Effect of Biaxial Mechanical Loading and Cement Type on the Fire Spalling Behaviour of Concrete

Fire spalling of concrete is a complex phenomenon, which might occur due to pressure build-up in the pores, thermal- and load-induced stresses. In this context, eight mid-size ordinary concrete slabs (4of B40-II and 4 of B40-III concrete: fc28 ≈ 40 MPa) were heated at the bottom face according to Standard Fire curve (ISO 834-1), while a constant biaxial compressive load was applied. Four different levels of biaxial mechanical loading have been investigated on both concretes. The test results showed that the loaded specimens are more prone to spalling than unloaded specimens, with increasing amount of spalling for higher values of applied load. Concrete made with CEM III cement (B40-III: 43 % of slag) exhibited less spalling than CEM II cement concrete (B40-II: 3 % of slag).