Title: Influence of Silica Fume Replacement of Cement on Physical Properties and Resistance to Sulfate Attack, Freezing and Thawing, and Alkali-Silica Reactivity

Author(s): R. D. Hooton

Publication: Materials Journal

Volume: 90

Issue: 2

Appears on pages(s): 143-151

Keywords: alkali-aggregate reactions; durability; freeze-thaw durability; permeability; silica fume; sulfate attack; Materials Research

DOI: 10.14359/4009

Date: 3/1/1993

Abstract:
Between 1983 and 1990, a series of test programs was conducted on the physical properties and durability of pastes, mortars, and concretes made with silica fume replacements as part of the portland cement. From these test programs, it was found that silica fume: 1) reduced the permeability of both cement pastes and concretes; 2) reduced the size of pores and total porosities of both cement pastes and concretes; 3) reduced the leachable calcium hydroxide contents of cement pastes (in some cases to zero); 4) reduced the level of alkalies leached from pastes (this has implications for reduced alkali- aggregate reactivity); 5) improved the resistance of ASTM C 441 pyrex mortar bars to deleterious expansion (10 percent replacement was adequate to meet limits); 6) provided resistance superior to that of a sulfate-resistant portland cement in ASTM C 1012 tests for sulfate resistance (10 percent replacement was adequate to meet limits); and 7) provided resistance to freezing and thawing to a series of high-strength, non-air-entrained concretes. (Indirect evidence suggested that ultra-low permeabilities and unreacted silica fume caused self-desiccation resulting in noncritical saturation levels.)