Abstract: Soda residue was mixed with class F fly ash and sodium sulfate to synthesize the mixing soils using for filling embankment.Several physical and mechanical tests were conducted to compare and analyze the effects of sodium sulfate and the engineering properties of mixing soils.Results show that the chemical interaction between soda residue and fly ash can be confirmed by the results of boundary moisture content and particle analysis at different curing time.The instantaneous chemical reactions have happened between Ca(OH)2 and CaCl2 to produce NaOH and CaSO4.The pores among solid particles are filled with gel substances from the alkali-activated fly ash and the cementation of soil structure is improved.The mechanical properties of soda residue mixing soils are significantly improved by sodium sulfate,and are increasing with contents in the range of 0%-8%.But the frost resistance performance of mixing soils is poor.And it is recommended that a small amount of cement or NaOH be added to improve the frost resistance performance.

Key words: soda residue;sodium sulfate;filling embankment;physical and mechanical property;chemical reaction