Project Details
19-688, TR-771
02/01/19
10/31/24
Iowa Department of Transportation
Iowa Highway Research Board
Researchers
About the research
Conventional bridge deck overlays made with high-performance concrete (HPC) and low-slump dense portland cement concrete (PCC) generally require a 72-hour wet curing time before they can be opened to traffic. Shorter opening times are desired to reduce the high cost of traffic control for heavily traveled urban highways. To meet this need, high early strength latex-modified concrete (LMC-VE) overlays are designed to open to traffic within 3 to 6 hours of placement. Research indicates that LMC-VE overlays are less prone to shrinkage-related problems and more resistant to chloride penetration than other early strength overlays. The high initial cost can be offset by the reduced need for traffic control and the extension in bridge deck service life by an additional 30 years, reaching a total service life of over 75 years.
In September 2019, the Iowa Department of Transportation placed Iowa’s first LMC-VE bridge deck overlay on the IA 15 bridge over Black Cat Creek in Emmet County. In this research, the overlay construction activities were thoroughly documented, and LMC-VE specimens were cast in the field to investigate a range of mechanical and durability properties in the laboratory. Additionally, the field overlay’s performance was monitored for 50 months through frequent field visits and testing. Lastly, a life-cycle cost analysis (LCCA) was performed to assess the economic value of the LMC-VE overlay relative to other overlay types.
The laboratory tests indicated that the LMC-VE mix reached 2,827 psi at 3 hours, which is sufficient for quickly opening a pavement to vehicular traffic, and exhibited sufficient long-term compressive and flexural strength, good chloride penetration resistance and high surface resistivity, comparable shrinkage and initial sorptivity to PCC, and mixed results for freeze-thaw durability. During field monitoring, the overlay exhibited some thin cracks, slight spalling/abrasion in a few localized areas, a slight decrease in friction over time, comparable initial and secondary sorptivity to HPC, and a good substrate-overlay bond. The LCCA results suggest that the high life-cycle cost of the LMC-VE overlay outweighs the lower user costs. However, when annual average daily traffic (AADT) values are above 3,300, the LMC-VE overlay could be a better alternative. The results of this research are expected to serve as a benchmark and assist in decision-making related to the selection of overlay alternatives for future bridge deck applications in Iowa.