تأثیر پوزولان طبیعی، خاکستر بادی و میکروسیلیس بر روند کسب مقاومت فشاری و جذب آب حجمی در بتن های دارای مقاومت بالا

Abstract:
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.