Accelarated Carbonation of Reactive Magnesium Oxide to form a Carbonated Magnesium Binder

Reactive Magnesium Oxide is gaining popularity as an alternative binder cements which can be used in structural and non-structural application as a replacement to Ordinary Portland Cement due to difference in their calcination temperatures (700 degree Celsius for rMgO vs 1450 degree Celsius for OPC). This study explores the potential of reactive MgO as a low-carbon binder through carbonation curing, which not only enhances mechanical properties but also sequesters CO₂. Reactive MgO, derived from low-temperature calcination of magnesite (MgCO₃), undergoes hydration and subsequent carbonation to form strength-contributing hydrated magnesium carbonates (HMCs) such as nesquehonite and hydromagnesite. The early carbonation was performed at low pressure and low temperatures to reduce the associated energy footprints as compared to traditionally used accelerated carbonation chambers. In this study early carbonation was performed in a polyethylene inflatable enclosing which is more practical and convenient to be used for practical applications. The carbonation efficiency, phase evolution, and microstructural development were analysed using XRD, TGA, and SEM-EDS. Mechanical testing revealed that direct carbonation achieved a compressive strength of 32 MPa at 7 days, while continuous carbonation yielded 48 MPa at 28days comparable to OPC-based systems. The carbonated MgO binder exhibited excellent early-age strength development, with a 28-day strength gain of up to 60% under optimized conditions. Microstructural analysis confirmed the formation of a dense HMC matrix, contributing to enhanced durability and reduced porosity. This study demonstrates that reactive MgO, when combined with carbonation curing, can serve as a high-performance, carbon-negative binder. The findings highlight its potential for sustainable construction, offering CO₂ sequestration while valorising industrial by-products. Further research is needed to optimize mix designs for large-scale applications.