This study aims to understand the effects and mechanisms of length, diameter, and functional group of carbon nanotubes (CNTs) on rheological behaviors of cementitious composites. The experimental results show that the addition of CNTs decreases the flow index and increases the critical shear rate of cementitious composites. CNTs with a sub-micrometer length and small diameter endow cementitious composites with high yield stresses and minimum viscosities. Influenced by the high water absorption of hydroxylic groups, the minimum viscosity of cementitious composites with hydroxyl functionalized CNTs is larger than that of composites with pristine carbon nanotubes (p-CNTs). By contrast, the yield stress and minimum viscosity of cementitious composites with carboxyl functionalized CNTs are smaller than that of cementitious composites with p-CNTs at most contents due to the high dispersion induced by carboxyl groups. The effect mechanisms of CNTs on rheological behaviors can be attributed to adsorption effect and entanglement effect, which are closely related to length, diameter and functionalization groups of CNTs. The established minimum viscosity prediction model considering the influence of CNT physicochemical features can provide guidance for regulating the workability and hardened performance of CNTs modified cementitious composites.

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.