According to the question known conditions to calculate the theoretical ratio of C25 concrete;
Concrete strength standard deviation C25-C35 = 5.0
Concrete strength = 25+1.64*standard deviation 5.0 = 33.2
Concrete strength = 25+1.64*standard deviation 5.0= 33.2
Regression coefficient; a b according to the stone species look up the table to get crushed stone a = 0.46 ,b = 0.07
1, according to the strength requirements of the calculation of water-cement ratio;
Cement actual strength = 42.5 * 1.1 = 46.75
W/C=0.46 * 46.75/(33.2+0.46 * 0.07*) = 0.62.75 46.75)=0.62
2, check whether the water-cement ratio is in line with the durability of the maximum permissible water-cement ratio of 0.65, calculated water-cement ratio of 0.62 less than the provisions of
3, to determine the amount of water per cubic meter of concrete;
Select the slump of 35-50mm, the maximum size of crushed stone 31.5-40mm check the table to get the water use of 175kg / m3
W/C = 0.46*46.75/(33.2+0.46*0.07*)=46.75 m3
4. Calculate the amount of cement per cubic meter of concrete;
Water consumption / water-cement ratio = 175/0.62 = 282kg/m3
Check whether the amount of cement is in line with the durability of the minimum permissible amount of cement 260kg/m3, the amount of cement calculated to be 282kg/m3 is greater than that required to comply with the
5. 36%
6, calculate the amount of sand and stone per cubic meter of concrete, according to the weight method;
Knowing that the amount of water per cubic meter of concrete = 175kg/m3, the amount of cement = 282kg/m3, the sand rate = 36%, assuming that the concrete mixture of 2400kg/m3
282 + G + S + 175 = 2400
S/(G+S)=0.36
G+S=2400-282-175=1943kg/m3
S=(G+S)*0.36=1943*0.36=699kg/m3
G=(G+S)-S=1943-699=1244kg/m3
By weight method Calculate the theoretical mix as follows;
Cement 282kg water 175kg sand 699kg gravel 1244kg
Match ratio; 1:0.62:2.48:4.41
7, according to the design of the match ratio to do the laboratory match ratio experimental adjustments, resulting in the laboratory match ratio;
8, the conversion of the construction mix ratio, based on Construction site of the sand, stone moisture content, to find the final actual construction ratio