摘要
湿度变化引起的收缩开裂在工程裂缝中占很大比重,而裂缝是混凝土结构性能退化和使用寿命缩短的主要原因之一。高模量聚乙烯醇(PVA)纤维的添加可以增强水泥基材料的韧性,使其呈现准应变硬化和多微缝开裂特性,从而显著改善结构的耐久性。自由收缩试验结果表明,应变硬化水泥基复合材料(SHCC)14d龄期能完成80%以上的总收缩,但纤维掺量对自由收缩的影响不显著。限制收缩试验表明,纤维掺量为1.5%的SHCC裂缝控制率可以达到90%以上,同时最大裂缝宽度控制在40μm左右,成为工程上认为的无害裂缝。因此,SHCC作为修复材料或新建结构的永久性模板,可带来巨大的经济效益和社会效益。圆环试验给出了基于耐久性能优化设计SHCC材料的一种实用方法。
For reinforced concrete （RC） structures, crack is one of the dominant reasons that will lead to performance deterioration and decreased service life. Shrinkage crack caused by moisture variation is common in engineer projects. In this paper, firstly, the experimental results indicated that high elastic modules Polyvinyl Alcohol （PVA） fiber could enhance the ductility of cementitious composites, therefore, the typical behavior of strain hardening and multiple-crack of SHCC would be presented and the durability of RC structures would be increased greatly. Secondly, free shrinkage tests illustrated that more than 80 % total shrinkage of SHCC had been completed during 14 days, whereas PVA fiber had little influence on drying shrinkage deformation. In addition, the fiber could efficently control the generation and propagation of cracks when hindered drying shrinkage occurred. Thirdly, for SHCC with fiber volume content of 1.5 %, the experiment results indicated that the crack-control ratio was more than 90% and the maximum crack width was only about 40tμm. As a result, this type of SHCC could be regarded as harmless crack. At last, it was concluded that SHCC was one kind of repair material or permanent formwork of new buildings, and the ring test could be recognized as a practical method to optimize the design of SHCC durability performance.
出处
《建筑科学》
北大核心
2007年第6期76-79,83,共5页
Building Science
基金
国家自然科学基金资助项目(50378045)
