There are several widely utilize concrete kinds,such as road portland cement, portland cement, common cement and slag cement.And the intensity of cement concrete decreases in turning.
Requirements on the coarse aggregate: Maximum particle size of the crushed stone should be under 30 mm and sandstone no more than 20 mm. Crushing value of the coarse aggregate should be under 12%, no more than 20%. Coarse aggregate needle flakiness content should be no more than 10%. Soil contained in the coarse aggregate will decrease the bending strength and shrinkage of the concrete.
Requirements on the fine aggregate: With the increase of sand fineness modulus, the flexural strength and compressive strength are slightly enhanced. When the sand is more and more coarse, the contribution of sand to the locking force gradually increases, and the increase in the locking force will inevitably lead to the increase of the flexural strength.
Requirements on the cement: With the increase of the amount of cement, the flexural strength of concrete increases, the compressive strength of concrete increases about 35% when the unit cement dosage increases 100kg / m3, the flexural strength of gravel concrete increases only 5%, but the flexural strength of crushed stone concrete increase about 12%.
When the water-cement ratio increases, the flexural strength decreases slowly and the compressive strength decreases rapidly at the same cement content. At the same time, the bending strength can be significantly improved with increasing cement dosage or decreasing water-cement ratio.