Materials

Analyzing Effects of Varied Silica Fume Sources within Baseline UHPC

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Abstract

Silica fume has been used for many years as a fine-grained supplementary cementitious material in ultra-high performance concrete (UHPC) to aid in improving strength and durability. Since silica fume is a waste product, much variability is present among different silica fume sources. This study compared the functionality of eight silica fume products in an otherwise identical cementitious matrix using a standard reference UHPC known as Cor-Tuf Baseline (CTB). The studied silica fumes were obtained from multiple suppliers and geographical locations. Both densified and undensified silica fumes were evaluated. Silica fumes were substituted one for another on a 1:1 basis (by mass) for initial batching. Fresh properties of interest in this study included mixing time and flow percentage. Hardened properties of interest included compressive strength and density. The effects of different mixing actions were studied as well as different high temperature curing conditions. Results of this study indicated that some silica fumes, while similar in composition to others tested, presented many difficulties in producing a UHPC. The state of silica fume densification did not exclusively determine its usefulness in the production of a UHPC. Increased shearing action during mixing was seen as advantageous for increased fluidity and ease of production. The use of a steam generator for high temperature curing was more beneficial in strength development than placing the samples in a high temperature water bath at the same temperature. Two of the eight silica fumes tested were found to be acceptable for CTB production.

Keywords: UHPC, silica fume, densification, compressive strength, fresh properties

How to Cite:

Williams, B. A., Scott, D. A., Burroughs, J. F. & Rushing, T. S., (2016) “Analyzing Effects of Varied Silica Fume Sources within Baseline UHPC”, International Interactive Symposium on Ultra-High Performance Concrete 1(1). doi: https://doi.org/10.21838/uhpc.2016.75