Alkali-silica reaction, delayed ettringite formation and corrosion effects on a bridge pier

Premature concrete deterioration in certain bridge piers in Texas, USA, has been attributed to the deleterious effects of alkali-silica reaction and delayed ettringite formation. A semi-empirical expansion model was used to estimate the maximum possible expansion strains from these causes. The compatibility-based strut-and-tie method was used to model the force-deformation behaviour of a bridge pier with and without such deterioration. The beneficial effects of prestressing forces in the reinforcement, along with modified cover and core concrete properties to account for coupled deterioration and confining action, were incorporated into the model of a bridge pier with deterioration. The model showed that large expansion strains and hence excessive cracking could be expected. However, the analysis showed that the load-carrying capacity of the deteriorated bridge pier was above its required design load capacity. The overall force-deformation response of the deteriorated bridge pier was slightly stronger and stiffer but had less displacement ductility. However, reinforcement corrosion in the beam-column joint significantly decreased its load-carrying capacity, ductility capacity and energy absorption. Even though these deterioration had a beneficial effect on the structure in the short term, severe reinforcement corrosion due to excessive cracking adversely affected the structure.