Associate professor, School of Civil Engineering, Purdue University, West Lafayette, IN
Senior research engineer, Office of Materials and Road Research, Maplewood, MN
Numerous research and field studies in the past have shown the ability of silica fume to improve the mechanical and durability properties of concrete. Despite these beneficial effects, some recent studies have raised concerns about the dispersibility of a few commercial dry densified silica fumes and the potential for development of alkali-silica reaction associated with the presence of undispersed agglomerates of silica fume in cement matrices.
In light of these developments, the present investigation focuses on determining the potential of undispersed silica fume agglomerates to participate in the alkali-silica reaction and the influence of such factors as size and morphology of the agglomerates on the extent of this reaction. An experimental program consisting of a modified ASTM C 1260 test procedure was used to identify and study distress associated with the presence of undispersed silica fume in cementitious pastes and mortars.
Results of this investigation indicate that undispersed silica fume agglomerates in cementitious pastes actively participate in alkali-silica reaction. The nature and the magnitude of the observed distress were found to be distinctly dependent on factors such as the size of the agglomerates, their morphology, and the water-binder ratio of the cementitious matrix. In addition, this paper presents suggested modifications to the ASTM C 1260 procedure to test for the reactivity of silica fume agglomerates.
Paper ID: CCA10475J