Strength Development and Absorption of High Strength Concertes Incorporating Natural Pozzolan, Fly Ash and Silica Fume

The effects of natural pozzolan, fly ash and silica fume as cementitious materials on strength development and absorption water capacity were investigated. Cubic specimens (100×100×100 mm) from 13 mix designs with 2 water-cement ratios of 0.3 and 0.46 were made. The specimens at the age of 28 days were dried and then immersed in water from 30 minutes to 7 days based on BS 1881, part 122, to study their cavity volume. The cement type 2 was replaced (by weight) with natural pozzolan and fly ash with 15, 30, 15 and 25 percent, respectively. Furthermore, in 0.3 water cement ratio specimens, the cement was replaced with silica fume at three percentages of 5, 8 and 11. It was concluded that natural pozzolan caused the decrease of compressive strength at both the early and later ages. Fly ash also caused the decrease of compressive strength at the early age, however, at the later age, it improved the compressive strength. Silica fume improved the compressive strength from the second day to the later ages. In 0.46 water cement ratio specimens, the absorption water capacity was decreased when the cement replacement with natural pozzolan and fly ash was 15%. Silica fume decreased the absorption water content when the immersion time was 7 days. In 0.3 water cement ratio specimens, the pozzolan materials had no considerable effect on the absorption water capacity.