Waste Clay Bricks as a Geopolymer Binder for Pavement Construction

Geopolymer binders that combine aluminosilicate materials (i.e., precursors) with alkali activators are a viable and environmentally friendly alternative to ordinary Portland cement. While fly ash, slag, silica fume, and metakaolin are the most extensively investigated precursor materials, recent studies demonstrate the feasibility of using low amorphous aluminosilicates (LAA) for geopolymer synthesis. Waste clay bricks (WCB) make an excellent LAA material for producing geopolymer binders, considering their chemical and mineralogical properties. Geopolymer binders with enhanced mechanical properties can be produced either by blending WCB with other aluminosilicate materials or by using WCB as the sole precursor, while providing appropriate production conditions, such as high-temperature curing. Until now, in pavement construction, WCB has been investigated only as a subbase material or as an aggregate for concrete. Since WCB is a potential geopolymer source material, it can also function as an alternative cementitious material (ACM), and stabilizing material in pavement construction. This work reviews the recent studies on producing WCB-based geopolymers, with the focus particularly on the properties of raw materials, activator types and their concentrations, curing conditions, blended geopolymer systems, and the mechanical properties of WCB-based geopolymer binders. Simultaneously, different pavement design requirements and currently available specifications for the use of geopolymer concrete were correlated to evaluate their feasibility as an ACM in pavement construction. Based on the current literature, WCB can be proposed as a suitable ACM to develop pavement-grade concrete and more promising results can be obtained by blending WCB with high-calcium sources, such as slag. Therefore, comprehensive studies on geopolymer concrete development, durability, and field performance are recommended.