New NDT techniques for the assessment of fire-damaged concrete structures

An extensive research programme has been performed at Politecnico di Milano in order to identify quick and easy methods for the assessment of the thermal damage undergone by reinforced concrete structures in consequence of a fire. As a result, three new investigation techniques have been proposed, which allow to assess the whole thermal damage profile in one single test: a simplified interpretation technique for the indirect Ultrasonic Pulse Velocity (UPV) method (based on the refraction of longitudinal waves), an affordable approach to concrete colorimetry and the real-time monitoring of the drilling resistance. In this paper, the pros and cons of the proposed techniques are pointed out, as revealed by laboratory tests. The actual in situ viability of each method is then discussed, after the investigations conducted on two full-scale structures: a precast R/C industrial building surviving a real fire and a concrete tunnel submitted to a series of hydrocarbon-pool fire tests.