The regeneration of cement from completely recyclable mortar: effect of raw materials compositions

Abstract

In this study, the cement was regenerated using completely recyclable mortar (CRM) as raw cement meals. The effects of silica modulus (SM) and aluminum modulus (AM) on the CRM properties, burnability of raw meal, and clinker properties were studied. The results showed that with a higher SM and lower AM, less melt would be available to facilitate the diffusion of CaO towards belite to form alite. The compressive strength of recycled cement increased with the increase of AM when SM=2.7 and 2.2 and decreased with the increase of AM at a low SM (SM=1.7). The suggested rate value of raw meals using CRM is a medium SM (SM= 2.2 or SM=2.7) and AM=1.5-1.8 with a calcination temperature of 1400 ℃. The strength of both CRM and the obtained recycled cement clinker is relatively high. Moreover, the calcination temperature could be further reduced to 1300℃ or 1350℃with a low SM (SM=1.7) and AM (AM=0.9-1.5). Though the CRM had a lower early strength, it had a relatively high strength in the later stage. However, its water absorption is significantly increased compared to the control group.