Study on Relationship between Water-cement Mass Ratio and Early Age Shrinkage of Concrete

The research of early age shrinkages of concrete is very important for the solutions of early age cracking of concrete engineering,especially for high performance concrete. In this paper,autogenous shrinkage under sealed condition and total shrinkage under dry condition of concretes with different water-cement mass ratio were measured from 6 hours to 3 days age with a newly-developed method. This method adopts a type of micro-displacement sensor and the concrete need not be touched during testing. The temperature changes in the concrete specimens were monitored at the same time. As a result, it is shown that autogenous shrinkage, total shrinkage under dry condition and the ratio of autogenous shrinkage in total shrinkage of concretes during early ages increase evidently with the decreasing of water-cement mass ratio and the relation between early age autogenous shrinkage and water-cement mass ratio can be figured by a cubic equation. It is also demonstrated that the total shrinkage under dry condition can' t be considered as the simple addition of drying shrinkage and autogenous shrinkage when the water-cement mass ratio of concrete is low because water loss of concrete due to drying at early age may counteract the hydration process of cement in a certain degree.