Influence of autogenous shrinkage on mass transport properties of concrete

Autogenous shrinkage in concrete is defined as the change of volume after initial setting occurs. It develops at very early ages as a result of chemical shrinkage and self-desiccation effect. These produce significant microcracks in high-strength concrete allowing the entrance of aggressive agents such as carbon dioxide, chlorides, and sulphates which cause concrete deterioration. Although considerable research of autogenous shrinkage has been done, uncertainty remains concerning the influence in concrete durability. Therefore, the purpose of this study was to quantify and analyse the effect of autogenous shrinkage on the mass transport properties of concrete using three transport tests: oxygen diffusion, oxygen permeation, and water absorption. Two methods, for three different binders, were first carried out to determine a control mixture that produces the least autogenous shrinkage: adding SRA and curing in a fog room. Subsequently, transport test results between the selected control mixture and mixtures highly affected by autogenous shrinkage were compared for different binders. Results revealed that specimens with SRA presented the least autogenous shrinkage; therefore, it is suggested to be considered as control samples. It was also found that autogenous shrinkage significantly affects the transport coefficients in concrete made with secondary cementitious materials which from a serviceability point of view could reduce the life span for any structure made with high-strength concrete. This investigation also confirmed that most of the autogenous deformation occurs during the first two weeks after casting therefore enough care should be taken when curing.