Geopolymer mortars having glassy materials considering mechanical and microstructural features

Abstract

In comparison with ordinary Portland cements, geopolymer-based cements are now gaining prominence as an eco-friendly substitute to decline CO2 emissions in the course of OPC manufacturing. In this study, mechanical/microstructural features of geopolymers under different curing heats using 12 M NaOH as alkaline activator, obsidian and waste glass powder as binder at different dosages (0 %, 25 %, 50 %, 75 % and 100 %) were investigated. The mixture calculations of 5 different series of geopolymer mortars were produced, as stated by ASTM C109. Samples were cured for 4 different temperatures (75, 90, 105 and 120 °C) for 72 h and then kept in ziplock bags at room conditions until the mechanical tests after curing of up to 90-day. At 7-90-day, samples' flexural/compressive strengths were detected, as stated by ASTM C348/349 standards, respectively. Microstructural examinations of mortar samples were also made by ensuing practices: XRD, SEM-EDS and FTIR. Laboratory findings disclosed that an ideal compressive/flexural strength of 52.6/13.75 MPa was obtained from mortars with waste glass and obsidian binder subjected to a curing temperature of 75 and 90 °C. In addition, one can clearly observe that it exists a substantial link between microstructure images obtained from SEM analysis and compressive/flexural strength results. From existing investigation, one could conclude that substitution of obsidian joining high reactive content into waste glass rose mortars’ flexural/compressive strengths. Considering mechanical/microstructural features obtained from the present investigation, it is seen that obsidian, an inert material, and waste glass, a waste material, could be employed separately or together to create a new geopolymer product.