SERVICE LIFE PREDICTION BASED ON SORPTIVITY FOR HIGHWAY CONCRETE EXPOSED TO SULFATE ATTACK AND FREEZE-THAW CONDITIONS

This report documents a study that investigated permeability as an indicator of the general durability of hydraulic cement concrete. Since many concrete deterioration mechanisms depend on the ingress of moisture and other materials into the concrete, it was theorized that permeability might be a good indicator of durability potential. During the project, it was determined that sorptivity is the most relevant transport characteristic of the concrete. A test method for sorptivity was therefore developed, which has two different setups, in order to better reproduce the exposure condition being simulated. User-friendly software, CONCLIFE, was then developed for estimating the service life of concrete pavements and bridge decks exposed to sulfate attack and freeze-thaw deterioration. CONCLIFE uses three concrete models and user-specified data on concrete properties and external environmental conditions to estimate the time at which the concrete surface spalls beyond a user-specified limit. Ingress of sulfate ions and water are the primary means of degradation considered by the software. CONCLIFE uses the results of the laboratory test described above, currently in the ASTM standardization process, for measuring concrete sorptivity. The software produces graphs of concrete sorptivity, annual precipitation, and estimated rates of concrete spalling based on the input. Details of the experimental program conducted in support of the software development and the underlying technical bases for the computer models employed in CONCLIFE are also included. \n