Iron ore tailing (IOT) chemical composition and content impact on the physical, mechanical, and durability properties of blended cement

Abstract

The IOT addition in cement prevents the construction of new tailings dams and reduces carbon dioxide emission in the atmosphere as the need for clinker in Portland cement decreases. This paper aims to evaluate the use of IOT as supplementary cementitious material and to investigate the impact of IOT chemical composition and Fe content on the physical, mechanical, and durability properties of cement blended with IOT. The motivation for this paper is that the literature presents chemical compositions of IOT with different percentages of Fe and Si, and the influence of this variation is still unknown, mainly with regard to high levels of Fe2O3 in the IOT. Basically, the IOT was benefited by magnetic separation, producing three materials: (i) IOT N (as collected), (ii) IOT S (low Fe content), and (iii) IOT F (high Fe content). IOT N, S, and F were processed by milling and characterized using XRF, XRD, and granulometry techniques. Pastes and mortars were produced to carry out isothermal calorimetry, thermogravimetry, compressive strength, water absorption, porosity, and sulfuric acid resistance tests. The accumulated heat of hydration, chemically bound water, remaining portlandite, and calcium carbonate were reduced for IOT cement. Regarding the compressive strength, 10 % IOT cement could be classified, according to the Brazilian standard, as CP–II–Z 40 while 20 % IOT cement as CP-IV 32. A small increase of less than 1 % for water absorption and IOT improved the resistance to sulfuric acid in the cement. The reference mortar (REF) showed 8.87 % mass loss during acid attack and the mortar with IOT F20 cement showed 6.81 % mass loss during acid attack, demonstrating greater durability under severe attack conditions. ANOVA verified that the IOT chemical composition and content statistically impacted all the results of the hardened cement blended with IOT. Hence, IOT as a partial replacement for clinker in Portland cement proved environmentally and commercially viable.