Corrosion Control by Using Aluminium as Sacrificial Anode Cathodic Protection (SACP) in Geopolymer Reinforced Concrete

Abstract

This paper presents corrosion control by using Aluminium as Sacrificial Anode Cathodic Protection (SACP) in geopolymer reinforced concrete. Geopolymer concrete for this research are the combination and reaction between kaolin, which is acting as a binder, fine aggregates such as river sand, coarse aggregates and an alkaline activator which contain 12 M of sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution with the ratio of NaOH/Na2SiO3 is 0.8. There are two types of sample preparation in this experiment which are the control sample without attaching with Aluminium and SACP sample that attach to Aluminium. Three testing were conducted in this research such as compressive strength, open circuit potential and gravimetric weight loss method and these results were observed after days 7 and 14. Compressive strength testing for this geopolymer concrete shows that the highest compressive strength was at sample 14 days which is 7.04 MPa while sample 7 days is 3.96 MPa. The result shows the potential values of SACP samples were lower than the control sample for both 7 and 14 days. The potential values for the SACP sample for 7 and 14 days are 0.0152 V and -0.037 V while for control sample was 0.048 V and 0.051 V respectively. From the Pourbaix diagram, the control sample was located in the passivity region while SACP sample was located in the immunity region. The corrosion rate of the reinforcement bar in concrete has been performed by the gravimetric weight loss method. Analysis of the resulting proved that the corrosion rate of SACP sample was lower than the control sample for both 7 and 14 days, which were 3.60 x 10−5 mm/yr and 1.427 x 10−5 mm/yr respectively. This is due to the presence of Aluminium which act as the sacrificial anode that protects reinforcement bar in geopolymer concrete from the corrosive agent.