Long-term influence and calculation model of temperature on strength of marine soft clay solidified with calcium carbide residue-fly ash geopolymer

Geopolymer solidified soil has been extensively studied and however, knowledge gaps exist regarding the long-term influence of temperature and its modelling on the strength characteristics of geopolymer solidified soil. Fly ash (FA), calcium carbide residue (CCR) and NaOH are among the most widely investigated precursor and activator materials. Owing to their excellent performance, a CCR-FA-NaOH geopolymer is adopted as the binder in this research. An attempt is made to investigate the long-term influence (7, 14, 28, 60, 90, 150, 180, 240 days) of temperature (20 °C, 30 °C, 40 °C) on strength of solidified marine soft clay. Strength calculation model regarding long-term temperature influence is proposed, modified and established. The model accuracy is verified and deviation between true and predicted values is within approximately 10%. The 7-day strength of the specimen cured at 40 °C reaches 2352.5 kPa, which is 2.44 times that of the specimen cured at 20 °C. Strength improvement index (SI) of temperature is defined, indicating that higher curing temperatures correspond to greater SI values. Surface microgram is obtained by scanning electron microscope, and the stabilization and temperature influence mechanisms are discussed. Strength development is mainly attributed to pore filling, cementitious products and ion exchange. Higher curing temperatures enhance the chemical reaction rate, promoting the generation of more cementitious products. The experimental results can provide theoretical guidance for achieving the target strength of geopolymer solidified soil under long-term temperature influence in engineering applications.