Dispersion and reinforcement efficiency of carbon nanotubes in cementitious composites

Abstract

Cement pastes reinforced with various concentrations of functionalised and unfunctionalised carbon nanotubes (CNTs) with different aspect ratios were studied in terms of their dispersion and reinforcement efficiency. Mechanical strength was correlated with geometrical characteristics of CNTs, as well as the microstructure of reinforced pastes. Optimal CNTs of 0·05–0·1 wt% were found effective in increasing the flexural and compressive strength of reinforced pastes up to 36% and 27%, respectively. Efficiently dispersed CNTs were effective in bridging microcracks up to around 1 μm width. The CNTs did not significantly affect the phase composition of cement pastes but accelerated the hydration process. Based on a proposed equation, strength improvement was correlated with CNT aspect ratio and volume concentration. This equation establishes guidelines for maximised strength development based on geometrical and compositional parameters; it can be used for more rational design of CNT-reinforced cement materials, covering different compositions, as well as types and amounts of CNTs.

Influence of Carbon Nanotubes on the Mechanical Behavior and Porosity of Cement Pastes Prepared by A Dispersion on Cement Particles in Isopropanol Suspension

“…Using these proportions and methodology, Rocha and Ludvig (2018) [9] achieved approximately 50% gain in compressive and splitting tensile strengths at 0.05% of CNTs, suggesting that the optimum range for incorporation of CNTs based on that methodology is close to this ratio. [3] also confirmed that amounts of CNTs, up to 0.10%, were more effective for increasing the flexural and compressive strengths.…”

“…In order to achieve effective composite preparation, good dispersion and homogeneous distribution of CNTs are essential. The hydrophobic behavior causes CNT agglomerations and the clusters formed by their presence in high amounts can compromise the mechanical properties [2][3][4]. In addition, due to this characteristic, the nanostructured cement composites' strength presents high variability [2], and consequently, reproducibility and statistical analysis are important to the validation of results.…”

Influence of Cracking on the Durability of Reinforced Concrete with Carbon Nanotubes

“…The concrete compositions are presented in Table 3. The CNT content, of 0.1% by weight of cement, was defined considering the results of previous studies [20,22,23] regarding the mechanical characterization of cement pastes and mortars with 0.015-0.1% of the same type of CNT. Concrete mixes were produced in a vertical shaft mixer with bottom discharge.…”

“…During the last decade, carbon nanotubes (CNT) have been studied as a reinforcement material for cement-based composites [16][17][18][19][20][21][22][23][24][25][26]. The growing interest in this field comes from the desire to modify the cement matrix at the scale of their main compounds, by taking advantage of the outstanding properties of CNT.…”

“…Regarding the characterization of CNT-reinforced cementitious materials, various studies have been carried out focusing on the physical, mechanical and durability characterizations of cement pastes and mortars [20,22,23,30], and few on those properties of CNT-reinforced concrete [16][17][18]21,24]. The studied properties of CNT-reinforced cementitious materials include compressive strength [16][17][18][19][20][21][22][23][24], flexural strength [17,19,20,23,24], splitting tensile strength [17], modulus of elasticity [17,18,22,23], ultrasonic pulse velocity [18,23], fracture toughness [17,23], steel-concrete bond [21], shrinkage [18,22,23], creep [18], microscopic analysis [17][18][19][20][22][23][24], capillary absorption [16,22,…”