Service Life Prediction of Concrete Parking Structures: Case Studies

Reinforced concrete (RC) parking structures are typically subjected to harsher exposure conditions than other RC buildings, which causes them to deteriorate at a faster rate. The parking decks are the structural components that are the most susceptible to deterioration, because of their direct exposure to airborne salt sprays, rainwater, mixtures of water, and chemicals transported by the vehicles, groundwater, snow, deicing salts, etc. Concrete cover is traditionally the main (in some cases, the only) form of protection to corrosion for the steel reinforcement. High performance concrete mix designs and surface-applied concrete coatings are other effective means to slow down corrosion initiation and propagation. Parking structure owners and managers are often faced with the task to determine the residual useful life of their structures. Also, the paper will discuss two case studies: one dealing with a parking structure approaching the end of its service life, and the other with a new structure. In both cases, the structural condition was assessed through visual observations, nondestructive, and laboratory testing. The authors used the data gathered from the review of the original design documents, the results of the field survey, and laboratory testing to estimate the service life of the structures. The service life prediction was conducted following guidance from the American Concrete Institute (ACI) Committee 365 Report on Service Life Prediction (ACI 365.1R-17) and the fib Bulletin 34 Model for Service Life Design. In addition to the case studies, the authors discuss future trends for in-situ monitoring and analytical simulation of concrete durability.