Study on the effect of fineness and dosage of fly ash on mechanical properties of concrete

Ultrafine fly ash concrete is one of the main directions for the development of concrete materials in the future. In order to study the mechanical properties of ultra-fine fly ash concrete, the compressive strength, splitting tensile strength and flexural strength of concrete under different ages and different ultra-fine fly ash particle sizes and dosages were tested. (1) The slump of concrete mix under different fly ash particle size increases with the increase of ultrafine fly ash content, but the rate of increase decreases gradually. Under the same fly ash content, the smaller the particle size of ultrafine fly ash particles, the greater the slump of the corresponding fly ash concrete, and it has the exponential relationship between the particle size and the particle size of fly ash. (2) The smaller the particle size of ultra-fine fly ash, the larger the optimum dosage in concrete. When the particle size of ultrafine fly ash is less than 5μm, the optimal dosage of ultrafine fly ash in concrete is 30% to ensure 60d compressive strength. (3) When the concrete curing age is 60d, the splitting tensile strength and flexural strength of ultra-fine fly ash concrete under different particle sizes increase first and then decrease with the increase of ultrafine fly ash content. The law of variation is that the split tensile strength and flexural strength of fly ash concrete are the highest when the content of ultrafine fly ash is 20%-30%.