According to the fineness of fly ash, water demand ratio, combustion vector, water content and sulfur trioxide, 45μm sieve allowance (%) is used as fineness index, and it is stipulated that the grade | ash is not more than 12%, the grade I ash is not more than 20%, the water demand ratio of the grade I fly ash is not more than 95%, the grade I ash is not more than 105%, and the combustion vector and combustion. Use of fly ash: Adding fly ash to concrete saves a lot of cement and fine aggregate. Reduce water consumption. The workability of concrete mixture is improved. Improve the pumpability of concrete. Reduce the creep of concrete, reduce hydration heat and thermal expansion. Improve the impermeability of concrete. Increase the decoration of concrete.