Expansive soils are widespread in many parts of the world. Due to its low strength, high compressibility, and massive volumetric changes, these soils are a potential origin of damage to roads, buildings, foundations and other geo-infrastructure. Extensive research has been conducted on the utilisation of fly ash to stabilize expansive soils. This paper describes how the efficiency of fly ash based soil stabilization can be improved using secondary additives. Class F fly ash, an industrial by-product, was used as the base additive. Lime, CSA cement, enzyme and polymers were utilized as secondary additives. A series of mechanical and microscopic tests (CBR, compaction test, SEM, XRD, FTIR and TGA) was carried out on different combinations of additives. The results indicate that secondary additives can be effectively used to improve the efficiency of fly ash based soil stabilization. Soil-fly ash-lime-enzyme was identified as an optimum combination to enhance bearing capacity while soil-fly ash-lime and soil-fly ash-enzyme also showed substantial improvements in subgrade performance. Findings from laboratory investigations were verified applying into 3-D numerical modelling to evaluate the pavement performance which revealed substantial benefits of pavement thickness reduction when fly ash stablized weak soils are treated using secondary additives.

膨胀土广泛分布于世界许多地方。由于其低强度、高压缩性和巨大的体积变化，这些土壤是道路、建筑物、地基和其他地质基础设施损坏的潜在来源。已经对利用粉煤灰稳定膨胀土进行了广泛的研究。本文描述了如何使用二次添加剂提高基于粉煤灰的土壤稳定的效率。F 级粉煤灰是一种工业副产品，用作基础添加剂。石灰、CSA 水泥、酶和聚合物被用作辅助添加剂。对不同的添加剂组合进行了一系列机械和微观测试（CBR、压实测试、SEM、XRD、FTIR 和 TGA）。结果表明，二次添加剂可以有效地提高粉煤灰基土壤稳定的效率。飞灰石灰酶被确定为提高承载力的最佳组合，而飞灰石灰和飞灰酶也显示出路基性能的显着改善。实验室调查的结果被验证应用于 3-D 数值模型以评估路面性能，这揭示了当使用二次添加剂处理粉煤灰稳定的弱土壤时，路面厚度减少的实质性好处。