The effect of two types of C-S-H on the elasticity of cement-based materials: Results from nanoindentation and micromechanical modeling

A multiscale micromechanics-hydration model for the early-age elastic properties of cement-based materials

Western boundary currents (WBC) influence the global ocean circulation and climate, whereas it locally reaches out differently the continental margins relief. This study analyses the response of WBC over their interactions with the corn of South America Margin. Particularly, the North and East sectors of Rio Grande do Norte (RN) on northeastern Brazil are investigated based upon bathymetry, in situ currents measurements, and simulations of oceanic currents using the CROCO model. The RN margin provides a critical pathway to the WBC along the East and North sectors, which are narrow and retracted shelves (up to 40 km offshore) with steep upper continental slopes (1:11). These sectors are separated by the shallower topography of the Touros High which extends 80 km offshore. The results reveal that the interactions of the Northern Brazilian Undercurrent (NBUC) with the RN northern margin physiography produces a recirculating current region forced by current shear. Eddies and meanders are explicit in February and August, with meander predominance in the latter month because of the increasing of wind intensity eastward. The accelerated core position of NBUC (> 1.0 m.s1) corresponds to the upper slope region of Touros High on both months, and confirms the constrain effect of the margin on the NBUC. The change of margin direction from the N-S to E-W leads to the decreasing of current velocity (~0.1m.s1) near the northern continental slope. This contrast produces an abrupt variation in the shear velocities forming vortices and meanders. Thus, the physiography of the Touros High, the margin directions, and the intensity of the winds control these features development on a regional scale. These oceanic events near the shelf slope affect the sedimentary and ecological system on Brazilian Equatorial continental shelves.

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Dissertação de Mestrado

Postbuckling of nanotube-reinforced composite cylindrical shells in thermal environments, Part I: Axially-loaded shells

Waste tire rubber constitute a serious worldwide problem due to the lack of landfills and the health hazards associated with these landfills. In addition to the environmental motivation for providing a means of recycling large quantities of waste tire rubbers, the use of tire rubber particles provides a new type of concrete that has unique mechanical and fracture criteria. This paper presents the results of recent experimental investigations on rubber concrete. Chipped and crumbed tire rubber particles were used to replace coarse and fine aggregate with different volume replacement levels. The mechanical and fracture properties of rubber concrete were examined. Quasi-brittle fracture mechanics models are used to determine the effect of incorporating tire rubber particles on the fracture performance of rubber concrete. Finally, some microstructural features of rubber concrete are also reported. It is concluded that the choice of the optimal replacement ratio of the tire rubber particles can yield concretes with desirable strength and fracture toughness criteria for different applications.

Mechanical, Fracture, and Microstructural Investigations of Rubber Concrete

Experimental Study of Cement-Asphalt Emulsion Composite

Four-phase sphere modeling of effective bulk modulus of concrete

Effective Young's modulus estimation of concrete

Impact response of single-lap composite joints

Composite pipe has been used in transporting corrosive fluid in many chemical processes in the petrochemical and pulp and paper industries. It is often subjected to external pressures due to process conditions (vacuum), water hammer, pump suction, and differences in elevation head. Most composite pipe designers are currently using traditional metallic pipe standards which do not take into account the anisotropic nature of composite materials. An analytical model for the buckling of orthotropic composite pipe under external pressure has been developed in this study. In this study, first-order laminated anisotropic plate theory was used to construct models of the kinematic and constitutive behavior of the composite cylinders. The Ritz Method was then applied to determine the buckling load under external pressure. Results obtained from the developed model were compared with the theory derived by Flugge for the case of metallic pipe. Due to the inclusion of shear deformation, the new model gave lower buckling...

Yi Zhao

Papers

Experimental Study of Cement-Asphalt Emulsion Composite

Four-phase sphere modeling of effective bulk modulus of concrete

Effective Young's modulus estimation of concrete

Impact response of single-lap composite joints

Buckling Analysis of Thick-Walled Composite Pipe under External Pressure