Low lime – low carbon cement: Achieving sustainability through reduction of CO2 emissions and utilizing limestone mining rejects

Abstract

To advance the cement industry’s decarbonization goals, this research introduces 'low lime – low carbon clinker (L3C2)’ as an alternative to conventional Portland clinker, proposing a switch from a hydraulic binder to a carbonatable non-hydraulic binder using limestone mining rejects, which are discarded due to low calcium oxide (CaO) content, high-magnesia (MgO) and high-silica (SiO₂) content. By maintaining a lower calcium oxide to silicon dioxide ratio (C/S ratio) of 1.0–1.5 (compared to 3.1–3.2 for conventional clinker), along with magnesia content up to 15 % in the raw material feed, L3C2 can significantly promote the formation of carbonatable Ca/Mg-silicate mineral phases, that increases the CO₂ uptake and reduces its carbon footprint by up to 50 % which requires shorter curing times (up to 7 days). The lower C/S ratio in L3C2 allows better utilization of discarded limestone mining rejects in the pyro-process, reducing the rejection ratio and providing a novel, implementable method to resolve the mining waste management issue and mitigate carbon emissions in cement production.