Repair of Reinforced Concrete Beams Damaged by Alkali-Silica Reaction

Abstract

High-performance fiber-reinforced cementitious (FRC) mixtures offer promise as a repair alternative for structures damaged by alkali-aggregate (silica) reaction (ASR). This paper investigates the effects of externally applied U-shaped high-strength FRC jackets on the flexural behavior of ASR-damaged reinforced concrete beams. A series of 13 under-reinforced high-strength concrete rectangular beams were cast, subjected to exposure conditions chosen to generate a rapid increase of ASR damage, repaired, and then tested under four-point loading to determine the effectiveness of the FRC jackets as a method of increasing the beams’ flexural capacity. The overall response of the beams (loaded up to failure); the onset of cracking; and cracking pattern, serviceability, stiffness, and ductility are described. Three types of fibers were used: high-performance polypropylene, hooked-end steel, and brass-coated steel with fiber content ranging from 1 to 2%. Results showed that all repaired beams exhibited a substantial improvement in their flexural behavior compared with the control beams. They regained a large proportion of the control beams’ ultimate load capacity, and showed a typical flexural failure with an increase in the first cracking and service loads. Beams repaired with a mixture of hooked steel and brass-coated steel fibers showed the highest improvement in flexural load capacity, while those repaired with brass-coated steel fibers exhibited the highest improvement in displacement ductility and toughness. An analytical model was developed and shown to be reliable for predicting the ultimate load capacity of the repaired beams. The findings from this study indicate that the proposed repair technique is an effective method for restoring the flexural capacity of ASR-damaged reinforced concrete members.