Concrete is divided into several strength grades according to its strength, and the strength grades of concrete are divided according to the cube compressive strength standard values fcu, K, K. The cube compressive strength standard value is a value in the overall distribution of cube compressive strength, and the strength percentage below this value does not exceed 5%, that is, there is a 95% guarantee rate. The strength of concrete is divided into seven grades: C7.5, C 10, C 15, C20, C25, C30, C35, C40, C45, C50, C55, C60, etc. 12.

Mix proportion of concrete refers to the proportional relationship between components (cement, water, sand and stone) in concrete. There are two ways to express it: one is to use 1 m3 of various materials in concrete, such as cement 300 kg, water 180 kg, sand 690 kg and stone 1260 kg; The other is expressed by the ratio of cement per unit mass to various materials and the water-cement ratio of concrete. For example, the precedent can be written as: C:S:G= 1:2.3:4.2, W/C=0.6.

common grade

C20

Water: 175kg cement: 343kg sand: 62 1kg stone: 126 1kg.

The mixing ratio is 0.51:1:1.81:3.68.

C25

Water: 175kg cement: 398kg sand: 566kg stone: 126 1kg.

The mixing ratio is 0.44:1:1.42: 3.17.

C30

Water: 175kg cement: 46 1kg sand: 5 12kg stone: 1252kg.

The mixing ratio is 0.38:1:1.11:2.72.