Behavior of mortars exposed to attack by sodium and magnesium sulfate

摘要

Mortars are subject to contact with aggressive agents from the environment. Sulfates are aggressive to the cement matrix, mainly due to the appearance of expansive reactions between these ions and hydrated products of the cement paste. This study aimed to analyze the behavior of mortars with two types of Portland cement, exposed to solutions with sodium sulfate (Na_2SO_4) and magnesium sulfate (MgSO_4). The following properties of mortars were evaluated during the exposure to sulfates (up to 42 days): linear variation, mass variation, and ultrasonic pulse velocity. The formation of a gel layer on the samples exposed to the MgSO_4 solution was observed, associated with the formation of brucite (Mg(OH)_2). This gel behaved as a protective barrier, reducing the ingress of sulfate ions. The intensity of changes in mortar properties was affected by the type of cement and the type of sulfate. Statistical analyzes were performed to support the analyses.