Concrete mixes should meet;. Total Chapter 5 Concrete Mix Design. Calculations. 2. Workability. (slump/Vebe). Compressive strength. Durability. (w/c ratio). Concrete is composed principally of aggregates, a portland or blended cement, and water, and may contain other cementitious materials and/or chemical. NOTE: FOR PROJECTS REQUIRING CONTRACTOR MIX DESIGN, The Engineer shall submit information for concrete mix designs to the.

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Designing Concrete Mixtures. There are three phases in the development of a concrete mixture: specifying, designing, and proportioning. ACI Mix Design. Answer: By use of two electronic databases. The Concrete Mix Design database is a plant-by-plant list of mix designs accepted for each plant. Data on each mix. the materials of concrete, plastic concrete and hardened concrete, is to enable a concrete technologist to design a concrete mix for a particular strength and.

The other factors, which are not directly considered in this design method includes aggregate to cement ratio, degree of compaction and curing. The strength of the concrete is related to the free-water in the mix, and is not dependent on the absorption properties of the aggregates. They have been obtained for a large number of different concrete mixes using different Portland cements and different types of aggregates. The data is applicable to concretes of medium richness cured in water at 20o C. With all other mix variables held constant, values of compressive strength given in Table 1 show that an uncrushed coarse aggregate generally produces a concrete with lower strength than one made with crushed coarse aggregate. If local knowledge indicates that this is not the case, values in Table 1 should be modified accordingly. Factors such as the type of fine aggregate, the maximum size of aggregate and the overall grading have only a small effect on compressive strength. This value is then plotted on Figure 1 and a curve is drawn from this point, parallel to the printed curves until in intercepts a horizontal line passing through the ordinate representing the previously calculated target strength. The lower value must be used. The calculated value must be compared with any specified maximum or minimum value. If the calculated cement content is less than the specified minimum cement content, the latter must be used. If the calculated cement content is higher than a specified maximum, then it is likely that the specification for both strength and workability requirements cannot be met simultaneously with the selected materials.

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Chennakeshava Reddy. Dhruv Sureja. Ravi Singh. No Downloads. Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. Concrete Mix Design 1. Mix design should ensure following objectives. So it is natural in mix design to aim at as lean a mix as possible. Therefore, all possible steps should be taken to reduce the cement content of a concrete mixtures without sacrificing the desirable properties of concrete such as strength and durability.

Basic Considerations 9. Workability It is usually achieved not by increasing the cement content, but by lowering the water at given cement content. Water demand can by lowered by throughout control of the aggregate grading and by using water reducing admixtures. Strength and Durability What is M 20? These mixes are called nominal mixes. Nominal Concrete Mixes and Design mix concrete CA M5 1: Design Mix Concrete Depending upon the degree of control available at site, the concrete mix is to be designed for a target mean compressive strength fck applying suitable standard deviation.

Factors Influencing Choice of Mix Design For concrete of grade M25 it is advisable to use 43 and 53 grade of cement.

Types of Cement A is determined by sieve analysis. The maximum nominal size of C.

But the smaller size of aggregates provide larger surface area for bonding with the mortar matrix which gives higher strength. In the case when the aggregate available from natural sources do not confirm to the specified grading, the proportioning of two or more aggregate become essential Grading of Combined Aggregates It is usually achieved not by increasing the cement content, but by lowering the water demand at a given cement content.

The procedure is based on the research work carried out at national laboratories. IS Method of Mix Design In the absence of such data, the preliminary free water-cement ratio corresponding to the target strength at 28 days may be selected from the relationship shown below However, this will need 28 days for testing of cement.

Depending upon the nominal maximum size and type of aggregate. F Nominal Maximum size of aggregate mm Water Content per cubic metre of concrete kg Sand as percentage of total aggregate by absolute volume 10 40 20 35 40 30 The quantity of material should be sufficient for at least three mm size cube concrete specimens S Method design a concrete mix for reinforced concrete structure for the following requirement. Example Water Cement F.

A Example Determination of fine and Coarse content: Example Step 8 Adjustment for water absorption and free surface moisture in F. A absorbs 0. Example Determination of F.

This can be read from Figure 2. It is also necessary to know or to be able to assume the relative density of the aggregate. An approximation can be made by assuming an average value of specific gravity of 2. The specific gravity of Australian aggregates generally ranges from 2. The proportion of fine aggregate found from Figure 3 will generally produce a satisfactory concrete in the first trial mix, which can then be adjusted as required to meet the prevailing conditions.

To determine the fine and course aggregate contents, multiply the value read from Figure 3 by the total aggregate content. Coarse aggregate content can be subdivided if single sized 10, 20 and 40 mm aggregates are to be combined. The best proportions will depend on aggregate shape and concrete usage, but the following ratios are suggested as a guide: for combination of 10mm and 20mm aggregates.

It is unlikely that the first mix design would achieve the target results. It usually takes a few trials before a satisfactory design is achieved.

After each trial mix, the concrete mix design should be adjusted before the next trial. The following items may be given consideration: Density: The density of the concrete measured during the trial mix should be checked against the assumed density during the mix design, and necessary adjustments should be made accordingly. A slump adjustment of 20 mm can be achieved by changing the water content by 5 kg and fine aggregate by 5 kg.