Title:
Treatment of Residual Cementitious Fines Obtained through Innovative Recycling for the Replacement of Primary Cement
Author(s):
Ekenstein
Publication:
Web Session
Volume:
ws_S25_Ekenstein.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
3/30/2025
Abstract:
Recycling concrete is important for advancing the sustainability of the concrete industry. Approximately 8% of the global CO2 emissions come from concrete production, mainly due to the clinker production process in cement. This means that to significantly reduce the environmental impact of concrete, the recycling industry should focus on retrieving high-quality residual cementitious materials with the potential to replace primary cement in new concrete mixtures. To do this, innovative recycling technologies are essential, because they not only produce secondary gravel and sand, but also residual cementitious fines (RCF), which opens up new implementation routes previously deemed unfeasible and potentially eliminates CO2 emissions associated with concrete. This research aims to evaluate possible upcycling methods to improve the quality of RCF to replace cement in new concrete mixtures. The RCF was treated through grinding (particles size <32 µm), carbonation, oven heating or flash calcination. These methods were evaluated by comparing the 28-day strength development of RCF-based mortar mixtures to reference mortars across three cement types: Portland (CEM I), blast furnace slag (CEM III/B) and fly ash (CEM II/B-V) cement. Only the Portland cement component was replaced, with replacement values of 50%, 75% and 100%. The results showed that the compressive strength increased as the replacement value decreased, with flash calcined RCF achieving the highest strength for all replacement values and cement types. Peak values include 33.7 MPa for 50% replacement in CEM I, 30.1 MPa for 75% in CEM III/B, and 17.9 MPa for 100% in CEM III/B.