Abstract Manager

The deterioration of highway bridge decks in Ontario due to the application of de-icing salts during winter maintenance has resulted in costly bridge replacements or rehabilitations.  The Ministry of Transportation of Ontario (MTO) has made significant changes in its corrosion protection strategy over the years to improve the performance of bridge decks, particularly its requirements for bridge deck waterproofing. Mastic waterproofing membrane was introduced in 1962, followed by hot applied rubberized asphalt waterproofing system in 1972, and protection board for waterproofing membrane was specified since 1975.  In 1988, the end-result specification for waterproofing was introduced in MTO contracts enforcing penalties for deficient material and workmanship.

The present study is divided into two parts. In the first part, a statistical analysis of chloride content was completed using data gathered from over 100 detailed bridge deck condition surveys to evaluate the effectiveness of the MTO’s waterproofing requirements.

The second part of this study utilizes data collected from 53 detailed bridge deck condition surveys and uses Fick’s Second Law of diffusion to determine the apparent diffusion coefficient and apparent surface chloride concentrations for each bridge site.  A step approach was used to project the ingress of the chlorides through the remainder of the structures 75-year service life. 

The result of this study demonstrates the benefit of the hot rubberized asphalt waterproofing system in preventing chloride ions from penetrating concrete. Additionally, the results can be used to inform decisions on the use of premium and corrosion resistant material and the selection of a rehabilitation strategy.