Research Output
Corrosion Control by Using Aluminium as Sacrificial Anode Cathodic Protection (SACP) in Geopolymer Reinforced Concrete
The Effect of Sodium Hydroxide (NaOH) Solution Concentration on Properties of Geopolymer Paste
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Publication
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.
Publication
This research analyzes the effect of sodium hydroxide (NaOH) solution concentration ranging from 8M to 12M as alkaline activator on the properties of geopolymer paste. Alkaline activator is essentially a mixture of sodium hydroxide and sodium silicate solution. In this research, the main component used was raw kaolin. In order to produce kaolin based geopolymer paste, the alkaline activator solution was prepared with 0.24:1.00 ratio of Na2SiO3/NaOH and this alkaline activator solution was prepared for 24 hours prior before used in another process. The solid-to-liquid ratio which is kaolin-to alkaline activator solution ratio was 0.80:1.00. The mixture of kaolin based geopolymer paste were placed in cube moulds with a size of 50x50x50 mm, and left for 24 hours until it hardened. Then, the samples were cured at 80? in the oven for 24 hours. The samples of kaolin based geopolymer paste were tested based on compressive strength, morphology analysis, water absorption and porosity after 28 days. In this project, 8M concentration of NaOH solution was the best concentration in order to study the synthesis of kaolin based geopolymer paste as the sample had the highest amount of compressive strength with 0.992 MPa and had the lowest water absorption and porosity with 1.246% and 24.08% respectively. Scanning Electron Microscope (SEM) was used to observe the morphological structure of the kaolin based geopolymer paste. The sample with 8M concentration of NaOH solution shows that least amount of unreacted particles. The structure of kaolin based geopolymer paste was more dense at 8M concentration as the size of pore decreases. The kaolin based geopolymer paste is suitable for use in the construction building industry as a finishing product such as coating.