关键词: 盐碱腐蚀;再生混凝土;冻融循环;粉煤灰;硅灰

Abstract: The effects of different freezing and thawing cycles of regenerated concrete in different concentrations of salinity solution were studied by freeze-thaw cycle test of recycled concrete in 3.5%NaCl,3.5%Na2SO4,3.5%NaCl+3.5%Na2SO4and water.Mass(△m)and dynamic elastic modulus (△E)of the post(N),and plot the curves of N-△m and N-△E.At the same time,the control group with single mix of 10%,20%fly ash and 2%,4%silica fume was used to study the effect of fly ash and silica fume on the frost resistance of 3.5%NaCl and 3.5%Na2SO4.The results show that the surface cracking and cracking of the concrete are obvious in the environment of the chloride salt environment, and the mass and dynamic elastic modulus are all serious.In the sulfate environment, the hydration products are produced during the freeze-thawing concrete.The swelling modulus of the sulfate salt is higher than that of the salt at the concentration of 3.5%, and the elastic modulus of the sulfate salt is increased.Freezing and thawing failure strength from strong to weak sorting for the chloride salt,sulfate frozen,composite salt,frozen;mixed with fly ash, the chloride environment of concrete frost resistance decreased,10% content is better than 20% content.After adding silica fume, the frost resistance of recycled concrete in sulphate environment is improved,the degree of damage is smaller than that of water freezing,and the content of 4% is better than 2%.Finally, the corrosion mechanism of concrete is analyzed.

Key words: salt alkali corrosion;recycled concrete;the freeze-thaw cycle;fly ash;silica fume