Materials design and strength development of a novel cold recycled mixture with asphalt emulsion and geopolymer

Cold recycling of asphalt pavement with asphalt emulsion is an important approach for achieving low-carbon and sustainable development in road engineering. Enhancing the performance of cold recycled mixtures has become a key research focus. The objective of this paper is to develop a novel cold-recycled asphalt mixture stabilised with asphalt emulsion and geopolymer (CRM-GE). Firstly, the effects of mixing sequence, geopolymer content, asphalt emulsion content and curing conditions on the strength of the mixture and its time-dependent law are studied. Then, the microstructure and composition of the mixture are analysed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results show that the optimum amount of asphalt emulsion is different under different geopolymer contents. The indirect tensile strength of the mixture specimen increases with the increase in the curing time and curing temperature. The microstructure analysis indicates that geopolymer reaction and asphalt emulsion demulsification in CRM-GE with 7-day curing are relatively limited, while asphalt film and the geopolymer reaction products are intertwined to achieve a denser microstructure in CRM-GE with 28-day curing. In addition, the element analysis further verifies the result of materials design and micromorphology analysis.