PVA纤维增强应变硬化水泥基材料韧性性能研究

Study on Toughness of Polyvinyl Alcohol Fiber Reinforced Strain Hardening Cementitions Composites (SHCC)

水泥基材料抗拉强度低、韧性差是其易于开裂、导致结构耐久性低劣的主要原因之一。高模量聚乙烯醇(PVA)纤维可增强水泥基材料韧性,使其呈现准应变硬化和多缝开裂特征,从而改善结构耐久性。本文通过四点弯曲试验得出了不同加载速率和不同配比应变硬化水泥基复合材料(PVA-SHCC)的力-变形曲线并用CONSOFT软件计算断裂能。结果表明,硅灰使材料的抗压强度有所提高,但最大抗弯承载力和变形下降,断裂能随之降低;甲基纤维素使PVA-SHCC脆性增大;随着加载速率的降低,材料表现出更好的应变硬化性能,微裂缝条数增多。

Lower tensile strength and worse toughness of cementitious composites are the dominant reasons for incidental crack and deterioration of durability for reinforced concrete （RC） structures. In this paper, the experimental results indicated that the ductility of the cementitious composites could be enhanced by the high elastic modules Polyvinyl Alcohol （PVA） fiber. In addition, the characteristics of strain hardening and multiple cracks were presented. Consequently, the durability of RC structure could be improved. Force-deflection curves of PVA-SHCC with different mix proportions and loading velocity were achieved by four-point bending tests, also fracture energy was calculated by CONSOFT software. The results indicated that the compressive strength was increased by the silica fume, while the maximum flexural load capacity, deflection and fracture energy were decreased. Meanwhile, the brittleness of PVA-SHCC was improved by the application of methyl cellulose. When the loading velocity was reduced, the number of muhiple cracks would be increased, and the performance of strain hardening behavior would be greatly enhanced.