Carbon-negative magnesium-based manufactured aggregates development for carbon negative cement-based materials

Abstract

An alternative approach to developing low-carbon concrete is through carbon mineralization in aggregates. This research focuses on carbon mineralized magnesium (Mg)-based manufactured aggregates. First, a low-carbon synthesis process for brucite [Mg(OH)₂] and the incorporation of silica fume to enhance the strength and carbon sequestration capacity were investigated. The 25% (by weight) of silica fume improved the mechanical strength (~31 MPa) and carbon sequestration capacity (~26 wt%) of manufactured aggregates. The underlying chemical and microstructural characterizations showed that silica fume acts as an inert filler. Carbon emission assessments yielded a negative carbon footprint of 0.186 kg CO₂/kg of aggregates. The 50% volumetric replacement of natural fine aggregates with manufactured aggregates in 50 MPa concrete retained the compressive strength, while also achieving a 10% reduction in embodied carbon. In the case of 20 MPa mortar, 100% of natural fine aggregates could be replaced with Mg-based manufactured aggregates developed in his study.