Load transfer mechanism at the calcium silicate hydrate/carbon nanotubes interface changed by carbon nanotubes surface modification investigated from atomic simulation

Abstract

The surface modification of carbon nanotubes (CNT) can further improve the ductility of the cement/CNT composites. Atomic simulations were employed to decode the alteration of the interfacial load transfer mechanism by PVA addition, non-covalent bond modification of CNTs. The results of the pull-out simulations show that PVA significantly enhances the load transfer at the organic–inorganic interface. Interfacial load transfer depends on effective interfacial interactions, which in turn depend on interfacial chemical bonding. The interfacial region is more complexly reorganized by PVA, accompanied by the renewal of interfacial bonding. The addition of PVA could add new ion pairs (OCNT-Ca-OPVA-Ca-OCSH and HCNT-OPVA-Ca-OCSH) and lots of hydrogen bonds without detriment to the original linkage (OCNT-Ca-OCSH), in turn forming a strong network of chemical bonds intertwined with direct and indirect connections. Due to the intertwined network, the load transfer at the interface is partitioned and transferred in multiple paths, contributing to an increased interfacial strength. During the pull-out process, the load distribution between CNT, PVA and CSH evolves constantly, which is beneficial to damage retardation of the cement/CNT composites.