地聚物稳定废旧沥青混合料的强度与微观结构研究

Strength and Microstructure of Geopolymer Stabilized Recycled Asphalt Mixture

发展高早强和低能耗的新型绿色道路建筑材料对我国公路建设与养护具有重要意义。本文采用地聚物稳定100%的废旧沥青混合料,制备了地聚物稳定冷再生混合料(GCRM),研究了矿渣掺量、水玻璃模数、激发剂用量以及地聚物掺量对GCRM劈裂强度的影响及其时变规律,通过扫描电子显微镜和EDS能谱分析了混合料的微观形貌及结构组成。结果表明,GCRM的早期强度发展较快,相较于水泥乳化沥青稳定冷再生混合料提升明显。当矿渣掺量为30%(质量分数)、水玻璃模数为1.0、激发剂用量为50%(质量分数)、地聚物总掺量为8%(质量分数)时,GCRM具有最佳的早期强度,7 d劈裂强度可达1.7 MPa。微观结构分析表明,GCRM破坏界面处裂缝易出现在地聚物反应程度偏低的位置。此外,水化硅铝酸钙(C-A-S-H)层状凝胶结构的形成更有利于混合料力学性能的发展。

Developing new green road building materials with high early strength and low energy consumption is of great significance to highway construction and maintenance in China.The geopolymer stabilized cold recycled mixture(GCRM)was prepared by using geopolymer to stabilize 100%recycled asphalt mixture in this paper.The effects of slag content,water glass modulus,activator content and geopolymer content on the splitting strength of GCRM with different curing time and its time-varying law were studied.The microscopic morphology and structural composition of the mixture were analyzed by scanning electron microscopy and energy dispersive spectroscopy.The results show that the early strength of GCRM develops rapidly,which is significantly higher than that of cement emulsified asphalt stabilized cold recycled mixture.GCRM has the best early strength and its 7 d splitting strength can reach 1.7 MPa when the slag content is 30%(mass fraction),the water glass modulus is 1.0,the activator content is 50%(mass fraction)and the geopolymer content is 8%(mass fraction).Microstructure analysis shows that the cracks of GCRM failure interface appear in the position with low geopolymer reaction degree.Besides,the calcium aluminosilicate hydrate(C-A-S-H)layered gel structure is more conducive to the development of the mechanical strength for GCRM.