Builders École d'ingénieurs

International audience

International audience

This study investigates the use of demolition waste as recycled coarse aggregates (RCAs) to replace natural coarse aggregates (NCAs), and the use of ground granulated blast slag (GGBS) and limestone filler (LF) as a supplementary cementitious material, in self-compacting concrete (SCC), with proportions of 150 kg/m3 for GGBS and 180 kg/m3 for LF. Various SCC mixtures were prepared with RCA proportions of 0, 25, 50, 75, and 100%, while maintaining fixed dosages of LF and GGBS. Initially, RCA was incorporated in a dry state, followed by a water dosage adjustment for mixtures containing 100% RCA, equivalent to 20 min of RCA absorption. The experimental investigation evaluated the evolution of flow properties through tests such as slump flow, flow time (T500), L-box, sieve stability, fresh density, and air content. The static yield stress and plastic viscosity were also calculated using mathematical models. Additionally, hardened properties, including short-term and long-term compressive strength and capillary water absorption, were assessed. An environmental impact analysis of using demolition waste was conducted, revealing that a total NCA replacement with RCA is viable for both fresh and hardened states, provided that the RCA water absorption is managed and a reactive mineral additive is incorporated. For a 50% replacement of natural aggregates with recycled aggregates, this approach significantly reduces environmental impacts, lowering fossil fuel consumption by up to 35% and greenhouse gas emissions by up to 32%.

This study examines concrete polishing waste (CFPW) potential as a partial cement substitute in mortar formulation. Concrete polishing waste, a by-product of the grinding and polishing of concrete surfaces, is mainly composed of fine particles of silica and calcium carbonate. The aim of the research was to assess this industry waste incorporation impact on various mortar properties. Four mixes containing different percentages of CFPW were tested for their physic-mechanical properties and environmental impact. The results show that increasing the CFPW percentage leads to higher porosity and shrinkage, as well as lower mechanical strength and density. However, a significant reduction in CO2 emissions was observed with CFPW incorporation (up to 29% reduction for 30% CPFW). Although CFPW use presents technical challenges, it offers an interesting opportunity to reduce mortars' carbon footprint. The study concludes that moderate CFPW use can offer a balance between environmental benefits and performance, highlighting the need to optimize formulations to maximize benefits while minimizing compromises on mechanical properties.