Iowa Department of Transportation
Kejin Wangkejinw@iastate.edu email >
PCC Engineer, CP Tech Center
Jinxin "Linda" Li
About the research
The early-age thermal development of structural mass concrete elements has a large impact on the future durability and longevity of the elements. If the heat of hydration is not controlled, the elements may be susceptible to thermal cracking and damage from delayed ettringite formation.
This study is aimed at developing guidelines for the design and construction of mass concrete placements associated with large bridge foundations. The study consisted of two phases: 1) literature review and 2) preliminary thermal stress analysis and in-depth thermal stress analysis and guideline development. This report describes the research activities conducted and results obtained from the Phase I study.
The published literature and current specifications on mass concrete, as well as the results of construction monitoring from the I-80 bridge at Council Bluffs, Iowa, were reviewed. Two computer programs, ConcreteWorks and 4CTemp&Stress, for thermal analysis of mass concrete, were explored.
Using ConcreteWorks, a sensitivity analysis was performed and various mix proportion, environmental, and construction parameters were examined. The results indicate that, not only concrete materials (such as fly ash and ground granulated blast furnace slag) and mix proportions (such as cement content), but also fresh concrete placement temperature, curing methods, and time of form removal have noticeable effects on thermal cracking.
Further understanding of the effect of each parameter on mass concrete thermal properties would help the Iowa Department of Transportation (DOT) and contractors to identify the most convenient and cost-effective methods to reduce the risk of thermal damage in mass concrete construction.