海水环境下混凝土的断裂能及其应变软化

通过带切口梁的三点弯曲试验和楔形劈拉试验，对完全干燥、半干燥、水浸泡、海水浸泡和5％、23．4％NaCl溶液浸泡的6种不同含水状态的混凝土试件进行了测试，根据荷载-位移曲线和逆向分析，计算得到混凝土的断裂能及其应变软化曲线。结果表明，随着混凝土中水、海水和高浓度盐溶液的侵入，孔隙溶液中液体的表面张力不断增大，造成表面能下降，承载力随之降低，水浸泡后混凝土的最大承载力较干燥时降低19．6％（三点弯曲）和14．5％（楔形劈拉），海水浸泡后下降28．9％和21．7％，高浓度盐溶液浸泡后降幅更大；海水和盐溶液浸泡时后，混凝土断裂能损失24％以上，软化阶段的开裂韧性也明显降低，裂缝更易形成和扩展。从表面能、断裂能和应变软化的角度研究了海水侵入对混凝土材料造成的不利影响。

Fracture Energy and Strain Softening ofConcrete under Seawater Environment

Both Three Points Bending (TPB) test on notched beams and Wedge Splitting Test (WST) were carried out on concrete specimens under six different conditions, under which they were totally dry, partially dry, water immersed, seawater immersed, 5% and 23.4% NaCI solution immersed, respectively. The fracture energy of each type of concrete and their strain softening curves were calculated according to the force-displacement diagrams and inverse analysis method. It was indicated that with water, seawater or salt solution penetrating into concrete, the surface tension of pore liquids in concrete increased, which resulted in the decrease of the surface energy and load bearing capacity of concrete. After water immersed, the maximum bearing loads of specimens' were reduced by 19.6% (TPB) and 14.5% (WST) compared with those of totally dry concrete. And for those of seawater immersed, 28.9% and 21.7% were reduced respectively. Furthermore, fracture energy of concrete was decreased more than 24% and fracture toughness was reduced significantly as well for concrete with high concentration salt solution, which made crack formation in concrete easier. The adverse influence of seawater on concrete materials had been investigated in detail from the aspects of surface energy, fracture energy and strain softening.