Compressive strength and microstructure analysis of geopolymer paste using waste glass powder and fly ash

The use of recycled materials in concrete is attractive for reducing the waste and consumption of natural material resources. Geopolymer is an inorganic binder material that has emerged as an alternative to conventional cement binders for the concrete industry. In this study, the compressive strengths and microstructures of geopolymer pastes containing waste glass powder and high-calcium fly ash were investigated. High-calcium fly ash with median particle size of 21.26 mu m was replaced by waste glass powder at the levels of 10%, 20%, 30%, and 40% by weight to produce the geopolymer pastes. The waste glass powders consisted of ground fluorescent lamp glass and ground container glass with median particle sizes of 4.65 and 11.72 mu m, respectively. Sodium hydroxide and sodium silicate were used as activated solutions. The alkaline liquid to binder ratio was 0.6 and that of sodium silicate to sodium hydroxide was 1.0. All samples were cured at 60 +/- 2 degrees C for 48 h and held at 23 +/- 2 degrees C until testing. The results indicated that waste glass powder could be used to replace fly ash to produce geopolymer pastes with 7-d compressive strengths of 34-48 MPa. The dense microstructure, characterized by scanning electron microscopy and mercury intrusion porosimetry, was closely related to the improved compressive strength; the use of 10-20% ground container glass to replace high-calcium FA yielded the optimum results. (C) 2017 Elsevier Ltd. All rights reserved.