Synthesis of nanoSiO2@graphene-oxide core-shell nanoparticles and its influence on mechanical properties of cementitious materials

Graphene oxide (GO) has enormous potential to improve properties of cementitious materials. Well dispersed GO in hardened cement matrix could be more effective in strengthening concrete compared to aggregated GO. While GO agglomeration is somewhat inevitable due to its fine nature, the degree of agglomeration could be tuned through particle separation. In this study, nanoSiO(2)@graphene-oxide (NS@GO) nanoparticles were synthesized using GO and colloid nanoSiO(2) (NS) by a electrostatic self-assembly method. NS, GO and the prepared NS@GO were characterized by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and Fourier transmission infrared, and, the influence of NS@GO addition on the mechanical properties of cementitious composites was investigated. The results show that NS@GO can increase the flexural strength of cement composites by 49.2% at later age. A "sandwich effect" was proposed as an important reinforcing mechanism of NS@GO based on the microstructure and hydration products of NS@GO added composites. Compared with the simple NS-GO blend, NS@GO can better maintain the spatial structure of GO when mixed with cement. In addition, there would be more interactions between calcium silicate hydrates and GO during the cement hydration process, which contributes to the strength gain in NS@GO added mix. The research sheds new light on using GO and NS to optimize cementitious material design, as well as spatial coordination of different types of nanoparticles. (C) 2019 Elsevier Ltd. All rights reserved.