Ozone treatment on the dispersion of carbon nanotubes in ultra-high performance concrete

This study aimed at investigating the effects of ozone treatment on the dispersion of carbon nanotubes (CNTs) in aqueous solution and the resulting influence on the material properties of ultra-high performance concrete (UHPC). The CNT suspension was fabricated by the ozone treatment and used to produce UHPC/CNT composites. Using spatially-resolved small angle X-ray scattering, the degree of dispersion of CNTs in UHPC matrix was quantitatively evaluated. It was confirmed that the ozone treatment enhanced the dispersion of CNTs in aqueous solution by formulating oxygenic and carboxylic groups on the surfaces of CNTs. Thus, interfacial interaction between the CNTs and UHPC was enhanced, leading to the higher nucleation effect at early ages. Ozone treatment did not significantly modify the hydration mechanism of UHPC. Instead, it provided multiple nucleation sites and double steric repulsion thorough the improved degree of dispersion of CNTs, which resulted in accelerated hydration at early ages and improved compressive strength at later ages. (C) 2020 The Authors. Published by Elsevier Ltd.