Project on Concrete Mix Design for various grades of Concrete
AIM : To calculate the concrete mix design for M35 grade concrete with fly ash.
Step 1 : Parameters for mix design
| A | Grade Designation | M35 | |
| B | Type of Cement | OPC 53 | IS 12269 |
| C | Type of Admixture | Fly ash | |
| D | Maximum Nominal Size of Aggregate |
20mm | Table 2 IS 10262-20009 |
| E | Minimum Cement Content | 340kg/m^3 | Table 5 IS-456-2000 |
| F | Maximum Cement Content | 450kg/m^3 | Table 5 of IS 456-2000 |
| G | Partial replacement of cement by Fly ash |
30% | as per requirement |
| H | Maximum W/C ratio | 0.45 | Table 5 IS-456-2000 |
| I | Workability | 100mm | |
| J | Chemical Admixture | PCS Type |
Step 2 : Test data for materials.
Various laboratory tests on materials are required to use in this action. Standard values are assumed below.
-
A Cement Used OPC 53 Confirming to IS-8112 B Specific Gravity of Cement 3.15 Test – IS: 2720 C Mineral Admixture Fly ash Confirming to IS-3812 Part 1 D Specific Gravity of Fly ash 2.90 E Chemical Admixture @0.6% IS-9103 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-IS 383 Fine aggregate Zone II Confirming to Table 4-IS 383
Step 3 : TARGET STRENGTH FOR MIX PROPORTIONING
f’ck =fck + 1.65 s
where,
f’ck = target average compressive strength at 28 days,
fck = characteristics compressive strength at 28 days, and
s = standard deviation.
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm^2.
Therefore, target strength = 35 + 1.65 x 5 = 43.25 N/mm^2.
Step 4 : Selection of water-cemet ratio
The maximum water-cement ratio for different grades of concrete is given in Table 5-IS456. We can reduce the water-cement ratio based on your requirements. The Water-cement ratio directly affects the strength of the concrete.
| Maximum W/C ratio | =0.45 | Table 5 IS-456 |
| Adopted W/C ratio | =0.45 |
Step 5 : Selection of water content
| Maximum Water Content | =186 L | Table 2 IS1026 |
Above water-content is for 25 to 50mm slump, but we need 100mm slump for our concert as per specification. So we need to increase the water-content to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence we to increase water content by 6% to get an additional 50mm slump for our concrete.
| Water-content for 100mm Slump | =186+(0.06*186) |
| =197.16 L |
Since we are using superplasticizers water-content can be reduced inorder to get strength in concrete. The amount of water-content to be reduced depends on the type of superplasticizer.
| Percentage of Reduction in water content | =20% |
| Water content requirement after SP | =198 – (0.20*198) |
| =157.73 | |
| Adopted Water Content | =160 L |
| Adopted Water Cement Ratio | =0.45 |
| Total Cementitious (Cement +Fly ash) requirement | = Water Content / Water-Cement ratio |
| =160/0.45 | |
| =355.55 kg/m^3 |
Since Fly ash is used the amount of Cementitious content (Cement+Fly ash) shall be increased to get good workability and strength. The percentage of cementitious content to be increased depends on the experience and research. Here we have increased the cementitious content by 10%.
| Final Cementanious Content (Cement+Fly ash) |
= 356*1.10 | |
| =391.6 kg/m^3 | ||
| Minimum Cement Content required for ‘severe’ exposure |
=340kg/m^3 | Table 5-IS456 |
| Adopted Cementious content | =391.6 kg/m^3 | > 340kg/m^3 |
| Fly ash content requirement | = 391.6 * 0.30 | 30% replacement |
| = 117.48 ~ 118 kg/m^3 | ||
| Cement Content requirement | =Cementious content – Fly ash | |
| =391.6-117.48 | ||
| = 274.12/m^3 |
Calculation of Super Plasticiers @ 0.6 percent to the mass of cementitious content = = 391.6*(0.6/100) = 2.35 kg
Step 7 : Proportion of C.A and F.A
| Coarse Aggregate ratio | = 0.62 | Table 3 IS-10262 (For W/C =0.5) |
| Coarse Aggregate ratio for 0.45 w/c ratio |
= 0.63 | (adding 0.01 for every decrease .05 and vice versa) |
| Final Fine Aggregate ratio | = 0.37 | (1-0.63) = 0.37 |
| A | Volume of Concrete | = 1 cu.m |
| B | Total Volume of Cement | = Cement/(S.G*1000) |
| = 275/(3.15*1000) | ||
| = 0.087 cu.m | ||
| C | Total Volume of Fly ash | = Flyash/(S.G*1000) |
| = 118/(2.5*1000) | ||
| = 0.041 cu.m | ||
| D | Volume of Water | =Water /(S.G*1000) |
| = 160/(1*1000) | ||
| = 0.160 cu.m | ||
| E | Volume of Superplasticizers | = Superplasticizers /(S.G*1000) |
| = 2.35/(1.12*1000) | ||
| = 0.002 cu.m | ||
| F | Total Aggregates requirement | = A – (B+C+D+E) |
| =1 -(0.087 +0.041+0.160+0.002) | ||
| =0.71 cu.m | ||
| G | Coarse Aggregate (C.A) | = F * C.A ratio * S.G * 1000 |
| = 0.71*0.63 *2.74 *1000 | ||
| = 1225.6 kg/m^3 | ||
| H | Fine Aggregate (F.A) | = F * F.A ratio * S.G * 1000 |
| = 0.71*0.37*2.74 *1000 | ||
| =719.8 kg/m^3 |
| S.No. | MATERIALS | QUANTITY |
| 1 | Cement | 275 kg/m^3 |
| 2 | Flyash | 118 kg/m^3 |
| 3 | Fine Aggregate | 720 kg/m^3 |
| 4 | Coarse Aggregate (20mm) | 1226 kg/m^3 |
| 5 | WATER | 160 L |
| 6 | PCE based SuperPlasticizer | 2 L |
To find the design mix ratio divide the calculated value of all materials by the weight of cement. Therefore Mix Ratio of M35 Grade concrete by weight is Cement : Flyash: F.A : C.A : Water = 1:0.4:2.6:4.46:0.58.
NOTE – Aggregates should be used in saturated surface dry condition. If otherwise, when computing the requirement of mixing water, allowance shall be made for the free (surface) moisture contributed by the fine and coarse aggregates. On the other hand, if the aggregates are dry the amount of mixing water should be increased by an amount equal to the moisture likely to be absorbed by the aggregates. Necessary adjustments are also required to be made In mass of aggregates. The surface water and percent water absorption of aggregates shall be determined according to IS 2386.
Step 10 : The slump shall he measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall he reworked for the actual water content and checked for durability requirements.
Step 11 : Two more trials having variation of ± 10 percent of water-cement ratio in Step 10 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall he plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.
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Aim : Calculate the Concrete Mix Design for M50 grade concrete.
AIM : To calculate the concrete mix design for M50 grade concrete.
Step 1 : Parameters for mix design
| A | Grade Designation | M50 | |
| B | Type of Cement | OPC 53 | IS 8112 |
| C | Exposure condition | Extreme | |
| D | Maximum Nominal Size of Aggregate |
20mm | Table 2 IS 10262-20009 |
| E | Minimum Cement Content | 340kg/m^3 | Table 5 IS-456-2000 |
| F | Maximum Cement Content | 450kg/m^3 | Table 5 of IS 456-2000 |
| G | Degree of supervision | Good | |
| H | Maximum W/C ratio | 0.35 | Table 5 IS-456-2000 |
| I | Workability | 100mm | |
| J | Chemical Admixture | Super plasticizer |
Step 2 : Test data for materials.
Various laboratory tests on materials are required to use in this action. Standard values are assumed below.
-
A Cement Used OPC 53 Confirming to IS-8112 B Specific Gravity of Cement 3.12 Test – IS: 2720 C Chemical Admixture @0.6% IS-9103 D Specific Gravity of Test – IS 2386 Coarse Aggregate 2.74 Fine Aggregate 2.56 Admixture PCE based 1.12 E Water Absorption Test – IS 2386 Coarse aggregate 0.5 % Fine aggregate 1 % F Sieve Analysis Test – IS 2386 Coarse aggregate Confirming to Table 2-IS 383 Fine aggregate Zone II Confirming to Table 4-IS 383
Step 3 : TARGET STRENGTH FOR MIX PROPORTIONING
f’ck =fck + 1.65 s
where,
f’ck = target average compressive strength at 28 days,
fck = characteristics compressive strength at 28 days, and
s = standard deviation.
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm^2.
Therefore, target strength = 50 + 1.65 x 5 = 58.25 N/mm^2.
Step 4 : Selection of water-cemet ratio
The maximum water-cement ratio for different grades of concrete is given in Table 5-IS456. We can reduce the water-cement ratio based on your requirements. The Water-cement ratio directly affects the strength of the concrete.
| Maximum W/C ratio | =0.45 | Table 5 IS-456-2000 |
| Adopted W/C ratio | =0.35 |
Step 5 : Selection of water content
| Maximum Water Content | =186 L | Table 2 IS 1026 |
Above water-content is for 25 to 50mm slump, but we need 100mm slump for our concert as per specification. So we need to increase the water-content to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence we to increase water content by 6% to get an additional 50mm slump for our concrete.
| Water-content for 100mm Slump | =186+(0.06*186) |
| =197.16 L |
Since we are using superplasticizers water-content can be reduced inorder to get strength in concrete. The amount of water-content to be reduced depends on the type of superplasticizer.
| Percentage of Reduction in water content | =27% |
| Water content requirement after SP | =198 – (0.27*198) |
| =143 L | |
| Adopted Water Content | =143 L |
| Adopted Water Cement Ratio | =0.35 |
| Cement content | = Water Content / WaterCement ratio |
| =143/0.45 | |
| =410 kg/m^3 |
Calculation of Super Plasticiers @ 0.6 percent to the mass of cementitious content = = 410*(0.6/100) = 2.46 kg
Step 7 : Proportion of C.A and F.A
| Coarse Aggregate ratio | = 0.62 | Table 3 IS-10262 (For W/C =0.5) |
| Coarse Aggregate ratio for 0.35 w/c ratio |
= 0.65 | In the present case, the water-cement ratio is 0.35. Therefore, the volume of coarse aggregate is required to be increase to decrease the fine aggregate content. as the water-cement ratio is lower by 0.10, the proportion of the volume of coarse aggragate is increased by 0.02(at the rate of -/+0.01 for every +-0.05 change in the water cement ratio = (0.65) |
| For pumpable concrete | Value should reduced by 10% | |
| Therefore, volume of C.A | = 0.65 x 0.90 | =0.585 |
| Volume of fine aggregate | =1-0.585 | 0.415 |
| A | Volume of Concrete | = 1 cu.m |
| B | Total Volume of Cement | = Cement/(S.G*1000) |
| = 410/(3.12*1000) | ||
| = 0.131 cu.m | ||
| C | Volume of Water | =Water /(S.G*1000) |
| = 143/(1*1000) | ||
| = 0.143 cu.m | ||
| D | Volume of Superplasticizers | = Superplasticizers /(S.G*1000) |
| = 2.46/(1.12*1000) | ||
| = 0.002 cu.m | ||
| E | Total Aggregates requirement | = A – (B+C+D+E) |
| =1 -(0.131 +0.143+0.002) | ||
| =0.719 cu.m | ||
| F | Coarse Aggregate (C.A) | Volume of all aggregate x volume of coarse aggregate x specific gravity of coarse aggregate x 1000 |
| =0.719x0.585x2.74x1000 | ||
| = 1152.48 kg/m^3 | ||
| G | Fine Aggregate (F.A) | Volume of all aggregate x volume of fine aggregate x specific gravity of fine aggregate x 1000 |
| =0.719x0.415x2.56x1000 | ||
| =763.86 kg/m^3 |
| S.No. | MATERIALS | QUANTITY |
| 1 | Cement | 410 kg/m^3 |
| 2 | Water cement ratio | 0.35 |
| 3 | Fine Aggregate | 763.86 kg/m^3 |
| 4 | Coarse Aggregate (20mm) | 1152.48 kg/m^3 |
| 5 | WATER | 143 L |
| 6 | PCE based SuperPlasticizer | 2 L |
Trial Mix ratio- 410:764:1153=1:1.86:2.80 (C:FA:CA)
NOTE – Aggregates should be used in saturated surface dry condition. If otherwise, when computing the requirement of mixing water, allowance shall be made for the free (surface) moisture contributed by the fine and coarse aggregates. On the other hand, if the aggregates are dry the amount of mixing water should be increased by an amount equal to the moisture likely to be absorbed by the aggregates. Necessary adjustments are also required to be made In mass of aggregates. The surface water and percent water absorption of aggregates shall be determined according to IS 2386.
Step 10 : The slump shall he measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall he reworked for the actual water content and checked for durability requirements.
Step 11 : Two more trials having variation of ± 10 percent of water-cement ratio in Step 10 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall he plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.