Effect of External and Internal Sulphate on Compressive Strength of Concrete

摘要

In this paper, the influence of external and internal effect of sulphate on normal and high performance concrete was studied. The aim of this experimental study is to evaluate the effect of external severe sulphate solution on compressive strength of concrete mixes containing two different internal sulphate. The experimental work included of casting and testing of 360 concrete cubes, half of them fully immersed in ground water solution with sulphate SO_4 =6965 ppm. The other half of cubes was immersed in tap water to be references. Sulphate resistance cement and ordinary Portland cement with 10% silica - fume used in mixes. Two types of locally available sand were used (standard SO_3= 0.2% and non-standard SO_3= 1.13%). The results showed that the compressive strength development continuously increases in specimens immersed in tap water and the development rate decreases when the w/c ratio decreases. The harmful effect of internal sulphate in concrete was decreased by using type I cement with 10% silica -fume replacement and low w/c ratio. The effect of internal sulphate was clearly appeared at early ages till 90 days when using non-standard sand in mixture with low w/c ratio 0.31. Using of silica fume concrete with w/c ratio of 0.45 is more effective to enhance the concrete resistance to external sulphate attack.