Abstract: Due to addition of a new type MgO material, RCC shows a stable expansion to compensate the shrinkage resulted from internal or external temperature gradient, thus minimizing the risk of cracking. Autogenous volume deformation of full -  sized RCC is tested, the experimental results show that the maximum expansion ratio is 114×10-6 and 168×10-6 at the age of 365 days under standard temperature or high temperature curing conditions, respectively. Expansion ratio of wet -  screened RCC is a little more than that of full -  sized RCC.