Alkali-Aggregate Reactivity (AAR) Potential of Selected Canadian Aggregates For Use in Offshore Concrete Structures

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Title: Alkali-Aggregate Reactivity (AAR) Potential of Selected Canadian Aggregates For Use in Offshore Concrete Structures

Author(s): B. Fournier, V. M. Malhotra, W. S. Langley, and G. C. Hoff

Publication: Special Publication

Volume: 145

Issue:

Appears on pages(s): 657-686

Keywords: accelerated curing; aggregates; alkali-aggregate reactions; blended cements; compressive strength; concretes; expansion; gravel; tests; flexural strength; harbor structures; limestone; modulus of elasticity; prisms; silica fume; splitting tensile strengt

Date: 5/1/1994

Abstract:
Three Canadian aggregates were evaluated for potential alkali-aggregate reactivity (AAR) in concrete mixes made with CSA Type 10 high-alkali cement and two silica fume blended cements. The aggregate types investigated included a quarried carbonate rock (limestone) and two gravels from glacial deposits mainly composed of granitic and sedimentary rock fragments. The concretes were proportioned to meet the requirements normally applied to offshore concrete structures, and therefore had high strengths and cement contents greater than 400 kg/m 3. The mechanical properties of these concretes, including compressive, flexural, and splitting tensile strengths, as well as Young's modulus of elasticity, were evaluated at various ages. The susceptibility to AAR of these "job-type" concrete mixes was evaluated by casting concrete prisms from the preceding mixes and subjecting them to the various accelerated curing conditions in the laboratory. For comparison purposes, mortar bars were also made and tested according to the ASTM P 214 (1990) accelerated mortar bar test procedure. Testing of the materials was replicated in two independent laboratories. The AAR concrete prism and accelerated mortar bar test results performed in this study showed that all three aggregates investigated may be considered potentially reactive. None of the concrete prisms made with these aggregates and the silica fume blended cements, however, showed significant expansion after 12 or 18 months of testing either in 1N NaOH or relative humidity > 95 percent at 38 C. More long-term concrete prism tests and/or field testing is needed to evaluate the effectiveness of blended cements in reducing the expansion due to AAR, especially for highly reactive aggregates.