Thermal and Mechanical Properties at High Temperature of a Very High-Strength Durable Concrete.

A very high-strength microconcrete (fc=125 MPa) containing polymeric fibers and quartzitic aggregates, but no silica fume, has been investigated both at high temperature and after cooling, in order to evaluate the thermal diffusivity and the mechanical decay as a function of the temperature, since there is still scanty information in the literature on the high-temperature behavior of this family of materials. The very high-strength concrete (VHSC) investigated turned out to be very efficient, since (1) its compressive strength exhibits a decay very close to that of normal-strength concrete, with no sizable differences between the “hot” and “residual” properties (250–750°C); (2) its specific fracture energy increases very much indeed with the temperature; and (3) its rather low thermal diffusivity guarantees good insulation properties. As an application of this material, the parking apron of an airport and its two-layered pavement subjected to a hot spot (T≤400°C) have been considered, in order to investigate whether delamination at the interface between the top VHSC layer and the bottom normal strength concrete layer and/or cracking in the bottom layer may occur. The performance of the pavement was analyzed for different values of the thickness of the top VHSC layer and also for different values of its thermal properties, and proved to be very satisfactory in terms of tensile behavior. However, the critical factor remains the initial heating rate. [ABSTRACT FROM AUTHOR]