Impact of silica aerogel addition on the electrical and piezo-resistive sensing stability of CNT-embedded cement-based sensors exposed to varied environments

Abstract

This study investigated the effects of adding silica aerogel on the electrical and piezo-resistive sensing stability of cement-based sensors exposed to varied environments. Cement-based sensors were fabricated using 50% cement and 50% fly ash as binder material, and 0.5% carbon nanotube (CNT) as conductive filler. Three different contents of silica aerogel (0, 0.25, and 0.5% by binder mass) were added, and the samples were exposed to different moisture states and varied environments, including water ingress and cyclic heating conditions, to observe their electrical stability. Results showed that the addition of silica aerogel with super-hydrophobic and low thermal conductivity properties mitigated the disturbances of the CNT particles from the water ingress and cyclic heating conditions, improving the electrical stability. Based on the long-term sensing result, the authors observed the electrical stability when the maximum compressive loading is applied to the samples. The observation showed that the proper addition of silica aerogel improved the long-term sensing stability, while excessive amounts induced agglomerates, affecting long-term sensing stability. From the experimental results, it can be said that the silica aerogel with super hydrophobic and low thermal conductivity properties can be a solution for improving the electrical and piezo-resistive sensing stability of cement-based sensors exposed to various environmental conditions.