Investigation of self-sensing properties of phosphoric acid activated metakaolin geopolymer

• Main Author: Goh, Han Sheng
• Other Authors: En-Hua Yang
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/157745
• Institution: Nanyang Technological University

Self-sensing properties of phosphoric acid activated metakaolin geopolymer was investigated, testing its piezoresistive and thermoelectric behaviour with the acid molar concentration as the variable. Mechanical performance was tested to ensure it is functional structurally and maximum strength of 50.74 MPa was achieved using a two-stage curing method (pre-curing at 40C for 24 h and second curing at 60C for 24 h). Piezoresistivity results show that it is comparable to alkali based metakaolin geopolymer with a fractional change of resistance (FCR) of the same order. A maximum gauge factor (GF) of 0.171 was achieved using 6 M of phosphoric acid, and it is proposed that ionic conduction contributes to the piezoresistive behaviour. For thermoelectric behaviour, the magnitude of the Seebeck coefficient is comparable to that of alkali based geopolymer, but several samples displayed inconsistent results, displaying both p-type and n-type behaviour. It is hypothesized that the Seebeck effect is dependent on the ionic conduction and the conduction due to the microstructure.