Viscoelastic Behavior of Silica Fume in Absence of Binder

The viscoelastic behavior of silica fume (with and without silane treatment) without a binder is evaluated under dynamic small-strain compression. The loss-tangent/solid-content, storagemodulus/solid-content, and loss-modulus/solid-content describe the solid part of the compact; they increase with silane treatment, and decrease with increasing frequency. The viscous character stems from the interparticle movement. The highest loss-tangent/solid-content is 0.57 and 0.41 for treated and untreated silica fume, respectively; the highest storage-modulus/solid-content is 24 and 12 psi (165 and 82 kPa) for treated and untreated silica fume, respectively. The treatment results in increased aggregation, <= 40% increase in the loss-tangent/solid-content (due to the viscous character of silane), <= 90% increase in the storage-modulus/solid-content (due to the increased cohesion), and <= 180% increase in the loss-modulus/solid-content. An increase in the solid content of the silane-treated silica fume results in a decrease in the loss-tangent/solid-content (due to the decreasing ease of interparticle movement), but an increase in the storage-modulus/solid-content (due to increased cohesion).