Retained properties of concrete exposed to high temperatures: Size effect

Abstract

Concrete as a construction material is likely exposed to high temperatures during fire. The retained properties of concrete after such exposures are still of great importance in terms of the serviceability of structures. This paper presents the effects of high temperatures on the physical, mechanical, and microstructural properties of concrete. Specimens with different sizes were exposed to high temperatures ranging from 200 to 1200°C. The compressive strength, splitting tensile strength, ultrasonic pulse velocity, and rebound numbers of the specimens were determined. The microstructures of the specimens were examined by scanning electron microscope (SEM) analyses. The test results indicated that the retained compressive strength of concrete considerably decreased with increase in temperature. The effect of specimen size on the retained compressive strength was not pronounced. The retained splitting tensile strength of concrete remarkably reduced as the temperature was increased. The specimen size played an important role on the retained splitting tensile strength of concrete up to 400° C. The test results revealed that ultrasonic pulse velocity (UPV) test can be successfully used in order to check the uniformity of fire-damaged structures. The rebound numbers decreased with increase in exposure temperature. SEM studies on specimens exposed to 800°C revealed significant changes in the microstructure of the concrete. Copyright © 2009 John Wiley & Sons, Ltd.