Managing Premature Concrete Deterioration in Bridges

Abstract

In recent years concrete bridge structures in the USA have been experiencing an unusually high level of premature concrete deterioration. The most common characteristics of this deterioration are longitudinal cracking along the bottom flange at the prestressed beam ends, cracking in unreinforced areas of cast-in-place concrete, and general map cracking with discoloration on concrete surfaces. Further testing of these bridges has revealed the cause of the deterioration is due to Alkali-Silica Reaction (ASR). This paper addresses key aspects in the detection and management of premature deterioration due to ASR for concrete bridges. Detection methods discussed include crack and surface discoloration mapping and as well as procedures for excising samples for petrography and expansion testing. Detailed visual observations of the distressed conditions as well as laboratory test results are then used to develop a course of action to manage further premature concrete deterioration from ASR. Management methods discussed include long-term monitoring, repair strategies that reflect the severity of the deterioration, and measures to mitigate water infiltration into the concrete surfaces.