盐碱与冻融耦合作用下再生混凝土耐久性试验研究

通过再生混凝土在3.5%NaCl、3.5%Na2SO4、3.5%NaCl+3.5%Na2SO4和水四种溶液中的冻融循环试验,分析再生混凝土在同浓度不同种类盐碱溶液中经过不同冻融次数后(N)的质量变化(△m)和动弹性模量变化(△E) ,绘制N-△m和N-△E的曲线.同时,设置单掺10%、20%粉煤灰和2%、4%硅灰为对照组,研究粉煤灰和硅灰组分别在3.5%NaCl和3.5%Na2SO4环境下混凝土的抗冻性能规律.结果表明:氯盐环境中,随冻融次数的增加,混凝土表面剥削、开裂现象明显,质量和动弹性模量损失严重,而硫酸盐环境中,冻融前期混凝土内部生成水化产物使质量增加,表面膨胀开裂,后期质量和动弹性模量急剧下降,与浓度3.5%氯盐盐冻相比,硫酸盐盐冻动弹性模量损失更大.冻融破坏强度由强到弱排序为氯盐冻、硫酸盐冻、复合盐冻、水冻;掺入粉煤灰后,氯盐环境下的混凝土抗冻性反而下降,10%掺量优于20%掺量.掺入硅灰后,硫酸盐环境下再生混凝土抗冻性提高,破坏程度要比水冻小,4%掺量优于2%掺量;最后分析了混凝土腐蚀机理.

Recycled Concrete Corrosion in Saline and Freeze-Thaw Cycle Coupling under the Action of Durability Research

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.