废弃玻璃替代河砂对地聚合物砂浆性能的影响

Impact of Substitution of River Sand by Waste Glass on Properties of Geopolymer Mortar

采用废弃玻璃替代天然河砂细骨料,研究了其对粉煤灰-矿渣基地聚合物砂浆力学性能和耐酸性的影响;利用X射线衍射仪(XRD)、傅里叶变换红外光谱(FTIR)和场发射扫描电镜-元素能谱(FESEM-EDS),探究了地聚合物砂浆在养护1~56 d时的结晶相组成和反应进程,重点分析了骨料界面过渡区(ITZ)的发展及受硫酸侵蚀后的破坏情况.结果表明:玻璃和河砂细骨料在养护早期均延缓了地聚合反应速率,全砂组砂浆试块养护28 d时在凝胶体系内的反应逐渐停止;而全玻璃组砂浆试块中的玻璃边缘在碱性环境下溶解出硅相,增大了体系内的n(SiO_(2))/n(Al_(2)O_(3)),提高了基体的后期密实度.地聚合物砂浆在硫酸溶液中的侵蚀机理主要为硅铝酸盐骨架脱铝破坏、碱金属浸出,以及石膏晶体生长所引起的微裂缝和骨料剥落;在经受硫酸浸泡后,玻璃与ITZ处的凝胶基体间仍具有较好的黏结效果,因而具有更低的抗压强度损失及质量损失.

The effects of using waste glass as substitution of natural river sand fine aggregate on the mechanical properties and acid resistance of fly ash-slag based geopolymer mortar were investigated.With the aid of X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),and field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy(FESEM-EDS),the crystalline phase compositions as well as the reaction process of the paste at the curing age from 1 d until 56 d were analyzed.Besides,the development of interfacial transition zone(ITZ)between paste and aggregates before and after sulfuric acid exposure was highlighted.The results show that both glass and sand slow the geopolymerization reaction rates in the early stages,and the reaction of the sand aggregate mortar is gradually stopped after curing up to 28 d.The compactness increase of glass aggregate mortar at later ages is attributed to the dissolution of the glass aggregate edge in alkaline environment,which increase n(SiO_(2))/n(Al_(2)O_(3))for the gel system.The degradation mechanism of the geopolymer mortar in a sulfuric acid environment is found to be based mainly on the destruction of alumina-silicate structure with dealumination,the leaching of metal cations,as well as the micro-expansion microcracks and aggregate falling off due to gypsum crystal growth.However,the glass introduces a better bond with the paste at the ITZ after acid attack,which results in a significantly low compressive strength and mass loss.