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. 2021 Apr 9;11(4):961.
doi: 10.3390/nano11040961.

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

Mohammadmahdi Abedi  1 , Raul Fangueiro  2 , António Gomes Correia  1
Affiliations

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

Mohammadmahdi Abedi et al. Nanomaterials (Basel). .

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.

Keywords: CNT/GNP; durability; mechanical; microstructural; piezoresistivity; self-sensing; stabilized sand.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
CNT and GNP morphology (dry mix).
Figure 2
Figure 2
Raman analysis results of CNTs and GNPs.
Figure 3
Figure 3
Representation of the specimen’s geometrical and electrode layout.
Figure 4
Figure 4
A schema of the climatic cycle protocol.
Figure 5
Figure 5
Compaction curves of plain and reinforced cementitious stabilized sand (CSS) by different carbon nanomaterial (CNM) concentrations.
Figure 6
Figure 6
Maximum dry density and degree of saturation for plain and reinforced CSS with different CNM concentrations.
Figure 7
Figure 7
“γd/γd(max)” vs. “Sr-Sr (opt)” relationship.
Figure 8
Figure 8
A schema of compacted: (a) Plain CSS, reinforced; (b) CSS by CNMs.
Figure 9
Figure 9
An ultrasonic wave passing time for plain and reinforced CSS with different CNM concentrations.
Figure 10
Figure 10
Scanning electron microscopy (SEM) images of the reinforced CSS by high CNM concentration CG (0.34%) (the areas with white markings are the areas selected for EDX analysis).
Figure 11
Figure 11
SEM morphology of CNTs and GNPs crack bridging and deviation mechanism in CNM-reinforced CSS.
Figure 12
Figure 12
Thermal analysis of plain and reinforced CSS by different concentrations of CNMs: (a) TGA thermograms, (b) DSC thermograms.
Figure 13
Figure 13
X-ray diffraction analysis (XRD) patterns of hardened plain and reinforced CSS by different CNM concentrations.
Figure 14
Figure 14
(a) Unconfined compressive strengths of different CSSs, (b) the amount of strain at the rupture point and E(50%) after 28 days of hydration.
Figure 15
Figure 15
Weight loss and ultrasonic wave passing time after 12 climatic cycles.
Figure 16
Figure 16
Electrical resistivity of hardened plain and reinforced CSS by different CNM concentrations.
Figure 17
Figure 17
The electrical resistivity of the specimen CG (0.34%) at optimum, 2% more than optimum, and 2% less than optimum water content.
Figure 18
Figure 18
Electrical resistivity of the reinforced specimens with different concentrations of the CNM after climatic cycles.
Figure 19
Figure 19
(a,b) CNM morphologies after climatic cycles (the areas with white markings are the areas selected for EDX analysis).
Figure 20
Figure 20
Raman spectra of the CNMs after climatic cycles.
Figure 21
Figure 21
The fractional change in resistivity and axial strain under cyclic compression loading for reinforced CSS by different CNM concentrations.
Figure 22
Figure 22
Variation of strain with the FCR for reinforced CSS by different CNM concentrations.
Figure 23
Figure 23
The fractional change in resistivity together with axial strain under cyclic compression loading for specimen CG (0.34%) at optimum, 2% more than optimum, and 2% less than optimum water content.
Figure 24
Figure 24
A schema of the compacted specimen composed of the CNMs: (a) fresh sample at optimum water content, (b) fresh sample at the higher or lower water content, (c) hardened specimen at the higher or lower water content, (d) hardened specimen at the higher or lower water content, subjected to the compression loading.
Figure 25
Figure 25
Variations of strain with the FCR for specimen CG (0.34%) at optimum, 2% more than optimum, and 2% less than optimum water content.
Figure 26
Figure 26
The fractional change in resistivity together with axial strain under cyclic compression loading for reinforced CSS by different CNM concentrations after climatic cycles.
Figure 27
Figure 27
Variation of strain with the fractional changes in electrical resistivity (FCR) for nano-intruded specimens after climatic cycles.
Figure 28
Figure 28
Variation of CNM reinforced specimens’ gauge factors under compression loading: (a) in normal condition, (b) with different water content, (c) after climatic cycles.
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