Strength Assessment of Concrete Bridge at Elevated Temperature using Destructive and Non-Destructive Methods

Abstract

Concrete bridge structure when subjected to fire, exhibit good behaviour as a result of their low thermal conductivity associated with their great capacity of thermal insulation. However, there is a fundamental problem of ‘spalling’ caused by high temperatures on concrete (separation of concrete masses from the body of the concrete element). To investigate this fundamental problem caused by high temperatures, concrete cubes of grade 25 were prepared, cured in water for 28 days and subjected to elevated temperature at varying degrees ranging from 100 to 600 oC for various timing of ½, 1, 1½, 2, 2½ and 3hrs, after which non-destructive (Rebounds Hammer and Ultrasonic Pulse Velocity) and destructive (Compression) testing methods were carried out to compare the compressive strengths obtained. Direct and deductive results obtained show that there was a drop in the compressive strength of the specimen after it had been subjected to elevated temperature for all methods. The result also showed that the non-destructive testing method is more reliable as it also allows a physical examination of the interior properties of the samples. In addition, the combined pulse velocity and rebound index method has no effect on the accuracy of the interpretation. However, it is clear that any of the three methods can be adopted depending on the situation at hand.