Freeze-thaw durability of air-entrained CSF concrete

Abstract

In recent years considerable attention has been given to research aimed at energy conservation in the cement and concrete industry. This is partly being accomplished by the use of less energy-intensive cementitious materials such as fly ash, slags and pozzolans in concrete. Lately some attention has been given to the use of condensed silica fume (CSF) as a possible partial replacement material for cement. This paper reports the results of a laboratory investigation to determine the strength and freeze and thaw durability of concrete incorporating various amounts of CSF. A total of five concrete mixes were made incorporating 0–12% CSF as partial replacement by mass of cement. All mixes were air entrained and had a constant water to cementitious materials ratio, W/ (C + CSF), of 0·4. CSF improved the compressive strength of 7-days and 28-days concrete. The flexural strength after 35 cycles of freezing and thawing was also increased with increasing CSF content. All the CSF concretes performed satisfactorily when subjected to freezing and thawing, even though the performance was somewhat inferior to that of the reference mix. There were no noticeable differences in the physical appearances of the concrete prisms after the 35 cycles of freezing and thawing.