Effects of accelerated carbonation and high temperatures exposure on the properties of EAFS and BOFS pressed blocks

Abstract

The accelerated carbonation of steel slag can improve its subsequent application as construction materials and can also store CO2 as stable minerals. Due to the differences in the production process, electric arc furnace slag (EAFS) and basic oxygen furnace slag (BOFS) acquire diverse physical and chemical properties, which expected to perform differently upon accelerated carbonation. Especially considering the potential use as green building material, thereby may be subject to fire risk. This research aims at comparing the influence of carbonation temperature, CO2 pressure, and carbonation time on mechanical properties and carbonation efficiencies of EAFS and BOFS pressed blocks, and emphasizing on their performances under elevated high temperatures. Results show that BOFS block has a much better performance than EAFS block, with about twice the compressive strength and CO2 uptake, owing to the higher calcium content and more reactive calcium mineral (portlandite) existed. The strengths of both two types of steel slag pressed blocks were found to increase with the increase of high temperature exposure up to 400 °C due to subsequent hydration reaction induced by elevated temperature. Although a slight decrease of compressive strength can be found after further heating at 600 °C, the residual strength was still comparably higher than that at 20 °C. However, with further increase of heating temperature up to 800 °C, a significant reduction in strength was noticed for both EAFS and BOFS blocks, associated to the decomposition of carbonates phases as the main contributor of bearing-strength within the blocks.