Abstract
In this study, a self-sensing cementitious stabilized sand (CSS) was developed by the incorporation of hybrid carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) based on the piezoresistivity principle. For this purpose, different concentrations of CNTs and GNPs (1:1) were dispersed into the CSS, and specimens were fabricated using the standard compaction method with optimum moisture. The mechanical and microstructural, durability, and piezoresistivity performances, of CSS were investigated by various tests after 28 days of hydration. The results showed that the incorporation of 0.1%, 0.17%, and 0.24% CNT/GNP into the stabilized sand with 10% cement caused an increase in UCS of about 65%, 31%, and 14%, respectively, compared to plain CSS. An excessive increase in the CNM concentration beyond 0.24% to 0.34% reduced the UCS by around 13%. The addition of 0.1% CNMs as the optimum concentration increased the maximum dry density of the CSS as well as leading to optimum moisture reduction. Reinforcing CSS with the optimum concentration of CNT/GNP improved the hydration rate and durability of the specimens against severe climatic cycles, including freeze–thaw and wetting–drying. The addition of 0.1%, 0.17%, 0.24%, and 0.34% CNMs into the CSS resulted in gauge factors of about 123, 139, 151, and 173, respectively. However, the Raman and X-ray analysis showed the negative impacts of harsh climatic cycles on the electrical properties of the CNT/GNP and sensitivity of nano intruded CSS.
Highlights
Among all monitoring methods, self-sensing composites with intrinsic stress, strain, and damage sensing capabilities based on piezoresistivity provide a more integrated, realtime, and practical solution for infrastructure damage detection, considering geomaterial properties and nature
Specimens composed of 0.17% and 0.24% carbon nanomaterials (CNMs) showed higher maximum dry density; they were accompanied by a declining trend, such that an excessive increase in the CNM concentration beyond 0.24% led to a decrease in the maximum dry density compared to plain cementitious stabilized sand (CSS)
The gauge factors of the specimens composed of 0.17%, 0.24%, and 0.34% CNM were reduced by 72%, 61%, and 30%, respectively, compared to the normal specimens
Summary
Self-sensing composites with intrinsic stress, strain, and damage sensing capabilities based on piezoresistivity provide a more integrated, realtime, and practical solution for infrastructure damage detection, considering geomaterial properties and nature. Self-sensing composites arise from the dispersion of the conductive phase in the non-conductive composite [6,7,8] These conductive components form a conducting electrical network within the composites. When the composites are subjected to strain, stress, or any other external factors, this conducting network is disturbed, leading to a change in the electrical resistivity [9,10,11,12]. The sensitivity and performance of self-sensing composite are affected by some factors such as electrode status, current, temperature, humidity, and loading, among which the type of conductive phase, their concentration, and distribution have particular importance [13,14,15,16]. Reinforcing cementitious composites by highly dispersed CNMs with low concentration
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