Degradation mechanism and life prediction of tailings and waste rock aggregate geopolymer concrete under freeze-thaw corrosion

Abstract

To study the durability of tailings and waste rock aggregate geopolymer concrete (TWGPC), a large number of tailings and waste rock were used to replace natural sand and stone as aggregates, and a fly ash geopolymer was used to replace cement as cementing material to prepare TWGPC. The slow freezing method was used to carry out single freeze-thaw and freeze-thaw corrosion tests. Scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS) were used to analyse the microstructure and reaction products of TWGPC. The degradation mechanism of TWGPC was studied, and the life of TWGPC was predicted. The results show that the higher the concentration of corrosion solution was, the more significant the change trend of the mechanical properties test results. In the early stage of the cycle, acinar gypsum and short columnar ettringite were generated to fill the pores and improve the compactness and frost resistance of TWGPC. In the late stage of the cycle: calcium-silicate-hydrate (C–S–H) was decomposed and gradually replaced by magnesium-silicate-hydrate (M–S–H). The cohesion between mortar and aggregate was reduced, and a large number of products were generated. Cl⁻ inhibited the transmission rate of SO₄ ²⁻ and reduced the erosion effect of SO₄ ²⁻ on TWGPC. The single freezing-thawing life prediction model had high accuracy, and the life prediction conclusion based on reliability was consistent with the appearance damage analysis, mechanical property testing and microscopic morphology analysis.