Accelerated Weathering of Limestone Bicarbonate Induced CaCO3 Precipitation in A Mixture of Sand, Fly Ash and CaO

Abstract

Excessive generation of CO2 and industrial wastes has sparked environmental concerns around the globe. In this research, Accelerated Weathering of Limestone (AWL) process uses calcium carbonate (CaCO3) to capture CO2 from ambient air. It achieved an absorption efficiency of 31.88 %. The calcium bicarbonate effluent produced via AWL is used to precipitate calcium carbonate in lime mortar (LM) mixture containing sand and calcium oxide (CaO) with fly ash, an industrial waste. This helps develop a novel utilization pathway for the respective wastes via production of a novel green construction material termed bicarbonate lime mortar infused with fly ash (BLMFA). The fly ash addition percentage in bicarbonate lime mortar (BLM) mix are 12.12, 17.15 and 21.63 wt.%. This project also studies the effect of curing time (7, 28 and 88 days) on development of BLMFA strength. Experimental results found that at 7 days, the strength of BLMFA (0.44 to 0.48 MPa) is lower than the conventional LM, which has a strength of 0.52 MPa. However, on 88 days, 17.15 wt.% BLMFA achieved a strength of 0.82 MPa, which is 0.060 MPa higher than the conventional LM sample. In addition, BLMFA also possesses high CaCO3 content of 36.7 to 44 wt.% out of the targeted 54.37 wt.% compared to conventional LM, which could only achieve 27.14 wt.% CaCO3. This indicates that infusion of fly ash can enhance the carbonation efficiency of calcium sources to CaCO3. All in all, AWL process and BLMFA precipitation possess the capability to diminish anthropogenic CO2 while beneficially utilizing industrial waste.