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Search Publications by: Nicos Martys (Fed)

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Displaying 51 - 75 of 92

Virtual Permeametry on Microtomographic Images

November 1, 2004
Author(s)
C H. Arns, M A. Knackstedt, W V. Pinczewski, Nicos Martys
We show that accurate numerical micropermeametry measurements can be performed on three dimensional digitized images of sedimentary rock. The sample size can be very small making it possible to predict properties from core material not suited for

The Rheology of Cementitious Materials: Chemistry, Colloids and Rocks

May 1, 2004
Author(s)
Robert J. Flatt, Nicos Martys
Knowledge of colloidal science has proven essential in the development of a new generation of dispersants for concrete. These polymer molecules induce steric repulsion between cement particles, reducing agglomeration and allow high workability to be

Relating Fresh Concrete Viscosity Measurements From Different Rheometers

May 1, 2003
Author(s)
Chiara F. Ferraris, Nicos Martys
The rheological properties of concrete need to be measured and predicted to enable the characterization of special concrete such as self-consolidating concrete (SCC). It was also shown by a round-robin held in 2000 [ , ] that different rheometers give a

Simulation of Droplet Breakup Using a Lattice Boltzmann Method

May 1, 2003
Author(s)
Frederick R. Phelan Jr., Nicos Martys
Droplet breakup in homogeneous shear flow at super critical Capillary numbers and a viscosity ratio of unity is studied using a lattice Boltzmann method. We find that the total number of child drops that form from an isolated super critical drop scales

Simulation of SCC Flow

November 1, 2002
Author(s)
Nicos Martys, Chiara F. Ferraris
Predicting the rheological properties of concrete is essential for its optimal use in situations such as flow between rebars. The aggregate gradation and shape, as well as the rheological properties of the mortar or cement paste will affect the flow of SCC

Research and Challenges of Multi-Scale Mechanics and Modeling

October 1, 2002
Author(s)
K P. Chong, Nicos Martys
One of the great challenges in the material sciences is to predict long term performance of materials and structures. Recent efforts have focused on linking nano/micro scalebehavior to meso-scale and macroscale behavior through computational modeling.In

Fresh Concrete Rheology - Recent Developments

December 1, 2001
Author(s)
Chiara F. Ferraris, F De Larrard, Nicos Martys
The design of concrete with specified properties for an application is not a new science, but it has taken on a new meaning with the wide use of high performance concretes. The following properties are related to fresh concrete: ease of placement and

A Classical Kinetic Theory Approach to Lattice Boltzmann Simulation

October 1, 2001
Author(s)
Nicos Martys
An approach to lattice Boltzmann simulation is described, which makes a direct connection between classical kinetic theory and contemporary lattice Boltzmann modeling methods. This approach can lead to greater accuracy, improved numerical stability and

A New Approach to Lattice Boltzmann Simulation

October 1, 2001
Author(s)
Nicos Martys
A new approach to lattice Boltzmann simulation is introduced which avoids the direct numerical determination of the single-particle distribution from the Boltzmann collision operator. Instead, one starts from the Chapman-Enskog expansion of the single

De la Pate de Ciment au Beton: Modlisation et Mesures Exprimentales des Proprietes Rhologiques. [Cement Paste to the Concrete Modisation and Measure Experimental of the Properties Rheology.]

October 1, 2001
Author(s)
Chiara F. Ferraris, Nicos Martys
The prediction of concrete rheological properties is essential for the correct use of the material. The composition of the concrete is nowadays complex. It is not limited to cement, aggregates and water but also includes admixtures and fillers. Therefore

Acquiring, Analyzing, and Using Complete Three-Dimensional Aggregate Shape Information

April 1, 2001
Author(s)
Edward J. Garboczi, Nicos Martys, H A. Saleh, Richard A. Livingston
The shape of aggregates, from whatever source, plays a crucial role in determining the properties of the composite material in which they are embedded (e.g., asphaltic or portland cement concrete). To properly characterize this three-dimensional shape

Critical Properties and Phase Separation in Lattice Boltzmann Fluid Mixtures

March 1, 2001
Author(s)
Nicos Martys, Jack F. Douglas
Basic equilibrium properties of Lattice Boltzmann (LB) fluid mixtures (coexistence curve, surface tension, interfacial profile, correlation length) are calculated to characterize the critical phenomena occurring in these model liquids and to establish a