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M40 grade stands for itâ€™s a mix of concrete with a characteristic compressive strength of 40 N/mm^{2}. The mix design procedure for M40 grade concrete as per ACI Method is discussed.Contents:
M40 Grade Concrete Mix Design Procedure
1. Required Data
- Grade of concrete = M40
- Specific gravity of cement = 3.15
- Specific gravity of Fine aggregate = 2.65
- Specific gravity of coarse aggregate = 2.7
- Bulk density of coarse aggregate = 1600kg/m^{3}
- Fineness modulus of fine aggregate = 3.0
- Maximum size of aggregate = 25mm
- Degree of super vision = Very good
- Non-Air entrained concrete type
2. Mean Design Strength
For very good degree of super vision standard deviation value for required grade of concrete is as follows.Grade of concrete | Standard deviation for different degree of supervisions (N/mm^{2}) | ||
Very Good | Good | Fair | |
M10 | 2.0 | 2.3 | 3.3 |
M15 | 2.5 | 3.5 | 4.5 |
M20 | 3.6 | 4.6 | 5.6 |
M25 | 4.3 | 5.3 | 6.3 |
M30 | 5.0 | 6.0 | 7.0 |
M35 | 5.3 | 6.3 | 7.3 |
M40 | 5.6 | 6.6 | 7.6 |
M45 | 6.0 | 7.0 | 8.0 |
M50 | 6.4 | 7.4 | 8.4 |
M55 | 6.7 | 7.7 | 8.7 |
M60 | 6.8 | 7.8 | 8.8 |
3. Water-Cement Ratio
Effective water cement ration for the design strength of 49.24mpa is not in the below table. So, consider minimum water cement ratio and that is 0.38.Mean design strength after 28 daysÂ (MPa) | Effective water cement ratio | |
Air entrained concrete | Non-air entrained concrete | |
15 | 0.71 | 0.8 |
20 | 0.61 | 0.7 |
25 | 0.53 | 0.62 |
30 | 0.46 | 0.55 |
35 | 0.40 | 0.48 |
40 | - | 0.43 |
45 | - | 0.38 |
4. Water Content and Air Content
For the slump of 35mm and 25mm maximum size of aggregate, water and air contents are selected from the following table and they are Water content = 180 kg/m^{3} Air content = 1.5%Slump/air content | Water content, kg/m^{3} of concrete for max size of aggregate | |||||||
10mm | 12.5mm | 20mm | 25mm | 40mm | 50mm | 70mm | 150mm | |
30-50mm | 205 | 200 | 185 | 180 | 160 | 155 | 145 | 125 |
80-100mm | 225 | 215 | 200 | 195 | 175 | 170 | 160 | 140 |
150-180mm | 240 | 230 | 210 | 205 | 185 | 180 | 170 | - |
Air content % | 3 | 2.5 | 2 | 1.5 | 1 | 1 | 0.3 | 0.2 |
5. Cement Content
Cement content is calculated from the water cement ratio. W/C = 0.38 180/C =0.38 Cement content C = 180/0.38 = 473kg per cu.m of concrete.6. Coarse Aggregate Content
Fineness modulus of fine aggregate = 3.0 Bulk density of coarse aggregate =1600kg/m^{3} Maximum size of aggregate = 25mm Therefore bulk volume of dry rodded coarse aggregate from below table = 0.65Maximum size of aggregate (mm) | Bulk volume of dry rodded coarse aggregate w.r.to fineness modulus | |||
2.4 | 2.6 | 2.8 | 3.0 | |
10 | 0.5 | 0.48 | 0.46 | 0.44 |
12.5 | 0.59 | 0.57 | 0.55 | 0.53 |
20 | 0.66 | 0.64 | 0.62 | 0.6 |
25 | 0.71 | 0.69 | 0.67 | 0.65 |
40 | 0.75 | 0.73 | 0.71 | 0.69 |
50 | 0.78 | 0.76 | 0.74 | 0.72 |
70 | 0.82 | 0.80 | 0.78 | 0.76 |
150 | 0.87 | 0.85 | 0.83 | 0.81 |
7. Fine Aggregate
Fine aggregate quantity is decided by knowing the unit weight of fresh concrete from below table. Fresh concrete density for 25mm size aggregate = 2375kg/m^{3}Maximum size of aggregate (mm) | Density of fresh concrete (kg/m^{3}) | |
Air entrained | Non air-entrained | |
10 | 2190 | 2285 |
12.5 | 2235 | 2315 |
20 | 2280 | 2355 |
25 | 2315 | 2375 |
40 | 2355 | 2420 |
50 | 2375 | 2445 |
70 | 2400 | 2465 |
150 | 2435 | 2505 |