Title: Tests for Oxidizable Sulfides in Aggregates: Applicability and Limitations

Author(s): Mona El-Mosallamy and Medhat H. Shehata

Publication: Materials Journal

Volume: 117

Issue: 2

Appears on pages(s): 229-240

Keywords: durability; mortar bar; oxidation mortar bar; oxygen consumption; pyrrhotite; sulfide; sulfide-bearing aggregate

DOI: 10.14359/51722401

Date: 3/1/2020

Abstract:
This paper examines the applicability of a recently developed testing protocol to evaluate the potential of sulfide-bearing aggregate—mainly from Ontario—to oxidize and cause damage when used in concrete. The protocol consists of three sequential tests: total sulfur (St), the oxygen consumption test (OCT), and the oxidation mortar bar test (OMBT). The paper suggests modifications to the OCT, and the expansion criteria of OMBT based on testing aggregates with different total sulfur contents. For OCT, using crushing equipment with cast-iron working surface was found to contaminate the samples and give high values of oxygen consumption. The OMBT showed lower expansion values for carbonate aggregates compared to aggregates with silicate. Exposing siliceous aggregate—whether alkali-silica reactive or not—to the high pH and temperature encountered in the OMBT produces high expansion regardless of the oxidizable sulfide content. As such, new expansion criteria are suggested, which take into consideration the silicate nature of some aggregates.