- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
In order to evaluate the risk of the source and quantity of cement SO3 on the expansion properties of mortars, this paper studied the influence of Gypsum, Bassanite and clinker sulfate on the cement paste expansion and the formation of delayed ettringite. The investigation covers the mortar cured at 20 °C and 80 °C and stored in water. In contradiction to many studies, the results showed that the cement produced with high sulfur clinker had lower expansion than that produced with classical gypsum or high soluble Bassanite. In addition to that, we have detected that the percentage of SO3, in the cement, could increase the risk of DEF if it surpasses the level of 3.5%. Also, the curing temperature at 80 °C affects the microstructure of concrete by generating cracks in the cement paste.
The main conclusions of this study are: 1. The solubility of sulfate added to the cement as regulator of setting time could have some impact on the specimen’s expansion. It did not show alone any role on the delayed ettringite formation. The usage of high percentages of Bassanite as setting time regulator could increase the risk of expansion. 2. The graphical treatment of microanalysis by energy-dispersive X-ray spectroscopy showed that the amount of SO3 in the cement is an important factor for the transformation of monosulfate to ettringite. Increasing the percentages of SO3 in the cement increase the risk of delayed ettringite formation. 3. The heat curing generates micro-cracks in the cement paste. It could lead with the interference of many other external and internal factors to the formation of delayed ettringite. 4. In contradiction to many hypotheses, the cement produced with clinker containing high sulfate showed the lowest expansion and the lowest risk of ettringite formation.