Mechanical, Swelling, and Thermal Properties of Geopolymer Mixture Containing Basic Oxygen Furnace Slag Aggregates

Basic oxygen furnace slag (BOFS) is a waste product generated during steel production. The utilization of BOFS in construction applications is considerably limited because of its inherent characteristics leading to volumetric expansion behavior caused by the chemical reaction between free lime (f-CaO) and water. The main objective of this paper is to investigate the material properties of normal mortar and geopolymer mixtures that contain BOFS aggregates. Three different aggregates were used to compare their performance, including siliceous river sand, fresh BOFS aggregate (within 1-month age), and stockpiled (more than 5-year age) BOFS aggregate. Test methods included a compressive strength test, accelerated mortar bar expansion test, and thermal conductivity test. Test results revealed that (1) geopolymer mixtures containing BOFS aggregate had comparable compressive strength with mortar mixture with river sand, (2) geopolymer mixtures have very low volume expansion, (3) thermal conductivity of geopolymer mixtures having both river sand and BOFS was lower than normal cement mortar mixture containing river sand. Therefore, geopolymer technology seems a key solution for converting BOFS slag into valuable construction materials. Therefore, a geopolymer mixture containing BOFS aggregate can be used as an energy-saving material.