Service life prediction of connectors in masonry veneer wall systems
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AbstractThe service life of a brick veneer wall system generally varies from 25 to 100 years depending on the function of the wall. Given that the connectors in brick veneer walls are not maintained with a regular maintenance schedule, the expected service life of the connectors in the wall must meet or exceed the design life of the wall. The intent of the research was to examine the sources of corrosion in six types of masonry veneer wall systems under specific service conditions and determine the expected life of the connectors in each wall system. The materials modeled for the fabrication of the connectors were: untreated steel, zinc-galvanized steel and austenitic stainless steel (type 316/304). The expected service life of the metal connectors was determined using a simulation that estimated the rates of corrosion of connectors embedded in mortar and connectors directly exposed to the micro-environment of the wall cavity. This was achieved by deriving expressions for chloride ion diffusion and carbonation and using the linear ISOCORRAG - Model A expression to model corrosion propagation. The result of the simulation was an estimate of the service life for the connector in a brick veneer wall system. Corrosion experiments were conducted to develop an instrument that could be used in the field or laboratory to obtain instantaneous corrosion rates of ties embedded in mortar. A potentiostat and corrosion probe were used on brick wall and brick prism specimens. The linear polarization resistance technique (LPR) was used to obtain the instantaneous corrosion rate from the polarization curves obtained with the potentiostat. The results of the research were: an initial effort in modelling the corrosion rate and resulting service life of steel connectors in brick veneer wall systems with demonstrated correlation to laboratory and historical corrosion rate results, an experimental procedure that can be used in the lab or field to obtain the corrosion rate of ties embedded in the mortar joint of brick veneer walls, and suggestions for future research in the area of connector corrosion in brick veneer wall systems.
Bibliography: p. 249-261