Enhancement of the durability characteristics of concrete nanocomposite pipes with modified graphite nanoplatelets

Enhancement of cement-based materials with graphite nanomaterials builds upon and complements the established practice of reinforcing cement-based materials with micro-scale fibers. Among graphite nanomaterials which have reached industrial-scale production, graphite nanoplatelets offer favorable economics for use in concrete. The planar geometry of graphite nanoplatelets is another distinguishing feature of this nanomaterial, which favors its role towards enhancement of the transport and durability characteristics of concrete. An experimental investigation was conducted in order to determine the contributions of graphite nanoplatelets to the durability of dry-cast concrete pipes in aggressive sanitary sewer environment. Laboratory studies were followed with industrial-scale production of concrete pipes incorporating graphite nanoplatelet and/or micro-scale polyvinyl alcohol (PVA) fibers. Special attention was given to dispersion and interfacial interactions of graphite nanoplatelets in concrete. For this purpose, nanoplatelet surfaces were modified by a polyelectrolyte, and the modified nanoplatelets were first dispersed in a fraction of the mixing water prior to addition to concrete. Significant improvements in the transport and durability characteristics of concrete pipes were realized by the addition of modified graphite nanoplatelets. These improvements could be attributed to the close spacing and high specific surface area of graphite nanoplatelets, which effectively hinder sorption of moisture and aggressive chemicals into concrete, and control growth of microcracks under aggressive exposures.