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

Vanessa Vilela Rocha,Péter Ludvig

doi:10.3390/ma13143164

Vanessa Vilela Rocha, Péter Ludvig

Open Access

https://doi.org/10.3390/ma13143164

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Abstract

Cement composites prepared with nanoparticles have been widely studied in order to achieve superior performance structures. The incorporation of carbon nanotubes (CNTs) is an excellent alternative due to their mechanical, electrical, and thermal properties. However, effective dispersion is essential to ensure strength gains. In the present work, cement pastes were prepared incorporating CNTs in proportions up to 0.10% by weight of cement, dispersed on the surface of anhydrous cement particles in isopropanol suspension and using ultrasonic agitation. Digital image correlation was employed to obtain basic mechanical parameters of three-point bending tests. The results indicated a 34% gain in compressive strength and 12% in flexural tensile strength gains, respectively, as well as a 70% gain in fracture energy and 14% in fracture toughness in the presence of 0.05% CNTs were recorded. These results suggest that CNTs act as crack propagation controllers. Moreover, CNT presence contributes to pore volume reduction, increases the density of cement pastes, and suggests that CNTs additionally act as nucleation sites of the cement hydration products. Scanning electron microscopy images indicate effective dispersion as a result of the methodology adopted, plus strong bonding between CNTs and the cement hydration product. Therefore, CNTs can be used to obtain more resistant and durable cement-based composites.

Highlights

Carbon nanotubes (CNTs) have been attracting the attention of the scientific community over the last few decades due to their extraordinary mechanical, thermal, and electrical properties
Water absorption and void index of the 0.05-ISO and 0.10-ISO pastes exhibit a certain decrease, the density of these samples increase as compared with the reference. These results indicate a lower level of porosity of cement pastes with CNT addition
The use of Multiwalled carbon nanotube (MWCNT) dispersed in non-aqueous isopropanol media on the surface of anhydrous cement particles was discovered to be an effective way for cement paste nanocomposite preparation

Summary

Introduction

Carbon nanotubes (CNTs) have been attracting the attention of the scientific community over the last few decades due to their extraordinary mechanical, thermal, and electrical properties. The nanocomposite produced with multilayer graphene shows approximately 100% higher splitting tensile and compressive strengths This present article aims to evaluate the effect of adding CNTs on the mechanical properties of cement. In order to achieve the objectives, predispersions in isopropanol media of CNTs on cement particles were prepared and used to evaluate the physical and mechanical behavior of cement pastes incorporating 0%, 0.05%, and 0.10% of CNTs according to cement weight 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. Hawreen et al (2018) [3] confirmed that amounts of CNTs, up to 0.10%, were more effective for increasing the flexural and compressive strengths

Materials and Methods

Materials

Dispersion Process

Evaluation of the Mechanical Behavior

Evaluation of the Physical Parameters

Conclusions