Assessing viability and leachability in fly ash geopolymers incorporated with rubber sludge

Abstract

This study explores the innovative use of rubber sludge (RS) from glove manufacturing as a partial replacement for fly ash (FA) in geopolymer production. The research investigates the physical properties, functional group analysis, microstructural analysis, phase analysis and compressive strength. The partial replacement of different types of RS, such as activated sludge (AS), pre-leaching sludge (PLS) and coagulant sludge (CS), will affect differently on the geopolymer integrity and performance. CS enriched with high calcium content, facilitated the formation of a denser geopolymer matrix with C(N)-A-S-H gel in conjunction with C-S-H, C-A-S-H and N-A-S-H gels, enhancing the compressive strength of FA/CS geopolymers up to 70.4 MPa, surpassing FA/AS and FA/PLS geopolymers. The fly ash/rubber sludge geopolymers exhibited compressive strengths ranging from 20.5 to 70.4 MPa, not only meeting ASTM standards for construction but also effectively immobilizing hazardous metals, particularly Zn (>98.4 %), the Zn leaching in geopolymers was reduced by more than 87.4 % compared to the rubber sludge itself, thereby mitigating environmental toxicity. This utilization addresses significant industrial waste management issues, providing a cost-effective and environmentally friendly alternative for construction. The findings contribute to advancing sustainable building materials and advocate for equitable utilization of industrial waste resources.