The effect of glass waste as an aggregate on the compressive strength and durability of fly ash-based geopolymer mortar

^1,3 Department of Civil Engineering Sciences, University of Johannesburg, South Africa
² Department of Engineering Sciences, University of the Free State, South Africa

^* Corresponding author: ndapandulakawalu@gmail.com

Abstract

Geopolymers have been introduced to limit the use of ordinary Portland cement (OPC), as its production contributes to the emission of about 7% of the world’s carbon dioxide, which has a negative effect on the environment. The present study aimed to investigate the effect of glass-waste aggregate on the mechanical properties of fly ash-based geopolymer and OPC mortars. In the study, fly ash geopolymer and OPC mortar mixtures were prepared using glass-waste as fine aggregate. In addition, geopolymer and OPC mortars were also prepared using silica sand as control mixes. A blended solution comprising sodium silicate and sodium hydroxide was used as an alkali activator in fly ash geopolymer mixtures. Fresh mixtures were subjected to workability measurements, while 50 mm cubes were made for compressive strength testing. Mortar prisms of 25 x 25 x 285 mm were prepared and subjected to drying shrinkage test. From the results, the use of glass-waste aggregate negatively affected the compressive strength of the mortars, regardless of the binder type. Geopolymer mortars made using glass-waste aggregate gave 55% lower compressive strength than those made using silica sand. However, mixtures made using glass waste aggregate exhibited better performance in drying shrinkage than those made using silica sand.