On September 30th the first balsa cored composite bridge deck installed in Louisiana was opened to traffic over the Pierre Part Bayou in Assumption Parish, LA. While BALTEK® end grain balsa has been used previously for other commercial and military road and bridge deck projects, this installation is believed to be the very first balsa-cored composite deck project containing Single-Walled Carbon Nanotubes (SWCNT’s) as well as the largest Nanotube object molded to date.

This project, an Investigational Bridge Research Deployment (IBRD) Grant originated with the Louisiana Transportation Research Center (LTRC). The development of the composite bridge deck was jointly undertaken by the Louisiana Department of Transportation and Development (LA DOTD), Louisiana State University (LSU), Crescent City Composites, and the Technical Services team of ALCAN BALTEK Corp., a part of ALCAN COMPOSITES Core Materials.

Using balsa cored composite panels has many advantages in that respect. These light weight composite panels allow for fabrication off site and quick installation, which results in less “down time” for the bridge and substantially less traffic disruption, as well as less constriction on important evacuation routes during Hurricane season. Moreover, these panels are immune to corrosion which shortens the life span of steel structures, especially over brackish waters.

Being replacement panels for existing steel construction means that the geometry, specifically the thickness of the panel, is dictated by the existing bridge structure. Therefore, to achieve the required stiffness within the restricted thickness, layers of Hardwire® high-tensile strength steel reinforcements were used in conjunction with conventional biaxial glass fiber in the structural skins.
The core chosen for this application was a specific density range of BALTEK® end-grain balsa. Only end-grain balsa could absorb both the high compression loads required of a bridge designed to withstand the continuous punishment of fully-loaded sugarcane trucks, and the high shear loads imposed by the restricted thickness and highly-loaded metal and fiberglass skins.

All panels were vacuum-infused on site at the Crescent City lamination facilities in East Texas and trucked to the LA DOTD in Baton Rouge, where they were adhesively bonded to steel girders. Future production is expected to take place in Louisiana.