The Effects of Supplementary Cementing Materials on Performance of Concrete Containing Alkali-Carbonate Reactive Aggregates of Marginal Expansivity

摘要

This study investigates the role of supplementary cementing materials (SCM's) on the alkali reactivity of carbonate aggregates that marginally meet the expansion limit for the concrete prism test (CSA A23.2-14A). With the increasing use of SCM's in concrete, it is of interest to investigate their role on the expansion of concrete containing marginally alkali- reactive carbonate aggregate. While it is understood that most SCM's reduce the alkalinity of concrete pore solution and are unlikely to trigger more expansion, some types of SCM, such as high-alkali and high-calcium fly ashes, could raise the alkalinity of pore solution's and promote expansion. The concrete prism expansion test was used to investigate the role of fly ashes of different composition, slag, and metakaolin on concrete expansion. The SCM's were used at different replacement levels that are likely to be used in concrete in North America. A highly reactive carbonate aggregate from Kingston, Ontario was blended with non-reactive carbonate aggregate at different ratios until a one-year expansion value slightly lower than the expansion limit of 0.040% was obtained. This was found at a blending ratio of 10% reactive and 90% non-reactive aggregate. This blend of coarse aggregates was used as a marginally alkali-reactive carbonate aggregate. The 2-year expansion results showed that, except for high-calcium fly ash with high-alkali content, SCM's do not trigger more expansion in concrete with marginally reactive aggregate. The concrete microbar test was found to underestimate the expansion of marginally and moderately reactive carbonate aggregate compared with expansion obtained in the concrete prism expansion test.