Carbonation Properties Of Composite Additives Modified Concrete

With the increasing of performance requirements of construction projects for economic and social development,polymer modified concrete has been widely used.Meanwhile,for the serious damage caused by concrete carbonation of constructions are common,especially for the concrete structures in cold saline areas,the neutralization of concrete caused by carbonation,together with the catalytic erosion action of Cl-caused by the chlorine salt diffuse into the concrete can accelerate the rebar corrosion.Therefore,it is an important basis for the scientific design of concrete durability to study the influence of composite additives and saline-alkaline erosion on carbonation of composite additives modified.This paper applies materials compound modification principle,tries to choose polymer powder,defoamer and silica fume as performance additive,manufactures composite additives modified concrete by adding composite additives.Based on the engineering environment and the compounding characteristics of concrete in cold saline-alkaline(SA)zone,the SA solution is prepared by simulating.The effects of the influencing factors on the carbonation properties including it under SA erosion action of composite additives modified concrete were investigated and the carbonation model of the relationship between depth and ages of carbonation on composite additives modified concrete was established through orthogonal and single factor test,with contrast and XRD,SEM analysis in this work.Some important conclusions are shown as follows:(1)The content of latex powder has the greatest effect on carbonation,next comes defoamer,followed by water-cement ratio,the least is silica fume.(2)The carbonation resistance of concrete is worst at the content of the latex powder is 4.0%,while is the best at 8.0%.Silica fume can decrease the alkalinity and improve the compactness of concrete,and defoamer is good for the concrete resistance because it can eliminate the air voids and reduce the pores of concrete.(3)The SA erosion not only weakens the concrete carbonation effects of the four factors,but also changes the importance order.The SA erosion makes a dual function to composite additives modified concrete by emerging expansion crack and filling compacting so that it can increase the carbonation of the relatively compacted concrete while decrease that of concrete with high content of coarse pores.Whether subjected to SA erosion or not,the influence of the content of latex powder on carbonation of concrete is the same.With the increase of the content of latex powder,the depth of carbonation increases firstly and then decreases gradually,and the carbonation depth reaches the deepest while the content of the latex powder is 4.0%.(4)Optimizing the water cement ratio of 0.40,polymer powder 8.0%,silicon fume 6%,defoamer content 0.8%as mixing parameters of composite additives modified concrete,the carbonation resistance of concrete is improved significantly.(5)The carbonation model of composite additives modified concrete was established through the test data fitting and regression analysis,and the correlation is significant by run test.(6)The structure and morphology of concrete were influenced significantly by water-cement ratio,defoamer and latex powder through the micro-analysis methods such as XRD and SEM.The carbonation ability of concrete is stronger while the water-cement ratio is 0.34 and defoamer content is 0.8%.