Preparation and characterization of a CO2 activated aerated concrete with magnesium slag as carbonatable binder

Abstract

• A novel carbonated aerated concrete integrating the large-scale CO 2 utilization and magnesium slag recycling is proposed. • The CAAC with various densities exhibits a high and rapid development of compressive strength and carbonation degree during the carbonation. • The addition of porous zeolite has a certain positive effect on the carbonation degree. Magnesium slag is an industrial by-product from magnesium production. Most of magnesium slag is disposed at landfills without being effectively recycled, posing a severe pollution to the environment. Here, a CO 2 activated aerated concrete (CAAC) with magnesium slag as the main carbonated binder is reported. Mechanical strength, microstructure, volume stability and CO 2 absorption efficiency of CAAC are investigated. Results show that the compressive strengths of CAAC after being carbonated for 2 h with varying densities (400, 600, 800 kg/m 3 ) can reach 2.83, 4.51, and 6.96 MPa respectively. This is associated with the high carbonation reactivity of magnesium slag and the addition of microporous zeolite, which promotes the CO 2 diffusion and synchronously increases the degree of carbonation from 45.2 % to 55.1 % in the case of 600 kg/m 3 mix. The high carbonation degree also leads to the absorbed CO 2 up to 28 wt%, and more than 90 % of the total CO 2 absorption efficiency can be achieved within the first 30 min. In addition, CAAC exhibits high volume stability by the consumption of f-MgO and f-CaO during carbonation. This study provides a new insight into preparation of carbonated aerated concrete integrating the large-scale CO 2 utilization and magnesium slag recycling.