Aggregate’s influence on thermophysical concrete properties at elevated temperature

• The mineralogical nature of aggregates influences the degradation and the mass loss of concretes.
• The crystallinity degree of aggregates governs the thermal conductivity and diffusivity of concretes.
• The moisture state of concrete influenced its specific heat.
• The physical phenomena related to water appear to have a major influence on the thermal gradients of concretes.

This study investigates the thermophysical properties evolution of concretes made of three types of aggregates (quartzite, flint and limestone) during and after heating. For each aggregate type, two paste matrices (W/C = 0.3 and 0.6) were tested. The thermal conductivity and the specific heat are measured by a hot disk device. The evolutions of thermal properties are related to the mineral composition of aggregates but also to the microstructural evolution of concretes during heating. Evolutions of porosity, mass loss and cracking are investigated for the different concretes. The influence of aggregate’s nature is then discussed regarding the thermal response of heated concrete cylinders.