Multi-scale modeling of the ionic diffusivity of cement-based materials

Abstract

A new multiscale numerical approach was presented to predict the ionic diffusivity of cement based materials, which incorporated the lattice Boltzmann method, the conjugate gradient method, and the random walk method. In particular, the lattice Boltzmann method was applied to model the ionic diffusion in pore space of cement paste, while the upscaling of effective ionic diffusivity from cement paste (mortar) to concrete was processed by means of the conjugate gradient method and the random walk method. A case study was then presented, i e, the chloride diffusivity of concrete affected by sand content and gravel content. It is shown that the results of numerical prediction agree well with those of experimental measurements adopted from literatures. The multiscale numerical approach provides a prior assessment of ionic diffusivity for cement based materials from a microstructural basis.

A Virtual System and Method for Autonomous Navigation Performance Testing of Unmanned Surface Vehicles

“…An effective approach to addressing these issues is to build upon existing platforms, which include commercial software and open-source simulation software. Unity3D, a representative of excellent commercial game engines, possesses powerful graphical processing capabilities and is widely used in ship visual simulation due to its ability to create realistic ocean scenes [11][12][13][14][15]. In addition to visual simulation, Wang et al utilized the Unity3D engine to construct virtual ocean testing scenarios.…”

Effect of nano‐SiO2 on properties and microstructure of polymer modified cementitious materials at different temperatures

“…[11][12][13][14][15] However, numerous studies showed that the compressive strength and the early flexural strength of PMC materials were decreased with the increase of polymer content, because polymer hindered the hydration of cement. [16][17][18] Some researchers found that CH produced in PMC materials was stronger than unmodified materials, 19 sbr-latex powders delayed cement hydration especially in early 72 hr and reduced the amount of CH and C-S-H, 20 hydroxyethyl cellulose hindered the cement hydration in early age 21 through X-ray Diffraction Analysis Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.…”

“…Meanwhile, polymer has water‐thickening effect that will prevent bleeding and segregation and film‐forming effect, a stronger cohesive film forms between cement and aggregate and intertwines with the cement hydration product to form a net structure, which can significantly improve the bending properties of cementitious materials . However, numerous studies showed that the compressive strength and the early flexural strength of PMC materials were decreased with the increase of polymer content, because polymer hindered the hydration of cement . Some researchers found that CH produced in PMC materials was stronger than unmodified materials, sbr‐latex powders delayed cement hydration especially in early 72 hr and reduced the amount of CH and C‐S‐H, hydroxyethyl cellulose hindered the cement hydration in early age through X‐ray Diffraction Analysis (XRD), Scanning Electron Microscopy (SEM), theoretical calculation and thermogravimetry (TG) analysis, isothermal calorimetry, and infrared analysis.…”