Effects of freezing and thawing cycles on the shear resistance of concrete lift joints

Abstract

Previous studies have shown that 19% of dam deterioration cases are due to freezing and thawing cycles. Considering that lift joints are planes of weakness and that the mechanical properties of concrete are diminished with increasing freeze and thaw cycles, the aim of this paper is to capture the impact of these cycles on the shear resistance of lift joints. Identical concrete joint replicas were subjected to different levels of alteration prior to being sheared in accordance with the standard direct shear test method. The results found in this study showed that initially (up to 87 cycles) frost action has a positive effect on the shear resistance of lift joints due to the increase in roughness the process generates exposed surfaces of concrete joints. However, as the process continues the internal micro-cracking and loss in compressive strength of concrete is such that they offset the positive effects of the increasing roughness and a lost in shear resistance is noticeable thereafter.