Thermal nondestructive testing (TNDT) of adhesively bonded composite reinforcements applied to concrete civil structures

Thermographic nondestructive testing (TNDT) was performed on composite reinforcements applied to two concrete civil structures: 1. Caltrans Qualification Test -University of California, Irvine - A reinforced cement column, which represented a freeway support column, was fabricated with a 14 inch square cross section. Fiberglass laminate shells up to 1/2 inch thick were adhesively bonded to the concrete column to simulate a proposed seismic retrofit. TNDT was used to evaluate the entire area of the fiberglass laminate. 2. Navy Pier 12, San Diego Naval Station - This structure is 50 years old and was rated for 30 ton loads. It was required that the deck loading capacity be upgraded from 30 to 50 tons. Several types of Graphite and Glass fiber reinforced composites were adhesively bonded to the concrete substructure to achieve the desired increase in deck loading capacity. TNDT evaluations were performed on a "random spot check" basis along typical sections of the each of the composite systems which were used to reinforce the concrete deck structure TNDT provided both qualitative and quantitative information. TNDT was successful in detecting both simulated and actual disbonds in several types of composite reinforcements. TNDT was an effective technique for inspecting some of the composites, but was unsuccessful in inspecting some of the thickest (1/2 ") composites. In several cases, it was possible to perform destructive investigations to confirm the results of TNDT testing. TNDT standards were created "in situ" for two of the composite materials used on these composite upgrades, and free standing TNDT standards were fabricated for several more. Information on the types of defects which occur in these structures and their locations has led to process improvements in the application of adhesively bonded laminated composites to steel reinforce concrete structures.