Investigating Effects of Sulfates on Compressive Strength of Different Types of Pozzolan Concrete and Measuring Penetration Rate by Ultrasound Tests at Different Ages

Today, one of the most important indices in the design, construction, and operation of concrete structures is paying particular attention to sustainable development and environmental issues so that the useful life of structures is increased in order for economic savings and environmental protection. Accordingly, researchers have proposed permanent concrete durability idea along with strength concrete and improved the strength and durability of concrete and also reduced cement consumption by replacing natural additives. In this regard, to assess the durability of pozzolan-containing concrete against sulfate attacks, in this paper, a variety of additives including zeolite, fly ash, metakaolin, as well as micro and nano silica was used as an alternative for a part of cement. In order to investigate the effect of different types of sulfates, concrete was placed within four saturation environments containing iron, magnesium, sodium, and calcium sulfates and the control saturation sample was made in limewater to compare all the designs. The samples were evaluated using compressive strength test and ultrasonic test at the ages of 7, 14, 28, 60, 180, and 360 days. The results showed the concrete containing micro and nano silica had maximum strength against sulfate attacks and the devastating effects of magnesium, sodium, and calcium sulfates and low effect of iron sulfate were respectively demonstrated. Investigating the velocity of ultrasonic waves also showed that wave velocity increased by increasing the age from 180 to 360 days and increasing the formation of Ettringite, a destructive substance, in concrete. The highest effect of increased velocity was observed by increasing Ettringite in the calcium sulfate samples.