回收轮胎聚合物纤维混凝土干缩性能研究

Study on Drying Shrinkage of Recycled Tyre Polymer Fiber Reinforced Concrete

为研究回收轮胎聚合物纤维(RTPF)对混凝土干缩性能的影响,对素混凝土、RTPF混凝土(体积分数分别为0.1%,0.2%,0.4%和0.8%)和聚丙烯纤维(PPF)混凝土(体积分数为0.1%)进行干缩试验和纤维作用机理分析.结果表明:不同掺量RTPF混凝土比素混凝土坍落度降低8.1%~62.2%,含气量增大11.2%~47.9%;RTPF混凝土的干缩率在0~7 d时增长速率较快,之后逐渐平缓,RTPF的加入降低了混凝土干缩的早期增长速率;混凝土干缩率随RTPF掺量的增加出现先降低后升高的趋势,当RTPF体积分数为0.2%时混凝土干缩率出现最小值,不同掺量RTPF混凝土在7 d和28 d时的干缩率分别比素混凝土降低了14.2%~36.0%和2.9%~27.2%;相同体积分数(0.1%)下PPF混凝土的干缩率比RTPF混凝土低,在抑制混凝土干缩方面体积掺量0.2%的RTPF可替代体积掺量0.1%的PPF;扫描电子显微镜测试表明,RTPF可与混凝土基体有效黏结,并承担来自混凝土基体的收缩应力;通过干缩率的拟合值与实测值对比得到适合RTPF混凝土的干缩计算模型.

To investigate the effect of recycled tyre polymer fiber(RTPF)on the drying shrinkage properties of concrete,dry shrinkage tests and analysis of the mechanism of fiber action were carried out on plain concrete,RTPF(volume fraction is 0.1%,0.2%,0.4%and 0.8%,respectively)concrete and 0.1%polypropylene fiber(PPF)concrete.Results indicated that the slump of RTPF concrete with different contents decreases by 8.1%~62.2%,and the air fraction increases by 11.2%~47.9%as compared with plain concrete.The drying shrinkage rate of RTPF concrete increases rapidly at 0~7 d and then tends to be stabilized.The addition of RTPF reduces the early growth rate of the drying shrinkage of concrete.The drying shrinkage rate of concrete decreases initially and then increases with the increase of RTPF content.When the volume fraction of RTPF is 0.2%,the concrete shows the minimum drying shrinkage rate.The drying shrinkage rates of RTPF concrete with different contents at 7 d and 28 d are 14.2%~36.0%and 2.9%~27.2%,respectively,which are lower than those of plain concrete.The drying shrinkage rate of PPF concrete is lower than that of RTPF concrete at the same volume fraction(0.1%).In terms of the inhibiting concrete drying shrinkage,RTPF with a volume fraction of 0.2%could replace PPF with a volume fraction of 0.1%.The scanning electron microscope showed that RTPF could bond well with the concrete matrix and transfers the shrinkage stress of the concrete matrix.Finally,by comparing the test data and fitting value of drying shrinkage rate,a drying shrinkage calculation model suitable for RTPF concrete was obtained.