Study on the carbonation degree of lime-activated low carbon cementitious materials: Based on the CO2 binding capacity of hydrates

Abstract

To investigate the CO2 uptake capacity of lime-activated low carbon cementitious materials (LCM), this work focused on the evaluation of the carbonation degree of LCM based on the phase assemblage, and Portland cement (PC) as a reference was compared in this work. According to the composition of carbonation products quantified by QXRD and TGA, an improved method to calculate the carbonation degree of LCM based on the CO2 binding capacity of hydrates was applied. Moreover, the origin of calcium carbonate of LCM after carbonation was analyzed, and the different carbonation zones of LCM were determined and compared based on the carbonation degree. The results showed that the calculation of the carbonation degree based on the CO2 binding capacity could better evaluate the carbonation degree of LCM compared to other method. For LCM, the calcium carbonate in the carbonation zone was primarily attributed to the carbonation of C-(A)-S-H rather than the carbonation of portlandite, and the calcium carbonate in the surface sample originating from the carbonation of C-(A)-S-H accounted for 74% of the total formed calcium carbonate. After accelerated carbonation for 28 d, the partial carbonation zone of LCM could be divided into two parts: the partial carbonation zones without calcium hydroxide (CH) and with CH.