Utilization of Condensed Silica Fume and Classified Fly Ash in High Strength Concrete

Abstract

This paper illustrates the study of condensed silica fume in combination with classified fly ash to makehigh strength concrete. Two brands of condensed silica fume were used in this experimental program. Fly ashfrom Mae Moh power plant was classified by air classifier to have high fineness (d₅₀ = 3.2 micron). Condensedsilica fume at 10% and classified fly ash at 0, 5, 15, 25, and 40% were used to replace Portland cement type I (byweight) to produce high strength concrete in order to compare with control concretes. The water to cementitiousmaterial ratio (W/B) of 0.27 was kept constant and the superplasticizer was employed in all concrete mixes tomaintain the slump of fresh concrete between 20 ± 2.5 cm. All concrete samples were cast in cylindrical moldsof diameter 10-cm and 20-cm in height. They were tested to determine the compressive strength at the ages of7, 28, 60, 90, and 180 days. The obtained results show that the replacement of cement by 10% of condensed silicafume and classified fly ash not more than 15% can give equal or higher compressive strength than those of theconcrete with 10% replacement of condensed silica fume and also higher than the control concretes.