The Electrical Resistivity of Geopolymer Paste by Using Wenner Four Probe Method

Abstract

This paper presents an experimental study of the electrical resistivity of geopolymer paste by using a non-destructive test employing Wenner four probe method. Geopolymer is produced from a combination mixture of aluminosilicate materials which is rich in Si and Al such as fly ash with an alkaline activator. Geopolymer paste in this study was made from a mixture of class F fly ash, sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution. An alkaline activator was prepared 24 hrs prior to use with the ratio mixture of Na2SiO3/NaOH being 2.5. Then, the prepared alkaline activator was mixed with the fly ash for about 30 minutes. After that, the mixture was placed in a 100 mm x 103 mm x 495 mm mould. After 24 hrs, the sample was taken out from the mould and cured at 60°C in the oven for 24 hrs. The sample was then tested after 7, 14 and 28 days. The current applied in this study was from 0.01 mA to 1.00 mA and the electrode spacing used were 0.02 m, 0.04 m, 0.06 m, 0.08 m and 0.10 m. The results showed that the geopolymer paste after 28 days with the current of 0.01 mA and 0.10 m electrode spacing showed the highest resistivity with 61575 Ω.m while the geopolymer paste after 7 days with 0.95 mA and 0.02 m electrode spacing showed the lowest resistivity with 537 Ω.m. Hence, the corrosion rate of geopolymer paste in this study was negligible and if occur, was very low.