Effects of Shale and CaO Incorporation on Mechanical Properties and Autogenous Deformation of Early-age Concrete

The pre-soaked shale employed as an internal curing agent and CaO employed as expansion agent were incorporated into concrete to investigate their effects on the mechanical properties and autogenous deformation of early-age concrete. We have conducted the relevant tests for setting time, mechanical properties, internal relative humidity and autogenous deformation of early-age concrete with shale or/and CaO incorporation. The results indicate that the set behavior is delayed by shale addition but is accelerated with CaO. The shale addition firstly enhances and subsequently decreases the strength, but CEA addition has a weakening effect. Additionally, shale or/and CaO incorporation deteriorates the elastic modulus. The shale and CaO incorporation significantly improve the internal relative humidity of concrete. The internal curing efficacy of shale could synergistically mitigate the autogenous shrinkage, that is, could enhance the expansion of CaO and then greatly reduce the contraction, which is significantly beneficial to impede the shrinkage-introduced cracks of early-age concrete.