Iowa Department of Transportation
Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer
Kejin Wangkejinw@iastate.edu email >
PCC Engineer, CP Tech Center
About the research
Transverse cracks in concrete bridge decks sometimes initiate in the early stages of the bridge service life, usually just after construction. Cracks in the bridge deck can accelerate the deterioration of the deck concrete, provide a direct pathway for the intrusion of water and chlorides to the deck reinforcement, and detract from the aesthetics. This eventually results in increased maintenance costs and reduced bridge service life.
The goal of this research was to identify factors that consistently lead to the formation of early-age transverse cracks for mitigation in the future. To obtain a comprehensive evaluation and include as many factors as possible in the research, the primary research investigation was conducted in three stages with varying numbers of bridges and factors considered in each stage.
The first stage was carried out on 2,675 bridges constructed in Iowa between 1900 and 2020. The goal of this stage was to identify the correlation between deck cracking and six parameters: deck concrete type (high-performance concrete [HPC] or non-HPC), maximum span length, maximum structure length, Iowa Department of Transportation (DOT) District, year built, and main structure type.
The second stage was conducted to include additional bridge parameters—but with a smaller number of bridges. A group of 20 bridges was selected after reviewing inspection reports for 116 bridges constructed between 2013 and 2018. Various bridge parameters in three main categories, structural, construction, and material, were investigated.
The third stage was carried out based on data collected from six field visits while deck concrete was being placed. The parameters investigated in this stage included evaporation rate (lb/ft2/h), air temperature (°F), concrete temperature (°F), relative humidity (%), and wind speed (mph).
The results from the three investigation stages were compared with the research results documented in another Iowa DOT report. Based on the research findings from each stage of investigation, the various parameters were classified as having either direct correlation, no correlation, slight positive correlation, or slight negative correlation.