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Search Publications by: Nicos Martys (Assoc)

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Displaying 1 - 25 of 92

Intermediate Scattering Functions of a Rigid Body Monoclonal Antibody Protein in Solution Studied by Dissipative Particle Dynamic Simulation

April 8, 2021
Author(s)
Yanqin Zhai, Nicos Martys, William L. George, Joseph E. Curtis, Jannatun Nayem, Y. Z, Yun Liu
In the past decade, there is increased research interest in studying internal motions of flexible proteins in solution using Neutron Spin Echo (NSE) as NSE can simultaneously probe the dynamics at the length and time scale comparable to protein domain

Hydrodynamic Factors Influencing Mineral Dissolution Rates

March 9, 2020
Author(s)
Nicos Martys, Jeffrey W. Bullard, Pan Feng, Shaoxiong Ye
Solution flow profiles near a mineral surface can have significant influences on the local thermodynamic driving force and, potentially, the rate-controlling kinetic mechanism of its dissolution or precipitation. These influences are investigated here both

Pipe Flow of Sphere Suspensions having a Power-Law-Dependent Fluid Matrix

March 5, 2020
Author(s)
Nicos Martys, William L. George, Ryan P Murphy, Kathleen M Weigandt
Measurement and prediction of suspension flow properties in cylindrical geometries represents a significant challenge for both the experimentalist and modeller. In this paper, results of a computational study of suspension flow in a pipe geometry using a

Certification of SRM 2497: Standard Reference Concrete for Rheological Measurements

April 22, 2019
Author(s)
Nicos Martys, Max A. Peltz, William L. George, Blaza Toman, Edward J. Garboczi, Chiara Ferraris
Rotational rheometers are commonly used to determine the rheological properties of fluids such as viscosity and yield stress [Fer12]. Manufacturers generally recommend the use of a standard oil of known viscosity to verify that the instrument is operating

Certification of SRM 2493:Standard Reference Mortar for Rheological Measurements

October 4, 2017
Author(s)
Alex Olivas, Chiara C. Ferraris, Nicos Martys, Edward Garboczi, Blaza Toman, William L. George
Rheological measurements are often performed using a rotational rheometer. In this type of rheometer, the tested fluid is sheared between two surfaces, one of which acts as the rotating surface [1]. Usually, the rotational velocity is imposed and the

Rheological Measurement of Suspensions Without Slippage: Experimental and Model

December 13, 2016
Author(s)
Alex Olivas, Michelle A. Helsel, Nicos Martys, Chiara C. Ferraris, William L. George, Raissa Ferron
The conclusion of international studies was that the optimal approach to calibrate concrete rheometers would be to develop a non-Newtonian standard reference material (SRM) that contained inclusions similar in size to aggregates used commonly in concrete

Modeling of Suspension Flow in a Pipe Geometry and Rheometers

May 18, 2016
Author(s)
Nicos Martys, Chiara F. Ferraris, William L. George
Abstract Measurement and prediction of the flow of suspensions like cement based materials represents a significant challenge for both the experimentalist and modeler. In this paper, results of a computational study of suspension flow in a pipe and a

Testing of Cementitious Materials Using a Dynamic MEMS Micro Rheometer

May 17, 2016
Author(s)
Yong Sik Kim, Nicholas G. Dagalakis, Chiara C. Ferraris, Nicos Martys
Incompatibility of cementitious materials with admixtures often requires time consuming testing. Usually, several mixtures need to be prepared either using concrete or paste to determine the optimum high range water reducer dosage (HRWRA) and type. The

Calibration of rheometers for cementitious materials

May 16, 2016
Author(s)
Chiara F. Ferraris, Nicos Martys, William L. George, Edward J. Garboczi, Alex Olivas
The calibration of rheometers to determine the rheological properties of cement based materials ranging from cement paste to concrete cannot be done using standard oils as they are cost prohibitive and do not possess sufficient granularity to test slip

Metrology Needs for Predicting Concrete Pumpability

June 22, 2015
Author(s)
Myoungsung Choi, Chiara C. Ferraris, Nicos Martys, Didier Lootens, Van Bui, Trey Hamilton
With the increasing use of pumping to place concrete, the development and refinement of the industry practice to ensure successful concrete pumping is becoming an important need for the concrete construction industry. To date, research on concrete pumping

Research Needs to Advance Concrete Pumping Technology

April 10, 2015
Author(s)
Chiara F. Ferraris, Nicos Martys, Myoungsung Choi, Van Bui, Trey Hamilton, Didier Lootens
With the increasing use of pumping to place concrete, the development and refinement of the industry practice to ensure successful concrete pumping is becoming an important need for the concrete construction industry. To date, research on concrete pumping

Universal scaling law for the flow of non-Newtonian colloidal suspension

October 1, 2014
Author(s)
Nicos Martys, William L. George, Maxime Liard, Pascal Hebraud, Didier Lootens
It has been observed that flow curves (viscosity vs shear-rate) of spherical non-colloidal particles suspended in a non-Newtonian fluid matrix can be rescaled so as to collapse onto the flow curve of the matrix fluid. This result is surprising given the

Corrosion Detection in Concrete Rebars Using a Spectroscopic Technique

January 11, 2014
Author(s)
Edward J. Garboczi, Paul E. Stutzman, Shuangzhen S. Wang, Nicos Martys, Dat Duthinh, Virgil Provenzano, Shin G. Chou, David F. Plusquellic, Jack T. Surek, Sung Kim, Robert D. McMichael, Mark D. Stiles, Ahmed M. Hassan
Detecting the early corrosion of steel in reinforced concrete is a goal that has been much pursued. Since 2010, NIST has been working on a large project to develop an electromagnetic (EM) probe that detects the actual corrosion products via spectroscopic

Measurement and Simulation of Millimeter Wave Scattering Cross-sections from Steel-Reinforced Concrete

January 11, 2014
Author(s)
Ahmed M. Hassan, Edward Garboczi, Robert McMichael, Jack T. Surek, Mark D. Stiles, David F. Plusquellic, Virgil Provenzano, Paul E. Stutzman, Shuangzhen S. Wang, Sung Kim, Michael D. Janezic, Jason Coder, Nicos Martys, David R. Novotny
Some iron oxide corrosion products exhibit antiferromagnetic magnetic resonances (AFMR) at around 100 GHz at normal temperatures. AFMR can be detected in laboratory conditions, which serves as the basis for a new non-destructive spectroscopic method for

Development of Standard Reference Materials for Cement-Based Materials

January 6, 2014
Author(s)
Chiara F. Ferraris, Nicos Martys, William L. George
Rotational rheometers are routinely used for homogeneous materials, but their usage for characterization of a granular fluid like concrete is a relatively new phenomenon. As measurements with rheometers can involve flow in a complex geometry, it is

Development of Standard Reference Materials for Cement-Based Materials

May 13, 2013
Author(s)
Chiara F. Ferraris, Nicos Martys, William L. George
Rheometers are used to determine the rheological properties of materials ranging from mayonnaise to concrete. While rotational rheometers are routinely used for homogeneous materials such as mayonnaise, their usage for characterization of a granular fluid

Modeling of the Influence of Transverse Cracking on Chloride Penetration into Concrete

April 23, 2013
Author(s)
Dale P. Bentz, Edward J. Garboczi, Yang Lu, Nicos Martys, Aaron R. Sakulich, William J. Weiss
Concrete service life models have proliferated in recent years due to increased interest in designing infrastructure elements with at least a 75-year service life, along with greater emphasis on life cycle costing in general. While current models consider

Measurement Science Needs for the Expanded Use of Green Concrete: Workshop Summary Report

February 6, 2013
Author(s)
Kenneth A. Snyder, Dale P. Bentz, Jeffrey W. Bullard, Chiara F. Ferraris, Nicos Martys, Paul E. Stutzman
In July 2012, NIST conducted the Green Concrete Workshop to bring together stakeholders from the concrete construction industry and identify critical needs for the expanded use of industrial by- product materials, such as fly ash and slag, in concrete

Concrete rheometers

May 1, 2012
Author(s)
Chiara F. Ferraris, Nicos Martys
The scope of this chapter is to introduce the current technology for measuring the rheological properties of concrete. The need to evaluate or assess the flow properties of concrete has resulted in the invention or design and standardization of hundreds of

Stress propagation in a colloidal suspension under shear

March 1, 2012
Author(s)
William L. George, Pascal Hebraud, Didier Lootens, Mouhamad Khalil, Nicos Martys
The stress propagation in a concentrated attractive colloidal suspension, under shear, is studied using mumerical simulations. A novel way of describing the intercolloidal stress field is proposed and its spatial correlations are studied. An inertia-like