Concrete mix design report


  • Concrete Mix Design M-25
  • Concrete Mix Design – ITS Acceptance
  • ACI Mix Design Example
  • Concrete Mix Design Calculation for M20, M25, M30 Concrete with Procedure & Example
  • Service Details
  • Concrete Mix Design M-25

    This is typical for pavement PCC. Maximum Aggregate Size Specified as No reinforcing steel will be used so the thumbrule pertaining to clear space between reinforcing bars is not applicable.

    Therefore, using the mixing water and air content estimation table , air-entrained PCC with a target 25 mm 1 inch slump and a Enough air-entraining admixture will be added to achieve a 5. Keep in mind that water-reducing admixtures can reduce water requirements by about 5 — 10 percent and several will also increase the entrained air content by about 0.

    Converting weight to volume, the recommended volume of mixing water in one cubic meter one cubic yard of PCC is 0. The amount of entrained air will be 5.

    Water-Cement Ratio Since the specified strength is flexural strength, a conversion factor must be used to obtain an approximate compressive strength in order to use the water-cement ratio vs. A good rule-of-thumb as used in the ACI Code is: where: equals compressive strength Solving for compressive strength, we get about This value is not listed in Table 17 for determining water-cement ratios.

    Therefore, a more involved determination of the water-cement ratio is needed. Water-cement ratios may also be determined using local experience.

    Keep in mind that Table 4 is rarely used in pavement PCC mix design. Additionally, ACI recommends a maximum water-cement ratio for PCC exposed to freezing and thawing in moist conditions such as curbs and gutters or PCC in the presence of deicing chemicals such as PCC pavement slabs of 0. In this instance, assume that local experience dictates a water-cement ratio of around 0. Cement Content Based on the previous mixing water content and water-cement ratio, cement content is calculated to be: The recommended volume of portland cement in one cubic meter one cubic yard of PCC is: Metric English Coarse Aggregate Content Using the coarse aggregate content table with the given nominal maximum aggregate size of This means that the coarse aggregate should occupy 71 percent of the total volume.

    However, this volume of aggregate includes the volume of air between the aggregate particles. Therefore, this 71 percent volume must be converted to a weight of aggregate.

    Concrete Mix Design – ITS Acceptance

    Admixture The admixtures available for concrete are numerous. While the discussion of each admixture is beyond the scope of this article, it is important to be aware of the general types of admixtures available. Other — Corrosion Inhibitors, Coloring Admixtures, etc. This requirement for the over-strength accounts for expected deviations in the strength of the delivered concrete. This design strength needs to be justified, either by field experience or by trial mix.

    The use of field experience to justify concrete strength involves the use of cylinder test results from previous placements to justify the specified strength. ACI provides factors for adjusting the field results based on the quantity of data sample available.

    The use of trial mixes involves the preparation of several design mixes in a laboratory with varying water to cementitious ratios. The results are plotted on a graph of the trial mixes. The mix is selected from the curve. Regardless of the methodology used in the mix design preparation, it is important to ensure that the results being used to justify the strength of the concrete are current, as many of the ingredients in the mix are natural and their properties can change over time.

    ACI permits the use of concrete mixes without test data for concrete strengths of 5, psi and lower when permitted by the SEOR. This latitude is not recommended except in specific isolated circumstances. ACI added the requirement that test results be no more than 12 months old. ACI extended this period to 24 months. As many of the materials are naturally derived, changes in sourcing or other changes may greatly impact the concrete performance.

    Mix Not Appropriate for Use A lot of varying issues can fit in this category. Most commonly, these issues are related to the placement slump — for example, receiving a mix design with a 3-inch slump for a project where all concrete is to be pumped.

    Other issues could include the use of larger than appropriate aggregate specified for a pump mix. With the wide variety of available admixtures and concrete products, virtually every single desired performance requirement is attainable with the proper mix design, making the use of generic concrete mixes unacceptable. Mix Usage Not Indicated Often there will be numerous design mixes on a project, their presence dictated by the need for varying design strengths or varying workability and performance concerns.

    Materials Not Available There are times where the components that make up a concrete mix may not be readily available. Lately, with the closing of coal-fired power generation plants and the scarcity of steel mills, the procurement of Fly Ash and Blast Furnace Slag has become a serious issue. Slag can be shipped from as far away as Brazil.

    Approving a mix with a material that is not readily available is not beneficial to the project and not environmentally sustainable. Compressive Strength Test Age Incorrect ACI is explicit that compressive strength is based on 28 days unless the design drawings or specification indicate otherwise. For high strength concrete, day and day mixes are not uncommon. However, the design mix should achieve the specified strength within the period requested.

    Remediation of structural elements where concrete has not met its design strength becomes more complicated when test information is unavailable for greater lengths of time. Problems with Test Data Errors in test data are hard to find and are mostly the results of a careless error by the preparer of the mix. Mix Design Issues for High Rise Construction High Rise Construction, along with other construction with high concrete demands, bring its own set of issues specifically related to the concrete mix design.

    Selecting the appropriate mixes for these types of projects is complicated, but it is worth mentioning some of the most relevant issues. High Compressive Strength Achieving high strength concrete goes beyond simple water to cementitious content ratio. Special consideration needs to go to the admixtures and the aggregate used. Carefully choosing the aggregate from specific quarries is important, and the sourcing needs to be consistent throughout the project.

    Modulus of Elasticity On tall buildings, it is often not only the strength but the stiffness of the concrete that is critical. The simple ACI equations to calculate the modulus of elasticity often are less accurate for higher strength concretes. ACI provides recommendations for adjusted values when using high strength concrete, but it is still often inaccurate when higher strength concretes come into play.

    The testing associated with the original code writing is one reason for this fall-off in accuracy. The majority of the prescribed provisions for elasticity, shear, etc. Extrapolation of these test results to concrete in the 10, psi and higher range is circumspect. It is, therefore, important to establish an appropriate testing program specifically tailored to the needs of your upcoming building. Tests to arrive at the correct Modulus of Elasticity MOE for a high strength design mix are time-consuming.

    Not all testing laboratories are equipped to perform them, and even lesser numbers of engineers and technicians are qualified to interpret the test results. These tests need to be planned and executed very early in the in the design to allow for adequate fine tuning of the design mix.

    Extended Workability Because of the quantities of concrete, the thickness of the members being poured, and the heights to which the concrete needs to be pumped, concrete for tall buildings requires extended workability.

    Hydration control admixtures and other admixtures help in keeping concrete workable for extended periods. They also help slow down the hydration process in large concrete members. Mix Design: Looking Forward As with many trends in the construction industry, there will be continued advances in concrete. Post-consumer recycled ground glass ground glass harvested from municipal recycling programs is already being tested as a substitute for Fly Ash and Blast Furnace Slag.

    The concrete using this sustainable material was designed to attain strengths up to 14, psi and will be commercially used on a cast-in-place concrete building sometime in the next few months. Reduction in Cement Because of the need to reduce the environmental impact of cement one pound of cement releases one pound of carbon monoxide into the atmosphere , municipalities have considered or passed edicts which require a reduction in cementitious content in the production of concrete.

    If these efforts are successful, then they will undoubtedly affect mix designs in the future. Self-Consolidating Concrete SCC The use of SCC to increase the speed of placement, quality of the finished surface and reduce labor costs is becoming more and more prevalent.

    In the future, more and more sites will be using SCC almost exclusively for formed members for these reasons. From The Plant to the Site Few engineers ever see the inside of the concrete plant which batches and distributes the concrete to project sites. Most concrete projects do not require special inspections at the plant. The engineer is, therefore, reliant on the supplier to properly batch the concrete without supervision.

    It is important for checks and balances to occur on-site to help ensure that any potential issues with the concrete batching are caught and resolved before placement. Initial Receipt of the Concrete on Site When concrete arrives at a construction site, the special inspector must check the batch ticket to ensure the concrete mix conforms to the approved mix.

    Thus, every truck must come with a computerized batch ticket. The batch ticket must indicate the truck number, the total batch size, the strength measured in psi, the batch time, and the amounts of materials added at the plant. The ticket should also indicate the percentage of moisture within the aggregate. The printout from the plant indicating concrete strength and batch size alone is not sufficient for verification of the mix design and any truck without a full batch ticket ought to be rejected since verification of the mix is not possible.

    It is imperative that this review happens when the truck first arrives on site. The Inspector should reject incorrect concrete mixes and instruct the truck to return to the plant. Adding Water on Site The most common reason for low concrete test results is the addition of unauthorized water to the concrete mix at the site.

    Concrete must have no more water in it than is indicated in the approved mix design. The best method to ensure this is to prohibit the addition of any water on site. Unfortunately, when transit time to the site is excessive, and a loss of slump occurs by the time the concrete is ready to be placed on the site, the most common response is the addition of water.

    Occasionally, due to long travel times, a concrete batch plant will send a truck with less than the prescribed amount of water. In these cases, the plant, Special Inspector and SEOR have agreed on a plan of action to combat delayed arrivals and the balance of the water may be added to the concrete at the site.

    After placing concrete from the truck, adding water to the mix is difficult since it is not possible to determine the quantity of concrete left in the truck nor the amount of water that can still be added. The contractor should be required to keep superplasticizer on site, to be used in specific instances to increase workability. The use of superplasticizer in this method should be planned with the SEOR in advance, along with other placement parameters like mixing times and ambient temperatures.

    Test cylinders need to be representative of the concrete being placed and need to be taken at the truck and the point of placement. In the event water was added to the concrete mix after the initial batching either authorized or unauthorized , take test cylinders after all materials have been added. Site Testing The standard tests done at each site include slump, air entrainment, temperature, and unit weight.

    Less common, but very important, is microwave testing. Microwave testing utilizes a microwave to remove the water from a concrete sample. Measurements of the sample before and after being microwaved allow for a field determination of the actual amount of water in the specific concrete sample tested.

    In high strength concrete, it is common to utilize this test for every concrete placement. For other projects, microwave testing may not be utilized but can be used as a tool in troubleshooting problems in the field. If concrete breaks are low on a project, implementing microwave testing can provide in situ information on the water to cementitious material ratio and can help pinpoint the issue, or at least eliminate the water content of the concrete as a potential issue.

    Accordingly, basic contingencies need to be in place should things not go per the initial plan. One common issue is the concrete tester arriving late or not arriving at all.

    Without an inspector onsite, in most jurisdictions, no concrete can be placed. Neither option is desirable. At a later date, test the cores and determine the strength after the application of appropriate reduction factors.

    Low Breaks Happen Even after meticulous planning, inspection, and execution, statistically low concrete strengths can and will happen.

    The concrete special inspector must document where the concrete from each concrete truck is placed within the structure. Concrete Placement Concrete placement consists of the conveying, depositing, and finishing of slabs and curing the concrete. Proper monitoring of each step is important. Once the concrete leaves the truck or pump, or both and placement begins, any changes that occur to the concrete will no longer be telegraphed through the concrete test cylinder results.

    Conveying and Depositing The primary concern when conveying concrete from the mixing apparatus to the point of placement is to avoid concrete segregation. Common issues where segregation can occur are: Free Falling Concrete Dropping concrete from heights over the reinforcement in columns and walls can cause the aggregate to segregate. In general, concrete shall be dropped from a chute when there is a concern about segregation. Over Vibrating Concrete To properly consolidate the concrete, the use of a vibrator is required.

    However, the use of the vibrator as a tool to move the concrete can over-vibrate and segregate the concrete.

    Special consideration needs to go to the admixtures and the aggregate used. Carefully choosing the aggregate from specific quarries is important, and the sourcing needs to be consistent throughout the project. Modulus of Elasticity On tall buildings, it is often not only the strength but the stiffness of the concrete that is critical. The simple ACI equations to calculate the modulus of elasticity often are less accurate for higher strength concretes.

    ACI provides recommendations for adjusted values when using high strength concrete, but it is still often inaccurate when higher strength concretes come into play. The testing associated with the original code writing is one reason for this fall-off in accuracy.

    ACI Mix Design Example

    The majority of the prescribed provisions for elasticity, shear, etc. Extrapolation of these test results to concrete in the 10, psi and higher range is circumspect. It is, therefore, important to establish an appropriate testing program specifically tailored to the needs of your upcoming building.

    Tests to arrive at the correct Modulus of Elasticity MOE for a high strength design mix are time-consuming. Not all testing laboratories are equipped to perform them, and even lesser numbers of engineers and technicians are qualified to interpret the test results. These tests need to be planned and executed very early in the in the design to allow for adequate fine tuning of the design mix.

    Extended Workability Because of the quantities of concrete, the thickness of the members being poured, and the heights to which the concrete needs to be pumped, concrete for tall buildings requires extended workability.

    Hydration control admixtures and other admixtures help in keeping concrete workable for extended periods. They also help slow down the hydration process in large concrete members. Mix Design: Looking Forward As with many trends in the construction industry, there will be continued advances in concrete.

    Post-consumer recycled ground glass ground glass harvested from municipal recycling programs is already being tested as a substitute for Fly Ash and Blast Furnace Slag. The concrete using this sustainable material was designed to attain strengths up to 14, psi and will be commercially used on a cast-in-place concrete building sometime in the next few months. Reduction in Cement Because of the need to reduce the environmental impact of cement one pound of cement releases one pound of carbon monoxide into the atmospheremunicipalities have considered or passed edicts which require a reduction in cementitious content in the production of concrete.

    If these efforts are successful, then they will freeflix tv passcode affect mix designs in the future.

    Self-Consolidating Concrete SCC The use of SCC to increase the speed of placement, quality of the finished surface and reduce labor costs is becoming more and more prevalent. In the future, more and more sites will be using SCC almost exclusively for formed members for these reasons. From The Plant to the Site Few engineers ever see the inside of the concrete plant which batches and distributes the concrete to project sites.

    Concrete Mix Design Calculation for M20, M25, M30 Concrete with Procedure & Example

    Most concrete projects do not require special inspections at the plant. The engineer is, therefore, reliant on the supplier to properly batch the concrete without supervision. It is important for checks and balances to occur on-site to help ensure that any potential issues with the concrete batching are caught and resolved before placement. Initial Receipt of the Concrete on Site When concrete arrives at a construction site, the special inspector must check the batch ticket to ensure the concrete mix conforms to the approved mix.

    Thus, every truck must come with a computerized batch ticket. The batch ticket must indicate the truck number, the total batch size, the strength measured in psi, the batch time, and the amounts of materials added at the plant. The ticket should also indicate the percentage of moisture within the aggregate.

    The printout from the plant indicating concrete strength and batch size alone is not sufficient for verification of the mix design and any truck without a full batch ticket ought to be rejected since verification of the mix is not possible. It is imperative that this review happens when the truck first arrives on site. The Inspector should reject incorrect concrete mixes and instruct the truck to return to the plant.

    Adding Water on Site The most common reason for low concrete test results is the addition of unauthorized water to the concrete mix at the site. Concrete must have no more water in it than is indicated in the approved mix design.

    The best method to ensure this is to prohibit the addition of any water on site. Unfortunately, when transit time to the site is excessive, and a loss of slump occurs by the time the concrete is ready to be placed on the site, the most common response is the addition of water. Occasionally, due to long travel times, a concrete batch plant will send a truck with less than the prescribed amount of water.

    In these cases, the plant, Special Inspector and SEOR have agreed on a plan of action to combat delayed arrivals and the balance of the water may be added to the concrete at the site. After placing concrete from the truck, adding water to the mix is difficult since it is not possible to determine the quantity of concrete left in the truck nor the amount of water that can still be added.

    The contractor should be required to keep superplasticizer on site, to be used in specific instances to increase workability. It is not enough to select a suitable concrete mix; it is also necessary to ensure a proper execution of all the operation involved in concreting. It cannot be stated too strongly that, competently used, concrete is a very successful construction material but, in the literal service of the word, concrete is not fool proof.

    The mix proportions once chosen, cannot expected to remain entirely immutable because the properties of the ingredients cement, sand, aggregate, water and admixture may vary from time to time. The above code clearly mentioned that the method of mix design should not be reported, yet in some mix design reports calculations are given. IS: Mix Design Code on last inside page 7th line state that: This standard does not debar the adoption of any other methods of concrete mix proportioning.

    Accordingly, if a expert conduct mix design as per required specifications and with given materials based on his experiences and published research papers he did not mention the calculations in the report, because the checker could not check the calculations, as the mix design report is based on expert experience and his published research works and these are not with the checker.

    In fact concrete mix design report should not be checked on table, as mix design is not a mathematical problem. It should be practically checked at site itself with the site actual available materials during checking time.

    Then only the mix should be allowed to be used in the construction. Water-cement ratios may also be determined using local experience.

    Service Details

    Keep in mind that Table 4 is rarely used in pavement PCC mix design. Additionally, ACI recommends a maximum water-cement ratio for PCC exposed to freezing and thawing in moist conditions such as curbs and gutters or PCC in the presence of deicing chemicals such as PCC pavement slabs of 0.

    In this instance, assume that local experience dictates a water-cement ratio of around 0. Cement Content Based on the previous mixing water content and water-cement ratio, cement content is calculated to be: The recommended volume of portland cement in one cubic meter one cubic yard of PCC is: Metric English Coarse Aggregate Content Using the coarse aggregate content table with the given nominal maximum aggregate size of This means that the coarse aggregate should occupy 71 percent of the total volume.


    Concrete mix design report