Ground-Penetrating Radar monitoring of concrete at high temperature

• Published in: Construction & building materials 2017-10, Vol.151, p.881-888
• Main Authors: Lo Monte, Francesco, Lombardi, Federico, Felicetti, Roberto, Lualdi, Maurizio
• Format: Article
• Language: English
• Subjects: Analysis; Concrete; Concretes; Drying; Fire; Ground-Penetrating Radar; High temperature; Pore pressure; Properties; Spalling; Vaporization; Water; Waterfronts
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2017.06.114

•Water front migration has an important role in hygro-thermal behaviour of concrete.•GPR proves to be able of detecting water front position in concrete during heating.•GPR and pressure measurement combination is very effective in spalling investigation.•Pore pressure peaks are reached in correspondence of the water front. Water front in concrete exposed to rapid heating is the layer where water vaporization and the subsequent pore pressure rise take place. Pore pressure is one of the main triggering factors in heat-induced explosive spalling (relevant for structures, such as tunnels, exposed to fire), while moisture migration influences concrete radiation shielding capability (important in containment shells of nuclear power plants and radioactive waste repositories). Hence, the experimental monitoring of water front in concrete at high temperature is a very interesting – though challenging – task. In a recent experimental campaign carried out at Politecnico di Milano, promising results have been obtained by coupling pore pressure-temperature measurements and water front monitoring through Ground-Penetrating Radar. This technique was implemented in a fire test performed on a concrete slab heated at the bottom face and proved to be effective in detecting the position of the water front during heating. The combination with pressure measurement allowed to confirm that pressure peaks are achieved in correspondence of the water front.