中文摘要：

研究超高性能水泥基复合材料的双K断裂参数，针对水泥基纤维复合材料和水泥基体两种不同材料设计了不同强度等级、不同尺寸以及不同初始缝高比的14组试件，进行3点弯曲梁断裂试验，测定其起裂荷载，并以此计算得到了起裂韧度的控制值；通过测定最大荷载及对应的裂缝张开位移计算失稳断裂韧度。结果表明，两种材料试件的起裂韧度和失稳韧度都随试件抗压强度的增大而增大；随初始缝高比的减小，水泥基纤维复合材料试件的起裂韧度和失稳韧度都明显增大，而水泥基体试件的起裂（失稳）断裂韧度增大不明显；尺寸效应均比较明显，试件尺寸的增大，水泥基纤维复合材料的起裂断裂韧度和失稳断裂韧度增大较为明显，而水泥基体试件呈现一定的离散型。

英文摘要：

Through the tests of 14 sets of three-point bending UHPCC beam specimens with the different compressive strength,sizes and initial crack-depth ratios, their double-K fracture parameters are studied. The initial fracture toughness KICini and unstable fracture toughness K are calculated from the initial load P, the maximum load Pro= and critical crack mouth open displacement CMODc. The results indicate that the K and K of UHPCC and cement- based specimens increase with the increasing of compressive strength. The K and K of UHPCC significantly increase with the decrease of initial crack-depth ratio,but the K （K） of cement-based specimens increase a little. The K and K of UHPCC significantly increase with the increase of specimen size, but that of cement-based specimens present some discreteness.