Assessment of the Cracking Problem in Newly Constructed Bridge Decks in Colorado: Fid-Bau Portal

Assessment of the Cracking Problem in Newly Constructed Bridge Decks in Colorado

Y. Xi / B. Shing / N. Abu-Hejleh / A. Asiz / A. Suwito

Early age cracking on concrete bridge decks has been experienced by many DOTs. In Colorado the cracking problem on newly constructed bridge decks has not been completely solved. In this study, the extent and causes of the cracking problem were investigated, and necessary changes to alleviate the cracking problem were identified. To achieve these goals, current CDOT practice was reviewed and compared with other DOTs practices for construction of bridge decks. A database analysis of field inspection results was performed. Presently, 18% of newly constructed bridge decks in Colorado have no early cracking problem, and the rest (82%) have various degrees of cracking problems. The results of the database analysis were then confirmed by field inspections conducted on nine newly constructed bridge decks. An extensive literature review was performed. Past research activities in Colorado were reviewed, current CDOT practices for controlling the bridge deck cracking problem were assessed, and recommendations to alleviate the cracking problem were identified. From the literature survey and previous research studies, the causes of cracking in newly constructed bridges can be categorized as material, design, construction, and environmental factors. High early age shrinkage of concrete is a major contributor among the adverse material factors. The cracking can also be a direct result of several structural design factors. Based on the results of field inspections, the cracks typically form above supporting members, such as girders or piers, and have large and uniform spacing. This is a result of tensile stresses from negative bending moments in the deck above supports. The construction and environmental factors (such as wind speed, temperature, and curing procedures) greatly affect the shrinkage of the concrete. Due to very limited information regarding deck curing or placement conditions, it has not been possible to determine the specific impact of these factors on early age deck cracking of the inspected bridges. Implementation: Recommendations to reduce the cracking problem in newly constructed bridges in terms of materials, design, and construction factors are presented. Based on the findings of Research Report No. CDOT-DTD-R-2001-11, new concrete mix designs Class H and Class HT have been implemented in the 2003 CDOT Standard Specification for Road and Bridge Construction. Most of the recommendations for construction of bridge decks have also been implemented in the 2003 CDOT specifications. The study recommendations for the structural design factors of bridge decks should been implemented in CDOT Bridge Guidelines.