Characteristic study of geopolymer fly ash fine aggregate and its influence on partial replacement of M-sand in the strength properties of mortar

Abstract

The utilization of fly ash waste from thermal power stations as a value-added product and the search for alternatives to traditional fine aggregates in concrete production are indeed important steps toward addressing environmental concerns and promoting sustainable construction practices. Applying the geopolymerization technique in the manufacture of fine aggregates is proving to be one of the greatest methods to utilize the waste materials instead of employing them directly. In this study, Geopolymer Fly ash Fine Aggregate (GFFA) was manufactured by fly ash geopolymerization and introduced as a partial M-sand substitute in cement mortar to mitigate both challenges. Physical, chemical, and microstructural properties of GFFA were satisfactory to ensure its application in cement mortar and concrete. The addition of 30 % GFFA to the cement mortar resulted in higher compressive, tensile and flexural strength values of 14.086 %, 13.03 % and 13.36 % over control mix which is attributed from the increased calcium silicate hydrate (C-S-H) and sodium aluminosilicate hydrate (N-A-S-H) formation. Relationship between W/C ratio and compressive strength was derived and Abram constants have been obtained as 49.47 and 3.743 for 28th day. Relationships between split tensile strength, compressive strength and flexural strength were derived and were compatible with the previous studies.