Sustainable concrete production: Mechanical and durability behaviour of slag-based geopolymer containing recycled geopolymer aggregate

Abstract

Geopolymer binders, synthesized by activating aluminous and silicate-rich materials with alkalis, are attracting great interest as an environmentally friendly building material to replace cement due to their low CO2 emissions and the possibility of disposing of industrial wastes. Intensive research on geopolymer binders and the prospect of their future widespread use have raised questions about end-of-life strategies for geopolymer concrete (GPC). In this study, the durability and mechanical properties of new geopolymer concrete (GRAC) produced from aggregate derived from one-part slag-based GPC subjected to ambient curing were investigated. In addition to the properties of recycled geopolymer aggregates (RGAs) such as ASR reactivity, water absorption rate, organic matter content, specific gravity, the effects of RGA size and amount on mechanical strength, SEM analysis, surface topography and length variation of new GRAC produced by adding different proportions of fine and coarse RGAs (30 %, 60 % and 100 %) were investigated. Consequently, it was observed that GRAC exhibited a mechanical strength comparable to that of GPC produced with natural aggregate, while the void content, water absorption rate, surface pores and microcracks of GRAC increased with the increase in RGA content. In addition, the resistance of GRAC to environmental degradation (acid, sulfate, salt and water effect) decreased with the increase in porosity. The high water absorption rate, porous structure and weak interface region (ITZ) of RGAs make GRAC produced with these aggregates more sensitive to external aggressive chemicals.