Recycling carbonated reactive magnesium cement (RMC) as a building material

Abstract This study assessed the recyclability of reactive magnesium cement (RMC). To simulate the condition of construction waste recovery, a carbonated RMC-based paste was ground and used as a replacement for fresh RMC at 20 and 40 wt%. Both paste and mortar specimens were prepared and subjected to carbonation under 20% CO2, 80% RH, and 30 °C. Calorimetry data revealed that the main hydration peaks were delayed. The cumulative heat flow values were reduced, attributable to an increase in pore solution pH and physical barrier created by amorphous phases, which were confirmed by the appearance of broad peaks coinciding with those of hydromagnesite. Under carbonation, the peaks became more apparent due to the transformation of the phases into crystalline hydromagnesite. At 20 wt% replacement, the composite incorporated with the recycled RMC attained an improved strength performance due to more formation of the amorphous phases and hydrated magnesium carbonates (HMCs) from brucite.