应变硬化水泥基复合材料-SHCC韧性性能试验研究

水泥基材料抗拉强度低、韧性差是其易开裂的主要原因之一。高模量PVA纤维可增强基材韧性,使其呈现准应变硬化和多缝开裂特征,改善结构耐久性。通过四点弯曲试验得出了不同加载速率和配比SHCC的力-变形曲线并用CON-SOFT软件计算断裂能。结果表明,硅灰使材料抗压强度有所提高,但最大抗弯承载力和变形下降,断裂能降低。甲基纤维素使SHCC脆性增大。加载速率降低,材料表现出更好的应变硬化性能,微裂缝条数增多。SHCC砂子最大粒径高于ECC,虽达不到后者的最大拉应变,但可降低成本并满足工程需要。韧性性能研究给出了基于耐久性能优化设计和评定SHCC的实用方法。

Study on Toughness of Strain Hardening Cementitious Composites (SHCC)

Lower tensile strength and worse toughness of cementitious composites are the dominant reason of incidental cracks and deterioration of durability for reinforced concrete (RC) structures. The experimental results indicate that high elastic modules Polyvinyl Alcohol (PVA) Fiber can enhance the ductility of the cementitious composites and present strain hardening and multiple cracks. Consequently,durability of RC structure can be improved. Force-deflection curves of PVA-SHCC with different mix proportions and loading velocity were achieved by four-point bending tests. Fracture energy was calculated by CONSOFT software as well. The results show that silica fume increases the compressive strength, while the maximum flexural load capacity, deflection and fracture energy decrease. High performance of methyl cellulose improves the brittleness of PVA-SHCC. When the loading velocity is reduced, numbers of multiple cracks manifold and strain hardening behavior manifest markedly. The maximum sand diameter of SHCC is larger than that of Engineered Cementitious Composites (ECC). Although the ultimate tensile strain is lower than that of the latter, it's suitable for application. Study on toughness of SHCC is one applied method, which can optimize SHCC durability oriented.