Influences of reinforcement on differential drying shrinkage of concrete

Shrinkage strain of concrete specimen with different reinforcement configuration was measured at various depths from the exposed surface by using several pairs of displacement sensors. Only one surface of the concrete specimen was exposed to dry condition during the experiment. The results show that differential shrinkage strain occurs in both plain and steel reinforced concrete specimens according to depths from the exposed surface. A higher reinforcement ratio results in a greater restraint against shrinkage of concrete nearby reinforcement rebar and a worse differential shrinkage strain distribution in the concrete specimen. The restraint against shrinkage of concrete becomes lower with the increasing distance from reinforcement rebar. Under the same reinforcement arrangement, a higher free shrinkage of concrete leads to a stronger restraint against shrinkage and a higher shrinkage stress formation in local concrete. The relationship between shrinkage strain and reduction of relative humidity in reinforced concrete structure is far different from that in plain concrete.