Effect of alkali silica reaction on pretensioned concrete bridge girders

Abstract

Alkali silica reaction (ASR) is an undesirable phenomenon that occurs between alkalis that usually originate from cement and certain types of siliceous aggregates in concrete. The result of this reaction is delayed expansion of hardened concrete in the presence of moisture, which may cause cracking and damage in an existing structure. The present paper investigates the general behavior and shear strength of pretensioned concrete bridge girders affected by ASR. Four identical pretensioned concrete AASHTO Type I girders were fabricated using reactive concrete and subjected to environmental conditioning at a relative humidity of 100% and a temperature of 45 degrees Celsius for up to 296 days to accelerate the development of ASR. During this period, ASR‐induced expansions, changes in surface strains of concrete, transfer lengths, and patterns of damage and cracking were monitored. Each specimen was subjected to shear‐critical loading until failure upon reaching the desired expansion level. The results showed that the existence of prestressing force played a significant role in limiting the ASR‐induced in‐plane expansion and cracking. Progress of ASR caused a reduction in the load corresponding to the first detected flexural crack but an increase by up to 14% in the load corresponding to the first diagonal cracking compared to the control specimen, likely due to the additional prestress caused by restrained ASR‐induced expansions. The ultimate shear strength of ASR‐affected girders was generally within 5% of the control specimens, and all specimens exceeded their nominal shear strengths according to AASHTO LRFD 2020 specifications. Until the unrestrained uniaxial expansion of 0.2%, no significant concerns were identified regarding the shear strength of the ASR‐affected pretensioned concrete specimens.