Simultaneous enhancement of mechanical robustness and self-sensing performance in fly ash-based geopolymer nanocomposites

Abstract

The simultaneous enhancement of both mechanical robustness and self-sensing capabilities in geopolymer nanocomposites significantly advances the precision and dependability of structural health monitoring systems. In this study, the uniform dispersion of graphene nanoplatelets (GNPs) within fly ash-based geopolymer composites is successfully achieved through the in-situ chemical synthesis of a silica (SiO₂) coating on the GNP surface. The resulting composite material exhibits a significant enhancement in sensitivity, which is attributed to the presence of the SiO₂ coating on the GNPs. In comparison to uncoated GNP/geopolymer composites, varying the concentration of the precursor tetraethyl orthosilicate (TEOS) from 0 to 8 ml enables the formation of SiO₂ coatings with different thicknesses, which effectively modulates the resistivity of the composite to meet specific sensing application requirements. The self-sensing sensitivity of the composite shows a considerable increase of 479.7 %, accompanied by a concurrent 89.1 % increase in elastic modulus. Notably, the gauge factor (GF) of geopolymer composites reached up to 491, which surpasses the results reported in recent literatures. The underlying mechanism suggests the in-situ SiO₂ coating significantly enhances the composite’s sensitivity and mechanical properties by improving the interface bonding between GNP and the geopolymer matrix, acting as a dielectric layer to reduce direct contact and particle agglomeration, and exhibiting excellent chemical and thermal stability. This advancement holds paramount importance in mitigating risks associated with structural failures, prolonging the operational lifespan of critical infrastructure, and ultimately improving public safety standards.