Jeffrey W. Bullard

Jeffrey W. Bullard
Texas A&M University | TAMU · Zachry Department of Civil and Environmental Engineering

Ph.D., Materials Science and Engineering

About

144
Publications
57,317
Reads
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5,591
Citations
Additional affiliations
April 2002 - July 2019
National Institute of Standards and Technology
Position
  • Researcher
October 1995 - December 1999
University of Illinois, Urbana-Champaign
August 1988 - June 1993
University of California, Berkeley
Education
August 1990 - June 1993
University of California
Field of study
  • Materials Science and Engineering
August 1988 - June 1990
University of California
Field of study
  • Materials Science and Engineering
August 1984 - May 1988
University of Missouri-Rolla
Field of study
  • Ceramic Engineering

Publications

Publications (144)
Article
Full-text available
In this paper, a nonlinear formulation approach using an artificial neural network (ANN) is proposed and applied for the first time to predict the behavior of rubberized cement composite for which there is neither a design formulation nor a closed-form prediction model. For this purpose, the experimental data on the rubberized composite was collect...
Article
Establishing human habitation on the Moon or Mars requires the development of a palette of interconnected reaction chemistries to transform their native soils into structural metals, fuels, propellants, and load-bearing forms. This article outlines key research needs relevant to the fundamental chemistry of in situ resource utilization.
Article
This study follows a first paper written on some three-dimensional geometrical quantities of a selection of sand particles from the United Arab Emirates (UAE), determined using a combination of X-ray microcomputed tomography (μCT) and spherical harmonic analysis, and their correlation to the properties of mortars made with these sands, with no adde...
Conference Paper
Full-text available
Building on research underway for military and expeditionary construction, this research aims to establish methods for the design and testing of the materials mixtures derived from the lunar surface with minimal or no additives that need to be transported from the Earth. This paper will review opportunities and challenges of demonstrated and experi...
Article
The great reactivity of tricalcium aluminate (C3A) with water and subsequent rapid precipitation of insoluble products are serious challenges to learning how salts affect its interfacial chemistry and physics during dissolution. Those challenges are addressed here with rapid in situ surface nanotopography monitoring and characterization of hydratio...
Article
The measured dissolution rate of a granular medium depends on its surface area and how the surface area changes during the course of the measurement. Moreover, the assumption that the specific surface area either remains constant or initially increases during dissolution is not always valid. This paper demonstrates that when the particle size distr...
Article
This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors Zachary Grasley and Jeffrey W. Bullard. The authors did not consent to being added as co-authors on this paper, they were not infor...
Article
Full-text available
Fly ash, an aluminosilicate composite consisting of disordered (major) and crystalline (minor) compounds, is a low‐carbon alternative that can partially replace ordinary portland cement (OPC) in the binder fraction of concrete. Therefore, understanding the reactivity of fly ash in the hyperalkaline conditions prevalent in concrete is critical to pr...
Article
This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). The originally stated co-authors “Poura Arabali, Jeffrey W. Bullard, and Zachary Grasley” informed the journal that they were included in the initially published version of the article without...
Article
Historically, sparingly soluble mineral dissolution in aqueous solutions is measured at macroscopic scales, mostly by indirect methods that track the solution composition over times ranging from minutes to years. Relatively fewer measurements have been made of dissolution rates of highly soluble minerals and their variability at microscopic length...
Article
Full-text available
Solution flow profiles near a mineral surface can exert 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 by in situ digital holographic microscopy of calcite in flowing pure water and by lattice Bo...
Article
Alkali-silica reaction (ASR) is a significant cause of the degradation of concrete structures. ASR results from the dissolution of reactive silicate aggregates and the subsequent formation of damaging, expansive ASR gels. Despite the prevalence of ASR, so far only lithium-based chemical admixtures have been shown to be successful in mitigating its...
Article
The reaction kinetics of gypsum dissolution are important for establishing an optimum gypsum content in portland cement. In this paper, the temperature dependence of dissolution rates was measured by tracking changes in solution composition and surface area with time. The rate coefficient increases with temperature and the specific surface area dec...
Article
Full-text available
Setting and strength development of ordinary portland cement (PC) binders involves multiple interacting chemical reactions, resulting in the formation of a solid microstructure. A long‐standing yet elusive goal has been to establish a basis for prediction of the properties and performance of concrete using knowledge of the chemical and physical att...
Article
This paper presents the results of the physical and chemical changes of Class F fly ashes exposed to either deionized water or to a 0.4 mol/L KOH solution for 15 min or 45 min. The changes in physical and chemical makeup of thousands of individual particles before and after being exposed to solutions are analysed using an autonomous scanning electr...
Article
Full-text available
The surface normal dissolution flux of beta dicalcium silicate is quantified using in situ digital holographic microscopy. The dissolution flux in highly undersaturated flowing solutions depends on the water activity to an empirically determined power of 1.7. A heterogeneous distribution of reactive surface sites (e.g., crystalline defects) at the...
Article
Full-text available
The dissolution of silicate minerals and glasses in aqueous solutions is important in many natural and engineered contexts including mineral weathering, nuclear waste stabilization, cementation, and infrastructure degradation. The influences of electrolytes on dissolution rates have been extensively studied but previous studies have used widely var...
Article
This paper studies a selection of fine sands, their particle shape and its effect on the plastic properties of mortars via the influence on the workability and packing of cementitious mixtures. Five sands from different sources were sampled, wet sieved, and classified into six size classes: 20 μm–75 μm, 75 μm–150 μm, 150 μm–300 μm, 300 μm–600 μm, 6...
Article
The dissolution rates, normalized by surface area, of two different gypsum powders in aqueous solutions were measured by tracking changes in solution composition as a function of time in a continuously stirred batch reactor. The powders were classified into different size ranges to observe the influence of particle coarseness on dissolution kinetic...
Article
Full-text available
The creep and relaxation of cement paste caused by dissolving solid hydration products is evaluated in this work. According to the second law of thermodynamics, dissolution or precipitation of solid constituents may be altered by the change of stress/strain fields inside cement paste via alteration of the stress power or strain energy. Thus, it is...
Article
Full-text available
The viscoelastic/viscoplastic behavior of cement paste may occur due to intrinsic calcium silicate hydrate (C-S-H) viscoelasticity/viscoplasticity and cement grain dissolution during the hydration process. A numerical model that combines a microstructure model and a finite element calculation model has been developed to predict the time-dependent b...
Article
Full-text available
Advances in nano-computed X-ray tomography (nCT), nano X-ray .fluorescence spec-trometry (nXRF), and high-performance computing have enabled the first direct com-parison between observations of three-dimensional nanoscale microstructure evo-lution during cement hydration and computer simulations of the same microstruc-ture using HydratiCA. nCT obse...
Article
Full-text available
In situ digital holographic microscopy is used to characterize the dissolution flux of polycrystalline cubic tricalcium aluminate (C3A-c). The surface dissolves at rates that vary considerably with time and spatial location. This implies a statistical distribution of fluxes, but an approximately steady-state median rate was obtained by using flowin...
Article
Fly ash which encompasses a mixture of glassy and crystalline aluminosilicates is an abundant supplementary cementitious material (SCM), valuable for replacing ordinary portland cement (OPC) in the binder fraction in concrete. Because higher OPC replacement levels are desired, it is critically important to better understand and quantify fly ash rea...
Article
Full-text available
Cementitious binders have become increasingly complex in their variety, mineralogical and chemical compositions, and structure over the past several decades, and there is no sign that the trend will stop or reverse in the future. Strategies for handling the complexity fall into one of two categories: (1) increasingly laborious trial-and-error explo...
Article
Full-text available
Digital holographic microscopy in reflection mode is used to track in situ, real-time nanoscale topography evolution of cleaved (104) calcite surfaces exposed to flowing or static deionized water. The method captures full-field holograms of the surface at frame rates of up to 12.5 s⁻¹. Numerical reconstruction provides 3D surface topography with ve...
Article
Full-text available
A recent microstructural model of near-surface external sulfate attack on cement paste is modified to incorporate diffusive ionic transport between the surface and interior of a macroscopic specimen that has been hydrated for 100 d prior to exposure to sulfates. The model estimates the driving force for local expansive growth of the Al2O3 - Fe2O3-t...
Article
Full-text available
Fly ash is a critical material for partial replacement of ordinary portland cement (OPC) in the binder fraction of a concrete mixture. However, significant compositional variability currently limits fly ash use. For example, the performance of OPC-fly ash blends cannot be estimated a priori using current characterization standards (e.g., ASTM C618)...
Article
Full-text available
Since its widespread use in concrete began over 100 years ago, the chemical composition and physical properties of portland cement have changed only incrementally in response to various and competing pressures of constructability and cost. Instead, the construction demands have been met largely through the development and introduction of chemical a...
Article
Full-text available
When cementitious materials are dried, internal stresses are generated that lead to desiccation shrinkage, a portion of which is irreversible. Previous research has indicated that, while a cementitious composite is subjected to a state of stress, dissolution of cement grains and precipitation of hydrates can yield irreversible creep strains, and it...
Article
The partial replacement of ordinary portland cement (OPC) by fine mineral fillers accelerates the rate of hydration reactions. This acceleration, known as the filler effect, has been attributed to enhanced heterogeneous nucleation of C-S-H on the extra surface provided by fillers. This study isolates the cause of the filler effect by examining how...
Article
Full-text available
Recent topography measurements of gypsum dissolution have not reported the absolute dissolution rates, but instead focus on the rates of formation and growth of etch pits. In this study, the in situ absolute retreat rates of gypsum (010) cleavage surfaces at etch pits, at cleavage steps, and at apparently defect-free portions of the surface are mea...
Article
The reasons for the start and end of the induction period of cement hydration remain a topic of controversy. One long-standing hypothesis is that a thin metastable hydrate forming on the surface of cement grains significantly reduces the particle dissolution rate; the eventual disappearance of this layer re-establishes higher dissolution rates at t...
Article
Disagreements about the mechanisms of cement hydration remain despite the fact that portland cement has been studied extensively for over 100 years. One reason for this is that direct observation of the change in microstructure and chemistry are challenging for many experimental techniques. This paper presents results from synchrotron nano X-ray to...
Article
Full-text available
To compute any physical quantity for a random particle, one needs to know the mathematical shape of the particle. For regular particles like spheres and ellipsoids, the mathematics are straightforward. For random particles, with realistic shapes, mathematically characterizing the shape had not been generally done. But since about the year 2002, a m...
Article
Full-text available
A model for an ideal solid solution, developed by Nourtier-Mazauric et al. [Oil & Gas Sci. Tech. Rev. IFP, 60 [2] (2005) 401], is applied to calcium–silicate–hydrate (C–S–H). Fitting the model to solubility data reported in the literature for C–S–H yields reasonable values for the compositions of the end-members of the solid solution and for their...
Article
Full-text available
X-ray powder diffraction (XRD) has been used for several decades to identify and measure the mass fractions of various crystalline phases in portland cement. More recently, a combination of scanning electron microscopy with X-ray microanalysis (SEM/XMA) and image processing has been shown to enable the quantitative characterization of microstructur...
Article
Tricalcium silicate does not undergo hydration at relative humidities (RH's) below 80%. But, the rate at which its hydration rate decreases as a function of the RH has not yet been elucidated. By invoking correspondence between RH and water activity (aH, unitless), both of which are related to the chemical potential of water, the reaction evolution...
Article
Full-text available
Abstract A microstructure model has been applied to simulate near-surface degradation of portland cement paste in contact with a sodium sulfate solution. This new model uses thermodynamic equilibrium calculations to guide both compositional and microstructure changes. It predicts localized deformation and the onset of damage by coupling the confine...
Article
Full-text available
The stabilities of Al2O3-Fe2O3-mono (AFm) and -tri (AFt) phases in the Ca-Al-S-O-H system at 25°C are examined using Gibbs energy minimization as implemented by GEM-Selektor software coupled with the Nagra/PSI thermodynamic database. Equilibrium phase diagrams are constructed and compared to those reported in previous studies. The sensitivity of th...
Technical Report
Full-text available
�e combination of scanning electron microscopy (SEM) with X-ray microanalysis and image processing provides a powerful ability to image and quantify microstructural features of con- struction materials. �is document provides guidance for collecting backsca�ered electron images and X-ray element maps of polished sections of Portland cement clinker....
Article
A computational model has been developed that combines finite element methods with microstructure development simulations to quantitatively predict the viscoelastic/viscoplastic relaxation of cement paste due to intrinsic calcium silicate hydrate viscoelasticity/viscoplasticity and cement grain dissolution associated with the hydration process. The...
Article
The ability of the VCCTL microstructural model to predict the hydration kinetics and elastic moduli of cement materials was tested by coupling a series of computer simulations and laboratory experiments, using different cements. The novel aspects of this study included the fact that the simulated hydration kinetics were benchmarked using real-time...
Article
Full-text available
A new model of 3D cement paste microstructure development is described and used to simulate the influence of leaching on hydrated cement pastes. In contrast to recent leaching models that have used empirical rules for phase dissolution, this model uses continual thermodynamic speciation and phase stability calculations to guide the microstructural...
Article
Full-text available
The electrical resistivity of cement-based materials can be used in quality control or service life prediction as an indicator of the fluid transport properties of these materials. Although electrical tests have the advantage of being easy and rapid to perform, several key factors can influence the results: (a) specimen geometry, (b) specimen tempe...
Article
Full-text available
Truncated spherical harmonic expansions are used to approximate the shape of 3D star-shaped particles including a wide range of axially symmetric ellipsoids, cuboids, and over 40 000 real particles drawn from seven different material sources. This mathematical procedure enables any geometric property to be calculated for these star-shaped particles...
Article
Portland cement is a fundamental structural and binding material for industry and society. Its structural and physical properties at different scales show a complexity that can presently be barely managed through experimental and computational methods. State of the art problems and trends in cement studies will be briefly assessed from the point of...
Article
Full-text available
Electrical properties are frequently measured in the concrete construction industry as a part of mixture qualification and quality control testing. Whereas there are several factors that influence the electrical response of concrete, one of the most important factors is its degree of saturation. Although current standard tests rely on the concrete’...
Article
Full-text available
Finely ground mineral powders are known to accelerate cement hydration rates. This “filler effect” has been attributed to the effects of dilution (w/c increase) when the cement content is reduced or to the provision of additional surface area by fine powders. The latter contribution (i.e., surface area increase) is speculated to provide additional...
Article
Full-text available
Hydration of portland cement is the cornerstone of the process responsible for microstructure development in concrete and ultimately controls the kinetics of all materials properties that make concrete such a useful product for society (properties such as setting, strength, permeability, and durability). A comprehensive understanding of, and model...
Article
Full-text available
The current state of knowledge of cement hydration mechanisms is reviewed, including the origin of the period of slow reaction in alite and cement, the nature of the acceleration period, the role of calcium sulfate in modifying the reaction rate of tricalcium aluminate, the interactions of silicates and aluminates, and the kinetics of the decelerat...
Article
Full-text available
Efforts to model and simulate the highly complex cementhydration process over the past 40 years are reviewed, covering different modeling approaches such as single particle models, mathematical nucleation and growth models, and vector and lattice-based approaches to simulating microstructuredevelopment. Particular attention is given to promising de...
Article
It has been observed that the hydration of cement paste stops when the relative humidity drops below about 80%. A thermodynamic analysis shows that the capillary pressure exerted at that RH shifts the solubility of tricalcium silicate, so that it is in equilibrium with water. This is a reflection of the chemical shrinkage in this system: according...