Flexural strength of beams affected by ASR

12th Inernational Conference on Alkali-Aggregate Reaction in Concrete, Beijing, CHINE, 15-/10/2004 - 01/01/1970Datailed experimental results were obtained within a large research program carried out at the Laboratoire Central des Ponts et Chaussées (LCPC - Publics Works Research Agency), with Electricité de France (EDF - French Power Company) as a partner, dealing with the reassessment of bridges and dams affected by ASR. The mechanical effects of drying and wetting on concrete structures damaged by ASR are of particular concern, and were reproduced experimentally on 3-m long beams made of plain or reinforced concrete. All the measurements have been carried out both on ASR affected specimens, and for direct comparisons purpose on beams cast with a nonreactive mix-design. A lot of companion specimens have been cast and tested to characterize the mechanical properties of the studied concrete mix-designs during the two years experiment. The present paper analyses the mechanical behavior of the concrete beams damaged by ASR after this two years, exposure in a 38° environment and differential water supply, leading to differential ASR expansion within the structures. Namely the effects of the ASR development have been quantified in a 4-point bending test of the beams, resulting in a lot of data among which the residual stiffness and the flexural strength of both plain and reinforced beams. For the plain concrete beams, the flexural strenght of reactive and non reactive structures has been analyzed using the mechanical characteristic measured on standard specimens. For reinforced concrete beams, the mechanical behavior of the two reactive beams has to be analyzed in comparison with the non reactive companion beam and using the classical design provisions of reinforced concrete beams as a reference, taking into account the evolution of the material mechanical characteristics as measured on specimens. This attempt of re-assessing the bearing capacity of ASR-damaged well-controlled plain and reinforced concrete structures, is a first step for validating a more general methodology for structural re-assessment in the case of bridges and dams affected by ASR