Experimental Study of Thermal-Hydraulic-Mechanical Coupling Behavior of High-Performance Concrete

The design of an underground nuclear waste disposal requires a full characterization of concrete under various thermo-hydro-mechanical-chemical conditions. This experimental work studied the characterization of coupled thermo-hydro-mechanical effects using concretes made with cement CEM I or CEM V/A (according to European norms). Uniaxial and triaxial compression under 5 MPa confining pressure tests were performed under three dif-ferent temperatures (T = 20 & DEG;C, 50 & DEG;C, and 80 & DEG;C). The two concretes were dried under relative humidity (RH) to obtain a partially saturated state of approximately 70%. The results showed that the effects of water saturation and confining pressure are more important than that of temperature. Drying in high RH at different target tempera-tures led to an increase in uniaxial and triaxial strength but drying at 105 & DEG;C had a negative effect on the strength and Young's modulus. Oven drying caused microcracking in the concrete. The microcracks deeply influenced the thermal damage to the material, affecting its mechanical behavior. The triaxial strength clearly increased due to the presence of confining pressure. Moreover, an important influence of cement type was observed on the mechanical properties; the concrete based on CEM V/A had a greater porosity than CEM I, and a finer pore struc-ture appeared due to the presence of mineral admixtures.