Investigation on effect of fly ash based geopolymeric coated BOF Steel Slag as Coarse Aggregate in concrete

GEOPOLYMERIC COATED STEEL SLAG BASED CONCRETE

Abstract

Considering the notable depletion of natural resources, leveraging basic oxygen furnace (BOF) steel slag (SS) aggregate as a replacement for natural coarse aggregate in concrete presents a promising technological response. The expansive properties of SS, attributed from the existence of free-CaO, present obstacles in achieving efficient utilization of concrete. This study explores the use of fly ash-based geopolymer-coated steel slag aggregate within a geopolymer matrix concrete, focusing on its influence on the compressive performance of the concrete. Three geopolymer pastes with varying molarities of sodium hydroxide (6M, 12.5M, and 16M), each with equal sodium silicate content, are considered experimental parameters for the complete replacement of natural coarse aggregate. Preliminary examinations encompass morphological, mineralogical, and microstructural analyses of fly ash and BOF steel slag, employing techniques such as XRF, SEM, XRD, FT-IR spectroscopy, and Optical microscopy. Furthermore, a series of axial compression tests are conducted on geopolymer-coated steel slag geopolymer concrete. The findings reveal that geopolymer paste with higher molarity establishes superior physical bonding between SS and the concrete matrix, exhibiting enhanced inhibition of SS expansion and consequently resulting in superior compressive strength. This research emphasizes the effective utilization of BOF SS coated with fly ash geopolymer as coarse aggregate in an unreinforced concrete product made with a fly ash-based geopolymer binder. This approach reduces waste, improves material handling, and mitigates environmental pollution.