Distribution of Carbon Nanofibers and Nanotubes in Cementitious Composites

Carbon nanofibers (CNFs) and nanotubes (CNTs) are known to be extremely strong and stiff, and their potential as reinforcement has been of interest to many investigators in the past decade. One of the most important keys for fully harnessing the properties of any type of fiber is to control the distribution in the material matrix. As far as CNFs-CNTs are concerned, the strong attraction among nanoscale fibers due to van der Waals forces makes this task difficult. This study focuses on some of the problems that prevent a uniform distribution of CNFs-CNTs in cement paste and the methods used in the past to enhance dispersion. The first phase of the experimental program investigates the effect of using superplasticizers accompanied by sonication on the dispersion of CNFs in water and paste. The second phase focuses on the problem of cement grain size and limitations that the use of fine grain cement causes. Finally, on the basis of results and past studies, suggestions are made for achieving enhanced dispersion of CNFs-CNTs in cement paste.