Development of a Novel Multifunctional Cementitious-Based Geocomposite by the Contribution of CNT and GNP

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.

Effects of Electrodes Layout and Filler Scale on Percolation Threshold and Piezoresistivity Performances of a Cementitious-Based Geocomposite

“…Since, in sand stabilisation, the cement content usually varies by approximately 10% owing to the target strength of the sand–cement [ 38 , 39 ], in this study, 10% cement (by the weight of the dry sand) was also utilized for SCG preparation. Based on the literature [ 3 , 21 , 40 ], the optimum water content for the CNM-reinforced stabilised sand with similar cement content and sand grading was around 7%. Hence, the amount of water content for all the specimens was considered to be 7% (by the weight of the dry sand) and they were fabricated by the compaction methods.…”

“…The electrical percolation threshold for a large-scale beam with dimensions of 10 × 10 × 85 cm 3 and a cubic 15 cm length specimen was calculated using the relations obtained by hybrid CNT/GNP. To investigate piezoresistivity, a four-probe method and direct current (DC) source was used ( Figure 5 ) [ 3 ]. The four-probe method is highly recommended for piezoresistivity investigations in previous studies as a more accurate technique for eliminating the influential resistance from current lines, joints, interfaces and polarization effects [ 15 , 46 , 47 , 48 ].…”

“…These intelligent materials can help to develop smart infrastructure integrated with health monitoring and sensing abilities, thus improving the safety, serviceability, durability, and reliability of the infrastructure [ 1 , 2 ]. SCGs have provided a new approach for maintaining sustainable development in roller-compacted concrete dams, rammed earth, ground improvement, and particularly in structural layers in transportation infrastructures, especially in critical zones, such as transition zones [ 3 , 4 ]. A piezoresistive cementitious-based geocomposite is a compounded material, which is composed of a conductive phase distributed in a non-conductive matrix.…”

“…However, percolation does not imply a fully physical connection, owing to the tunnelling conductivity. Indeed, percolation threshold content and type of the filler are the most important factors to achieve economical self-sensing cementitious composites with proper mechanical properties and potential for use in the field [ 3 , 6 , 21 ]. Literature assessment shows that many studies have been conducted on the factors affecting the percolation threshold including the type of conductive fillers, their aspect ratio and geometrical shapes, dispersion, type of non-conductive matrix, size and shape of aggregate, etc.…”

Multiscale Innovative Materials and Structures (MIMS)

“…The first work of the SI [ 1 ] deals with the functionalization of multi-walled carbon nanotubes, showing the effects of different conditions and milling processes on thermal and electrical conductivity. Another challenging topic regarding advanced sensing applications is explored in [ 2 ], where hybrid carbon nanotubes are employed to develop a self-sensing cementitious stabilized sand by virtue of the piezo-resistivity principle. Advancements in nonlocal continuum field theories are given in [ 3 ], where an effective model of a nonlocal foundation is presented, providing an accurate and well-posed displacement-driven formulation in modeling soil–structure interactions.…”