Project on Concrete Mix Design for various grades of Concrete
| A | Grade Designation | M35 |
| B | Type of Cement | OPC 53 |
| C | Type of Admixture | Fly ash |
| D | Maximum Nominal Size of Aggregate |
20m |
| E | Minimum Cement Content | 340kg |
| F | Maximum Cement Content | 450kg |
| G | Partial replacement of cement by Fly ash |
30% |
| H | Maximum W/C ratio | 0.45 |
II. TEST DATA FOR MATERIALS
Materials must be tested to find its below physicals and chemical properties. Standard values are considered below.
| A | Cement Used | OPC 53 | |
| B | Specific Gravity of Cement | 3.15 | |
| C | Mineral Admixture | Fly ash | |
| D | Specific Gravity of Fly ash | 2.90 | |
| F | Specific Gravity of | Test – IS 2386 | |
| Coarse Aggregate | 2.74 | ||
| Fine Aggregate | 2.74 | ||
| Admixture PCE based | 1.12 | ||
| G | Water Absorption | Test – IS 2386 | |
| Coarse aggregate | 0.5 % | ||
| Fine aggregate | 1 % | ||
| H | Sieve Analysis | Test – IS 2386 | |
| Coarse aggregate | Confirming to Table 2-IS383 |
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| Fine aggregate | Zone II | Confirming to Table 4-IS383 |
III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE
The strength of concrete may vary depending on the quality of the material, the mixing method and the construction procedures. Therefore the target strength (Fck) must be greater than the required strength of the concrete (fck).
Table 1 of IS456 gives the standard deviation value (s) for different grade concretes.
| Fck | = fck+1.65s | “S” from Table1-IS10262 |
| Fck | = 35+1.65×5 | |
| Fck | = 43.25 N/mm2 |
IV. SELECTION OF WATER-CEMENT RATIO
The maximum water-cement ratios for different grades of concrete are given in Table 5-IS456. You can reduce the water-cement ratio based on your needs.
The water-cement ratio directly affects the strength of the concrete.
| Maximum W/C ratio | =0.45 | Table 5-IS456 |
| Adopted W/C ratio | =0.45 |
V. SELECTION OF WATER CONTENT
| Maximum Water Content | =186 L | Table 2-IS1026 |
The water content above is for a slump of 25 to 50 mm, but according to the specification our concrete requires a slump of 100 mm. Therefore, to get the desired slump, the water content must be increased. Clause 4.2 of IS1026 recommends increasing the water content by 3% to obtain an additional 25 mm slump. Therefore, to obtain a slump of 50 mm in addition to our concrete, the water content must be increased by 6%.
| Water-content for 100mm Slump | =186+(0.06*186) |
| =197.16 L |
As we use super plasticizers we can reduce the water content to gain strength in the concrete. The amount of water-content to be reduced depends on the type of super plasticizer.
| Percentage of Reduction in water content | =20% |
| Water content requirement after SP | =198 – (0.20*198) |
| =157.73 | |
| Adopted Water Content | =160 L |