稻壳灰对本地化高延性水泥基材料性能的影响

Effect of Rice Husk Ash on the Performance of Domestic High Ductility Cementitous Composites

为了降低高延性水泥基复合材料的生产成本,提高废弃稻壳的建材资源化利用,利用国产涂油PVA纤维和天然河砂分别替代进口PVA和石英砂,探究本地化高延性水泥基复合材料的配制工艺;在此基础上,试验研究稻壳灰作为辅助胶凝材料替代部分水泥对高延性水泥基复合材料流动度、抗压强度、拉伸性能和弯曲性能的影响。结果表明:采用国产涂油PVA纤维和天然河砂可成功配制强度等级可达C30,且14 d的极限拉伸应变可达到1.44%的国产化高延性水泥基复合材料;水胶比和PVA纤维掺量分别是影响高延性水泥基复合材料抗压强度和拉伸强度的主要因素。相比对照组,随着稻壳灰替代率的增加,浆体流动度由于稻壳灰的吸水性逐渐下降,最大可降低10%;基体14 d抗压强度略有提高后大幅降低;试件抗拉强度呈略微下降趋势,而极限拉伸应变则显著提高,可高达2.94%;基体弯曲强度呈先增加后逐渐降低的趋势,且纯弯段裂纹数量明显增多,裂纹宽度均低于100μm。因此,稻壳灰替代10%的水泥有利于高延性水泥基复合材料抗压强度、极限拉应变和弯曲强度的提高,同时对浆体流动度影响较小。微观分析可知,具有良好火山灰活性的稻壳灰可与水泥水化产物反应,提高胶凝产物总量,同时降低Ca(OH)_(2)数量,进而增强了高延性水泥基复合材料的强度。

This study aims to reduce the cost of high ductility cementitious composites(HDCC)and enhance the utilization of waste rice husks as building materials.The possibility of domestic oiled PVA fiber and natural river sand for HDCC production based on the orthogonal test was investigated;moreover,the workability,compression strength,tensile,and bending performance of HDCC with the substitution of cement by rice husk ash(10%,30%,50%,mass ratio)were systematically researched.Moreover,X-ray diffraction(XRD)was also employed to analyze the hydration products of cementitious materials.The results showed that HDCC possessed the ultimate tensile strain of 1.44%and the compressive strength of C30 could be obtained using domestic oiled PVA fiber and natural river sand;meanwhile,the water-binder ratio and PVA fiber were the main influence on the compressive and tensile strength of HDCC,respectively.Compared with the reference group,as the increment of rice husk ash,the slump of mortar tended to decrease,while the substitution of cement by 10%rice husk ash decreased the slump by 10%.Moreover,the compressive strength tended to first increase slightly and then gradually decreased,while the tensile strength showed a negative correlation;however,the tensile strain of HDCC increased significantly.The bending strength of HDCC increased with the increase of rice husk ash content,while the addition of 10%rice husk ash increased the bending strength by 37.1%;meanwhile,all the crack widths were gradually decreased and under 100μm.Hence,the optimum substitution of cement by rice husk ash at 10%was conducive to improving the ultimate tensile strain,compressive,and bending properties of HDCC,while showing no obvious influence on the slurry mobility.The microstructure analysis revealed that rice husk ash could react with cement hydration products,thus resulting in reducing the Ca(OH)_(2)content and enhancing the strength of HDCC.