ITZ volume fraction in concrete with spheroidal aggregate particles and application: Part I. Numerical algorithm

ABSTRACTIn portland cement mortar and concrete, interfacial zones exist around the aggregate particles that have larger pore sizes and pore volumes than the bulk cement paste. If there are enough aggregate particles present, these zones may overlap so as to percolate. A computer simulation model has been developed that can predict this percolation point as a function of interfacial zone thickness, volume fraction of aggregates, and aggregate particle size distribution. The model was used to simulate 1cm3 of mortar, using approximately 10,000 aggregate particles. Results from this model are used to explain recent mercury porosimetry results on mortars having a variety of sand contents. The implications of interfacial zone percolation for the transport properties of mortar and concrete are discussed.

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Analytical and modeling investigations of volume fraction of interfacial layers around ellipsoidal aggregate particles in multiphase materials

Modelling and Simulation in Materials Science and Engineering ◽

10.1088/0965-0393/21/1/015005 ◽

2012 ◽

Vol 21 (1) ◽

pp. 015005 ◽

Cited By ~ 23

Author(s):

W X Xu ◽

H S Chen

Keyword(s):

Volume Fraction ◽

Interfacial Layers ◽

Multiphase Materials ◽

Aggregate Particles

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Numerical Investigation of Internal Vortex Structure in Two-Dimensional, Incompressible Richtmyer-Meshkov Flows

Fluids Engineering ◽

10.1115/imece2005-82723 ◽

2005 ◽

Author(s):

Nicholas J. Mueschke ◽

Wayne N. Kraft ◽

Malcolm J. Andrews ◽

Jeffrey W. Jacobs

Keyword(s):

Numerical Algorithm ◽

Vortex Structure ◽

Stokes Equations ◽

Volume Fraction ◽

Variable Density ◽

Small Scale ◽

Two Dimensional ◽

Viscous Effects ◽

Two Fluids ◽

Velocity Impulse

Richtmyer-Meshkov (RM) instability occurs when one fluid is impulsively accelerated into a second fluid, such that ρ1 ≠ ρ2. This research numerically investigates RM instabilities between incompressible media, similar to the experiments reported by Niederhaus & Jacobs [1]. A two-dimensional, finite-volume numerical algorithm has been developed to solve the variable density Navier-Stokes equations explicitly on a Cartesian, co-located grid. In previous calculations, no physical viscosity was implemented; however, small scale fluctuations were damped by the numerical algorithm. In contrast, current simulations incorporate the physical viscosities reported by Niederhaus & Jacobs [1] and are explicitly used. Calculations of volume fraction and momentum advections are second-order accurate in space. Unphysical oscillations due to the higher-order advection scheme are minimized through the use of a Van Leer flux limiting algorithm. An initial velocity impulse [2] has been used to model the impulsive acceleration history found in the experiments of Niederhaus & Jacobs [1]. Both inviscid and viscous simulations result in similar growth rates for the interpenetration of one fluid into another. However, the inviscid simulations (i.e. no explicit viscosity) are unable to capture the full dynamics of the internal vortex structure that exists between the two fluids due to the absence of viscous effects.

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A numerical algorithm for the ITZ area fraction in concrete with elliptical aggregate particles

Magazine of Concrete Research ◽

10.1680/macr.2007.00123 ◽

2009 ◽

Vol 61 (2) ◽

pp. 109-117 ◽

Cited By ~ 25

Author(s):

J.J. Zheng ◽

F.F. Xiong ◽

Z.M. Wu ◽

W.L. Jin

Keyword(s):

Numerical Algorithm ◽

Area Fraction ◽

Aggregate Particles

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Chemical partitioning of elements in Ni-base MC-carbide reinforced eutetic superalloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010007504x ◽

1983 ◽

Vol 41 ◽

pp. 250-251

Author(s):

E. F. Koch ◽

E. L. Hall ◽

S. W. Yang

Keyword(s):

Alloy Composition ◽

Volume Fraction ◽

Lattice Mismatch ◽

Turbine Blades ◽

Eutectic Alloys ◽

Alloy Matrix ◽

X Ray ◽

Gas Turbine Blades ◽

Analytical Electron ◽

Analytical Electron Microscope

The plane-front solidified eutectic alloys consisting of aligned tantalum monocarbide fibers in a nickel alloy matrix are currently under consideration for future aircraft and gas turbine blades. The MC fibers provide exceptional strength at high temperatures. In these alloys, the Ni matrix is strengthened by the precipitation of the coherent γ' phase (ordered L12 structure, nominally Ni3Al). The mechanical strength of these materials can be sensitively affected by overall alloy composition, and these strength variations can be due to several factors, including changes in solid solution strength of the γ matrix, changes in they γ' size or morphology, changes in the γ-γ' lattice mismatch or interfacial energy, or changes in the MC morphology, volume fraction, thermal stability, and stoichiometry. In order to differentiate between these various mechanisms, it is necessary to determine the partitioning of elemental additions between the γ,γ', and MC phases. This paper describes the results of such a study using energy dispersive X-ray spectroscopy in the analytical electron microscope.

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Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071326 ◽

1973 ◽

Vol 31 ◽

pp. 176-177

Author(s):

D. E. Fornwalt ◽

A. R. Geary ◽

B. H. Kear

Keyword(s):

Electron Microscope ◽

Grain Boundaries ◽

Volume Fraction ◽

Rupture Life ◽

Stress Rupture ◽

High Volume ◽

Precipitate Morphology ◽

Stress Rupture Life ◽

Nickel Base ◽

Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

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Instrumentation For Quantitative Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078584 ◽

1977 ◽

Vol 35 ◽

pp. 206-209

Author(s):

B. Ralph ◽

A.R. Jones

Keyword(s):

Volume Fraction ◽

Three Dimensional ◽

Two Dimensional ◽

Automatic Data ◽

Phase Volume Fraction ◽

Statistical Confidence ◽

Resultant Data ◽

Automatic Data Collection ◽

Third Dimension ◽

Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

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Formation of Persistent Slip Band in Fatigued Copper Single Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054807 ◽

1982 ◽

Vol 40 ◽

pp. 470-471

Author(s):

N. Y. Jin

Keyword(s):

Volume Fraction ◽

Fatigue Cracks ◽

Wall Structure ◽

Matrix Structure ◽

Dislocation Dipole ◽

Slip Bands ◽

Persistent Slip Bands ◽

The Matrix ◽

Hard Shell ◽

Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

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Grain Refinement in Titanium-Erbium Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052626 ◽

1974 ◽

Vol 32 ◽

pp. 522-523

Author(s):

B. B. Rath ◽

J. E. O'Neal ◽

R. J. Lederich

Keyword(s):

Electron Microscopy ◽

Size Distribution ◽

Grain Refinement ◽

Grain Growth ◽

Volume Fraction ◽

Pure Titanium ◽

Systematic Investigation ◽

Second Phase ◽

Titanium Matrix ◽

Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

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