Long-Term Effects of Different Cementing Blends on Alkali- Carbonate Reaction

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Title: Long-Term Effects of Different Cementing Blends on Alkali- Carbonate Reaction

Author(s): Medhat H. Shehata, Steven Jagdat, Chris Rogers, and Mohamed Lachemi

Publication: Materials Journal

Volume: 114

Issue: 04

Appears on pages(s): 661-672

Keywords: alkali-carbonate reaction; concrete microbar test; concrete prism test; long-term expansion; scanning electron microscopy; supplementary cementitious materials

Date: 7/1/2017

Abstract:
The long-term effect of supplementary cementitious materials (SCMs) on alkali-carbonate reaction was evaluated using the concrete prism test for up to 10 years. None of the SCMs showed complete mitigation effects, although some types were more effective than others in reducing the expansion. Blending 10% reactive with 90% nonreactive aggregates was effective in meeting the 0.040% expansion limit at 1 year; however, the expansion was 0.074% after 10 years at room temperature. The chemical method for evaluating aggregate was found to give false negative or underestimate the potential expansion of blends of reactive and nonreactive aggregates. The use of SCMs with blends of aggregates that marginally meet the 1-year expansion limit provides some benefits in reducing the expansion at later ages. The concrete microbar test provides good correlations with the concrete prism test containing 100% reactive aggregates with and without SCM, but underestimates the expansion of blends of aggregates.