Recycled cement production energy consumption optimization

The concrete industry has made a firm commitment to reduce its excessive carbon footprint, es-sentially related to clinker production. Recycled cement (RC) from the thermoactivation of hard-ened 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 re-sources consumption. The implementation of RC at an industrial scale depends on the environ-mental and economic viability of its production. In this context, this paper aims to model the en-ergy consumption and carbon emissions of RC production using a novel separation method re-cently 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 produc-tion. Moreover, up to 80% savings in carbon emissions are estimated. The high low-carbon and low-embodied energy potential of RC is shown.

Automated summary

The concrete industry is committed to reducing its excessive carbon footprint, specifically through reducing clinker production. Recycled cement (RC) from the thermoactivation of hardened cement waste at low temperature shows great potential in reducing the clinker factor, reusing construction and demolition waste, and minimizing natural resource consumption. This study models the energy consumption and carbon emissions of RC production using a newly patented separation method. Results indicate that the air method (AM) and dry method (DM) significantly reduce energy consumption compared to the wet method (WM). Adopting AM or DM can lower RC's energy consumption by 30%-40% compared to clinker production, resulting in estimated carbon emission savings up to 80%.