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Influence of Silica Fume on the Stresses Generated by Alkali Silica Reaction

C. Ferraris, E. Garboczi, P. Stutzman, J. Winpigler, J. Clifton

National Institute of Standards and Technology, Bldg. 226, rm B350, Gaithersburg MD 20899

Abstract

Present test methods for determining the suitability of a given combination of cement and aggregates with respect to the potential for alkali-silica reaction (ASR) are based on the measurement of the expansion of the concrete/mortar under prescribed conditions. The scope of this study was to determine the influence of the addition of silica fume, as a cement replacement, on the stresses generated by the specimen, a parameter that could be useful for the engineer. Cylindrical specimens were placed in a frame equipped with a load cell that fixed the axial strain at approximately zero and measured the axial stress generated over time. A replacement of cement by silica fume at a dosage of 15 %, by mass, for two different w/c ratios, led to a significant decrease of the measured stress. SEM observations helped to provide a tentative explanation for the stress and expansion reduction mechanisms with addition of silica fume.

Keywords: Alkali-silica reaction, mortar, silica fume, stress measurements, stress relaxation

• Introduction
• Background
• Measurements
• Specimen preparation
• Results and Discussion
• Conclusion
• Acknowledgments
• References