Mechanical performance and microstructure of the calcium carbonate binders produced by carbonating steel slag paste under CO2 curing

摘要

Calcium carbonate binders were prepared via carbonating the paste specimens cast with steel slag alone or the steel slag blends incorporating 20% of Portland cement (PC) under CO2 curing (0.1 MPa gas pressure) for up to 14 d. The carbonate products, mechanical strengths, and microstructures were quantitatively investigated. Results showed that, after accelerated carbonation, the compressive strengths of both steel slag pastes and slag PC pastes were increased remarkably, being 44.1 and 72.0 MPa respectively after 14 d of CO2 curing. The longer carbonation duration, the greater quantity of calcium carbonates formed and hence the higher compressive strength gained. The mechanical strength augments were mainly attributed to the formation of calcium carbonate, which caused microstructure densification associated with reducing pore size and pore volume in the carbonated pastes. In addition, the aggregated calcium carbonates exhibited good micromechanical properties with a mean nanoindentation modulus of 38.9 GPa and a mean hardness of 1.79 GPa. (C) 2016 Elsevier Ltd. All rights reserved.