In this publication theoretical and experimental studies of development of properties of early age concrete are presented. The use of high-performance concrete's means higher content of binders and lower water to binder ratios in comparison with the use of plain concrete. A simulation model of early age concrete is presented for the prediction of development of the degree of hydration and structure formation in cement and chemical and mineral admixtures bared materials. Mathematical model showing the dependence between concrete compressive strength and porosity coefficient of its structure is presented as well. The general idea of modelling is to predict early age strength growth of Plain and High Performance Concrete's. Concrete structures treated by outer load are exposed to loads resultant from material properties and technology of structure. These loads are mainly caused by unsteady, coupled fields of temperature and humidity. Cracks can be made in zones of tensioned concrete on the surface of solid. In this publication thermal stresses of two experimental concrete blocks are presented.