Effect Of Internal Curing And Magnesium Oxide Expansive Agent On The Performance Of Concrete

Because of the poor using effect of the traditional external water curing,the internal curing technology and the shrinkage-compensating technology have gradually attracted the attention of the academia and engineering.However it is found that both internal maintenance and compensation shrinkage technology have their own advantages and limitations in study.In order to overcome the limitations of the two technologies,recombination of internal curing and shrinkage-compensation have been proposed.The recombination of internal curing and ettringite expansion agent in the study is the most popular.The influences of the combination of the internal curing use SAP and Magnesium Oxide expansive agent on the properties of concrete needs to be studied.Especially,the effects of the composite on the performance of concrete in different curing method need to be further studied.In this study,through comparing ordinary concrete with the concrete blended with Pre-soaked super-absorbent polymer(SAP),concrete blended with Magnesium Oxide expansion agent,concrete blended with 4%Magnesium Oxide expansion agent and Pre-soaked super-absorbent polymer(SAP),concrete blended with 8%Magnesium Oxide expansion agent and Pre-soaked super-absorbent polymer(SAP),the workability,shrinkage characteristics,mechanical properties and durability were analyzed in three different curing conditions,which were dry,closed and 7 days moisture retention.The conclusions are as follows:(1)The workability of concrete combined admixture of Pre-soaked super-absorbent polymer(SAP)and Magnesium Oxide expansive agent have little change;the bulk density of concrete after mixing was little changed,but the air content increased slightly.(2)In the three curing conditions,the mass loss and shrinkage deformation of the concrete were the greatest under the drying conditions.The combined effect of Pre-soaked super-absorbent polymer(SAP)and Magnesium Oxide expansive agent can not only reduce the mass loss of concrete under the three curing conditions,but also completely eliminate its autogenous shrinkage and effectively reduce its drying shrinkage.From the test result,the reduction effect is better when the Magnesium Oxide expansion agent is 8%.(3)The combined effect of Pre-soaked super-absorbent polymer(SAP)and Magnesium Oxide expansive agent will not only have adverse effects on the strength and modulus of elasticity of concrete,but also increase the growth rate of strength and modulus of elasticity when the age over 7 days.The curing condition has a great influence on the tension-compression ratio.After the 7 days moisture retention curing,the ratio of the tension-compression ratio of the concrete is the largest,which fully indicates curing to the toughness of concrete is very important.(4)The combined effect of Pre-soaked super-absorbent polymer(SAP)and Magnesium Oxide expansive agent can improve the frost resistance and resistance against chloride ion Penetration,but the combined effect in different curing conditions is different.The effect of composite action is more obvious under the drying and closed condition.