Abstract
A fundamental research was carried out on silica fume concrete in order to obtain some properties such as workability, air entrainment, porosity, development of strength and durability to freezing and thawing action. A silica fume containing 85% of silica by weight, produced in Japan, was used in this study. Three levels of silica fume content, 0, 15 and 25% of replacement ratio to cement by weight, and five levels of water-to-cementitious materials ratio (W/(C+SF)) from 30% to 70% were chosen. The decrement in slump caused by the incorporation of silica fume was adjusted by the use of superplasticizer.
The dosage of superplasticizer needed to keep the same workability as that of the control concrete increased linearly with silica fume content. It is difficult in practice to entrain the air of more than 4% in the mix of low W/(C+SF) ratio where the silica fume replacement ratio is 25%. The optimum replacement ratio of silica fume to cement was 15% as far as the development of strength and the durability to freezing and thawing action were concerned. The air-entrained concrete with the silica fume replacement ratio of 15% showed satisfactory result for durability to freezing and thawing action up to 300 cycles, although the air-entrained concrete with the silica fume replacement ratio of 25% did not show any good result for durability to freezing and thawing action, even though it had the entrained air of 4.4% and W/(C+SF)=50%.
