The concrete formula proportion table is prepared according to the strength, which is divided into C15, C21, C25 and C31. The specific proportions are as follows:

1. One side is C15 concrete, and the mixing ratio is cement: sand: gravel: water = 1: 2.47: 4.76: 1.61. That is to say, one side of C15 concrete needs 284kg of cement, 712kg of sand, 1351kg of gravel and 172kg of water.

2. C21 concrete on one side, the mixing ratio is cement: sand: stone: water = 1: 1.86: 3.79: 1.51. That is to say, one C21 concrete needs 343kg of cement, 637kg of sand, 1311kg of crushed stone and 175kg of water.

3. One side of C25 concrete, the mixing ratio is cement: sand: stone: water = 1: 1.46: 3.23: 1.44. That is to say, one C25 concrete needs 371kg of cement, 582kg of sand, 1287kg of crushed stone and 175kg of water.

4. One side of C31 concrete, the mixing ratio is cement: sand: stone: water = 1: 1.11: 2.72: 1.38. That is to say, one C31 concrete needs 411kg of cement, 512kg of sand, 1252kg of crushed stone and 175kg of water.

Precautions for concrete mixing

1. Material selection: select appropriate cement, aggregate and additives to ensure that they meet relevant standards and regulations. The variety of cement should be selected according to the specific engineering requirements, the aggregate should meet the requirements of strength and particle size, and the additives should be fully tested and verified.

2. Proportion design: carry out reasonable concrete proportion design, taking into account factors such as strength, fluidity and durability. Proportion design should be carried out according to the requirements of specific projects and design standards, and can be calculated through laboratory tests or professional procedures.

3. Water-cement ratio control: Water-cement ratio refers to the mass ratio of water to cement in concrete. The reasonable control of water-cement ratio has an important influence on the strength and durability of concrete. Generally speaking, a lower water-cement ratio can provide better strength and durability.

4. Uniform mixing: When mixing concrete, ensure sufficient mixing to avoid unevenness and accumulation. The mixing time and method should meet the relevant requirements to ensure the uniform distribution of concrete components.