Influence of bauxite residue (red mud) on corrosion of rebar in concrete

Abstract

This paper examines the corrosion of rebar embedded in concrete when cement is partially replaced with toxic bauxite residues, known as red mud (RM). The concrete mixtures were made with 100% ordinary Portland cement (OPC), and OPC replaced with 5% of RM (95% OPC + 5% RM). In order to evaluate the rebar corrosion in aforesaid concrete mixes, 5% calcium chloride was admixed while preparing the concrete. The corrosion performance of rebar in OPC concrete and concrete blended with RM was monitored by corrosion potential and linear polarization resistance. In addition, the performance of concrete blended with RM is evaluated through IR (Ohmic drop) compensated electrical resistivity. After 420 days of corrosion monitoring, concrete samples were broken, and visual observations were made on the rebar. X-ray powder diffraction analysis is also carried out on concrete powder samples collected from the steel–concrete interface. The experimental results have shown that the RM blended concrete performed better to resist the corrosion of rebar as compared to OPC concrete across the testing period of 420 days in the case of concrete made of w/cm 0.48. However, the overall corrosion current density increased in RM blended concrete as compared to normal concrete for the w/cm 0.51.