Study On The Frost Resistance Of Concrete Subjected To The Combination Of Sulphate And Frost In Saline Soil Of Cold Regions

Saline soil is a kind of special soil with high salinity content,which is very aggressive to concrete structures.The coupling of the saline soil and freeze-thaw cycles greatly accelerates the deterioration of concrete structures,which damage the functions and safety,shortens the service life and reduces the durability of the structure.In this paper,the concrete with the individual silica fume,the individual fly ash and the mixture of silica fume and fly ash are studied to improve the durability of concrete.(1)The rapid freeze-thaw test of three types of concrete,individual silica fume,individual fly ash and mixture of silica fume and fly ash,were performed.The mass loss and relative dynamic elastic modulus were used to assess the frost resistance of concrete.The mechanical properties of concrete after freeze-thaw cycles were evaluated by cubic compressive strength loss and splitting-tensile strength loss.(2)Three types of concrete,the individual silica fume,the individual fly ash and the mixture with silica fume and fly ash,were tested in two kinds of sodium sulfate solution with the concentration of 6% and 12% during the rapid freeze-thaw test.The mass loss and the relative dynamic elastic modulus of the three kinds of concrete were analyzed.The mechanical properties of the concrete were analyzed by using the cubic compressive strength loss and the splitting-tensile strength loss.The sulfate-resistance and the mechanical properties of concrete after freeze-thaw damage in sulfate conditions were given.(3)The effects of silica fume and fly ash on the frost resistance and the mechanical properties of concrete under ordinary-freezing and sulfate-freezing conditions were discussed.The mechanism of frost resistance was analyzed.A mixing design suggestion for concrete structures subjected to freeze-thaw environment was proposed.The research has manufactured 210 specimans for freeze-thaw test in water and 168 specimans in sulfate solutions.With widely covering,the data gained from the research have certain reference value.