Influence of bicarbonate ions on the deterioration of mortar bars in sulfate solutions

Journal Article · Fri Feb 15 04:00:00 EST 2013 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2012.10.016· OSTI ID:22149369

Lothenbach, B. ^[1]; Scrivener, K. ^[2]

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1. Empa, Laboratory for Concrete and Construction Chemistry, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)
2. EPFL, Laboratory of Construction Materials, CH-1015 Lausanne (Switzerland)

This work investigates the influence of bicarbonate ions on the deterioration of cementitious material exposed to sulfate ions. Mortars based on a CEM I and on a CEM III/B cement were investigated. Experimental investigations were compared to thermodynamic modeling and phase characterization to understand the differences in deterioration. The presence of bicarbonate ions significantly reduced the expansion of the CEM I mortars. Thermodynamic modeling showed that at high concentrations of bicarbonate ettringite and gypsum become unstable. Microstructural characterization combined with information from thermodynamic modeling suggests that conditions of high supersaturation with respect to ettringite are unlikely in the samples exposed in solutions containing bicarbonate. Consequently, expansive forces are not generated by the crystallization pressure of ettringite. There was little expansion of the CEM III/B sample even in the sodium sulfate solution. In the bicarbonate solution this mortar showed a highly leached zone at the surface in which calcite was observed.

• OSTI ID: 22149369
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Journal Issue: Complete Vol. 44; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACID CARBONATES
CALCITE
CONCENTRATION RATIO
CRYSTALLIZATION
GYPSUM
LEACHING
MICROSTRUCTURE
MORTARS
PORTLAND CEMENT
SODIUM SULFATES
SUPERSATURATION
SURFACES