Development and Optimisation of an Industrial Waste-Based Additive for Improving Concrete Performance

This study investigates the development and optimization of a multi-component modifying additive based on industrial waste for improving the mechanical and durability properties of concrete. The additive consists of microsilica (Ms), phosphogypsum (PhG), soapstock (Sp), and post-alcohol bard (PaB), and its performance was evaluated using a staged experimental approach. The results showed that the optimal content of microsilica is 20% of the cement mass; the optimal content of phosphogypsum is 15% of the combined mass of the cement and microsilica; the optimal content of soapstock is 10% of the total mass of the cement, microsilica, and phosphogypsum; and the optimal post-alcohol bard is 5% of the water mass. At these concentrations, the compressive strength increased by up to 28.3% compared to the reference sample. Soapstock significantly reduced water absorption (up to 36.8%) and improved freeze–thaw resistance due to the hydrophobization of the cement matrix. However, excessive soapstock content led to a reduction in strength. The addition of post-alcohol bard provided a plasticizing effect and reduced water absorption, with the optimal concentration for strength being 2.5%, while the highest freeze–thaw resistance was observed at 5%. The combined effect of the components resulted in the formation of a denser microstructure and improved durability of concrete. These findings demonstrate the effectiveness of industrial waste-based additives in enhancing concrete performance and durability, contributing to sustainable material development.