Influence of red mud addition in alkali-activated mortars on corrosion resistance of steel

University of Zagreb, Faculty of Civil Engineering, Department of Materials, Zagreb, Croatia

^* Corresponding author: marijana.serdar@grad.unizg.hr

Abstract

Alkali-activated materials (AAM) consist of a precursor, which is a source of aluminosilicates, and an alkali source. The precursors are usually waste materials from various industries such as fly ash from thermal power plants and slags from the metallurgical industry. Due to the increasing use of these materials in the cement industry and strategies for decommissioning coal-fired power plants, alternative raw materials from waste streams are increasingly being explored. One of these materials is waste from the aluminium industry, known as red mud. Due to its chemical composition, which is similar to that of other cementitious materials, red mud is suitable for use in the cement industry. It can also be used as a source of aluminosilicates in the synthesis of AAM. In this study, the corrosion behaviour of steel in chloride exposed AAMs based on fly ash and slag was investigated with and without the addition of red mud. During exposure of AAM to tap water and a 3.5 wt.% NaCl solution, the corrosion process was monitored by corrosion potential and polarisation resistance. AAM mixes containing red mud exhibited better corrosion resistivity and lower current density values compared to mixes without red mud, indicating a possible contribution of the red mud to chloride binding and improving the passivity of the steel.