C15, C20, C25 and C30 are commonly used for rural self built houses, and the cement is 325# cement.

Brick concrete structure: C15 strength is used for foundation cushion, and C20 or C25 strength concrete is used for strip foundation, column, slab and beam.

Frame structure: C15 strength is used for foundation cushion, and C30 strength concrete is used for independent foundation, column, slab and beam.

Other conditions: C30 concrete is used for independent foundation, raft foundation, basement, etc.

One cubic meter of C15 concrete, with the mix proportion of cement: Sand: Stone: water = 1:2.47:4.76:0.61. In other words, one cubic meter of C15 concrete needs 284kg of cement, 702kg of sand, 1351kg of gravel and 172kg of water.

One cubic meter of C20 concrete, with the mix ratio of cement: Sand: Stone: water = 1:1.86:3.79:0.51. In other words, a cubic meter of C20 concrete needs 343kg of cement, 637kg of sand, 1301kg of gravel and 175KG of water.

One cubic meter of C25 concrete, with the mix ratio of cement: Sand: Stone: water = 1:1.46:3.23:0.44. In other words, a cubic meter of C25 concrete needs 370kg of cement, 582kg of sand, 1287kg of gravel and 175KG of water.

One cubic meter of C30 concrete, with the mix proportion of cement: Sand: Stone: water = 1:1.11:2.72:0.38. In other words, one cubic meter of C30 concrete needs 400kg cement, 512kg sand, 1252kg gravel and 175KG water.

The above mixing design is only for reference in rural building. Slag powder and water reducing agent should be used for high-grade concrete (above C30) in the mixing plant to avoid bubbles in the concrete, and fly ash should be used for low-grade concrete.