Title: Site Study of Factors Leading to a Reduction in Durability of Reinforced Concrete
Author(s): David Griffiths, Marton Marosszeky, and Davod Sade
Publication: Symposium Paper
Appears on pages(s): 1703-1726
Keywords: absorption; carbonation; concrete durability; corrosion; cover; evaluation; failure; impact hammer tests; surveys; Design
Much of the research in the area of concrete durability has focused on material science issues in an attempt to improve the durability of the concrete. A major study carried out at the Building Research Centre, University of South Wales, set out to identify the main cause of reinforcement corrosion on buildings in the Sydney metropolitan area. First, a macro survey was undertaken to determine the frequency of corrosion failures on 95 buildings. The data is sufficiently detailed to enable identification of frequency by member and by orientation as well as an aggregate for each building. In a closer examination, concrete quality and reinforcement position were assessed at durability faults relative to other locations on the building. Concrete quality was assessed by a measure of relative strength using an impact hammer, the depth of carbonation, and the initial rate of absorption. Reinforcement cover was measured visually and using a covermeter. The findings of both the macro and detailed survey are discussed in the paper. For the 95 buildings surveyed, a multiple regression analysis did not indicate a higher density of failures on buildings near the coast or harbor than buildings up to 27 km from the coast. Conclusions drawn from the detailed evaluation of 41 faults on existing buildings were that carbonation, absorption, and strength were not useful indicators of failure in the cases examined. However, the mean cover-to-reinforcement at 227 faults was found to be 5.45 mm, clearly indicating that lack of cover is a major problem associated with failures.