ABSTRACT Title of Thesis: NON DESTRUCTIVE EVALUATION OF CHLORIDE IN CONCRETE

Bridge decks in the cold climate region of the country, which have snow part of the year, are exposed to deicer salt in order to overcome the public demand for safe pavements. The chloride content in the salt can penetrate into the concrete through hairline cracks or diffusion in the concrete. This can establish galvanic corrosion microcells, and ultimately damage the concrete and reduce the life performance of the structure through expansive forces created by corroded steel. The issue of chloride penetrating into concrete has been under study and research for a long time. There is a critical need in civil engineering for methods that can nondestructively measure the condition of existing reinforced concrete structures. The focus of this thesis is on a nondestructive prompt gamma neutron activation (PGNA) chloride detector. This technique is a specialized use of prompt gamma/neutron activation, a spectroscopic technique for elemental analysis of materials. The elements of PGNA are identified by characteristic gamma rays emitted from the target material while it is being bombarded with neutrons. The objective of this research is to design a test program for determining the calibration factor, which relates the detected chloride gamma ray counts to the actual chloride concentration in the concrete, and its uncertainties through the use of cast concrete samples with known chloride contents. NON DESTRUCTIVE EVALUATION OF CHLORIDE IN CONCRETE b