Digital simulation of the aggregate–cement paste interfacial zone in concrete

1991 ◽  
Vol 6 (1) ◽  
pp. 196-201 ◽  
Author(s):  
Edward J. Garboczi ◽  
Dale P. Bentz
Keyword(s):  
Cement Paste ◽  
Digital Simulation ◽  
Particle Packing ◽  
Diffusion Reaction ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Two Dimensional ◽  
Portland Cement Concrete ◽  
Quantitative Image ◽  
Characteristic Features

Researchers using backscattered scanning electron microscopy, along with quantitative image analysis techniques, have clearly demonstrated the existence of a highly porous interfacial region between aggregate particles and the cement paste matrix in ordinary Portland cement concrete. This paper presents the results of a digital-image-based simulation model of this interfacial zone. A dissolution-diffusion-reaction-like cycle of hydrating cement particles is directly simulated using cement particles packed around a simple nonreactive aggregate particle. The model is two-dimensional, as we are comparing to experimental results obtained on two-dimensional images of polished sections. The qualitative features seen experimentally, such as large amounts of porosity and calcium hydroxide in the interfacial zone, are accurately reproduced. A new mechanism, one-sided growth, is proposed, along with the more usual particle-packing ideas, as an explanation of the origin of the characteristic features of the interfacial zone.

A Stludy of the Interfacial Region Between Cement Paste and Aggregate in Concrete

1987 ◽  
Vol 114 ◽  
Author(s):  
Karen L. Scrivener ◽  
Alison K. Crumbie ◽  
P. L. Pratt
Keyword(s):  
Image Analysis ◽  
Cement Paste ◽  
Quantitative Image Analysis ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Preliminary Results ◽  
Quantitative Image

ABSTRACTThe application of quantitative image analysis to the measurenent of microstructural gradients in the interfacial zone in concrete is described. Some preliminary results are presented and discussed.

scholarly journals Interfacial transition zone of cement paste-reactive aggregate in cement-zeolite mortars

2015 ◽  
Vol 63 (1) ◽  
pp. 31-34 ◽  
Author(s):  
Z. Owsiak ◽  
P. Czapik
Keyword(s):  
Cement Paste ◽  
Natural Zeolite ◽  
Mineral Admixtures ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Sodium Potassium ◽  
X Ray ◽  
Reactive Aggregate ◽  
Alkali Aggregate Reaction ◽  
Mortar Bar

Abstract Alkali-aggregate reaction is an expansive chemical reaction between the alkalis present in cement paste and minerals contained in aggregates. Mineral admixtures can mitigate the detrimental processes caused by this reaction. One of the minerals that reduce the effects of the alkali-aggregate reaction is natural zeolite. This study attempts to explain the process that takes place in the zone surrounding reactive gravel in the cement mortar made with an addition of natural zeolite. Mortar bar expansion tests were performed and a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer was used to observe the paste-aggregate interfacial zone. The results confirmed the influence of the zeolite on the reduction in reactive aggregate-based mortar expansion. The microstructure of the aggregatepaste interfacial region was described and particular sub-zones varying in terms of calcium, sodium, potassium and silicon contents were determined.

Microstructural Gradients in Cement Paste Around Aggregate Particles

1987 ◽  
Vol 114 ◽  
Author(s):  
Karen L. Scrivener ◽  
Ellis M. Gartner
Keyword(s):  
Image Analysis ◽  
Cement Paste ◽  
Interfacial Zone ◽  
Microstructural Investigation ◽  
Analysis Technique ◽  
Single Piece ◽  
Quantitative Image ◽  
Backscattered Electron ◽  
Condensed Silica Fume ◽  
Aggregate Particles

ABSTRACTThe effectiveness of condensed silica fume as a strength enhancing additive in concrete has been attributed to its ability to modify the interfacial zone between paste and aggregate. This paper describes a microstructural investigation of this interface using backscattered electron (bse) imaging combined with quantitative image analysis.Composite specimens were made in which a single piece of aggregate was embedded in cement paste. Granite, dolomite and garnet aggregates were used. After curing, the specimens were sectioned perpendicular to the surface of the aggregate particles and polished. The variation in porosity, amount of anhydrous material and calcium hydroxide (CH), with distance from the aggregate surface was measured. It was found that the porosity increases in the paste close to the interface, while the content of anhydrous grains decreases. No significant increase in CH content was found near the interface.The results confirm the applicability of the bse - image analysis technique, but indicate that the interfaces in specimens prepared in this manner may not be representative of aggregate paste interfaces in concrete.

Dynamic Response of Surface-Moored Vertical Barrier to Wave Action by Analog and Digital Simulation

1974 ◽  
Vol 96 (1) ◽  
pp. 335-342
Author(s):  
J. R. Fowler ◽  
E. I. Bailey
Keyword(s):  
Theoretical Model ◽  
Digital Simulation ◽  
Nonlinear Problems ◽  
Analog Computer ◽  
Two Dimensional ◽  
Test Program ◽  
Analog Simulation ◽  
Vertical Barrier ◽  
Amplitude Data ◽  
Lab Test

The two-dimensional dynamics of an oil containment barrier, which was designed to have very low tensile loads due to current and waves, were simulated with a theoretical model. The model was solved on both analog and digital computers, and a lab test program conducted to verify the model. For nonlinear problems such as this, for which “exact” solutions do not exist, the analog computer has many advantages, principally rapid parameter studies and convenient plotting output, plus giving the engineer a real time “feel” for the problem. The problem treated here was especially well-suited to analog simulation. Charts and graphs present maximum force and amplitude data, and experimental verification of the solution was obtained from wave tank studies.

scholarly journals Effect of Carbon Nanofiber Clustering on the Micromechanical Properties of a Cement Paste

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 223
Author(s):  
Lesa Brown ◽  
Catherine S. Stephens ◽  
Paul G. Allison ◽  
Florence Sanchez
Keyword(s):  
Cement Paste ◽  
Mechanical Response ◽  
Carbon Nanofiber ◽  
Homogenization Method ◽  
Indentation Modulus ◽  
Interfacial Zone ◽  
Micromechanical Properties ◽  
Significant Interest ◽  
Low Stiffness ◽  
Portland Cement Paste

The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the cement paste micromechanical properties and relation to the mechanical response at the macroscopic scale are still not fully understood. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive spectroscopy was used to determine the local elastic indentation modulus and hardness of a portland cement paste containing 0.2% CNFs with sub-micro and microscale CNF clusters. The presence of low stiffness and porous assemblage of phases (modulus of 15–25 GPa) was identified in the cement paste with CNFs and was attributed primarily to the interfacial zone surrounding the CNF clusters. The CNFs favored the formation of higher modulus C–S–H phases (>30 GPa) in the bulk paste at the expense of the lower stiffness C–S–H. Nanoindentation results combined with a microscale–macroscale upscaling homogenization method further revealed an elastic modulus of the CNF clusters in the range from 18 to 21 GPa, indicating that the CNF clusters acted as compliant inclusions relative to the cement paste.

scholarly journals Two-Dimensional Accretion Disk Models of a Neutron Star

1998 ◽  
Vol 188 ◽  
pp. 374-375
Author(s):  
M. Fujita ◽  
T. Okuda
Keyword(s):  
Neutron Star ◽  
Electron Scattering ◽  
Radiation Transport ◽  
Compact Object ◽  
Compact Objects ◽  
High Mass ◽  
Two Dimensional ◽  
Accretion Rates ◽  
The Difference ◽  
Characteristic Features

We investigate the accretion disks around compact objects with high mass accretion rates near the Eddington's critical value ME, where radiation pressure and electron scattering are dominant. This raises next problems: (a) whether stable disks could exist in relation to the theory of thermal instabilities of the disk and (b) what characteristic features the disks have if the stable disks exist. A non-rotating neutron star with the mass M = 1.4M⊙, radius R* = 107cm and the accretion rate Mac = 2.0 and 0.5Mac (models 1 and 2) is considered as the compact object. We assume the α-model for the viscosity and solve the set of two-dimensional time-dependent hydrodynamic equations coupled with radiation transport. The numerical method used is basically the same as one described by Kley and Hensler (1987) and Kley (1989) but we include some improvements in solving the difference equations (Okuda et al. 1997). The initial configuration consists of a cold, dense, and optically thick disk which is given by the standard α-model (Shakura and Sunyaev 1973) and a rarefied optically thin atmosphere around the disk.

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