Abstract: Due to the high carbon emissions, energy consumption, and environmental pollution associated with cement grout in the construction of post-grouted piles in calcareous sand, this study employed two types of green, low-carbon grouting materials (geopolymer and high polymer) to solidify calcareous sand. The experimental results were compared with those obtained from the traditional cement grouting materials. The study investigated the effects of different grouting materials, curing times, and material ratios on the strength of stabilized soil in calcareous sand using unconfined compressive strength tests. Additionally, techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and nuclear magnetic resonance were combined to analyze the microstructure and mineral composition of the stabilized soil with different grouting materials, revealing the micro solidification mechanism. The results show that increasing the curing time and material ratio enhances the strength of the stabilized soil. High polymer-stabilized soil exhibits the highest strength, with a faster early strength growth. The compressive strength at 7 d is approximately 90% of that at 28 d. The compressive strength of geopolymer-stabilized soil is slightly lower than that of cement-stabilized soil. However, its strength increase rate with curing time gradually surpasses that of cement-stabilized soil, indicating a potential advantage in long-term stability. Additionally, geopolymer and cement-stabilized soil significantly enhance compressive strength by filling gaps between sand grains and binding the sand particles through hydration products. However, the strength improvement of high polymer-stabilized soil is attributed to its inherent properties. The pores in 7 d cured geopolymer and high polymer-stabilized soils are primarily small, accounting for over 95% of total pores. This proportion gradually increases with curing time and is significantly higher than that in cement-stabilized soil. This positively affects strength enhancement. The research findings can serve as a reference for applying green, low-carbon grouting materials in engineering projects involving post-grouted piles in calcareous sand.

Key words: calcareous sand, post-grouted piles, grouting materials, stabilized soil, mechanical performance tests, microscopic mechanism