Project on Concrete Mix Design for various grades of Concrete
STIPULATIONS FOR PROPORTIONING.
- Grade Designation: M35
- Type of Cement: OPC 53 Conforming to IS-8112
- Type of Admixture: Fly ash
- Maximum Nominal
Size of Aggregate: 20mm - Minimum Cement Content: 340kg/m^3(From Table 5 of IS-456-Exposure Condition.
- Maximum Cement Content: 450kg(As per code)
- Maximum Nominal
Size of Aggregate: 20mm - Maximum W/C ratio: 0.45(From Table 5 of IS-456)
- Workability: 100mm(slump value for pumpable concrete)
- Degree of Supervision: Good
- Type of aggregate: Crushed angular aggregate.
- Chemical admixture type: Superplasticizer
TEST DATA FOR MATERIALS.
- Specific Gravity: 3.15(Test-IS:2720)
- Mineral admixture used is fly ash conforming to is-12089
- Specific Gravity of fly-ash: 2.90
- Chemical admixture: Superplasticizers (@0.6%) IS9103
- Specific Gravity of Coarse Aggregate: 2.74
- Fine Aggregate: 2.74
- Water Absorption-Coarse aggregate: 0.5 %
- Fine aggregate: 1 %
- Sieve Analysis: Test – IS 2386
- Coarse aggregate: Confirming to
Table 2-IS383 - Fine aggregate : Confirming to
Table 4-IS383(Zone II)
TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE
FCK= fck+1.65s(“S” from Table 2: IS10262)
Fck= 35+1.65×5(Value of standard deviation(s) for different grade of concrete is given in Table 1 of IS456.)
| Fck | = 43.25 N/mm2 |
SELECTION OF WATER-CEMENT RATIO
Maximum W/C ratio: =0.45(TABLE 5 OF IS-456)
SELECTION OF WATER CONTENT
Maximum Water Content: =186 L (Table 2: IS10262)
Above water-content is for 25 to 50mm slump but the slump we require is 100mm. hence we need to increase the water content to get the required slump for good workability. Clause 4.2 of IS1026 suggests an increase of 3% of water content from its original value for every increase of 25mm. Here we have a 50mm increase in the water content hence we have to increase the water content by 6 %.
| Water-content for 100mm Slump | =186+(0.06*186) |
| =197.16 L |
if superplasticizers are also usedused water content can be reduced to get good strength of concrete. Percentage of reduction of water depends on the type of superplasticizers used in the concrete.
| Percentage of Reduction in water content | =20%(assumed) |
| Water content requirement after Super Plasticizers | =198 – (0.20*198) |
| =157.73 | |
| Adopted Water Content | =160 L |
VI. CALCULATION OF CEMENT AND FLY ASH CONTENT
| Adopted Water Cement Ratio | =0.45 |
| Total Cementitious (Cement +Fly ash) requirement | = Water Content / (W/C) ratio |
| =160/0.45 | |
| =355.55 kg |
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 increase depending on experience and research. Here we increased the cementitious content by 1.1 %.
| Final Cementitious Content (Cement and Fly ash) |
= 356*1.1 | |
| =391.6 kg | ||
| Minimum Cement Content required for ‘severe’ exposure |
=340kg | Table 5-IS456 |
| Adopted Cementous content | =391.6 kg | > 340kg |
| Fly ash content requirement | = 391.6 * 0.30 | 30% replacement |
| = 117.48 ~ 118 kg | ||
| Cement Content requirement | =Cementous content – Fly ash | |
| =391.6-117.48 | ||
| = 274.12 |
VII COARSE AND FINE AGGREGATE
| Coarse Aggregate ratio | = 0.62 | Table 3 of 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 |
VIII MIX CALCULATIONS OF M35 GRADE CONCRETE
| 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 | Total Aggregates requirement | = A – (B+C+D+E) |
| =1 -(0.087 +0.041+0.160+0.002) | ||
| =0.71 cu.m | ||
| F | Coarse Aggregate (C.A) | = F * C.A ratio * S.G * 1000 |
| = 0.71*0.63 *2.74 *1000 | ||
| = 1225.6 kg | ||
| G | Fine Aggregate (F.A) | = F * F.A ratio * S.G * 1000 |
| = 0.71*0.37*2.74 *1000 | ||
| =719.8 kg |
Cement Flyash Sand Aggregate Water and needed for M35 grade concrete
| MATERIALS | QUANTITY |
| Cement | 275 kg |
| Flyash | 118 kg |
| Fine Aggregate | 720 kg |
| Coarse Aggregate (20mm) | 1226 kg |
| WATER | 160 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
Stipulations for Concrete Mix Design
- Grade designation : M 50
- Type of cement : OPC 53 grade confirming to IS 8112
- Maximum nominal size of aggregate : 20 mm
- Minimum cement content : 360 kg/m3
- Maximum water-cement ratio : 0.35
- Workability : 50-75 mm (slump)
- Exposure condition : Extreme (for reinforced concrete)
- Method of concrete placing : Pumping
- Degree of supervision : Good
- Type of aggregate : Crushed angular aggregate
- Maximum cement content : 450 kg/m3
Test Results and assumptions.
Specific gravity of cement : 3.12
Specific gravity of Coarse Aggregate : 2.74
Specific gravity of Fine Aggregate : 2.56
Procedure for Concrete Mix Design of M 50 Concrete
1. Target Strength for Mix Proportioning
Target F = fck + 1.65 x s
According to the table 1 of IS-10262:2009
standard deviation, s = 5.0 N/mm2
Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm2
2. Selection of Water/Cement Ratio
From Table 5 of IS-456:2000,
Maximum water-cement ratio = 0.35
3. Selection of Water Content
From Table 2 of IS 456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.
Estimated water content for 100 mm slump =186+(6/100) x 186 =197 liters.
4. Calculation of Cement Content
Water-cement ratio = 0.35
Cement content = 197/0.35 = 562.8 OR 563 kg/m3
From Table 5 of IS 456, minimum cement content for ‘Extreme exposure’ condition = 360 kg/m3
563 kg/m3 > 360 kg/m3, hence, O.K.
5. Proportion of Volume of Coarse Aggregate and Fine Aggregate Content
From Table 3 of IS 10262. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.
In the present case, the water-cement ratio is 0.35. Therefore. the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio).
Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.
NOTE – In case the coarse aggregate is not angular one, then the volume of coarse aggregate may be increased by 10 percent based on experience.
For pumpable concrete, these values should be reduced by 10 percent.
Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.585.
Volume of fine aggregate content =1 – 0.585 =0.415
6. Mix Calculations
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)
= (563/3.12) X (1/1000)
= 0.18 m3
c) Volume of Water = (Mass of water/specific gravity of water) X (1/1000)
= (197/1) X (1/1000)
= 0.197 m3
d) Volume of all aggregate = (a – (b + c ))
= 1 – (0.18 + 0.197)
= 0.623
e) Mass of coarse aggregate = Volume of All Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000
= 0.623 x 0.585 x 2.74 x 1000
= 901.30
f) Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000
= 0.623 x 0.415 x 2.56 x 1000
= 661.87 kg
7. Concrete Mix Proportions
- Cement = 563 kg/m3
- Water = 197 kg/m3
- Fine aggregates = 661.87 kg/m3
- Coarse aggregate = 901.30 kg/m3
- W/c = 0.35