Associated Engineering reviewed the use of compaction piles which was found to be too costly and investigated the use of elliptical steel or traditional reinforced concrete jackets which would need to be massive and alter the profile of the pier and visibility at the site. The British Columbia Ministry of Transportation and Infrastructure opted for a solution that involved Ductal® jacketing of the south bank pier.
In addition to a substantial saving of $1.5 million (CDN), Ductal® also delivers exceptional high seismic deformation capacity using a thin jacket. The project also provided the opportunity to demonstrate the effectiveness of a new Ductal® solution that can be used on similar projects in future.
The retrofit involved two tapered, rectangular columns 2.1 m x 2.6 m on a height of approximately 3.2 m from the base. The design required the use of 25-mm diameter dowels into the existing concrete. Rebars, spaced at 230 mm in both directions, was attached to the dowels. The contractor constructed strong formwork around the columns to withstand the high pressures involved in placing the fluid concrete, and a 225-mm thick Ductal® jacket was cast.
To minimize the number of cold joints, Lafarge utilized its ready-mix concrete plant in Abbotsford, British Columbia to batch and supply a total of 18 m3 of Ductal® using two ready-mix trucks, making two trips each. This solution, which brings together different Lafarge product lines ("One Lafarge" approach), was selected instead of using portable mixers onsite.
It was the first time that Ductal® has been batched in ready-mix trucks for a project in British Columbia. The formwork was then filled from the top using a standard hopper, with the casting completed in one day.