Recycled cement production energy consumption optimization

Abstract

The concrete industry has made a firm commitment to reduce its excessive carbon footprint, essentially related to clinker production. Recycled cement (RC) from the thermoactivation of hardened cement waste at low temperature is a very promising approach, tackling the reduction of the clinker factor, the reuse of construction and demolition waste and the reduction of natural resources consumption. The implementation of RC at an industrial scale depends on the environmental and economic viability of its production. In this context, this paper aims to model the energy consumption and carbon emissions of RC production using a novel separation method recently patented by the authors. Three alternative processes were considered towards the best compromise between energy and separation efficiency: dry method (DM); wet method (WM); air method (AM). Results from this study indicate that the AM and DM led to a significant reduction of the energy consumption on RC production, compared to WM. Differences between AM and DM are not significant. The slightly higher energy consumption in AM is compensated by the higher purity of concrete waste derived cement fraction. Adopting the low-energy intensive AM or DM, the estimated energy consumption of RC was 30%–40% lower than that used in clinker production. Moreover, up to 80% savings in carbon emissions are estimated. The high low-carbon and low-embodied energy potential of RC is shown.