龄期对碾压混凝土双K断裂参数影响的试验研究

Influence of Age on Double-K Fracture Parameters of Roller Compacted Concrete

为了研究龄期对碾压混凝土双K断裂参数的影响,制作了龄期为28,60,90 d共18个楔入劈拉碾压混凝土试件并进行了断裂试验,结合双K断裂参数公式,得到了不同龄期试件的有效裂缝长度、起裂断裂韧度和失稳断裂韧度等断裂参数,并分析了龄期对碾压混凝土断裂性能的影响。试验结果表明:起裂荷载和失稳荷载均随龄期的增大而增大,且起裂和失稳荷载的比值趋于稳定,伴随着龄期的增加,起裂荷载占失稳荷载的比重越来越大;龄期从28 d增加到90 d,起裂和失稳断裂韧度分别增加了0.216 0 MPa·m1/2和0.292 2 MPa·m1/2,起裂和失稳断裂韧度的比值基本在0.5～0.6;有效裂纹长度随龄期的增大而减小,相同尺寸下,龄期越小,裂缝亚临界扩展量越大,试件的韧性越好。

The influence of age on Double-K fracture parameters of roller-compacted concrete(RCC)was investigated via fracture test on eighteen RCC wedge splitting specimens at different ages(28 d,60 d,and 90 d).The effective crack length,initial fracture toughness and unstable fracture toughness of the RCC specimens of different ages were acquired.Results revealed that with the growth of age,the critical pressure for initial cracking and critical pressure for instability both expanded,and the ratio of critical pressure for initial cracking to critical pressure for instability also increased.With the age increasing from 28 d to 90 d,initial cracking toughness K ini IC and unstable cracking toughness K un IC climbed by 0.216 0 MPa·m^1/2 and 0.292 2 MPa·m^1/2,respectively;the ratio of K ini IC to K un IC maintained between 0.5 and 0.6 in general.Effective critical cracking length and subcritical crack extension both changed in a negative relation with age,implying that smaller age results in better toughness of specimens.