超细粉煤灰粒径和掺量对混凝土力学性能的影响研究

Study on the Effect of Fineness and Dosage of Fly Ash on Mechanical Properties of Concrete

超细粉煤灰混凝土是未来混凝土材料发展的主要方向之一。为分析超细粉煤灰混凝土的力学性能,本文对不同龄期、不同超细粉煤灰粒径和掺量条件下混凝土的抗压强度、劈裂抗拉强度以及抗折强度等进行了试验研究。研究结果表明:(1)不同粉煤灰粒径下混凝土拌合物的坍落度均随超细粉煤灰掺量的增大而逐渐增大,但增大的速率却逐渐减小;同一粉煤灰掺量条件下,超细粉煤灰颗粒粒径越小,相应的粉煤灰混凝土的坍落度越大,且其与粉煤灰颗粒粒径减小的幅度呈指数递增关系。(2)超细粉煤灰粒径越小,其在混凝土中的最优掺量就越大,当超细粉煤灰粒径小于5μm时,为提高60 d抗压强度,超细粉煤灰在混凝土中的最优掺量宜为30%。(3)当混凝土养护龄期为60 d时,不同粒径下超细粉煤灰混凝土劈裂抗拉强度和抗折强度都随超细粉煤灰掺量增大出现先增大后减小的变化规律,在超细粉煤灰掺量为20%～30%时,粉煤灰混凝土的劈裂抗拉强度和抗折强度最高。

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. The results shows that： （ 1 ） The slump of concrete mix under different fly ash particle sizes increases with the increase of uhrafine fly ash content, but the rate of increase decreases gradually. Under the same fly ash content, the smaller the particle size of ultra：fine 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 uhra-fine fly ash, the larger the optimum dosage in concrete. When the particle size of uhrafine fly ash is less than 5 Ix m, the optimal dosage of ultrafine fly ash in concrete is 30 % to ensure 60 d compressive strength. （ 3 ） When the concrete curing age is 60 d, 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 ultra.fine 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 %.