Q.: We have a project consisting of repair of a pier on the Atlantic Ocean in a subtropical climate. The job consists of repairing the original concrete piles that have been damaged not only by the effect of the seawater but by mechanical abrasion due to ships. What procedure should be used?
A.: The piles can be repaired by removing loose and unsound concrete and then casting new concrete around them within special jackets.
One kind of jacket is a nylon fabric sleeve that surrounds the pile and is closed with a vertical zipper. Such jackets are available from Construction Techniques Inc., 11900 Shaker Boulevard, Cleveland, Ohio 44120.
Another kind of jacket is made of a fiberglass-reinforced plastic sheet that can be bent into a cylindrical shape and held in place by an interlocking closure that is part of the sheet. Special jackets are also available with rectangular cross-sections and several kinds of accessories. Concrete or mortar is pumped in through a valve at the bottom. The forms are available from Symons Corporation, 200 East Touhy Avenue, Des Plaines, Illinois 60018.
Another solution is to repair by shotcreting. After removing unsound concrete, steel mesh or anchors should be attached to the piles. Shotcreting would have to be done at low tide. The shotcrete layer should be thick enough to provide 2 inches of cover over the steel.