A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Capacitive probe for non destructive inspection of external post-tensioned ducts
A lot of bridges include 'external' post-tensioned cables (not in the concrete material, hence potentially accessible for measurement), either originally or an after reinforcement of structure. The cables are generally placed in High Density Poly-Ethylene (HDPE) ducts, where the residual space is filled under high pressure with a cement grout intended to prevent corrosion. Nevertheless, in some cases, the cables breaking occur in non-protected zones because of the presence of a 'white paste' or grout voids. The white paste is a exudation product of the cement grout which is not a hardened grout, containing a high concentration of the water and has a high pH (of the order of 13-14). Moreover, an analysis showed that a high value of the pH of the material promotes the corrosion of the steel cables. The detection of such defects inside an opaque duct is unachievable visually from the outside. This paper presents an analysis of the capabilities and characteristics of the capacitive probe used to evaluate the injection in the external post-tensioned ducts. Numerical simulations, based on an analytical model and a finite element simulation, give the sensitivity of the probe as a function of the materials inside the duct. The measurements on a laboratory specimen are in good agreement with numerical simulations. An investigation on a bridge shows an example of detection of voids and white paste, confirmed by an aperture on the duct envelope.
Capacitive probe for non destructive inspection of external post-tensioned ducts
A lot of bridges include 'external' post-tensioned cables (not in the concrete material, hence potentially accessible for measurement), either originally or an after reinforcement of structure. The cables are generally placed in High Density Poly-Ethylene (HDPE) ducts, where the residual space is filled under high pressure with a cement grout intended to prevent corrosion. Nevertheless, in some cases, the cables breaking occur in non-protected zones because of the presence of a 'white paste' or grout voids. The white paste is a exudation product of the cement grout which is not a hardened grout, containing a high concentration of the water and has a high pH (of the order of 13-14). Moreover, an analysis showed that a high value of the pH of the material promotes the corrosion of the steel cables. The detection of such defects inside an opaque duct is unachievable visually from the outside. This paper presents an analysis of the capabilities and characteristics of the capacitive probe used to evaluate the injection in the external post-tensioned ducts. Numerical simulations, based on an analytical model and a finite element simulation, give the sensitivity of the probe as a function of the materials inside the duct. The measurements on a laboratory specimen are in good agreement with numerical simulations. An investigation on a bridge shows an example of detection of voids and white paste, confirmed by an aperture on the duct envelope.
Capacitive probe for non destructive inspection of external post-tensioned ducts
Kapazitive Sonde für die zerstörungsfreie Prüfung extern nachgespannter Kanäle
Taillade, F. (author) / Cottineau, L.M. (author) / Aubagnac, C. (author)
2008
8 Seiten, 7 Bilder, 22 Quellen
Conference paper
Storage medium
English
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