A study on corrosion behavior of Mild Steel in Granulated Blast Furnace (GBFS) fly ash geopolymer

Abstract

This research presents the corrosion behavior of mild steel embedded in geopolymer paste that produced by the reaction of fly ash and slag with an alkaline activators (NaOH molarity of 12 M, Na2SiO3/NaOH ratio of 2.5). Geopolymer is an alternative to the Ordinary Portland Cement (OPC) due to the environmental friendly, low cost production, workability and good corrosion resistance. Tests were carried out on 50 mm x 50 mm x 50 mm cube geopolymer paste and to study the corrosion 100 mm length and 15 mm diameter of mild steel bar is needed. The compression strength, water absorption and Open Circuit Potential (OCP) testing were conducted after 3, 7, 14 and 28 days cured. The highest compressive strength of about 37.35 Nmm-2 was achieved for the geopolymer paste containing 70% of fly ash class F and 30% of slag with using 12 M of NaOH solution after 28 days. Meanwhile, the corrosion behavior of reinforcement bar has been conducted by OCP method and recorded with time. From Pourbaix diagram, all the potential values were located in passivity region due to oxide formed to protect the reinforcement bar from corrosive agents.