Advances in Deflocculant Utilisation in Sustainable Refractory Concrete with Refractory Waste

In the last 10–15 years, the use of waste refractory materials has significantly increased because it is not economically justified to transport such expensive materials to landfills. This work compared the physical and mechanical properties of refractory concrete samples with those of individual deflocculants—polycarboxilate, sodium tripolyphosphate, and a deflocculant mixture. Three refractory concrete compositions with individual deflocculants and a deflocculant mix were created to choose the best main properties of refractory concrete. Five compositions of refractory concrete specimens were created by partial replacement of chamotte aggregate (CA) by refractory concrete waste (RCW) (100, 75, 50, and 25%). Exothermal profile, structure development and spread were determined for fresh refractory concrete pastes. It was found that with an increase in CA replacement level to RCW, the EXO maximum temperature, spread and structure evolution speed decreases. SEM and porosity tests confirmed density, compressive strength results and structural parameters. The study shows that RCW replacement slows the hydration process, particularly at replacement levels above 33%. However, replacement levels of up to 25% improve compressive strength by 13% due to the additional amount of cement minerals in RCW aggregates, which can participate in the hydration process, making it a viable option for applications where enhanced durability is required, such as in non-critical zones of industrial refractory linings.