Effect of spalling on normal strength concrete (NSC) at transient high temperature

Abstract

Investigation is carried out on the behaviour of some normal strength concrete (NSC) grades 20, 25 and 30, having heated up the specimens in a regulated industrial oven from room temperature of about 280C to 10000C. The effect of heat flow induces various kinds of stresses that move at cross-lines generating strains and deformation that give rise to the phenomenon referred to as spalling. This is an irreversible destructive or deformable plastic state of concretes. This paper has established that spalling in normal strength concrete (NSC) takes place between 6500C and 8000C with concrete grade 20 exhibiting higher resistance to spalling than the other concrete grades. However, concrete grade 30 has the tendency of having explosive spalling due to its range of conflicts of stresses involved, which is shorter than the rest, as can be seen in the graphical representations. The result therefore, is that concrete grade 20 has smaller flexural cracks and deflections at transient high temperature compared to other concretes.