Experimental Investigation on Macroscopic and Microscopic Mechanical Properties of Geopolymer-Stabilized Macadam

Geopolymer, as a promising inorganic binding material, holds potential for use in constructing base layers for highway pavements. This study aims to evaluate the mechanical properties of geopolymer-stabilized macadam (GSM) at both the micro- and macro-scale by a series of tests, demonstrating that high-Ca GSM is a high-quality material for pavement base layers. The results demonstrated that GSM exhibits outstanding mechanical and fatigue properties, significantly surpassing those of cement-stabilized macadam (CSM). Performance improvements were particularly notable with higher binder-to-aggregate ratios. GSM derived from a high-Ca precursor achieved a relatively higher fatigue life and resistance to permanent deformation under cyclic loading, outperforming CSM. Furthermore, relationship models developed from the indirect tensile fatigue test results provide a valuable framework for evaluating GSM's long-term road performance. Microstructural analyses revealed that geopolymer features a reticulated gel structure and a denser, more continuous internal matrix, which contribute to its superior properties. The interface products of GSM, including C-A-S-H gel and C(N)-A-S-H gel, enhance mechanical interlocking and promote early strength development, accounting for its exceptional mechanical strength and fatigue resistance. These findings offer valuable insights and technical guidance for employing geopolymer as a sustainable and effective alternative to cement-stabilized macadam in base layer construction.