Exposing Sustainable Mortars with Nanosilica, Zinc Stearate, and Ethyl Silicate Coating to Sulfuric Acid Attack

Abstract

Obtaining durable materials that lengthen the service life of constructions and thereby contribute to sustainability requires research into products that improve the durability of cementitious materials under aggressive conditions. This paper studies the effects of sulfuric acid exposure on four mortar types (control mortar, mortar with nanosilica, mortar with zinc stearate, and mortar with an ethyl silicate coating), and evaluates which of them have better performance against the acid attack. After 28 days of curing, the samples were exposed to a sulfuric acid attack by immersing them in a 3% w/w of H2SO4 solution. Physical changes (mass loss, ultrasonic pulse velocity, open porosity, and water absorption), and mechanical changes (compressive strength) were determined after the sulfuric acid exposure. A scanning electron microscope (SEM) was used to characterize the morphology of the surface mortars after the exposure. The control mortar had the highest compressive strength after the acid attack, although of the four types, the zinc stearate mortar showed the lowest percentage of strength loss. The zinc stearate mortar had the lowest mass loss after the acid exposure; moreover, it had the lowest capillary water absorption coefficient (demonstrating its hydrophobic effect) both in a non-aggressive environment and acid attack.