Abstract
Carbon nanofibers/tubes (CNF/Ts) are very strong and stiff and as a result, are expected to be capable of enhancing the mechanical properties of cementitious materials significantly. Yet there are practical issues concerning the utilization of CNF/Ts in cementitious materials. This study summarizes some of the past efforts made by different investigators for utilizing carbon nanofilaments in cementitious materials and also reports recent experimental research performed by the authors on the mechanical properties of CNF-reinforced hardened cement paste. The major difficulties concerning the utilization of CNF/Ts in cementitious materials are introduced and discussed. Most of these difficulties are related to the poor dispersibility of CNF/Ts. However, the findings from the research presented in this work indicate that, despite these difficulties, carbon nanofilaments can significantly improve the mechanical properties of cementitious materials. The results show that CNFs, even when poorly dispersed within the cementitious matrix, can remarkably increase the flexural strength and cracking resistance of concrete subjected to drying conditions.
Highlights
Due to their excellent mechanical properties, carbon nanofibers/tubes (CNF/Ts) have been the subject of many investigations in the past decade where they have been used as inclusions in composite materials
The results showed that utilizing CNFs with only a CNF to cement weight ratio (CNF/c) weight ratio of 0.1% increased the flexural strength of hardened cement paste by over 80%, the dispersion of CNFs in cement paste was not uniform
Several existing challenges concerning the utilization of carbon nanofilaments in cementitious materials were discussed
Summary
Due to their excellent mechanical properties, carbon nanofibers/tubes (CNF/Ts) have been the subject of many investigations in the past decade where they have been used as inclusions in composite materials. CNTs exhibit elastic Young’s moduli of more than 1 TPa (1.5 × 108 psi) [1]. Their theoretical strength is 100 times that of steel, at only 1/6th the specific gravity [2]. CNTs are highly flexible, being capable of bending in circles or forming knots. Like macroscopic tubes, they can buckle or flatten under appropriate loadings [5]. The CNFs that they investigated had a tensile strength between 2 and 5 GPa (2.9 × 105–7.3 × 105 psi) with an average Young’s modulus of elasticity of 300 GPa (4.4 × 107 psi)
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