Use of Condensed Silica Fume in Portland Cement Grouts

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Title: Use of Condensed Silica Fume in Portland Cement Grouts

Author(s): P. L. Domone and S, B. Tank

Publication: Special Publication

Volume: 91

Issue:

Appears on pages(s): 1231-1260

Keywords: cement content; compressive strength; dynamic modulus of elasticity; grouts; heat of hydration; mixing; plasticizers; rheological properties; silica; viscosity; water-cementitious ratio.

Date: 2/1/1986

Abstract:
The effects of the partial replacement of portland cement in grouts with condensed silica fume were studied. Initial experiments examinedthe fluid properties of fresh grouts, using concentric cylinder viscometry. An effective mixing procedure using a high-shear mixer was developed Replacements of up to 20% of the cement by silica fume and with water- solids ratios of 0.3 to 0.6 were examined. Two commercially available superplasticers were used - a sulphonated melamine and a sulphonated naphthalene formaldehyde. To maintain fluidity the admixture dosage needs to be increased approximately proportionally to the silica fume content. The grouts are thixotropic and more stable than plain OPC grouts. The silica fume leads to an enhanced alite peak in the rate off heat output during hydration, but the use of the superplasticiser leads to a masking of changes of the time to the peak. Compressive strength at one day and from three days onwards is increased by incorporating condensed silica fume, with greater proportional effects being obtained at higher water-solids ratios . Dynamic elastic modulus values do not show the same increase, and for equal strengths, grouts containing condensed silica fume are less tiff