Ultrasonic Assessment of the Concrete Residual Strength after a Real Fire Exposure

Abstract

After a fire, the assessment of concrete residual strength can be a challenge. Since the strength reduction depends on the distance from the heated surface examination based on destructive test, i.e., core samples, is not precise enough. Therefore, more detailed methods can establish the influence of the high temperature in the zone, which no longer has visible cracks. That method can be used to assess layer thickness to remove due to the fire damage. The Ultrasound Pulse Velocity (UPV) method with point heads was used in the paper to examine samples taken from a structure after the real fire. Moreover, to make the analysis more precise, an effect associated with the porosity in concrete was also considered to separate pure fire effect.

A Literature Review of Concrete Ability to Sustain Strength after Fire Exposure Based on the Heat Accumulation Factor

“…Destructive and non-destructive assessment of strength is possible [ 11 , 12 , 13 , 14 ], but providing enough information for structural calculations is a crucial issue. The temperature field inside the concrete element depends on many uncertain parameters, and this results in residual properties that are difficult to estimate.…”

The influence of adding alccofine and nano-silica on the behavior of concrete at elevated temperatures

“…The use of assumed tests for compressive strength of concrete employing NDT tests is preferred in terms of structure protection in fire and the ease with which data concerning the fire situation can be collected (9) . Numerous nondestructive techniques are often used to evaluate concrete loss and degradation after subjected to a fire, but UPV and rebound hammer (RH) tests can be effectively used to measure residual strength after fire (10,11) . The ultrasonic approach is widely used to assess the durability of concrete buildings in place (12,13) .…”

Thermal Infrared Radiation and Laser Ultrasound for Deformation and Water Saturation Effects Testing in Limestone

“…These methods comprise destructive methods involving load testing under different loading conditions [11,12] and semi-destructive mechanical tests with simultaneous measurement of acoustic emission [13,14]. Non-destructive in situ and laboratory methods for inspecting natural materials are addressed in [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], including thermal control [16][17][18][19][20], multispectral optical remote sensing [21], ground penetrating radar [22,23], ultrasonic inspection [25,26], gamma-ray logging [27], terahertz spectroscopy [28], X-ray tomography [29,30], neutron radiography [31], and others [32].…”

“…At present, the most common methods are thermography [16][17][18][19][20] and different versions of ultrasonic inspection [25,26].…”

“…However, it would be more efficient to use this method together with ultrasonic diagnostics so as to comprehensively assess the condition and internal structure of geomaterials. Conventional ultrasonic flaw detectors and tomographs operate, as a rule, at a certain resonance frequency [24][25][26], which makes it difficult to determine the geometry and location of different-scale defects. The use of piezoelectric transducers exciting and receiving broadband ultrasonic signals results in a sharp decrease in radiated power and a significant decrease in sensitivity, which means that the dynamic range becomes narrower.…”