Damage evaluations of oven-dried mortar subjected to one-directional fire

Abstract

Concrete structures can be damaged by various factors in extreme service conditions. Analytical methods that can predict the strength of structural concrete after exposure to fire are needed to facilitate decisions regarding whether to repair, strengthen, or demolish fire-damaged buildings. However, appropriate and widely applicable material models have not yet been proposed. This paper presents an experimental study in which we assess damage, including changes in flexural strength, porosity and residual cement hydrates, to oven-dried mortar that has been fired and immediately cooled in the air. Mortars were made from calcareous and siliceous aggregates, and one face of each specimen (100×100×400 mm) was exposed to fire curves of ISO 834 and ASTM E119. Specimens for quantitative assessment were hewed to ten layers from the originalspecimens. Experimental results indicate that the in-depth flexural strength of a thin specimen is substantially diminished by fire exposure, especially for specimens with existing fire cracks. In addition to the loss in strength, changes in porosity and chemical properties occur. Based on the experimental evidence obtained from this study, the relationships between each property are discussed.