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In this research, Firming agent (FA) and a small amount of hydrated lime were used to stabilize soil. Five types of soil, 0.2L/m 3 of FA, and several low dosages of hydrated lime were selected. Total 15 different soil mixes were studied. The unconfined compressive strength (UCS) of each stabilized soil was tested at the age of 7, 14, 28, and 90 days. Test results show that FA and a low dosage of hydrated lime could effectively stabilize clay soil, but are not suitable for silt. A highly significant linear correlation exists between the UCS of stabilized soil and the cation exchange capacity (CEC) of the soil. The greater the CEC, the higher the strength is. Among the three factors of plasticity index (PI), clay particle content, and CEC, the CEC is the most direct and reliable indicator that reflects whether t h e soil is suitable for being stabilized with FA and hydrated lime. Minimum criterion of CEC of soil was approximately calculated as 10m mol/kg. If PI is used as a criterion, stabilization results can be ideal when the PI is about 15~ 22.

Roadpacker plus is a liquid cationic-exchanger made from Canada. It can fundamentally change the soil surface’ s properties by its intense ion. Under pressure, soil’ s strength format more quickly and has good water resisting property after adding it. So the Roadpacker plus can accelerate the stabilization and strength of soil. 4%, 5%, 6% lime and 0.15ml/m 3 ,0.2 ml/m 3 , 0.25 ml/m 3 Roadpacker plus are separately added in different types of soil. The unconfined compressive strength test, immersion tensile splitting strength test, drying shrinkage test, temperature shrinkage test and environment impact test of the Roadpacker solidified limestone soil are done. Researches on the strength performance including the resistance to drying-shrinkage and temperature shrinkage, the construction curing method and the environment influence. The researches indicate that Roadpacker solidified limestone soil’ s early strength grows more quickly and it has better resistance to drying shrinkage and temperature shrinkage. Specially, its ductility and crack resistance are better than inorganic binder stabilized soil, simultaneously the Roadpacker can reduce the content of heavy metal in soil. Therefore, as a new environment protection material, Roadpacker solidified limestone soil can be used as the subbase of superhighway or first class highway and the base course of second-class road or lower grade road, specially the country road. The researches offer the design standards of the Roadpacker solidified limestone soil (different types of soil) and the proper ratio of