高延性偏高岭土-粉煤灰基地聚合物的制备及拉伸性能

Preparation and Tensile Property of Metakaolin-Fly Ash Based Engineered Geopolymer Composites

在水玻璃和氢氧化钠配制而成的碱激发剂作用下,以粉煤灰为主要原材料,偏高岭土为辅助材料,共同制备了高延性偏高岭土-粉煤灰基地聚合物(MFA-EGC),并研究了其单轴拉伸性能.结果表明:MFA-EGC试件经单轴拉伸后具有良好的多缝开裂特性,裂缝分布均匀,裂缝间距为2~5mm,残余裂缝平均宽度约为25μm;最优配比试件3,7,28d抗拉强度分别为3.2,3.7,3.8MPa,极限拉伸应变可高达6.8%,6.4%,5.2%,初裂强度分别为1.4,1.5,1.9MPa;3种因素对MFA-EGC试件抗拉性能的影响程度依次为养护温度>偏高岭土掺量>PVA纤维掺量.通过三点弯曲和单裂缝拉伸试验计算出的MFA-EGC应变硬化性能(PSH)指数与由单轴拉伸试验得到的极限拉伸应变变化趋势相吻合,由此很好地解释了这一材料的高延性机理.

Activated by alkaline activator prepared by sodium metasilicate and sodium hydroxide, the metakaolin-fly ash based engineered geopolymer composites(MFA-EGC) was prepared using fly ash as the main raw material and metakaolin as auxiliary material, and uniaxial tensile property of MFA-EGC were explored. The results show that MFA-EGC has good multi-cracking behavior after uniaxial direct tensile test. The distribution of cracks is uniform, and the crack spacing is in the range of 2-5 mm, and the average width of residual cracks is about 25μm. The tensile strength for the optimum proportion at 3, 7, 28 d is 3.2, 3.7, 3.8 MPa respectively, and the ultimate tensile strain can be up to 6.8%, 6.4% and 5.2% respectively, and initial crack strength is 1.4, 1.5, 1.9 MPa respectively. The order of influence of factors on the tensile properties is as follows:curing temperature>metakaolin content>PVA fiber content. Through the three-point bending and the single-crack tensile test, it is shown that the calculated pseudo-strain hardening(PSH) index is consistent with the trend of ultimate tensile strain by the uniaxial direct tensile test, which can well explain its high ductility.