High temperature effect on mechanical properties of autoclaved aerated concrete

In this paper, an experimental study on mechanical properties at high temperature of a typical autoclaved aerated concrete (AAC) tested in compression is presented (compressive strength = 5 MPa and density = 600 kg/ m(3) at 20 C-degrees). Parameters such as the compressive strength, strain at the peak stress, and elastic modulus are investigated, along with the stress-strain response in the thermal range 20-700 C-degrees. The behavior of the AAC tested in this research project is different from that of normal concrete, because of a series of chemo-physical processes occurring at high temperature. Between 100 and 600 C-degrees, the compressive strength increases and then starts decreasing (+51% at 600 C and +10% at 700 C-degrees compared to ambient conditions). The strain at the peak stress increases as well with the temperature similar to - but more than in - normal concrete. The stressstrain curves and the failure modes show that AAC's behavior is brittle at any temperature and that the damage inside the material increases with the temperature in such a way that the existing models for normal concrete exposed to high temperatures cannot be used in the case of AACs. Hence, a new polynomial model is proposed to properly describe the constitutive behavior of AACs at high temperature.