CHLORIDE ION MEASUREMENT SYSTEM FOR RC STRUCTURE BY NEAR-INFRARED SPECTROSCOPY

Aging deterioration of reinforced concrete structures is mainly due to chemical reactions of rebar corrosion, carbonation, alkali-aggregate reaction, and the like, whereas collection of chemical information is effective to accurately grasp these signs. The recently introduced nondestructive measurement method of chloride ion concentration using a near-infrared (NIR) spectroscopy system detects an NIR peak of Friedel’s salt that is immobilized on a concrete surface, followed by application of a multispectral method. Herein, a prototype of a small-scale, NIR spectroscopy system that does not require seismic isolation was developed, using imaging-type two-dimensional Fourier spectroscopy technology, and the applicability of twodimensional imaging of chloride ion concentration on concrete surfaces by this system was evaluated. Apparently, measurement by the system could be performed in a short time and with measurable accuracy. Moreover, the two-dimensional imaging of chloride ion concentration was possible in an outdoor environment with almost no associated difficulty. In addition to measuring Friedel’s salt, it was possible to observe cracks on the concrete surface by measuring water.