Evaluating Applicability of ASTM C 928 Approach in Assessing Adequacy of Patch Repair of Bridge Piers

Abstract

Severe environmental conditions in many parts of Iran could adversely affect infrastructures, especially bridge piers. This research evaluates the efficiency of fiber-reinforced polymer-modified self-compacting concrete in patch repair of bridge piers. The efficiency of this material for repair has been verified using ASTM C 928 and a novel testing method (patch test) that uses a cylindrical compression test simulating indirect force transfer from old (existing) concrete to new (patch repaired) concrete. To investigate the efficiency of self-compacting concrete in patch repair and derive the correlation between bond strength and patch strength, two sets of specimens have been included in the experimental program. These include 24 and 27 specimens which are prepared for patch and slant shear tests, respectively. Test results show significant improvement in strength due to use of polymer modified and fiber reinforced self-compacting concrete in slant shear tests, where strength enhancement as much as 50% (compared to undamaged specimens) was observed. Meanwhile, in the patch tests, repaired specimens are only able to barely exceed the original strength of undamaged specimens. In the slant shear tests, the use of polymer is very effective in increasing bond strength and using fibers reduces observed variation in the strength of repaired specimens. Considering force path in the patch repair and regardless of materials used for repair, the results show that judging the efficiency of the repair method based on the slant shear test, as proposed by ASTM C 928, in the case of patch repaired elements could be misleading.