Study On Admixture Concrete In Saline-alkali Soil Environment In Cold Area

In the north of China,the weather is cold and the environment is bad.Especially in some saline-alkali soil areas,the safety problems of buildings,bridges and other concrete structures caused by the durability of concrete emerge in endlessly,which attracts more and more attention.In this paper,the durability of concrete is studied experimentally and theoretically from the material level.Through experimental research on the influence of various factors on the mechanical properties and durability of concrete,these factors include the influence of the type,amount and air entraining agent of admixtures.Through technical and economic comparison and selection,the admixtures concrete which not only meets the requirements for durability but also is relatively economical in construction cost under the environment conditions of saline-alkali soil in cold areas is found.The results show that,1?The effect of mineral admixture on the 28 day strength of concrete will be affected by water to binder ratio.When water to binder ratio is relatively high(0.42,0.40),the strength of mineral admixture concrete other than silica fume concrete for 28 days is basically lower than that of ordinary contrast specimens,while water to binder ratio is relatively low(0.33),it is almost higher than ordinary contrast specimens;2?In the aspect of resistance to chloride ion penetration,adding mineral admixtures can improve the resistance to chloride ion penetration of concrete,especially the concrete with silica fume alone.The results of electric flux measurement of concrete are reduced by more than 70% compared with the common contrast specimens,which greatly improves the resistance to chloride ion penetration of concrete.The addition of air entraining agent can also improve the resistance to chloride ion penetration of concrete,especially double mixing of fly ash and slag powder concrete,the electric flux of concrete decreased by more than half after the addition of the air entraining agent;3?Both mineral admixtures and air entraining agent can improve the frost resistance of concrete,in which the relative dynamic elastic modulus of double doped fly ash + mine powder concrete with 25 % +30 % admixture can reach 99.24 % when it is 300 times,showing excellent frost resistance;4?Through comprehensive comparison of technical performance and economy of concrete,duplex fly ash + mine powder concrete is generally superior to other concrete,and has certain market prospects.It can be widely used and compared.