This study focused on forensic investigation of fire-affected reinforced concrete buildings. Post-fireudinvestigation was conducted on structural elements in three selected fire-affected concrete buildings, in order toudascertain their in situ residual strengths and also to provide data for use in future assessment of fire-affectedudbuildings. The selected sites for investigation include a five-storey building at Alagbaka and a bungalow atudAdegbola in Akure, and a ten-storey building in Benin, Nigeria. Rebound hammer and ultrasonic pulse velocityudare two non-destructive tests apparatus used for this investigation. Average values of pulse velocity were fittedudinto an established model in order to estimate the probable temperature, which the buildings were subjected to.udTests were conducted on beams, columns and slabs in both the affected and the unaffected parts of theudbuildings. From the results, visual examination of the fire-affected buildings revealed changes in the colour ofudthe concrete, delamination of plaster of slab and exposure of reinforcement for severe cases at various locationsudon the concrete members. In addition, there was notable reduction in the in situ strengths of the fire-affectedudstructural members when compared with the unaffected members. It was deduced that concrete membersudsubjected to temperatures above 6000C lost about 70 % of its strength.
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