Effectiveness of Fly ash in Reducing Expansion of Concrete Made with Reactive Aggregates from New Brunswick, Canada

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Title: Effectiveness of Fly ash in Reducing Expansion of Concrete Made with Reactive Aggregates from New Brunswick, Canada

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

Publication: Special Publication

Volume: 153

Issue:

Appears on pages(s): 561-590

Keywords: accelerated tests; alkali-aggregate reactions; cement aggregate reactions; concretes; expansion; fly ash; tests; Materials Research

Date: 6/1/1995

Abstract:
Three reactive aggregates from New Brunswick, Canada, a greywacke, a gneiss, and a meta-volcanic rock were evaluated for their potential alkali reactivity (AAR) in concrete mixtures incorporating 420 kg/m 3 of cementitious materials. The concrete mixtures consisted of the control made with CSA Type 10 low- and high-alkali cements and mixtures incorporating ASTM Class F fly ash at 20, 30, and 56 percent replacement levels of the high-alkali cement. The susceptibility of the concretes to AAR was evaluated by casting test prisms and subjecting these to various accelerated curing conditions in the laboratory. For comparison purposes, mortar bars were also made and tested according to the ASTM C 1260-94 Accelerated Mortar Bar Test procedure. The AAR concrete prism tests performed in this study have shown that none of the test prisms cast from concrete mixtures incorporating 20, 30, and 56 percent fly ash showed significant expansion after two years of testing at 38 C and relative humidity >95 percent. These results were in good accordance with those obtained in the accelerated mortar bar test. Some alkaline immersion tests results would indicate, however, that concrete incorporating 20 percent fly ash might not offer adequate protection against potential deleterious expansions with highly reactive aggregates.