养护环境与配合比对PVA-FRCC收缩性能的影响

Effect of Curing Environment and Mix Proportion on Shrinkage and Quality Loss of PVA-FRCC

通过14组聚乙烯醇纤维水泥基复合材料(PVA-FRCC)试件的收缩试验,研究了纤维体积率、水胶比、砂胶比和养护环境对PVA-FRCC收缩性能与质量损失的影响。结果表明:加入PVA纤维对减小水泥基材料长期收缩的作用较小,对降低其早期收缩的作用较大,对质量损失的影响也较小;PVA-FRCC的收缩值和质量损失率随水胶比的提高而增大,随砂胶比的提高而降低;高水胶比/高砂胶比试件和低水胶比/低砂胶比试件的收缩均不大,而中等水胶比/低砂胶比试件的收缩较大;在同一龄期,高水胶比/高砂胶比试件的质量损失率高于低水胶比/低砂胶比试件;环境湿度越高,PVA-FRCC试件的中后期收缩值越小,但早期有可能相反。通过电镜试验反映的材料内部微观形貌对部分收缩现象进行了解释。给出收缩及质量损失率随时间变化的数学表达式,计算结果与试验结果吻合较好。

Based on the shrinkage test of 14 groups of specimens of polyvinyl alcohol fiber reinforced cementitious composite(PVA-FRCC),the effect of fiber volume fraction,water-binder ratio,sand-binder ratio and curing environment on the shrinkage performance and mass loss of PVA-FRCC was studied.The results show that adding PVA fiber has little effect on reducing the long-term shrinkage,but has a significant effect on reducing the early shrinkage of cement base materials,and also has little effect on mass loss rate of specimens.The shrinkage value and mass loss rate of PVA-FRCC increase with the increase of water-binder ratio,but decrease with the increase of sand-binder ratio.The shrinkage of specimens with high water-binder ratio/high sand-binder ratio and specimens with low water-binder ratio/low sand-binder ratio is small,while the shrinkage of specimens with medium water-binder ratio/low sand-binder ratio is large.At the same age,the mass loss rate of specimens with high water-binder ratio/high sand-binder ratio is higher than that of specimens with low water-binder ratio/low sand-binder ratio.The higher the ambient humidity,the smaller the shrinkage value of PVA-FRCC specimens in the mid to later stage,but it may be greater at the early stage.Some shrinkage phenomena are explained by the microscopic morphology of the material reflected by the SEM test.The mathematical expressions of shrinkage and mass loss rates to time are given,and that are in good agreement with the experimental results.