size of the reference value

(c) The amount of cement water, and

(d) Preservation of penalty collection.

• Water content and percentage of fine aggregate and adjust for any differences in performance. Finally the size of the ingredients per unit of concrete volume is calculated in the form of absolute volume. This method works for both underground pozzolana centers.
• The final amount of compounds selected after the experimental mixing, may require minor adjustments. In the case of fly ash cement, the water content can be reduced by about 3 to 5% and a good portion can be reduced by 2 to 4%.

4. American Concrete Institute Method of Mix Design:

• Although the ACI committee published its mixing method in 1944 and almost all concrete dams using a lot of Indian works were designed using the ACI committee method used at the time of mixing. Since then many improvements have been introduced in a practical way. Here is a discussion of the latest method of constructing concrete mixes based on ACI 211-1 of 1991 manual part-time concrete recommendations.

The ACI committee took the following basic ideas:

1. The new collapsed concrete provided and containing a fully proportional measure of the maximum given size will have a fixed water content, regardless of the w / c ratio and the cement content associated between the maximum range of operating parameters.

2. The maximum stiffness of the coarse aggregate per unit of concrete per unit depends on its maximum size and the correct modulus of the fine compound as shown in table 20.39 taking into account the minimum particle size. The effect of angularity is reflected in the empty content. So angular green joints require more mud than circular joints .

3. Regardless of the compaction methods, even when complete compaction has been achieved, a certain percentage of air remains in the concrete and is proportional to the maximum volume.

Mix Design Process:

For compound design, the following data is required to be collected:

(a) Fineness modulus of selected fines.

(b) The unit has the weight of the selected dry fine.

(c) The gravitational force of coarse and fine aggregate in saturated, dry areas.

(d) Absorption of combined rates and penalties.

(e) The gravitational force of cement.

5. Quick methods Mixing:

• Measuring the initial amount of cement water according to purpose means the actual strength will be to combine it with 28 days of cement strength. Feature strength is found to be better related to 28 days of cement strength than in age. This method will therefore require 28 days to determine the size of the cement and the next 28 days of testing mixing the strength of the concrete. The 28-day strength of the cement can be considered as that provided by the curves

Fig no 1 Graph of compression strength of concrete

• 28 days or 56 days is too long for the contractor to wait for the results of the merger. There is a tendency to use direct mixing without trying experiment mixing. To reduce the time required for the mixing of experiments, the Cement Research Institute of India (CRI) has developed a method called rapid method, in which the compressive strength of cement and cement is obtained using a rapid therapeutic method as discussed in IS 9013-1978. This method reduces the recovery time of experimental compounds from 28 days to only 3 days.
• 28 days of concrete hardening is found to be highly correlated with statistics and rapid strength. Therefore the combination of temptation in line with the target means faster energy than the target means 28 days of energy, with the help of a combination between the two.
• This mixture is obtained independently by the type or characteristics of the cement used i.e. the mixture is not affected by the type of cement used, probably because it affects the fast and normal concrete strength of 28 days equally, so that the result is neutral in comparison. The advantage of each operation is such a combination can be established by the type of building material and assembled to the size to be used.

Fig no 2 Strength of concrete vs accelerated strength

• On the other hand, the results of a stable acceleration test in standard cement mortar such as IS 4932-1968 Were not found to be reliable. This problem is overcome by inspecting the cement and quickly and determining its speed.
• The concrete composite concrete or the fastened concrete mixing strength has a w / c value of about 0.35 and the performance is much lower with slump 0 to 10 or compacting factor 0.8 per available cement i.e. (cement in hand).
• The maximum size of the crushed natural compound name should be 10 mm and a good composite should correspond to area II of table 4 of IS-383-1970.

Key takeaways

1. It’s crucial to optimize concrete to make sure the bottom fee even as keeping the very best power of your aggregate.
2. Concrete blend layout is frequently mistakenly stated as “cement blend layout.” However, cement is sincerely one of the substances of concrete.
3. It is a binding substance that lets in concrete to set, harden, and cling to different substances.
4. The following points highlight five methods of concrete construction. The methods are:

• American Method of Mix Design
• Graphic Method of Mix Design
• Mix Design by Indian Standard Method
• American Concrete Institute Method of Mix Design
• Quick Method of Mix Design.

4.2 FACTORS AFFECTING THE MIX DESIGN

• Strength and sturdiness of the concrete blend layout are established upon the subsequent factors:
• Grade designation: Concrete’s power is measured in N/mm2 whilst issue to check after curing in any curing medium. The preference of concrete grade relies upon on its utilization.
• Choice of cement: Cement preference varies relying on utilization. The cement have to be examined for overall performance required with the aid of using their utilization earlier than being examined with inside the layout blend.
• Choice of mixture size: Aggregates wanted for every blend depends upon the bodily houses wanted for the layout. All aggregates need to be nice sized earlier than use.
• Type of water: Any water used for concrete blend layout is to be examined earlier than use to make certain it's far with inside the variety of water required for concrete. Most all consumable water is right for concrete work, however have to nevertheless be examined.
• Water to cement ratio: The ratio of water to cement have to be examined for consistency, preliminary and very last setting, soundness of the cement, workability, hunch of the concrete and compacting factor.
• Workability: This is the degree of ease of blending concrete without segregation or bleeding. It by and large relies upon at the designed hunch of the concrete.
• Durability: This is the degree of the specified power (N/mm2) of any concrete grade after 28 days of curing. Durability have to be manipulate examined on site.

Key takeaways

1. Here different type of factors which affects mix proportion are durability, workability, water to cement ratio, type of water, choice of mixture size, choice of cement, grade designation.

4.3 QUALITY CONTROL

The quality of concrete construction on site can be done in three different phases as follows

1. Quality control before integration

2. Quality control during integration

3. Post-construction quality control

STAGE 1 (QUALITY CONTROL BEFORE CONCRETING)

This phase of quality control has two steps.

• Assessment of specification requirements regarding mining, forms, consolidation and embedded repairs etc.

• Control test for concrete ingredients (eg cement, composite and water)

Cement

Cement quality is obtained by performing strength tests of cement cubes. However with effective control cement:

• It should be tested first and foremost for each source and then tested every once every two months

• It should be protected from moisture

• It should be returned after the last 3 months, if long-term storage is unavoidable

• It should be rejected if a large lump is found in the cement bags.

Aggregate

Concrete composites should be validated at specified values ​​as standard specifications.

The quality of concrete is affected by the various physical and mechanical properties of the composite, namely structure, proportions, durability, gravity and water absorption etc. These composite structures should be tested before using them to produce concrete.

The amount of horror and natural pollution should also be considered.

Sand connections are also an important asset in a number of ways. Provides incorrect results when volume encryption is performed .It increases the amount of water cement which also reduces energy.

With aggregate functional controls:

• They need to be tested once in the beginning to allow the source

• If it is to be checked once or twice daily the moisture content and grant must be made for the combined moisture content.

Water

Water quality should be assessed for needs as defined at the appropriate level. Chemical analysis will be performed to authorize the source. In the event of contamination, it is necessary to store the water for a period of time to allow it to settle. In case of doubt the concrete cubes made of this water are examined. A maximum of 28 days of pressure for at least three cubes or cylinders or a set size, prepared for the proposed water use shall not be less than 90% of the strength between three cubes of the same concrete prepared with distilled water.

STAGE 2 (QUALITY MANAGEMENT DURING CONCRETING)

Careful precaution during concrete is required for all assembly operations such as baking, mixing, transporting, placing, coating and curing. Follow-up safety measures should be taken during concreting operations.

1. The concrete mix should be built into the laboratory and the materials to be used on site.
2. As far as possible the concrete should be driven by weight. If weight assembly is not possible, volume collection can be allowed with proper monitoring in the presence of the lead engineer.
3. During mixing the mixer should be charged in full. Building materials should be fed in the right order. The mixer speed should be from 15 to 20 fluctuations per minute. The mixing time should not be less than 2 minutes in any case. Separation should be avoided when loading concrete into the mixture.
4. The performance of concrete is an important material of concrete while concrete is in its new state. Therefore testing of slump or compaction factor should be performed to check the performance of the concrete. About three tests should be performed on every 25 m3 of concrete.
5. Care should be taken so that no separation occurs during the concrete transfer.
6. Concrete should not be lowered from a height of not more than 1 m. if the height of the drop is more than 1 m chutes should be used.
7. To avoid re-release the concrete should be placed in its final position as much as possible.
8. Vibrators should be used to connect the concrete. Internal vibrator installation space should not exceed 0.6 m. It should be lightly painted so that no holes are left in the concrete. Vibrator frequency should not be less than 7000 cycles / minutes.
9. The treatment should be done over a period of time so that the concrete develops the required strength. Concrete should be covered with hessian as soon as it becomes hard.
10. The form function must be aligned with the final form of the form. It should be checked before the start of integration. The inside of the forms should be cleaned and oiled. Forms must be removed after the deadline.
11. Concrete should be protected from hot and cold weather at an early age. Concreting should not be performed at temperatures below 4.50C and above 400 In very hot weather water and aggregates should be cooled. Approved quality retards can be used.
12. In very cold weather water and aggregates should be heated. Approved quality Accelerators can also be used.

STAGE 3 (QUALITY CONTROL AFTER CONSTRUCTION)

• Once the concrete has been laid and assembled, a pressure test is performed on the tubes made of this concrete. With standard concrete, cubes are made of concrete made in the workplace.
• Reinforced concrete should be considered to be true in size, shape and size as specified in each design. The appearance of the concrete surface should also be checked. Sizes are available in various sizes. Reinforcement should have adequate concrete cover and if reinforcement is visible on the part of the structure, the part should be rejected or appropriate action taken.

Concrete strength is usually obtained by cube or cylinder samples tested within 28 days. In the event that the power received is less than the specified minimum, one or more of the following steps may be taken.

• Load testing and deviation of the deviation and / or difficulty (structural quality can also be obtained by calculating back concrete strength)

• Cutting cores from structures and testing them for strength

• Non-destructive tests such as the Schmidt rebound hammer or ultrasonic pulse velocity test. These tests give a very complex view and are used to find structural similarities.

• Chemical analysis of hard concrete.

Key takeaways

1. The quality of concrete construction on site can be done in three different phases as follows

• Quality control before integration
• Quality control during integration
• Post-construction quality control

4.4 VARIABILITY OF LABORATORY TESTS RESULTS

1. The quality of clinical laboratory testing is important to to promote and maintain public health. In 1988, the US Congress has made improvements to the Clinical Laboratory 1988 Amendments (CLIA) in response to the concern laboratory errors were important in public health matters.
2. In time the pre-CLIA debate, little scientific evidence was available to record frequency and type of laboratory errors affect, among other things, accuracy and reliability of laboratory test results.
3. CLIA provisions thereafter instructed the US Department of Health and Human Services that check the nature of laboratory-related problems. Initially, Centers for Disease Control and Prevention (CDC) has published a review of related scientific literature CLIA.2 In 1990, the CDC requested a study proposal to address it study areas defined in CLIA.
4. Insufficient resources, however, it restricted the use of the proposed design.4, 5 Thus, the CDC began to operate with an independent focus problem-solving projects that would be addressed by complete composition.
5. In 1994, the CDC began developing and evaluating a prototype process4,5 using split-specimen (SS) and an audit design (AS) to determine frequency and type of problems that occurred in certain parts of the full examination the process of certain laboratory tests performed by a physician hospital offices and laboratories. 3 month study of members a test was conducted to determine the feasibility of such a monitoring system problems in the testing process.
6. Based on these findings, a complete trial7 was initiated involving 1,378 patients from 11 medical clinics with their office laboratories (n = 8) or working with different hospital laboratories (n = 3).
7.  Two of the 3 analytics tested in the feasibility study selected in a complete study: serum total cholesterol (TC) and serum potassium (K). The results of the full test helped to test the feasibility of this project lens come from part of the complete experimental process
8. The purpose of the current study was to use it again compare 2 ways to test for variance in test results using AS design only or integrated with SS make-up; to our knowledge, the first account of use of such controlled testing programs to do so in various medical and laboratory facilities.
9. The methods described here can be used to test the concentration decrease in laboratory test results. Audit samples (also sometimes and separated specimens) already collected in
10. Multiple retrieval laboratories (and similar testing) to test the reliability of laboratory results. That sharp results were obtained using blood samples collected from 302 randomly selected patients in each Clinical participants participated in 1,378 patients a comprehensive exploration study.
11. For 1 of 3 types collected from these 302 patients, audit samples prepared and sent to the participating laboratory and laboratory transmission for re-analysis, as well in the referee's laboratory for review.
12.  This report has been read is psychologically different and different which was about being able to use SS design6 and by testing the modified AS-SS structure in any laboratory result (related to non-laboratory tests exclusion and bias), in contrast to the difference in outcome (related to test imprecision), tested.7
13. The current report is not true testing of the same AS-SS test design project,  but uses the same design to present 2 data analyzes methods used to evaluate variability in laboratory test results.

Key takeaways

1. The quality of clinical laboratory testing is important to to promote and maintain public health. In 1988, the US Congress has made improvements to the Clinical Laboratory 1988 Amendments (CLIA) in response to the concern laboratory errors were important in public health matters.
2. In time the pre-CLIA debate, little scientific evidence was available to record frequency and type of labtory errors affect, among other things, accuracy and reliability of laboratory test results.

4.5 ACCEPTANCE CRITERIA

(A) Compression strength

Concrete will be considered in accordance with energy requirements when both of the following conditions are met:

a) The rating power is determined by any group of four consecutive non-consecutive test outcomes, corresponding to the appropriate limits

b) Any individual test result complies with the appropriate limits

(B) Flexural Strength

When both conditions are met, the concrete complies with the specified flexural strength.

a) Fixed force determined in any consecutive test result group that exceeds the specified feature strength by at least 0.3 N / mm2

b) The power determined in any test result is not less than the specified feature strength of less than 0.3 N / mm2

Key takeaways

1. Compression strength
2. Flexural Strength

4.6 GRADE DESIGNATION AND IS REQUIREMENT AS PER IS 456 (EXPOSURE CONDITIONS, MINIMUM AND MAXIMUM CEMENT CONTENT AND MAXIMUM W/C RATIO

EXPOSURE CONDITION

1. Mild

Concrete surfaces protected against weather or aggressive conditions, except those situated in coastal areas

2. Moderate

Concrete surface sheltered from severe rain or freezing whilst wet; concrete exposed to condensation and rain, concrete continuously under water; concrete in contact or buried under non-aggressive soil/ground water; concrete surfaces sheltered from saturated salt air in coastal area

3. Severe

Concrete surfaces exposed to severe rain, alternate wetting and drying or occasional freezing whilst wet or severe condensation; concrete completely immersed in sea water; concrete exposed to coastal environment

4. Very serve

Concrete surfaces exposed to sea water spray, corrosive fumes or severe freezing conditions whilst wet; concrete in contact with or buried under aggressive sub-soil/ground water

5. Extreme

Surfaces of members in tidal zone; members in direct contact with liquid/solid aggressive chemicals

MINIMUM AND MAXIMUM CEMENT CONTENTS

• Generally, cement content will not play a direct role in strength of concrete; if cement content is required to amplify the performance of the concrete mix of the scale given to the water cement, and then the compressive strength can be increased by the richness of the mixture. However, at a certain rate the water cement will be @ways be optimum cement content that results in a 28-day capacity having a very high capacity (see Fig. 24'3. To add cement content in excess of a large amount may not increase the strength of the concrete especially at low concentrations the water level of the cement and the maximum size of the size '.
• Recommendations for making strong concrete in various codes of hypothetical practices for the amount of cement water, minimum Cement content, cover cover, type of cement and chloride size and sulphates in concrete, etc. All of these recommendations have been taken together it often leads to the concrete being soft, functional, laid and as as to reduce penetration under a given condition.
• Therefore, adherence to one limit without looking at the othe, or similar use of these recommendations without regard to the nature of the placement, because for example, tightening of reinforcement, thickness of cover, performance of concrete or composite features, may not guarantee the fulfillment of the purposes.
• In addition, cement content is preferred by two other factors. First, it must ensure sufficient balance (pH value of concrete) in order to to provide an artificial environment against metal corrosion, for example, in concrete in the sea or in seawater, the cement is minimal a content of 350 kg / m3 or more is required for this consideration 13 + 28. Second, the content of cement and the water content of cement are very selective the result of a sufficient volume of cement paste to fill more voids in integrated integration.
• Obviously, this will depend on the type and the name the maximum size of the total amount used. For example, crushed rock or river stones are 20 mm round the maximum size of the joint, in generally, I have 27 and 22 percent respectively posts. A cement content of 400 kg / m3 and a water content of 0.45 cement will the effect of attaching volume to 30 percent may be suitable for former (that crushed rock 20 mm large size of the scale), and
• A cement content of 300 kg / m3 and a water content of 0.50 will result 25% volume attachment (Fig. 37) enough to fill voids by 20 mm composite of round stone stones. Increasing cement content will do led to higher performance.
• IS: 456-1978R3 calculates the requirements for solid concrete according to the content of the cement is the minimum, type of cement and water volume the required amount of certified concrete structures to ensure durability against: (a) the specified conditions of exposure, and (b) otherwise concentration of sulphates present in groundwater and groundwater. These are reproduced in Tables 23 and 24 respectively. Similar requirements for pre-installed concrete structure such as IS: 1343-19802 ’were also produced Tables 25 and 26. The purpose of the cement content specification is at least to ensure the appropriate strength as described above.
• The values ​​specified in Tables 23 and 24 are generally 20 mm per name the maximum size of the compound. Cement content should be reduced or increase as the maximum size of the combined word increases or decreasing, respectively.

MAXIMUM WATER CEMENT RATIO

• You may have encountered an engineer’s attempt to incorporate design and structural requirements. Only 4000 psi is required for construction purposes. However, if the specific is concerned with rigidity - because, say, exposure to sulphate or salt extraction - concrete should reach 5000 psi to 5500 psi. Your identifier did not specify in accordance with ACI 318 "Requirements for the Code of Concrete Building and Architecture".
• Prior to 2008, it was common to specify design strength and high water / cementitious materials ratio (w / cm) and / or cementitious factor. To keep the annotations in the selection of these values ​​unchecked, ACI modified 318 in 2008 to follow euro code-based exposure classes, indicating the w / cm magnitude or minimum of a dependent factor depending on the conditions concrete is expected to experience during its lifetime.
• High w / cm values ​​are designed to produce concrete with low durability or high resistance to abrasion rather than blending with the standard construction strength requirement.
• However, about 10 years after the ACI exposure classes were combined, most of the data did not apply. Of course, project owners and designers can specify whatever they want, but deviations from the code should not be underestimated.
• Therefore, the design strength details should indicate the size of w / cm or the minimum cementitious element in the exposure stages. But since the relationship between w / cm and power depends on the materials used, how can the specter determine the correct correction before the supplier is selected
• In addition to the rigidity concerns, there may be other requirements - such as those affecting the slide finish - for this combination. Section 8.4 of ACI 302.1R-15 "Guide to Concrete Construction and Construction of Slabs" (2015) incorporates the design requirements of the upper w / cm and the cementitious factor. The ACI 302.1 guide, however, is not mandatory. Any specified information you wish to include in the contract documents must be clearly included.
• P.S. Starting in February, the American Concrete Institute will provide guidelines, recommended methods, and other non-compulsory documents free of charge to members.

Key takeaways

1. Exposure condition

• Mild, moderate, serve, very serve, extreme

2.     Minimum and maximum Cement content

• Generally, cement content will not play a direct role in strength of concrete; if cement content is required to amplify the performance of the concrete mix of the scale given to the water cement, and then the compressive strength can be increased by the richness of the mixture. However, at a certain rate the water cement will be @ways be optimum cement content that results in a 28-day capacity having a very high capacity (see Fig. 24'3. To add cement content in excess of a large amount may not increase the strength of the concrete especially at low concentrations the water level of the cement and the maximum size of the size

3.     Maximum w/c ratio

• High w / cm values are designed to produce concrete with low durability or high resistance to abrasion rather than blending with the standard construction strength requirement.

4.7 B) METHODS OF MIX DESIGN - IS CODE METHOD AND DOE METHODS (WITH AND WITHOUT MINERAL ADMIXTURE)

IS CODE METHOD

Introduction

• The process of selecting suitable concrete ingredients and determining their corresponding value for the purpose of producing the required concrete, strength, durability, and economic viability as possible, is called concrete construction. The distribution of the concrete ingredient is governed by the required performance of concrete in 2 provinces, namely plastic and solid surfaces. If the plastic concrete does not work, it cannot be properly laid and bonded. Functional assets, therefore, become more important.
• The compressive strength of reinforced concrete is often considered an indication of some of its properties, depending on many factors, e.g. quality and quantity of cement, water and composite; batching and mixing; placement, congestion and treatment. The cost of concrete is made up of the costs of building materials, plant and labor. The difference in material costs comes from the fact that cement is more expensive than quantity, so the goal is to produce as much concrete as possible. From a technical point of view, rich mixing can lead to high shrinkage and cracking of structural concrete, as well as high hydration temperature changes in large concrete that can cause cracks.
• The actual cost of concrete is related to the cost of the materials required to produce low-level energy called the element strength specified by the architect. This depends on quality control measures, but there is no doubt that quality control adds to the cost of concrete. The extent of quality control is often an economic compromise, and it depends on the size and type of work. Personnel costs depend on the performance of the mixer, e.g., concrete mixing inadequate performance can lead to higher labor costs to obtain the quality of mixing and equipment available.

Requirements for the design of concrete joints

The foundations that form the basis for the selection and distribution of integrated ingredients are:

a) Minimum compression strength is required in structural considerations

b) Adequate functioning required to fully integrate with available assembly equipment.

c) The maximum amount of water cement and / or high cement content to provide sufficient durability for certain site conditions

d) High cement content to avoid shrinking cracks due to the heat cycle in large concrete.

Types of Mixes

1. Selected mixes

In the past the specification of concrete determined the size of the cement, the good and the good combination. These are compounds of compacted concrete that ensure sufficient strength called composing mixtures. This delivers easily and under normal circumstances, has more page power than described. However, due to the diversity of the mixing ingredients the given performance composite varies greatly in strength.

2. Standard mixes

The called concentrations of the fixed cement (figure) vary greatly in strength and can lead to lower or higher concentrations. For this reason, low pressure forces are included in most specifications. These compounds are called standard mixes.

IS 456-2000 has selected concrete mixes in many subjects such as M10, M15, M20, M25, M30, M35 and M40. In this term the word M refers to a mixture and a number in a 28-day cube power specified in N / mm2. The combination of marks M10, M15, M20 and M25 is almost identical to the equilibrium ratio (1: 3: 6), (1: 2: 4), (1: 1.5: 3) and (1: 1: 2) respectively.

3. Designed Mixes

In these mixtures the performance of concrete is defined by the composer but the size of the mixtures is determined by the concrete producer, unless the minimum cement content can be reduced. This is a very sensible approach to choosing the size of a mixture of certain substances in the brain with different or different characteristics. This approach leads to the production of concrete with the most economically viable structures. However, the customized mix does not act as a guide because this does not guarantee the right mixing capacity for the specified performance.

Concrete that works without requiring word-for-word or standard mixtures (cut into codes by the amount of dry ingredients cubic meters or less) can only be used for very small works, where the 28-day concrete strength does not exceed 30 N / mm2 .No control tests are required of the required reliability placed on the bulk of the ingredients.

Factors affecting the choice of mixing equity

The various factors that affect the composition of a combination are:

1. Compressive strength

It is one of the most important components of concrete and influences many other descriptive structures of hard concrete. The critical pressure force required in certain years, usually 28 days, determines the amount of water-cement mixture. Another factor affecting the strength of concrete over a given year was reheated to a temperature determined by the density. According to the law of Abraham the strength of fully integrated concrete contradicts the water balance of cement.

2. Workability

The level of performance required depends on three factors. These are the size of the section to be installed, the amount of reinforcement, and the method of integration to be used. In a small and complex section with many corners or inaccessible parts, the concrete must have high performance so that the full joint is obtained with the right effort. This also applies to the installed metal sections. The desired performance depends on the integration equipment available on site.

3. Durability

The strength of concrete is resistant to aggressive environmental conditions. High-strength concrete tends to last longer than low-strength concrete. In cases where high strength is not required but conditions of exposure are such that high durability is important, the need for durability will determine the amount of water cement to be used.

4. Maximum nominal size of aggregate

Generally, the larger the total size of the mix, the less the requirement for a cement of a certain amount of water cement, as the performance of the concrete increases with the increase in the total size of the cement. However, the compressive strength tends to increase with the reduction in compound size.

IS 456: 2000 and IS 1343: 1980 recommend that the size of a compound word should be as large as possible.

5. Grading and type of aggregate

The placement of the composite affects the measurement of the specified performance mix and the amount of water cement. Coarser measuring leaner will be a disposable mix. Highly dependent mixtures are not desirable because they do not contain enough particles to make the concrete mix.

The type of compound strongly influences the cement ratio of the required performance and the set amount of water set. An important feature of a satisfying combination is the similarity of placement that can be achieved by mixing components of different sizes.

6. Quality Control

The level of control can be statistically measured by the variability of the test results. The variability is due to differences in the composition of the mixing ingredients and the lack of precise control of the mixing, mixing, packaging, treatment and testing. Reducing the difference between low power and low power mixing will be cement content. The factor that controls this difference is called quality control.

Mix proportion designation

The most common way to determine the size of the concrete mixing components is for cement or parts of cement, positive and negative aggregates. For example, a concrete mixture of 1: 2: 4 means that cement, good and bright mixture in a ratio of 1: 2: 4 or mixtures consist of one part cement, two parts good mix and four parts green joints. Size can be by volume or by size. The water level of the cement is usually indicated by the quantity

Factors to consider in the design of integration

• A designation of the range that gives the concrete strength attribute.
• The type of concrete affects the rate of growth of the compressive strength of the concrete.
• The maximum size of the composite to be used in concrete may be as large as possible within the limits set by IS 456: 2000.
• Cement content should be restricted from shrinkage, cracking and movement.
•  The performance of concrete in satisfying placement and compaction is related to the size and shape of the section, quantity and reinforcement spaces and techniques used for transport, placement and reinforcement.

The process

1. Obtain target targets directly from the specified compression strength feature within 28 days of f c k and quality control level.

Where S is the standard deviation found in the Table of thought content provided after the integration of the design.

2. Find the cement ratio for the purpose you want using the relationship between the compressive strength and the selected water cement to check the water cement ratio. The preferred water-cement ratio is also evaluated with a reduced water-cement ratio for the rigidity requirements given in the table and using a minimum of two values.

3. Measure the amount of air trapped by the maximum size of the combination from the table.

4. Select the contents of the water, with the required usability and the maximum size of the compounds (composite in a dry state) on the table.

5. Find the percentage of fine finishes in total composites with the total volume from the concrete table using a crushed folded collection.

6. Adjust the water content values ​​and the percentage of sand as provided in the table for any differences in performance, the amount of water cement, the measurement of good collection and the combined aggregation of the values ​​given in the table.

7. Calculate the cement content form of the cement water cement and the final water level as it arrives after preparation. Test the cement compared to the low cement content from the durability requirements, and a high acceptance of two values.

8. From the amount of water and cement per unit of concrete volume and the percentage of sand already determined in steps 6 and 7 above, calculate the raw and clear composite content for each concrete unit in the following relationships:

Where V = the total volume of concrete

               = total volume (1m 3) subtracts air volume

Sc = gravitational force

W = Bulk of water per cubic meter of concrete, kg

C = weight of cement per cubic meter of concrete, kg

p = ratio of fine aggregate to total aggregate in total volume

f a, Ca = total amount of fine and dark aggregates, per cubic meter of concrete, respectively, kg, and

S f a, S c a = gravity for a full face dry and compacted, respectively

DOE METHOD

• The DOE method of mixing construction is better than the Road Note No. method. 4. This method of concrete construction or separation is mainly based on a wide range of laboratory experiments and experiments conducted by the UK Road Research laboratory The Road Note 4 method was first published in 1950. This hybrid design was very popular and was widely used until the 1970's. Most of the Indian Concrete roads and airfields were designed this way, but they are no longer functional.
• The DOE method was first published in 1975 and revised in 1988. The DOE method of mixing design applies to all types of concrete mixes including roads, while Road Note No. 4 operated only on airways and airports. This method can be used for concrete containing fly ash. The DOE approach is the most common form of integration in the UK now. This method used the relationship between water / cement ratio and compressive strength depending on the type of cement and the size used.
• The water content required to provide the various levels of performance, as low, low, medium and elevated in terms of fall or time Vee Bee or composite material, is determined by these two types of compositions such as crushed aggregate and gravel. This method is suitable for the design of a standard concrete composite consisting of 28 days of a pressure cube of up to 75 MPa on airtight concrete.

The step-by-step process of integration is provided below:

Process:

Step 1:

• Determine the directional power used from the power of the specified feature. Target means power = specified feature strength + standard deviation x Risk factor.
• (Risk is taken into account assuming that 5% of the results are allowed to fall below the specified factor).

Step 2:

• Calculate the water / cement ratio from Fig. From table  the compressive strength of the concrete is made at a rate of 0.5 free water / cement.

Fig no 3 Table of compressive strength

• From table , find the 28-day power of cement type and C.A. Now mark the point on the y-axis of Fig.  is equal to the compression strength read from Table 20.46, which is in w / c ratio 0.5.

Fig no 4 Relation between comprehenssive strength and free w/c ratio

• From this point draw a curved dotted curve near the intersection point using this curve, read the w / c ratio compared to the mean mean force. This method will be clearer in the example below.

Step 3:

• Find the water content with the required usability, taking into account the size of the compound and its type from Tables

Fig no 5

Table of water content required

Step 4:

• Cement Content Determination - The amount of cement can be determined from the total water content and w / c ratio.

• e.g., cement content = [(Water weight) / (w / c ratio)]

• The amount of cement obtained by the above relationship should be compared with the minimum cement content specified from the 2800 hardness. The height of the two values ​​should be acceptable. When specifying the contents of the maxi 2600 cement, the content of the calculated suspension must be less than the specified cement content.

Step 5:

• Determination of total composite content - To determine the total content of composite content, a stable water content of fully compacted concrete is required. This can be found from Fig. with approximate water content and gravitational gravity. If the specified size of the compound is not known its value of unmixed compound can be considered as 2.6 and 2.7 of the compacted compound can be considered as shown in curves A and B of Fig. The composite content is determined by removing the weight of the cement and the water content from the weight of the new concrete read in Figure

Fig no 6 Estimated wet Density for fully compacted concrete

Step 6:

• Positive merger determinations - Part of the total compensation collection is determined from Fig. is 10 mm in size,  is 20 mm in size, Fig. is of 40 mm compact size. The parameters involved in Fig. high. integration size, water content, performance level and percentage of good integration passing through a 600 micron filter.

Fig no 7 Recommended% of fine aggregate

• Knowing the amount of good integration from Fig. the weight of a good combination can be obtained by multiplying the total weight of the combination by this measure. Knowing the good combination, a coarse aggregate weight can be obtained. The composite collection can be further subdivided into different components depending on the nature of the composite. Generally the figures given in Table  may be accepted.

Fig no 8Water cement ratio

Fig no 9 Table of proportion of coarse aggregate

Key takeaways

1. IS CODE METHOD

The process of selecting suitable concrete ingredients and determining their corresponding value for the purpose of producing the required concrete, strength, durability, and economic viability as possible, is called concrete construction. The distribution of the concrete ingredient is governed by the required performance of concrete in 2 provinces, namely plastic and solid surfaces. If the plastic concrete does not work, it cannot be properly laid and bonded. Functional assets, therefore, become more important.

2.     DOE METHOD

The DoE method of mixing construction is better than the Road Note No. method. 4. This method of concrete construction or separation is mainly based on a wide range of laboratory experiments and experiments conducted by the UK Road Research laboratory The Road Note 4 method was first published in 1950. This hybrid design was very popular and was widely used until the 1970's. Most of the Indian Concrete roads and airfields were designed this way, but they are no longer functional.

4.8 USE OF SPREAD SHEET/ PROGRAMMING/ SOFTWARE FOR CONCRETE MIX DESIGN.

• Mixing design plays an important role in community building projects. For the purpose of obtaining an accurate measurement of any construction site, the use of this easy-to-use concrete mixing spreadsheet is absolutely necessary. This useful building sheet will give you a number of integration projects for your construction site.
• Concrete mixing design refers to the process of selecting suitable concrete ingredients and establishing their reasonable values ​​to produce concrete as high strength, durability and economic viability as possible.

The following structures are required to extend the basis for the selection and classification of integrated ingredients:

-The smallest amount of compressive force is a burden on the structure

-Sufficient performance is considered necessary for complete integration with available sewing machines.

-Extreme water-cement ratio and high cement content provide sufficient power in certain site conditions

-Highly cement content to eliminate shrinkage due to the heat cycle in large concrete.

Fig no 10 Estimated Format/ Excel calculator

Key takeaways

1. Mixing design plays an important role in community building projects. For the purpose of obtaining an accurate measurement of any construction site, the use of this easy-to-use concrete mixing spreadsheet is absolutely necessary. This useful building sheet will give you a number of integration projects for your construction site.

References

1. Concrete Technology by M L Gambhir, Tata McGraw Hill. 3. Concrete technology by A. M. Neville. 1. Brooks, Pearson,

2. Microstructure and Properties of Conctete by P. Kumar Mehta, Prentice Hall.

3. Durability Design of Concrete Structures, by A. Sarja and E. Vesiari. E & FN Spon Publication, 1996.