Abstract

As the primary cause of concrete bridge deck deterioration in the United States is corrosion of the steel reinforcement as a result of the application of chloride-based deicing salts, chloride concentration testing is among the most common techniques for evaluating the condition of a concrete bridge deck. The objectives of this research were to 1) compare concrete drilling and powder collection techniques to develop a sampling protocol for accurately measuring chloride concentrations and 2) determine the number of chloride concentration test locations necessary for adequately characterizing the chloride concentration of a given bridge deck. Laboratory experiments on concrete drilling and powder collection were conducted to compare current concrete powder sampling techniques, including constant and stepwise drilling methods and spoon and vacuum powder collection methods. In addition, three charts were prepared to determine the number of chloride concentration test locations necessary for adequately characterizing the chloride concentration of a given bridge deck. The number of samples is dependent on reliability, spatial variability in chloride concentration, and an allowable difference between sample and population means. For the experiment on drilling, this research shows that the practice of decreasing the size of the drill bit in a stepwise fashion with increasing sampling depth reduces the possibility of abrading concrete from the sides of the hole above the sampling depth, where the chloride concentrations are higher, during drilling of lower lifts. For the experiment on powder collection, this research demonstrates that representative samples of concrete powder can be collected with either a spoon or a vacuum. Based on the results of this research, the stepwise drilling method and either the spoon or vacuum powder collection method are recommended for application. In addition, the charts developed in this research are recommended for estimating the number of chloride concentration test locations necessary for adequately characterizing the chloride concentration of a given bridge deck. This research will be helpful in effectively assessing the condition of concrete bridge decks with respect to chloride-induced corrosion of the reinforcing steel and prioritizing bridge maintenance and rehabilitation projects.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

Rights

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