Recycled waste glass as precursor for synthesis of slag-based geopolymer

Abstract

The current study assesses the effectiveness of recycled waste glass as a precursor in the synthesis of slag-based geopolymer. Fractional substitution of slag was made with powdered waste glass (WG) with 10%, 20%, 30% and 40%-part replacement. The early age, hardened and microstructural properties of slag-waste glass-based binary geopolymer synthesized with 6 M sodium hydroxide solution were assessed. The hardened and microstructural properties were examined on the 28 days cured specimens subjected to 24 h initial heat curing at 60 °C. The presence of alkali cations in the WG speeds up the setting time of the binary geopolymer as slag is partly replaced with WG. The mix proportion with 10% WG achieved a peak 28-day compressive strength of 42.7 MPa. Further, it also attains a low pore volume in the hardened matrix, confirming sorptivity index values and microstructural images. However, the incorporation of higher WG contents causes a significant decrease in mechanical strength with high pore volumes. The energy dispersive spectroscopic analysis showed an enhancement in Si/Al ratio with the incorporation of WG. In addition, the development of calcium silicate hydrates and sodium aluminosilicate hydrates in slag-WG geopolymer was identified from mineralogical studies. These results confirm that WG has a substantial influence on the gel formation mechanism in the matrix and alters the mechanical behaviour. The outcomes of the present study encourage the incorporation of WG as a fractional substitute of slag in the manufacturing process of sustainable geopolymer binders.