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Stress Due to Alkali-Silica Reaction in Mortars.


pdf icon Stress Due to Alkali-Silica Reaction in Mortars. (619 K)
Ferraris, C. F.; Garboczi, E. J.; Davis, F. L.; Clifton, J. R.

Materials for the New Millennium. Proceedings. Materials Engineering Conference, 4th. Volume 2. American Society of Civil Engineers (ASCE). November 10-14, 1996, Washington, DC, American Society of Civil Engineers, New York, NY, Chong, K. P., Editor(s), 1379-1387 pp, 1996.

Keywords:

building technology; alkali-silica reaction; hydration; moduli; mortar; stress (mechanics); stress relaxation

Abstract:

Alkali-silica reaction (ASR) deterioration in mortars and concretes is often attribute to the swelling of gel formed by the reaction of alkali hydroxides with reactive silica in aggregates, in the presence of water. The swelling of the gel can generate sufficient tensile stresses resulting in expansion and cracks. Most tests designed for ASR rely on measurements of the length change. A new test, designed to measure the stress generated by the swelling of the gel, has a cylindrical mortar specimen placed in a frame under a load cell. The force required to prevent expansion is measured over time while the specimen and frame are immersed in a solution of 1-N NaOH at 50 deg C. The design of the apparatus, together with some early results, are presented. The ASR-induced stress and expansion caused by different aggregates was investigated. Stress measurements showed a strong influence of stress relaxation and self-desiccation/water absorption on the mechanical response of the material subjected to ASR. A preliminary study of the effect of hydration on stress relaxation and self desiccation/water absorption was made, using non-reactive aggregate.