Effectiveness of Supplementary Cementing Materials in Reducing Expansion Due to Alkali-Aggregate Reaction in High-Performance Concrete

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Title: Effectiveness of Supplementary Cementing Materials in Reducing Expansion Due to Alkali-Aggregate Reaction in High-Performance Concrete

Author(s): B. Fournier and V. M. Malhotra

Publication: Special Publication

Volume: 149

Issue:

Appears on pages(s): 729-752

Keywords: accelerated tests; aggregates; alkali-aggregate reactions; blended cements; concretes; expansion; high-performance concretes; silica fume; Materials Research

Date: 10/1/1994

Abstract:
Two Canadian aggregates, a reactive siliceous limestone and nonreactive crushed granite, were evaluated for their potential alkali reactivity (AAR) in high-performance concrete. The concretes were proportioned to have high strength and cement content greater than 400 kg/m 3. Concrete mixes were made using a silica fume blended cement and a cementitious system in which 25 percent of a CSA Type 20 low-alkali cement was replaced by ASTM Class F fly ash. Also, control mixes were made with a CSA Type 10 high-alkali cement. The susceptibility to AAR of these concrete mixes was evaluated by casting concrete prisms and subjecting them to various accelerated storage 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. The AAR concrete prism tests performed in this study have shown that none of the concrete prisms made with silica fume blended cement and low-alkali cement incorporating fly ash showed significant expansion after 18 to 24 months of testing either in 1N NaOH or in exposure conditions of 38 C and relative humidity greater than 95 percent. The accelerated mortar bar test results, however, suggest that long-term testing may be needed to evaluate the effectiveness of blended cements in reducing expansion due to AAR, especially for highly reactive aggregates.