Modeling the mechanical properties of cementitious materials containing CNTs

Ramezani, Mahyar; Kim, Young Hoon; Sun, Zhihui

doi:10.1016/j.cemconcomp.2019.103347

Cited by 82 publications

(56 citation statements)

References 44 publications

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“…To understand the mechanisms of CNTs within cementitious materials (e.g., bonding, dispersion and cement hydration rate mechanisms), three critical factors were proposed in the authors' previous work [17] to capture the interactions between the important experimental variables to predict the mechanical properties including the flexural strength. 1) dispersion factor (η D ) to correlate CNT dispersion as a functions of AR, CNT volume fraction in aqueous solution (v f Àw ), superplasticizer-to-CNTs (SP/CNTs) ratio and Ultrasonication Energy Indicator (UEI) 2) matrix factor (η M ) to include the influence of water-to-cement ratio (w/c) and sand-to-cement ratio (s/c) 3) hydration age factor (η H ) to consider the interactions between CNT concentration (κ) and hydration age of cement (t)…”

Section: Critical Factors Affecting Cnt Mechanisms In Cementitious Comentioning

confidence: 99%

“…The discrepancy can be attributed to the CNT dispersion and bonding states within the cement matrix [14][15][16]. The bond strength between CNTs and the cement matrix is governed by multiple factors including CNT type, surface condition and dispersion quality [17][18][19]. Through performing extensive statistical analysis of experimental test data reported in the literature, the authors found that CNT dispersion quality significantly contributed to the mechanical properties [7].…”

Section: Introductionmentioning

confidence: 99%

“…The improper combinations of these factors often lead to degradation of the interfacial bond and flexural strengths. These phenomena are explained in the authors' previous works [7,17,20]. To address these phenomena, an analytical model can be a viable option to estimate the bond strength between CNTs and the matrix considering the contributions of multiple experimental variables for maximizing the flexural strength of CNT-cement composites.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the literature data was analyzed to identify the most important variables and their interactions affecting the dispersion quality, bond strength and the flexural strength [7]. Besides, the influence of CNTs on the rate of cement hydration is another important variable affecting the flexural strength that needs to be considered in the prediction model [7,17,31].…”

Section: Introductionmentioning

confidence: 99%

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Probabilistic model for flexural strength of carbon nanotube reinforced cement-based materials

Ramezani

Kim

Sun

2020

Composite Structures

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The bond between carbon nanotubes (CNTs) and cementitious materials is the key characteristic for predicting the flexural strength. However, CNT dispersion quality may change the bonding mechanism. A probabilistic approach can benefit the deterministic models to capture the uncertainties affecting these characteristics. This study proposes a probabilistic model using the Kelly-Tyson theory to predict the flexural strength of CNT-cement nanocomposites. The proposed model considers the effects of experimental variables on CNT dispersion quality, bonding mechanism and the flexural strength. To this end, a Bayesian methodology is employed to calibrate the unknown model parameters and various sources of uncertainty using extensive test data. The model is then used to identify the optimum ranges of variables to maximize the flexural strength through computing the failure probability which is defined as the probability of not meeting certain strength requirements (herein, 50% increase compared with the control). The model suggests that CNT aspect ratio ranges from 400 to 800 and concentration between 0.08 and 0.18 c-wt% yields the highest flexural strength. Finally, the effect of changes in experimental variables on the probability estimates is examined using sensitivity and importance measures. The analysis reveals that the proposed model can capture the experimentally observed trends with reasonable accuracy. For example, the importance of age increases as CNT concentration increases.

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Section: Critical Factors Affecting Cnt Mechanisms In Cementitious Comentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Probabilistic model for flexural strength of carbon nanotube reinforced cement-based materials

Ramezani

Kim

Sun

2020

Composite Structures

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“…Using Equation 2-6, Pukanszky adhesion parameters (B) is calculated for the available database from the literature [11,12,16,28,29,[111][112][113]142] and this research. The minimum, maximum, mean, median, and standard deviation of B parameter is shown in [104].…”

Section: Flexural Strengthmentioning

confidence: 99%

Design and predicting performance of carbon nanotube reinforced cementitious materials : mechanical properties and dispersion characteristics.

Ramezani¹

2020

Preprint

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Recently, Carbon Nanotubes (CNTs) are drawing considerable attention of researchers for reinforcing cementitious materials due to their excellent mechanical properties and high aspect ratio (length-to-diameter ratio). However, CNTs might not disperse well within the cement matrix, resulting in little improvement or even degradation of concrete properties. The uncertainty in producing the consistent results in different studies might be attributed to multiple interactions between the experimental variables affecting the nanotube dispersion and the final properties of CNT-cement nanocomposites. Therefore, this research mainly focused on proposing equations that can reliably capture these interactions in order to correlate CNT dispersion with the mechanical properties. The main experimental variables studied included CNT concentration, aspect ratio, ultrasonication energy, ultrasonication amplitude, surfactant-to-CNTs ratio, water-to-cement ratio, sand-to-cement ratio, and hydration age of specimen. The study reported in this research was conducted in two parts: experimental program and modeling. In the experimental part of this research, a total of 63 different mix proportions were used to evaluate the flowability, mechanical properties, and durability characteristics of cement pastes and mortars containing CNTs. Using experimental test results reported in this study and the literature, three critical relations were proposed to consider the CNT dispersion, cement matrix composition, and hydration age of cement. The proposed critical relations were then added to available theoretical models in the literature. The flexural strength and elastic modulus of CNT-cement nanocomposites were predicted through a state-of-the-art probabilistic model using a Bayesian methodology. Finally, the developed probabilistic models were used to identify the optimum ranges of the experimental variables to maximize the mechanical properties. This was done through computing the conditional probability of not meeting the specified design requirement. The experimental results indicated that addition of CNTs could significantly improve different properties of cementitious materials, if the optimum range of each variable was used. Also, to achieve the desired mechanical properties, various combinations of the experimental variables might be used. The proposed prediction models were shown to capture the interactions between the experimental variables for predicting the mechanical properties within ±15% and ±18% of the experimental test results for flexural strength and elastic modulus, respectively. Based on the findings of this research, contour plots were developed to provide practical guidelines for future engineers to design CNT-cement nanocomposites.

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Carbon nanotube reinforced biobased poly(urethane urea) covalent adaptable network composite

Xie,

Li,

Zeng

2023

Journal of Polymer Science

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A solvent‐free approach was developed to incorporate carbon nanotube (CNT) into castor oil derived poly(urethane urea) (PPU) covalent adaptable network (CAN) based on dynamic piperidine‐urea bonds to fabricate CNT reinforced PPU composites. The approach includes two steps i.e., pre‐polymerization of castor with isophorone diisocyanate in flask and subsequent chain‐extension with 1,3‐bis(4‐piperidinyl)propane (PIP) in the presence of CNT in an internal mixer. The effect on CNT content of the morphology, mechanical property, stress relaxation, and reprocessability of the PPU/CNT composites was investigated in detail. The results demonstrated that CNT dispersed well in the PPU networks due to the applied strong shear force which facilitated the dispersion of CNT in the PPU matrix before cross‐linking. The well‐dispersed CNT reinforced the mechanical properties of PPU significantly and the Young's modulus (E) of the composites were enhanced significantly when the content of CNT was ≥6 wt% due to the formation of CNT network in the PPU matrix. When the content of CNT was 10 wt%, the E of PPU‐10%CNT was 927.59 ± 149.05 MPa, which was improved by ~60% compared to PPU. The reprocessability of the PPU network was remained although the stress relaxation rate was reduced with incorporation and increasing content of CNT. In addition, the PPU/CNT composites could be degraded chemically to recycle CNT through reaction of the dynamic piperidine‐urea bonds with additional PIP.

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Modeling the mechanical properties of cementitious materials containing CNTs

Cited by 82 publications

References 44 publications

Probabilistic model for flexural strength of carbon nanotube reinforced cement-based materials

Probabilistic model for flexural strength of carbon nanotube reinforced cement-based materials

Design and predicting performance of carbon nanotube reinforced cementitious materials : mechanical properties and dispersion characteristics.

Carbon nanotube reinforced biobased poly(urethane urea) covalent adaptable network composite

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