Nondestructive Evaluation of Thermal Damage in Concrete by Single-Sided Nuclear Magnetic Resonance

Abstract

A new technology to coat concrete with coherent layers of glass by flame-spraying is currently developed at the Institutes of Building Materials Research and Mineral Engineering of RWTH Aachen University in Germany through a joint program. A major factor influencing the pull-off strength of the flame-sprayed glass coating is thermally induced damage in the underlying concrete substrate. In this article, the authors present a nondestructive test method using single-sided H1 nuclear magnetic resonance (NMR) to evaluate the thermally induced damage in concrete specimens. The particular NMR device used in this project primarily detects water and can qualitatively assess the water content as well as the relative size of water-filled voids such as pores and cracks. To do so, the specimens are water saturated and subsequently analyzed by NMR. Changes in the NMR-signal are interpreted in terms of change in porosity and development of cracks inside the cement stone as a function of depth from the concrete surface.