Study On Deterioration Performance Of Concrete Under Salt-Soaking,Dry-Dry,Freeze-Thaw And Multi-Coupling

In order to study the hetao area of Inner Mongolia saline soil degradation mechanism of concrete under complicated environment in the laboratory simulation actual environment conditions,preparation of NaCl and Na2SO4,NaHCO3,Na2CO3 composite salt solution,preparation of 7 kinds of mixture ratio(15%,10% fly ash concrete,concrete fly ash concrete,20% fly ash concrete,10% metakaolin concrete,metakaolin concrete,15% and 20%)metakaolin concrete composite salt leaching-wet-freezing and thawing cycles,water-dry wet-freeze-thaw cycling test.The strength,mass loss rate and relative dynamic modulus were used as evaluation indexes to study the deterioration performance of concrete.The results show that metakaolin concrete is superior to the reference concrete and fly ash concrete in the performance of salt-leaching-dry-wet-freeze-thaw cycle.In the range of this test,concrete with 20% metakaolin is superior to concrete with 10% and 15% metakaolin in its salt-leaching--dry-wet--freeze-thaw cycle performance.Concrete is more seriously damaged by the coupled action of multiple factors of composite salt-dry-wet-freeze-thaw cycle than the combined action of single factor or two factors.The combined effect of multiple factors is not a simple superposition effect of salt-leaching,dry-wet cycle and freeze-thaw cycle.And set up multiple coupling under the action of concrete compressive strength,relative dynamic elastic modulusdegradation prediction model,the test range,under the action of multiple coupling compound salt-dry wet-concrete after freeze-thaw cycling test compressive strength degradation prediction model is the minimum correlation coefficient is 90%,under the action of multiple coupling compound salt leaching-dry wet-concrete after freeze-thaw cycling test relative loss modulus degradation prediction model is the minimum correlation coefficient is 93%.In the prediction model,metakaolin concrete with a content of 20% has the lowest degradation coefficient and the slowest degradation rate,so III20 is the optimal content for predicting compressive strength.