Abstract:

To address the problems of high carbon emissions and insufficient durability of ordinary Portland cement concrete in sulfate-rich environments， this study used slag， fly ash and steel slag as composite precursors to prepare multi-source solid waste-based geopolymer concrete. Through orthogonal tests combined with grey relational analysis for auxiliary evaluation， the influences of steel slag dosage， alkali activator modulus， alkali activator dosage and external water-to-binder ratio on the compressive strength of geopolymer concrete were investigated， and the optimal mix proportion was determined. On this basis， sulfate wet-dry cycling tests were carried out， and combined with mass change， compressive strength corrosion resistance coefficient， X-ray diffraction （XRD） and scanning electron microscopy （SEM）， the sulfate resistance performance and damage mechanism of the multi-source solid waste-based geopolymer concrete were analyzed. The results show that the influence degree of the factors on the compressive strength of geopolymer concrete， in descending order， is alkali activator modulus， alkali activator dosage， external water-to-binder ratio， steel slag dosage. The optimal mix proportion is steel slag dosage of 20% （mass fraction）， alkali activator modulus of 1.2， alkali activator dosage of 50% （mass fraction）， and external water-to-binder ratio of 0.40. After 150 sulfate wet-dry cycles， the compressive strength corrosion resistance coefficient of the multi-source solid waste-based geopolymer concrete reaches 80%， which is higher than that of ordinary Portland cement concrete， and the mass change rate is only -0.6%. Microstructural analysis shows that the deterioration of ordinary Portland cement concrete is mainly related to the formation of expansive products such as gypsum and ettringite， and their continuous accumulation leads to the initiation and propagation of internal microcracks and structural spalling. In contrast， no obvious identifiable characteristic peaks of gypsum or ettringite are observed in the multi-source solid waste-based geopolymer concrete， and its damage is mainly manifested as local microcracks induced by sodium sulfate crystallization and slight loosening of the interfacial zone， without forming rapid deterioration dominated by the accumulation of a large amount of expansive sulfate products. The research results can provide a reference for the engineering application of multi-source solid waste-based geopolymer concrete in sulfate erosion environments.

Key words: multi-source solid waste, geopolymer concrete, optimized design, mechanical performance, sulfate resistance, grey relational analysis