孔隙水吸(压)力对非常早期混凝土裂纹扩展的影响

Crack propagation in concrete at very early ages roles of pore moisture suction(pressure)

为了探讨孔隙水对非常早期混凝土裂纹的影响,本文以有限深度混凝土板和半无限深板为研究对象,考虑混凝土受孔隙水吸力与孔隙水压力的作用,求得非常早期混凝土板的应力强度因子解析式;并绘出应力强度因子-裂纹深度曲线,探讨裂纹的失稳扩展,并确定了裂纹经历扩展、稳定、再次失稳扩展并贯穿混凝土板的深度范围。研究结果显示:裂纹面所受幂函数分布吸力指数越大,初始裂纹越稳定;非常早期混凝土板中孔隙水的表面蒸发率越高,初始裂纹越容易失稳扩展。这些探究有助于更好地了解非常早期混凝土材料的性能,以及更好地设计与维护混凝土结构。

The finite deep concrete slabs and a semi-infinite plate were analyzed respectively in this paper. Considering the pore moisture suction and pore moisture pressure of concrete,the weighted function method and numerical integration were used for the determination of stress intensity factor of very early-ages concrete slab when the initial surface defects or cracks were less or greater than the desiccation depth. Meanwhile,the fracture toughness of very early-ages concrete was obtained,and then drawn the stress intensity factor crack depth curve. The crack propagation mechanism and influencing factors were studied. The results show that when the crack was subjected to the distributed force of the different power function,in which the initial crack will extend,and after that whether it will stop extending or extend unsteadily until throughout the whole concrete slab. The larger the power function distribution index of the crack face was,the less the initial crack was hard to extent unsteadily. The higher the surface evaporation rate of pore moisture in concrete slabs at very early-ages,the deeper the formation of dry layer,so that the initial crack is easier to extent unsteadily. The purpose of these investigations is to better understand the properties of very early concrete materials and to minimize the risk of very early cracking.