Evaluation of the SR Portland cement against sodium and magnesium sulfate attack: a physical and comparative analysis of mortars

D J De Souza,M H F Medeiros,J Hoppe Filho

doi:10.1590/s1983-41952018000500009

Abstract

Abstract Sulfate attack is a term used to describe a series of chemical reactions between sulfate ions and hydrated compounds of the hardened cement paste. Thus, the chemical composition of the binders used is important for the durability of the structure against this aggressive agent. The objective of the present research is to evaluate the influence of sodium and magnesium sulfates on physical properties (linear expansion, flexure tensile strength, and compressive strength) of mortars composed by SR cement (CP V - ARI RS), as commercially sold in Brazil. The results indicate that SR cement complies the requirements established by Brazilian standards, as to chemical composition and resistance to sodium sulfate. However, for magnesium sulfate, SR cement was harmful to mortars mainly in mechanical.

Highlights

Concrete deterioration can be caused by physical, chemical, or a combination of both
Sulfate attack is a term used to describe a series of chemical reactions between sulfate ions and hydrated compounds of the hardened cement paste
The results indicate that SR cement complies the requirements established by Brazilian standards, as to chemical composition and resistance to sodium sulfate

Summary

Introduction

Concrete deterioration can be caused by physical, chemical, or a combination of both. The interaction between sulfate ions and hydrated Portland cement products, such as calcium hydroxide, to form gypsum; and, with aluminates, to form ettringite, can increase the volume, about 1.2 to 2.2 times, the initial products and, as consequence, there is formation of internal stresses in the cement paste, which can cause expansion, cracking and resulting in damage [3][6]. In the sodium sulfate solution, the reaction with the hydrated products of the cement occurs, in the main part, with the ions SO42-, and its main reaction is with the calcium hydroxide Ca(OH), forming gypsum, and, when there is interaction between gypsum and aluminates phases (AFm), there is the formation of ettringite [8], while Na+ ions interact with the OH- released in the formation of the gypsum, causing a small increase in pH, which can work as a catalyst for the deleterious reaction and for stabilization of the ettringite [9]. MgSO4 has its reaction with Ca(OH) forming brucite [Mg(OH)2] and gypsum, ettringite (in interaction with aluminate phases) and can react with the C-

Objectives

Methods

Results

Conclusion