Why does quaternary outperform ternary and binary? Unveiling the synergy of multi-component solid waste in sustainable low-carbon cementitious materials

Solid waste-based cementitious materials effectively reduce environmental pollution and cement industry carbon emissions. However, excessive solid waste use may degrade materials properties. To address this challenge, this study proposes a quaternary solid waste synergistic activation strategy, aiming to simultaneously enhance the utilization rate of solid waste and optimize materials performance. Through systematically comparing the mechanical properties, microstructure and environmental behavior of binary, ternary and quaternary system, the strengthening mechanism of the quaternary system was clarified.

The results indicate that the quaternary system exhibits superior comprehensive properties, achieving a 28 d compressive strength of 45.33 MPa, which represents a 6.6 % and 37.5 % improvement over the ternary and binary systems, respectively. The key mechanism involves the synergistic activation of alkaline and sulfate solid wastes, enhancing the reactivity of silicate-aluminate components. This promotes the interwoven coexistence of gel and ettringite, increasing the proportion of gel pores (<10 nm) to 30.81 % and optimizing the pore structure. Furthermore, the system achieves a Na⁺ solidification effect of 98.4 % for red mud, ensuring controllable environmental risks. Additionally, the carbon emission is reduced to 189.14 kg CO₂/m³ (a 59 % reduction compared to pure cement), while the carbon emission per unit strength decreases by 61 %, demonstrating significant dual-carbon-reduction characteristics and supporting its feasibility as a sustainable and low-carbon cementitious materials.

This study confirms that the synergistic effects of multiple solid wastes can overcome the traditional performance limitations of cement, providing a theoretical foundation and technical pathways for the efficient resource utilization of solid wastes and the development of low-carbon building materials.