Temperature and humidity influence on the strain sensing performance of hybrid carbon nanotubes and graphite cement composites

Cement composites with hybrid conductive fillers carbon nanotubes (CNT) and graphite products (GP), have been tested as strain sensors under varying temperatures (0 °C–60 °C), and moisture conditions (0%–100% saturation degree (SD)). Cement pastes with 1% CNT and 5% GP (purified expanded graphite) presented resistivity values between 50 and 75 Ohm·cm, and their strain sensing response was observed to be independent of the loading conditions. However, the gage factor increased up to four times for higher temperatures, and was influenced by the temperature time history. Gage factors were also increased when drying the material up to a SD of 71% or with entirely dried samples.