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Search Publications by: Kenneth A. Snyder (Fed)

Displaying 51 - 74 of 74

Estimating the electrical conductivity of cement paste pore solutions from OH-, K+ and Na+ concentrations

June 4, 2003

Author(s)

Kenneth A. Snyder, X Feng, T O. Mason

A proposed method for estimating the electrical conductivity of cement paste pore solution at 25 degrees Celsius is based on the concentrations of HO-, K+ and Na+. The approach uses an equation that is a function of the solution ionic strength, and

Estimating the Electrical Conductivity of Alkaline Cementitious Pore Solutions

June 1, 2003

Author(s)

Kenneth A. Snyder, X Feng

A method is proposed for estimating the electrical conductivity of cementitious pore solutions. The method is based on an equation that is a function of the solution ionic strength, and requires a single empirical coefficient for each ionic species. As a

Calculation of Ionic Diffusion Coefficients on the Basis of Migration Test Results

April 1, 2003

Author(s)

E Samson, J Marchand, Kenneth A. Snyder

Migration tests are now commonly used to estimate the diffusion coefficients of cement-based materials. Over the past decade, variousapproaches have been proposed to analyze migration test results. In many cases, the interpretation of test data is based on

Concrete Degradation Modeling in the Evaluation of Entombment as a Decommission Option.

December 1, 2002

Author(s)

Kenneth A. Snyder, J Philip

Reply to the Discussion by S. Chatterji of the Paper Effects of Speciation on the Apparent Diffusion Coefficient in Nonreactive Porous Systems

December 1, 2002

Author(s)

Kenneth A. Snyder, J Marchand

We received two copies of the discussion: one from the journal and a corrected version directly from Dr. Chatterji. Based on the differences between the two versions, we realized that our choice of wording in the paper could be improved upon. While we were

Modeling Ion Transport Mechanisms in Unsaturated Porous Media

August 27, 2002

Author(s)

J Marchand, E Samson, Kenneth A. Snyder, J J. Beaudoin

The transport of ions in colloids, granular and consolidated porous media is important to a wide variety of environmental and engineering problems. Typical examples are the transport of contaminants in marine sediments, the containment of hazardous waste

Concrete Degradation Modeling in the Evaluation of Entombment as a Decommissioning Option

August 1, 2002

Author(s)

Kenneth A. Snyder, Jacob Philip

For entombment to be a viable option for the decommissioning of nuclear structures, the effectiveness of available engineered barriers must be assured. Barrier performance must be estimated with the aid of computer models that can accurately predict the

Effect of Speciation on the Apparent Diffusion Coefficient in Nonreactive Porous Systems

December 1, 2001

Author(s)

Kenneth A. Snyder, J Marchand

A combined theoretical and experimental study is made of the effect that concentration and ionic speciation have on the apparent diffusion coefficient is performed using a nonreactive porous material in a diffusion apparatus. Varying the ionic species

The Relationship Between the Formation Factor and the Diffusion Coefficient of Porous Materials Saturated With Concentrated Electrolytes: Theoretical and Experimental Considerations

December 1, 2001

Author(s)

Kenneth A. Snyder

It has been proposed previously that the formation factor, in conjunction with the self-diffusion coefficient, can be used to determine the apparent diffusion coefficient. Strictly speaking,this application is incorrect. The formation factor is equal to

The Stereological and Statistical Properties of Entrained Voids in Concrete: A Mathematical Basis for Air Void System Characterization

December 1, 2001

Author(s)

Kenneth A. Snyder, K C. Hover, K Natesaiyer

To understand the freeze-thaw properties of hardened concrete, the air void system must be characterized. Studies of the stereological and statistical properties of entrained air voids in concrete have often involved a number of steps: sample preparation

Validation and Modification of the 4SIGHT Computer Program (NIST IR 6747)

May 1, 2001

Author(s)

Kenneth A. Snyder

The original version of the 4sight computer program was written to facilitate the performance assessment of buried concrete structures based deterministic calculations of service life, using data supplied by the user. In an effort to assure reliability in

Dimensional Analysis of Ionic Transport Problems in Hydrated Cement Systems - Part 1: Theoretical Considerations

December 1, 2000

Author(s)

R Barbarulo, J Marchand, Kenneth A. Snyder, S Prene

The validity of the local equilibrium assumption in hydrated cement systems, that a particular chemical reaction is instantaneous with respect to transport, is examined using a dimensional analysis of electrochemical transport in cementitious materials

Using Impedance Spectroscopy to Assess the Viability of the Rapid Chloride Test for Determining Concrete Conductivity

July 1, 2000

Author(s)

Kenneth A. Snyder, Chiara C. Ferraris, Nicos Martys, Edward Garboczi

The suitability of using the initial current from the rapid chloride test (ASTM C 1202) to determine specimen conductivity is tested using impedance spectroscopy with a frequency spectrum of 10 Hz to 1 MHz. The specimen conductivity has an analytical

Effect of Drying Shrinkage Cracks and Flexural Cracks on Concrete Bulk Permeability

May 1, 2000

Author(s)

Kenneth A. Snyder

A review of the computer program 4sight has revealed that an accurate prediction of water transport through the concrete depends upon an accurate prediction of the crack formation within the concrete. A model for predicting both the width and the spacing

Protected Paste Volume in Concrete: Extension to Internal Curing Using Saturated Lightweight Fine Aggregate

November 1, 1999

Author(s)

Dale P. Bentz, Kenneth A. Snyder

One difficulty in the field use of high performance concrete is the extensive self-desiccation and autogeneous shrinkage that may occur due to its lower w/c ratio and the addition of silica fume to the mixture proportions. Several researchers have proposed

Advances in Concrete Mixture Optimisation. Keynote Paper

September 8, 1999

Author(s)

Kenneth A. Snyder, G J. Frohnsdorff, M Simons

The complexity of high performance concrete (HPC) mixture designs continues to increase, along with the number of criteria that a particuhu mixture must satisfy. Robust statistical methods exist that can be used to not only determine the mixture for a

Estimating the 95th Percentile of the Paste-Void Spacing Distribution in Hardened Cement Paste Containing Air Entrainment

June 1, 1999

Author(s)

Kenneth A. Snyder

The spacing equations of Powers, Philleo, and Pleau and Pigeon are used to estimate the uniform thickness of paste surrounding entrained air voids that is required to encompass 95 % of the air-paste system. Spacing equation accuracy is determined by

A Hard Core/Soft Shell Microstructural Model for Studying Percolation and Transport in Three-Dimensional Composite Media

January 1, 1999

Author(s)

Dale P. Bentz, Edward J. Garboczi, Kenneth A. Snyder

This user's manual provides documentation and computer program listings for the three-dimensional hard core/soft shell microstructure model developed at the National Institute of Standards and Technology. The model has been developed to represent the three

Concrete Mixture Optimization Using Statistical Mixture Design Methods.

October 22, 1997

Author(s)

E S. Lagergren, Kenneth A. Snyder, M J. Simon

The optimization of mixture proportions for high-performance concretes, which contain many constituents and are often subject to several performance constraints, can be a difficult and time-consuming task. Statistical experiment design and analysis methods

A Prototype Computer-Integrated Knowledge System: Predicting Service Life of Chloride-Exposed Steel-Reinforced Concrete

December 2, 1996

Author(s)

Dale P. Bentz, Kenneth A. Snyder, J R. Clifton

In the last decade or so, numerous advances have occurred in the field of information technology. Through the use of computers, the amount of available information and the speed at which it can be retrieved have both increased dramatically. The

A Prototype Computer-Integrated Knowledge System: Predicting Service Life of Chloride-Exposed Steel-Reinforced Concrete

December 2, 1996

Author(s)

Dale P. Bentz, J R. Clifton, Kenneth A. Snyder

Computer Program to Facilitate Performance Assessment of Underground Low-Level Waste Concrete Vaults.

January 1, 1996

Author(s)

Kenneth A. Snyder, J R. Clifton, J M. Pommersheim

A computer program (4SIGHT) to facilitate performance assessment of underground concrete vaults for low level waste (LLW) disposal facilities is being developed at the National Institute of Standards and Technology (NIST). Specifically, the program

4SIGHT Manual: A Computer Program for Modelling Degradation of Underground Low Level Waste Concrete Vaults

June 1, 1995

Author(s)

Kenneth A. Snyder, J R. Clifton

A computer program has been written to facilitate performance assessment of concrete vaults used in Low Level Waste (LLW) disposal faciliites. The computer program is a numerical computer model of degradation in concrete. A one-dimensional finite

Freeze-Thaw Susceptibility of High Performance Concrete

July 1, 1994

Author(s)

Kenneth A. Snyder, J R. Clifton, Lawrence I. Knab

Freeze-thaw susceptibility of high performance concrete (abstract to come).