Tensile and shear bond strength between cement paste and aggregate subjected to high temperature

In the framework of studying the leakage rate of concrete containment of nuclear power plants during an accident, the mechanical characterization of interface between cement paste and limestone aggregate was performed with mechanical tests at the local scale, inside the laboratory of micromechanics and integrity of structures (MISt). The evolution of tensile and shear bond strength between cement paste and aggregate after heating was determined. It was revealed that the tensile bond strength was strongly affected by the temperature rise, with a decrease of about 71% at 60 degrees C. Moreover, the shear bond strength increased almost linearly with the increase of normal stress. According to the Coulomb criterion, the cohesion and the internal friction angle were determined. These parameters decreased after heating, which indicates occurrence of thermic damage between cement paste and limestone aggregate. Finally, it appears that the tensile bond strength is more affected by the thermal damage than the shear bond strength.