Mechanical and electrothermal properties of lightweight graphite/geopolymer composites

Abstract

Graphite/geopolymer composite is a promising smart material that can be used in various applications. This paper reports the design of strong self-heating graphite/geopolymer composites with high graphite percentages up to 120 wt% of metakaolin. The physical, mechanical, electrical, and electrothermal performance of composites were investigated; the compressive strength was tested at various ages and the electrothermal performance was tested using AC and DC voltages. The results showed that a compromise between high compressive strength and high electrothermal conversion can be achieved when a specific balance between the percentage of the graphite and the water content is established. The current study specified the reason for the deterioration of the electrothermal performance of the graphite/geopolymer composites, that is, the formation of a barrier layer between the electrode and the sample surface; it has been found that this can be avoided by removing the free ions from the geopolymer via washing. A composite with 47 ± 1 MPa compressive strength and stable electrothermal performance of 98°C at 6 DC volts can be prepared using 90 wt% graphite and 57 mL water content. This work is a step in the future innovation of smart construction using self-heating and antifreezing construction materials.