Title:
Crack-Free "Surround Concrete" Repairs Oland Bridge Piers
Author(s):
Ingvar Nilsson
Publication:
Concrete International
Volume:
16
Issue:
7
Appears on pages(s):
26-31
Keywords:
bridge piers; crack-free repair; sliding layer; surround concreting; Construction
DOI:
Date:
7/1/1994
Abstract:
Damaged bridge piers are being repaired by placing new concrete around them. Durability requirements demand that this concrete is completely crack-free. When the surrounding concrete cools and contracts, the old pier heats up and expands. This results in large tensile stresses and a risk of through cracks. It was not possible to achieve a crack-free result solely by casting cooled concrete. The use of a sliding layer between an old pier and its surrounding concrete is a new method of obtaining a crack-free structure. Based on measured load-deformation curves for the sliding layer respecting of both normal forces and shearing forces, surround concreting of the piers with a sliding layer can be dimensioned so that no cracks result from the heat of hydration and shrinkage. If a cellular plastic layer is included in the sliding layer, one must select a material with closed cells and low water absorption. Otherwise, there is a risk of bursting under freezing conditions. For the Oland Bridge, cellular plastic is used only at the pier ends where the movement requirement is greatest. Furthermore, the cellular plastic is enclosed between two watertight asphalt membranes.