Wisconsin Department of Transportation
Behrouz Shafeishafei@iastate.edu email >
Structural Engineer, BEC
Peter Taylorptaylor@iastate.edu email >
Director, CP Tech Center
About the research
Placing concrete under water has been a necessity for several bridges built over water streams. Based on the current practice, there are two main approaches to construct underwater reinforced concrete (RC) structural elements: (1) drying the site first by using cofferdams and pumps and then pouring concrete as usual and (2) placing concrete in the presence of water. The former approach has been employed with a relative success from a technical perspective. However, it can cause a range of safety and environmental concerns, especially if the required equipment experiences any failure. Furthermore, the former approach costs notably more than the latter one (i.e., up to twofold). The outlined issues have encouraged transportation agencies to consider the latter approach, in which concrete is directly placed underwater, thus eliminating significant (and costly) site preparation requirements. Despite advantages, however, construction of RC structural elements, such as piers and abutments, without cofferdams can be challenging in aquatic environments. In particular, the quality of the concrete placed under water can be adversely affected because of the issues with segregation of the concrete and loss of the cement paste. Consequently, strength and durability of the RC structural elements placed in water can be compromised, requiring significant maintenance and repair.
To address the outlined issues and identify best practices for the placement of concrete underwater and deep drilled shafts, WisDOT has expressed interest in a comprehensive research on the subject of underwater concrete for bridge substructures. The goal of this research is to assess WisDOT current policy, standards, and specifications, the policy and practices of other DOTs, and current industry practices (including other marine environment construction industries), and then provide guidance to be used in improving WisDOT policy, standards, and specifications related to underwater concrete placement.