Abstract

As the production of Portland cement (PC) is energy intensive and responsible for 5-8% of global anthropogenic CO2 emissions, many global initiatives are looking into the development of cements with lower carbon footprints. Reactive magnesia (MgO) cements, which are blends of PC and MgO in different proportions depending on the application, were developed with this objective in mind. Reactive MgO is manufactured at much lower temperatures than PC and has the ability to sequester substantial quantities of CO2 , leading to significant increases in strength. In this study, the use of MgO alone as the binder in porous blocks is investigated for the optimisation of the carbonation process. For an optimised carbonation, certain variables including the cement component (e.g. water/cement ratio and MgO content), curing conditions (RH, CO2 concentration, wet/dry cycling, curing duration under ambient and accelerated CO2 curing), aggregates component (aggregate type and particle size distribution), and the inclusion of certain additives were investigated. Cylindrical samples were tested for unconfined compressive strength (UCS), porosity, and permeability in addition to microstructure by SEM after being subjected to two different curing environments: accelerated carbonation (20˚C, 70-90% RH, 20% CO2 ) and natural curing (20˚C, 60-70% RH, ambient CO2 ). Thermogravimetry/differential thermal analysis (TG/DTA), X-ray diffraction (XRD), density measurements and acid digestion were used to quantify carbonation, providing guidance towards determining the optimal design parameters of MgO-cement blocks.