The Virginia Polytechnic Institute and State University commissioned a petrographic examination of sample concrete cores as part of an evaluation of significant deterioration at various locations within their underground concrete tunnel system. Pedestrian tunnels were originally constructed in the 1930s while steam tunnels were subsequently added in the 1970s. Field evaluation revealed delamination of overhead concrete and significant corrosion of embedded steel reinforcement. Petrographic examination of sample cores was used to evaluate the existing condition of the concrete and to identify other possible sources of distress within the existing concrete matrix.
CTLGroup performed comprehensive physical and chemical evaluations of the concrete core samples taken from select locations throughout the tunnel system. Results showed concrete of similar composition at both the pedestrian and steam tunnels with an overall ‘fairly good’ rating condition. Cracking and delamination were attributed to corrosion of the embedded reinforcement steel. There was no evidence of deleterious chemical reactions within the cement paste or any other materials-related distress. The cores exhibited prolonged moisture infiltration, which was expected considering age and exposure conditions of the analyzed concrete.