粉煤灰掺量对混凝土结构断裂性能的影响

Influence on fracture properties of concrete structure by the dosage of fly ash

为了提高混凝土结构的断裂性能,对粉煤灰掺量0～50%的混凝土进行断裂韧度试验研究。采用楔入劈拉法测得试件的双K断裂参数。通过—裂缝尖端张开位移(P-CTOD)曲线上升段能够捕捉到混凝土的起裂荷载PQ,由PQ和初始裂缝长度a0计算出起裂韧度值KIQC,由最大荷载Pmax和有效裂缝长度ac计算出失稳韧度值KICS。其中,有效裂缝长度ac通过裂缝口张开位移(P-CMOD)曲线得到。试验结果表明:掺入粉煤灰能够有效地改善混凝土的断裂性能;粉煤灰掺量在30%时,混凝土的起裂韧度和失稳韧度均达到最高值。

With the aim to improve fracture properties of concrete structure,a test is carried out for the investigation of fracture toughness with the dosage of fly ash changing from 0 to 50%.Wedge splitting specimens are applied to determine the double-K fracture parameters.According to the information provide by the ascending branch of the load-crack tip opening displacement（P-CTOD） curve recorded in the test,the initial cracking load PQcan be evaluated.The initial toughness KQIC can be obtained by inserting PQ and the preformed notch length a0.The unstable toughness KSIC can also be calculated by inserting the maximum load Pmax,and the critical effective crack length ac,in which the critical effective crack length ac is measured by the load-crack mouth opening displacement（P-CMOD） curve.The experimental results show that fly ash can effectively improve the fracture properties of hydraulic concrete dams.When the dosage of fly ash is by 30%,the cube initiation toughness and unstable toughness are in the highest value.