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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Mechanical Characterization of Low Modulus Polymer-Modified Calcium-Silicate-Hydrate (C-S-H) Binder

Calcium-silicate-hydrate (C-S-H) represents a key microstructural phase that governs the mechanical properties of concrete at a large scale. Defects in the C-S-H phase are also responsible for the poor ductility and low tensile strength of concrete. Manipulating the microstructure of C-S-H can lead to new cementitious materials with improved structural performance. This paper presents an experimental investigation aiming to characterize a new synthetic polymer-modified synthetic calcium-silicate-hydrate (C-S-H)/styrene-butadiene rubber (SBR) binder. The new C-S-H/SBR binder is produced by calcining calcium carbonate and mixing this with fumed silica (SiO 2 ), deionized water and SBR. Mechanical, physical, chemical and microstructural characterization was conducted to measure the properties of new hardened C-S-H binder. Results from the experimental investigation demonstrate the ability to engineer a new C-S-H binder with low elastic modulus and improved toughness and bond strength by controlling the SBR content and method of C-S-H synthesis. The new binder suggests the possible development of a new family of low-modulus silica-polymer binders that might fit many engineering applications such as cementing oil and gas wells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Cerium oxide impact on fresh and hardened properties of cementitious materials

Cements used in global nuclear waste treatment, storage, and disposal require thorough testing of fresh and cured properties to demonstrate regulatory compliance. Using actual radioactive wastes is often cost-prohibitive during early scoping tests necessitating the use of non-radiological surrogates. Cerium (Ce) is often used as a surrogate for actinides uranium (U) and plutonium (Pu) in spent nuclear fuel, yet few studies have explored how Ce impacts the properties used to qualify a cement for use. Here, this work compares the fresh and cured properties of three classes of cements – ordinary portland cements, ultra-high performance cement composites, and magnesium phosphate cements – each with and without ceria (CeO 2 ). Due to CeO 2 sorption of water (54 vol%) that effectively decreases the water available to hydrate and form binding cement phases, variations in key cement properties were detected that suggest surrogate CeO 2 –cementitious matrices may not be representative of matrix behaviors when using U and Pu sources.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Modeling the corrosion of steel casing and the damage of well cement in a borehole system

This work presents the effect of chloride-induced corrosion in an underground borehole system, specifically considering the steel casing and further damage to the surrounding cement. In the past four decades, oil well cement has been successfully used for underground construction. However, high concentrations of chloride ions gradually degrade the functionality and durability of well cement. Gasses and liquids can leak from deterioration caused by chloride ions, and thus motivate this study. The chemo-mechanical coupling diffusion model and a classical fracture mechanics model are applied. The model is validated with OPC concrete corrosion data from literature, and then applied to well cement using experimentally obtained material property data. The time when crack initiation, peak pressure, and complete fracture is reached in the model of the cement sheath provides a quantification of the expected service life of the borehole system.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Physical Properties of Hilti HIT-RE 500 V3 After Irradiation: Slant Shear, Tensile, Flexural, and Compressive

There are various applications in which epoxy adhesives may be used within hot-cell environments. These epoxies currently see limited use within hot cells since it is known that organics see degradation after small doses even as low as 50 kilogray (kGy). These losses in physical property strengths limit the use of these epoxies to non-structural applications. In modern construction, however, the use of epoxies to bond structural components such as rebar or threaded anchors is becoming increasingly prevalent. To employ these types of materials the Idaho National Laboratory (INL) has begun investigating the specific degradation properties of epoxies for use in structural applications in environments where radiation is present. Hilti HIT-RE 500 V3 is used extensively in new construction and renovation projects across the world. The INL has conducted various tests on this epoxy for low dose environments. These tests include tensile, flexural, compression, and slant shear tests following the American Society for Testing Material International (ASTM) standards D638, D790, D695, and C882/882M respectively. Two sample sets for each test were created where the baseline specimens were not irradiated, and another set was irradiated to an accumulated dose of approximately 50-60 kGy. All the samples were destructively tested and analyzed focusing on the change in physical properties, examples of these tests are shown in Figures 1-4. Tensile testing results indicate a 0.9% loss in maximum load capacity, a 0.5% loss in tensile stress at maximum load, a 1.4% loss in tensile strain at break, and a 15% decrease in modulus of elasticity. Flexural testing results display an increase in all the following: 12% in strain at maximum load, 10% in maximum load capacity, 5% in stress at maximum load, and 3% in young’s modulus. The compressive physical properties after irradiation display a 1% increase in maximum load, a 3% decrease in stress at yield, and a 5% decrease in modulus of elasticity. The maximum compressive stress saw no measurable change after irradiation. The slant shear specimens after irradiation displayed a 2% increase in maximum load capacity and maximum compressive stress. Though a structural analysis would have to be completed as is normal for building design the increases and decreases in the measured physical properties indicate that this material may be used for structural applications in low dose hot-cell environments without adhesive failure.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A review of the effect of nanoclays on the fresh and hardened properties of cement-based materials

This paper provides an overview of the use of nanoclays in cement-based materials. The effect of nanoclays on shear rheological properties will be discussed, with a focus on structural build-up behavior. This macroscale flow behavior will then be tied to the effect of nanoclays on the fresh microstructure as characterized via in-situ particle size measurements and rheological techniques. This will provide insight on the mechanisms underlying the effect of nanoclays on fresh state properties through an improved understanding of their effect on flocculation and coagulation behavior. In addition, secondary effects nanoclays have on the hardening and hardened properties will also be discussed. Examples of casting applications in which nanoclays have been effectively utilized as rheological modifiers, i.e. reducing self-consolidating concrete formwork pressure, extrusion, semi-flowable concrete for slipform paving, and 3D concrete printing, will be presented. Finally, some thoughts on potential directions for future work will be shared.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Development of Calcined Clay/Calcium Sulfate Blends for Robust Performance of LC3 Concrete

This report documents the development of robust blends of calcined clays (CCs) with calcium sulfate (gypsum) for application in limestone calcined clay cement (LC3) systems. The U.S. cement industry faces supply chain constraints and high energy intensity, motivating the need for alternative supplementary cementitious materials. Calcined clays are abundant and highly reactive when properly processed, but their variable physical and chemical characteristics can negatively impact hydration balance, rheology, and admixture demand in LC3 concretes. To address this, five calcined clays, two Portland cements, ground limestone, gypsum, and a polycarboxylate dispersant were procured. Isothermal calorimetry and mini-cone flow tests were used to determine sulfate and dispersant demand. Results show that the addition of approximately 6.7% gypsum, relative to the calcined clay weight, consistently balanced sulfate consumption across the LC3 systems studied. Dispersant demand, however, varied significantly with clay source, demonstrating the need for tailored admixture strategies. These findings confirm that supplying CC–gypsum blends directly to concrete producers is a viable approach to overcoming current manufacturing constraints, enabling reliable fresh and hardened performance of LC3 concretes, and supporting broader adoption of calcined clays in the U.S. market.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Alkali-silica reaction expansion model for confined concrete with stress-dependency and casting direction anisotropy

Alkali-silica reaction (ASR) is a deleterious chemical reaction between alkali hydroxyl ions and types of silica found in some aggregates of concrete. Owners and regulators of nuclear power plants aim to ensure the safety of the concrete structures with optimal maintenance strategies. A new model was developed for predicting the expansion of concrete structures affected by alkali-silica reaction. The model includes a novel combination of existing models as an alkali-silica reaction advancement model, a casting direction anisotropic expansion model, a stress-dependent anisotropic expansion model, and a material property evolution model dependent on the degree of ASR expansion. The model parameters were calibrated based on existing literature data and data generated by previous efforts of this study. The calibrated model was then validated with the experiments carried out in previous efforts of this study. The model was shown to accurately predict the ASR-expansion of large-scale reinforced concrete specimens with confinement.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Corrosion of rebar in concrete. Part III: Artificial Neural Network analysis of chloride threshold data

Active corrosion of carbon steel in reinforced concrete occurs when the chloride ion concentration exceeds the chloride threshold (CT). CT is affected by many physical and chemical parameters including primary variables (pH, corrosion potential, breakdown potential, and temperature) and secondary variables (cemenet composition, concreete porosity, and water/cement ratio). A Kohonen-self organized map (KSOM) and regression artificial neural network (ANN) coupled methodology was developed to find the missing values of independent variables in the sparse database and for quantitatively evaluating the effects of these variables on CT values that are expressed in %TotalCl/cem (or %FreeCl/cem), and [Cl - ]/[OH - ].

36 MATERIALS SCIENCE↗
DOE OSTI2021

Corrosion of rebar in concrete. Part II: Literature survey and statistical analysis of existing data on chloride threshold

The literature is reviewed with respect to defining, measuring, and interpreting the chloride threshold (CT). CT was defined with a strong fundamental basis in the Point Defect Model. which also dictates the nature of the statistical analysis of surveyed CT values. A database of CT for various primary and secondary independent variables has been established. Statistical analyses reveal that CT is lognormally distributed, in accordance with the PDM, with most probable values being 0.85, 0.69, and 1.19 for %total Cl/cem, %free Cl/cem, and [Cl - ]/[OH - ], respectively. The breakdown and corrosion potentials follow normal distributions with means of 0.056 and -0.322 V SCE , respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Influence of pH on chloride binding isotherms for cement paste and its components

In this paper, chloride (Cl{sup −}) binding isotherms are developed for cement hydration compounds, specifically, calcium-silicate-hydrates (CSH) and AFm phases including mono-sulfate aluminate, hydroxy-AFm, monocarbonate-AFm, and hemicarbonate-AFm, in simulated concrete pore solutions to account for the effect of pH and the presence of other ions. pH and the presence of other ions have a strong influence on the Cl{sup −} binding capacity of cement compounds, which have not been taken into consideration in previous research. A novel experimental technique is developed to characterize the binding capacity from very low (1 mM) to very high concentrations (5 M). To overcome the existing challenges of measuring both low and high Cl{sup −} concentrations without significant dilution and in the presence of SO{sub 4}{sup 2−} and OH{sup −} ions, a potentiometric method was used. The amorphous CSH in the hydrated cement paste; thus, the heterogeneity of the hydrated components of the cement paste was also quantified and accounted for in this study.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Higher-order topology induced by structural buckling

Abstract Higher-order topological insulator (HOTI) states, such as two-dimension (2D) HOTI featured with topologically protected corner modes at the intersection of two gapped crystalline boundaries, have attracted much recent interest. However, the physical mechanism underlying the formation of HOTI states is not fully understood, which has hindered our fundamental understanding and discovery of HOTI materials. Here we propose a mechanistic approach to induce higher-order topological phases via structural buckling of 2D topological crystalline insulators (TCIs). While in-plane mirror symmetry is broken by structural buckling, which destroys the TCI state, the combination of mirror and rotation symmetry is preserved in the buckled system, which gives rise to the HOTI state. We demonstrate that this approach is generally applicable to various 2D lattices with different symmetries and buckling patterns, opening a horizon of possible materials to realize 2D HOTIs. The HOTIs so generated are also shown to be robust against buckling height fluctuation and in-plane displacement. A concrete example is given for the buckled $\beta $-Sb monolayer from first-principles calculations. Our finding not only enriches our fundamental understanding of higher-order topology, but also opens a new route to discovering HOTI materials.

42 ENGINEERING↗
DOE OSTI2020

Irradiation-induced damage in concrete-forming aggregates: revisiting literature data through micromechanics

The radiation-induced volumetric expansion (RIVE) of aggregate-forming minerals causes damage in concrete exposed to high levels of fast neutrons fluence ( \(>\,\sim \,10^{19}\, \hbox {n}\,\hbox {cm}^{-2}\) at kinetics energy above 0.1 MeV). Historical post-irradiation RIVE and Young’s modulus data obtained in test reactors were revisited using a polycrystalline homogenization model (self-consistent scheme) accounting for the aggregates’ minerals content and the formation of voids/cracks during irradiation. It was found that the formation of extra voids/cracks can contribute to the aggregate expansion more substantially than the cumulated expansions of aggregate-forming minerals. Furthermore, the rate of void creation appears to be inversely correlated to the silica content, although aggregates of higher silicate contents exhibit higher RIVEs. The loss of Young’s modulus decreases exponentially with the aggregates’ expansion. At a comparable RIVE level, the relative loss of modulus is more significant in aggregates of higher silica content.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Cathodic Protection Modeling for Hanford Underground Double-Shell Tank Farms

Hanford stores millions of gallons of radioactive and chemically hazardous waste from the production of weapon materials in tank farms consisting of underground carbon-steel storage tanks surrounded by reinforced concrete. Six of these Hanford tank farms use double-shell storage tanks (DSTs). The DST farms were constructed from 1968 to 1986 with a planned 40–50 year design life, so some are already operating beyond their initial life expectancy. Ultrasonic testing (UT) has indicated significant thinning on the bottom of the secondary (outer) liner of these tanks, believed to arise from groundwater intrusion driving concrete side corrosion. There is no direct access to the steel/concrete interface between the tank and the concrete pad, making it difficult to apply a chemical-based mitigation strategy or to conduct repairs, but cathodic protection (CP) is a possible method to inhibit further concrete-side corrosion. Hanford already uses CP to protect below grade steel piping within the tank farms and connected to the tanks, but this system was not designed to protect the tank bottoms. CP design must account for the structures surrounding the DSTs, including the steel reinforcing bars (rebar) within the concrete pad and vault, various process lines, and the existing CP system. In this study, finite element analysis (FEA) modeling was carried out to simulate CP protection of 1) a single tank and CP anode to develop options for modeling the rebar and to compare to a simpler circuit model and 2) the entire Hanford AN tank farm as a representative example consisting of seven tanks, associated piping, and both existing and new CP anodes. Both circuit and FEA models predict that significant protective current could be delivered to the bottoms of the tanks with the addition of tank-protection anodes below the depth of the tanks. Simulations with only the existing pipe-protection anodes active confirmed that only a very small current to the tank bottoms is predicted under present conditions. Multiple simplified representations of the dome and wall rebar were tested to reduce the computational complexity of the tank-farm simulations, resulting in modeling the rebar as edge elements with a prescribed effective circumference that matches the real rebar surface area. The geometry of the rebar is also simplified into horizontal hoops around the tank walls and radial rebar over the dome with increased effective circumference to retain the target surface area. This simplification was found to greatly reduce the complexity and solution time of the models without large changes in current distributions, especially to the tank bottom. A range of values were tested for model parameters such as soil and concrete resistivities and polarization resistance to investigate their impact on the current and electric potential distributions. Depending on the parameters used, FEA simulations predict some risk of overprotection, particularly on the piping system; since overprotection can also lead to surface damage associated with hydrogen gas generation at the interface (e.g. hydrogen embrittlement or damage to coatings), this needs to be considered when refining the design of the new CP system. Comparison between the FEA models and the circuit model representation demonstrated that the circuit model could not match the predicted FEA current distribution, even when using the exact same surface areas. This discrepancy appeared to be at least partly attributable to the impact of the relative positions of the tank components and anodes to each other and to the ground surface. The FEA model accounts for the relative positions since it solves the governing equations in three dimensions, but the circuit model cannot account for the positioning. In particular, the circuit model underpredicts the current to the tank bottom and overpredicts the current to the dome compared to FEA for the baseline geometry. The FEA models omitted the electrically isolated rebar in the bottom concrete slab. However, a circuit based stray current model estimated that only 2.1% of the total current through the slab would stray into the rebar, corresponding to ~0.21 A for a target current density of 2 mA/ft2 to the tank bottom. The estimated corrosion driven by this amount of stray current is predicted to yield a lifetime of >400 years for the minimum rebar diameter, assuming an acceptable cross-section area loss of 10%.

d'Entremont, Anna [Savannah River National Laborat↗
DOE OSTI2021

Multi-scale investigation on mechanical behavior and microstructural alteration of C-S-H in carbonated Alite paste

Carbonation treatment is a promising option to enhance recycled concrete aggregate (RCA) quality and eventually improve concrete performance. This study investigated the multi-scale mechanical properties of calcium silicate hydrates (C-S-H) in a mature alite paste subjected to accelerated carbonation treatment by testing macro compressive strength, microhardness and nanoindentation. The results show that, carbonation treatment resulted in a heterogeneous distribution of carbonation products in the alite sample. Reinforcement of C-S-H by the randomly precipitated calcite and vaterite crystals prevailed over the nano-structural and compositional alteration of C-S-H induced by carbonation, leading to an increase of nano-indentation modulus at the edge of the sample. Also, the microhardness at the edge zone was markedly higher than that at the core of the carbonated sample. The carbonated peripheral zone with improved nano-scale modulus and microhardness was likely serving as a “hard shell”, contributing to the improved macro compressive strength. The new insights into the multi-scale mechanical properties of carbonated C-S-H contribute to further understanding of the enhanced properties of RCA after carbonation treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2021

In situ TEM observation of calcium silicate hydrate nanostructure at high temperatures

Fire poses a substantial threat to concrete structures because calcium silicate hydrate (C-S-H) is not thermally stable at high temperatures. Herein, in situ TEM at temperatures from 20 to 800 °C was conducted to study the thermal-induced structural changes in C-S-H. We captured C-S-H shrinks at an average rate of 0.02 μm{sup 2}/{sup o}C upon heating with three stages observed, including induction, constant, and rapid periods. Our observation revealed that an 800 nm pore could be healed during pore structure evolution owing to the reconstruction and deformation among C-S-H blocks. The Ca/Si ratio was dropped at higher temperatures because of the leakage of calcium ions from the C-S-H structure to form CaO precipitates. The temperature-driven phase transformation and degradation were also detected using electron diffraction that C-S-H was transformed into metastable calcium silicate minerals above 800 °C. This work provides insights into the nanoscale transformation of C-S-H at high temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Penetration of Fission Products Ions into Complex Solids and the Effect of Ionic Wash Methods

During washing of radiologically impacted building surfaces, penetration of radionuclide ions into complex solids associated with these surfaces may occur. This study investigates the penetration of Cs-137, Sr-85, and Eu-152 solutions into numerous common building materials and radionuclide behavior when these materials were exposed to a static bath or low-pressure flow of tap water, 0.1 M potassium chloride (KCl), and 0.5 M KCl. The decontamination efficacy and the depth profile for residual contamination were measured to determine the conditions under which applying a wash solution has benefit compared to physically removing the surface material. On asphalt, 70-80% of the radionuclides were found to be within 0.02 mm of the surface. Concrete is more porous than asphalt, and 80% of the radionuclides were within 0.2 mm of the surface for Cs-137 and Eu-152 and 50-80% for Sr-85. Water effectively removed all contaminants from hard nonporous surfaces. Finally, this paper illustrates that a wash penalty factor concept-defined as ratio of the depth at which 50% of the radioactivity is found in the washed sample divided by the depth at which 50% of radioactivity is found in the control-can serve as a way to quantify whether the wash method increases the depth at which contamination penetrates into the material and thus the material becomes more difficult to decontaminate.

building materials↗
DOE OSTI2022

Microbial Curing of Cement for Energy Applications

Rutgers University, Lawrence Livermore National Laboratory, and the University of Arizona executed this program over 36 months with a 4-Task Program: (M1)-Microbial Engineering (M2)-Microstructure Modelling, (M3) Cement and Concrete Formulation, (M4)-Techno-economic analysis (TEA) and lifecycle assessment (LCA). This program developed a new carbonate cement concrete manufacturing process called microbial curing (MBC). MBC utilizes in-situ microbial production of CO 2 that dissolves into pore-bound water to carbonate a cementitious material creating a bonding matrix of CaCO 3 and SiO 2 that hardens and densifies the material. This is the first work of this type where calcium silicate was used in microbial studies. All other work reported in the literature always used a soluble form of calcium. This final report describes the work done in the final quarter, the best procedures and results, and the final techno-economic and lifecycle analyses. This quarter, we cast and cured twenty-five (4”x8”) cylinder samples. The compressive strength, split tensile, Young’s modulus, chloride permeability, and creep measurements were performed. These measurements demonstrated that MBC of calcium silicate concrete exhibits scaling problems due to the escape of ammonia gas, a product of the microbial reaction to generate CO 2 . As curing proceeds, the ability for the gas to escape from within the cylinder is restricted by the outer cylindrical portions densifying, making the outer portion highly impermeable to gas flow. In contrast, the small samples cured are uniformly cured, forming materials whose mechanical properties are 7x better than the large samples. This problem needs to be solved before this technology can be commercialized. The techno-economic and lifecycle analyses indicate that the technology developed in this program exhibits a significant opportunity to reduce the cost of cement and CO 2 emissions associated with concrete, provided the curing issue associated with larger samples can be addressed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

MOSAIC: An Effective FFT-based Numerical Method to Assess Aging Properties of Concrete

As the nuclear fleet in the United States ages and subsequent license renewal applications grow, the prediction of concrete durability at extended operation becomes more important. To address this issue, a Fast-Fourier Transform (FFT) method is utilized to simulate aging-related degradation of concrete within the Microstructure Oriented Scientific Analysis of Irradiated Concrete (MOSAIC) software. MOSAIC utilizes compositional phase maps to simulate damage from radiation-induced volumetric expansion (RIVE), applied force, creep, and thermal expansion. This compositional detail allows each mineral in the microstructure to be assigned specific material properties, allowing the simulation to be as accurate and representative as possible. The principal goal of MOSAIC is to simulate the effects of nonlinear aging mechanisms occurring in nuclear concrete on the macroscopic mechanical properties, using only the aggregate microstructure compositional information as a starting point. Here, several realistic example simulations are shown to demonstrate the utility and uniqueness of the MOSAIC software.

36 MATERIALS SCIENCE↗