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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Development of a nuclear mixing process for high performance cementation - 15064

In the CEA Project 'Cementation of LLW/ILW Slurry' EIRICH and CEA developed together a high performance mixing process matching the French security regulations for nuclear facilities. Since 2010 mixing tests had been carried out by CEA to develop and verify a new cementation process. In 2012 EIRICH started the development of the mixing equipment for the cementation plant together with CEA. This new cementation plant will be put into operation in 2016 at the CEA site in Marcoule. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Influence of Particle Size on the Basic and Time-Dependent Rheological Behaviors of Cemented Paste Backfill

The rheological properties of cemented paste backfill (CPB) significantly influence the material’s transportability, and these properties are strongly affected by the material’s particle size. This paper mainly focuses on the influence of particles size on the basic and time-dependent rheological behaviors of CPB. The rheology tests and microstructure analysis were conducted using multiple CPB samples with different solid contents, cement contents, and particle sizes. Results show that the CPB samples with finer particle sizes have a lower apparent maximum packing density compared to the CPB samples with larger particle sizes. Fresh CPB mixture samples exhibit shear thinning characteristics which are more pronounced in samples with larger particle sizes and higher volume fraction to apparent maximum packing density (ϕ/ϕ{sub m}) ratios. When the ϕ/ϕ{sub m} ratio is lower than 0.875, the samples with finer particle sizes display a higher yield stress but less time-dependent rheological behavior than coarser samples. In all CPB samples that contained cement, the shear stress decreases first and then increases over the shearing time when samples are sheared at a constant shear rate. In the CPB samples without cement, samples with finer particle sizes show lower apparent viscosities, and it is observed in the sample with the finest particles that the shear stress only decreases over the shearing time. Moreover, it is found that the number of hydration products and the rate of particle sedimentation are both higher in samples with larger particle sizes, which result in these samples having higher apparent viscosities.

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

Simultaneous x-ray and neutron 4D tomographic study of drying-driven hydro-mechanical behavior of cement-based materials at moderate temperatures

The drying of cement-based materials is intimately related to their durability, which has significant economic, social and environmental repercussions. The evolution of the saturation of the pore network and the associated drying shrinkage are in fact leading causes of cracking and of the ensuing penetration of aggressive chemicals. This process is highly heterogeneous, due to the thermo-hydric spatial gradients developing in the material from the exposed surfaces to its core and because of local effects, driven by the intrinsically heterogeneous micro-structure (e.g., by the distribution of pores and aggregates). It follows that macroscopic, sample-scale measurements cannot fully disclose the complexity of the underlying processes. In the last few decades, significant advances in full-field techniques have allowed an unprecedented insight into these local processes. For cement-based materials, x-ray and neutron tomography lend themselves as ideal, and highly complementary, tools for the study of their thermo-hydro-mechanical behavior. Notably, the high sensitivity to density variations of x-ray imaging gives access to the developments of fractures, in 4D (3D + time). On the other hand, neutron tomography allows the study of the evolution of the moisture field in 4D, thanks to its high hydrogen sensitivity. The combination of these two techniques provides a unique insight in thermo-hydro-mechanical couplings, e.g., the effect of cracks on the water content field. This contribution presents novel 5D datasets (3D tomographies along time, plus truly simultaneous x-ray and Neutron rapid acquisitions) in-operando of a cement paste and of a concrete sample heated at moderate temperatures (up to 140{sup ∘}C). The analysis of this 5D data-set (once aligned in time and across modalities) allows for example a quantification of the 4D moisture profiles which were found to predict an overall water loss at hydric equilibrium coherent with the corresponding analytical analysis. In the cement paste sample, the x-ray dataset captures the evolution of an extensive cracking network, opening and propagation toward the core of the sample. A novel analysis procedure is here proposed which allows the extraction of these fractures and the analysis of their interplay with local drying as captured through neutron imaging. This for example reveals the depth of penetration of drying in the vicinity of the fractures along time, which is essential for the assessment and calibration of hydro-mechanical coupled models.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Main components of PM10 in an area influenced by a cement plant in Catalonia, Spain: Seasonal and daily variations

Highlights: • Constituents and main components of airborne PM{sub 10} near a cement plant were studied. • A clear seasonality was found, with higher levels in winter. • A daily pattern was not observed, when comparing weekdays and weekends. • Road traffic had a significant contribution to PM{sub 10} levels. Particulate matter (PM) composition has a key role in a wide range of health outcomes, such as asthma, chronic obstructive pulmonary disease, lung cancer, cardiovascular disease, and death, among others. Montcada i Reixac, a municipality located in the Barcelona metropolitan area (Catalonia, Spain), for its location and orography, is an interesting case- study to investigate air pollution. The area is also characterized by the presence of different industrial emission sources, including a cement factory and a large waste management plant, as well as an intense traffic. In this study, PM{sub 10} levels, trace elements, ions, and carbonaceous particles were determined for a long time period (2013–2016) in this highly polluted area. PM{sub 10} samples were collected during six consecutive days in two campaigns (cold and warm) per year. A number of elements (As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, K, La, Li, Hg, Mg, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Sr, Tb, Th, Ti, Tl, U, V, W, Y, Yb, and Zr), ions (Cl{sup -}, SO{sub 4}{sup 2-}, NO{sub 3}{sup -}, and NH{sub 4}{sup +}), and carbonaceous content (total carbon, organic plus elemental carbon, and CO{sub 3}{sup 2-}), were analysed. These data were used to identify the PM{sub 10} main components: mineral matter, sea spray, secondary inorganic aerosols, organic matter plus elemental carbon, trace elements or indeterminate fraction. Although a clear seasonality (cold vs. warm periods) was found, there were no differences between working days and weekends. Obviously, the cement plant influences the surrounding environment. However, no differences in trace elements related with the cement plant activity (Al, Ca, Ni and V) between weekdays and weekends were noted. However, some traffic-related elements (i.e., Co, Cr, Mn, and Sb) showed significantly higher concentrations in weekdays.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Shear strength and permeability of the cement-casing interface

Here, the shear strength and hydraulic permeability of the interface between well cement and casing was investigated using a triaxial direct shear apparatus. For the first time, these experiments provide measurements under controlled stress conditions with fluid flow measurements along the interface. The low cohesion (1.1 ± 1.1 MPa) and the high friction angle (43.4 ± 2.0°) indicates that the shear strength of the interface is provided by friction. This implies that the state of stress of the cement is critical to well integrity. The hydraulic aperture of the undamaged cement-steel samples was 6.8 ± 1.0 microns. Shear damage to the interface caused a decrease (-20 %) in hydraulic aperture for samples aged up to 1 month, and an increase (+300 %) for samples cured for two years. We performed numerical simulations to estimate the leakage potential from a carbon storage operation. This model predicts negligible leakage amounts (47 tonnes) in a shear-damaged well for the modeled injection of ~1.26 million tonnes of CO 2 . Thus, our measurements indicate that the cement-casing interface is not a significant leakage pathway in its intact or damaged state, and that shear-driven failure scenarios for this interface are not a significant risk to CO 2 storage security.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Cement paste surface roughness analysis using coherence scanning interferometry and confocal microscopy

Scanning electron microscopy and scanning probe microscopy have been used for several decades to better understand the microstructure of cementitious materials. Very limited work has been performed to date to study the roughness of cementitious materials by optical microscopy such as coherence scanning interferometry (CSI) and chromatic confocal sensing (CCS). The objective of this paper is to better understand how CSI can be used as a tool to analyze surface roughness and topography of cement pastes. Observations from a series of images acquired using this technique on both polished and unpolished samples are described. The results from CSI are compared with those from a STIL confocal microscopy technique (SCM). Comparison between both optical techniques demonstrates the ability of CSI to measure both polished and unpolished cement pastes. - Highlights: • Coherence scanning interferometry (CSI) was used to analyze cement paste surfaces. • The results from the CSI were compared with those from a confocal microscopy. • 3D roughness parameters were obtained using the window resizing method. • Polished and unpolished cement pastes were studied.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structure-property relation and Weibull analysis of calcium aluminate cement pastes

Highlights: • Weibull distribution analysis was conducted for calcium aluminate cement pastes with 52 wt% and 71 wt% of alumina contents. • Compressive strength ranged from 10 to 45 MPa. • The hydrated phases found showed diverse polymorphisms of Gibbsite (Nordstrandite, Bayerite, Hidrogarnet and Gehlenite). - Abstract: In this investigation calcium aluminate cement (CAC) pastes with 52 wt% and 71 wt% of alumina contents were fabricated and characterized with different techniques. Samples were made with 0.4 and 0.5 water to cement (W/C) ratios. Both the raw cement powders and their corresponding samples after hydration were characterized in their microstructure by scanning electron microscopy, X-ray diffraction (with Rietveld refinement), X-ray fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), density, and compression tests. With the compressive strength results, Weibull distribution analysis was conducted for 20 samples per composition. The higher compression strength obtained was about 45 MPa, which corresponds to samples with the higher W/C contents. The hydrated phases found showed diverse polymorphisms of Gibbsite (Nordstrandite, Bayerite, Hidrogarnet and Gehlenite).

36 MATERIALS SCIENCE↗
DOE OSTI2017

Isotopically zoned carbonate cements in Early Paleozoic sandstones of the Illinois Basin: δ 18 O and δ 13 C records of burial and fluid flow

SEM/SIMSimaging andanalysis of δ 18 O and δ 13 C in sandstonesfrom a transect through the Illinois Basin(USA) show systematic μm-scale isotopic zonation of up to 10‰ in both carbonate and quartzcements of the middle-Ordovician St. Peter and Cambrian Mt. Simonformations. Quartz δ 18 O values are broadly consistent with the model of Hyodo et al. (2014), wherein burial and heating in the Illinois Basinis recorded insystematically zonedquartz overgrowths. Observations of zoned dolomite/ankerite cements indicate that they preserve a more extended record of temperature and fluid compositionsthan quartz, including earlydiagenesis before orduring shallow burial,and late carbonates formed after quartzovergrowths. Many carbonate cements show innermostdolomite withδ 18 O values (21-25‰ VSMOW) that are too low to have formed by depositionat low temperatures from ancient seawater(δ 18 O>-3‰)and most likelyreflect mixing with meteoric water. A sharp increase in Fe content is commonly observed in zoned carbonate cements to be associated with a drop in δ 18 O and an abrupt shift in δ 13 C to higher or lower values. These changes are interpreted to record the passage of hot metal-richbrinesthrough sandstone aquifers,that wasassociated with Mississippi-Valley Type (MVT) Pb-Zn deposits (ca. 270 Ma) of the Upper Mississippi Valley. Local variability and individual trends in δ 13 Care likely controlled by the sources of carbon and the degree to which carbonis sourced fromadjacent carbonate units or thermal maturation of organic matter. Quartz overgrowths in sandstones provide an excellent record of conditions during burial, heating, and pressure-solution, whereas carbonate cements in sandstonespreserve a more-extendedrecord includinginitial pre-burial conditions and punctuated fluid flowevents.

58 GEOSCIENCES↗
DOE OSTI2017

Incorporating Nanoscale Effects into a Continuum-Scale Reactive Transport Model for CO 2 -Deteriorated Cement

We present that wellbore cement deterioration is critical for wellbore integrity and the safety of CO 2 storage in geologic formations. Our previous experimental work highlighted the importance of the portlandite (CH)-depleted zone and the surface dissolution zone in the CO 2 -attacked cement. In this study, we simulated numerically the evolution of the CH-depleted zone and the dissolution of the cement surfaces utilizing a reduced-dimension (1D) reactive transport model. The approach shows that three nanoscale effects are important and had to be incorporated in a continuum-scale model to capture experimental observations: First, it was necessary to account for the fact that secondary CaCO 3 precipitation does not fill the pore space completely, with the result that acidic brine continues to diffuse through the carbonated zone to form a CH-depleted zone. Second, secondary precipitation in brine begins via nucleation kinetics, and this could not be described with previous models using growth kinetics alone. Third, our results suggest that the CaCO 3 precipitates in the confined pore space are more soluble than those formed in brine. Finally, this study provides a new platform for a reduced dimension model for CO 2 attack on cement that captures the important nanoscale mechanisms influencing macroscale phenomena in subsurface environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Determination of Diffusion Profiles in Altered Wellbore Cement Using X-ray Computed Tomography Methods

The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining “effective linear activity coefficients” (ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO 2 -rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment.

15 GEOTHERMAL ENERGY↗
DOE OSTI2020

The sponge effect and carbon emission mitigation potentials of the global cement cycle

Cement plays a dual role in the global carbon cycle like a sponge: its massive production contributes significantly to present-day global anthropogenic CO 2 emissions, yet its hydrated products gradually reabsorb substantial amounts of atmospheric CO 2 (carbonation) in the future. The role of this sponge effect along the cement cycle (including production, use, and demolition) in carbon emissions mitigation, however, remains hitherto unexplored. Here, we quantify the effects of demand- and supply-side mitigation measures considering this material-energy-emissions-uptake nexus, finding that climate goals would be imperiled if the growth of cement stocks continues. Future reabsorption of CO 2 will be significant (~30% of cumulative CO 2 emissions from 2015 to 2100), but climate goal compliant net CO 2 emissions reduction along the global cement cycle will require both radical technology advancements (e.g., carbon capture and storage) and widespread deployment of material efficiency measures, which go beyond those envisaged in current technology roadmaps.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

The role of gas flow distributions on CO 2 mineralization within monolithic cemented composites: coupled CFD-factorial design approach

The carbonation kinetics of monolithic cementing composites are strongly affected by gas transport which is, in turn, influenced by microstructural resistances and the presence of liquid water within pore networks. The non-uniform gas flow distribution within the CO 2 mineralization reactor can impart mass transfer resistance in the monolith microstructure, which affects the uptake of CO 2 (“carbonation”) of the cementing composites. This paper demonstrates how the gas spatial distribution (velocity and flow rate; quantified by CFD analysis) and processing conditions (temperature, relative humidity, and flow rate; quantified by factorial design) affect drying and carbonation, and in turn, the engineering properties of a representative ‘monolithic’ carbonate-cemented concrete component (i.e., herein concrete masonry unit: CMUs, also known as concrete block). It is shown that the gas flow distribution affects drying front penetration and results in moisture and carbonation gradients within the monolith. Particularly, variations in drying kinetics caused by non-uniformity of the contacting gas velocity impose gradients in moisture saturation, which results in increasing microstructural resistance to CO 2 transport. The resultant non-uniform carbonate-mineral formation (i.e., carbonate cementation), if not controlled, can produce gradients in mechanical properties and may alter failure patterns upon loading. Finally, these insights inform the optimal design of gas flow distribution systems and processing conditions within CO 2 mineralization reactors for the manufacturing of low-CO 2 concrete components using CO 2 -dilute industrial flue gas streams.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

The shard test and nanoporomechanics reverse classical paradigm of cement hydration being contractive

Le Chatelier in 1887 and Powers in 1947 demonstrated that the volume of nanoscale C-S-H (calcium silicate hydrate) particles formed during hydration is smaller than the combined volume of the reactants—the anhydrous Portland cement and water. Hydration has thus been considered as contractive. An experiment shows that the opposite is true above the nanoscale. The porous skeleton of cement paste expands as the growing C-S-H particles push each other apart, similar to crystal growth pressure. This is significant for high-performance concretes (HPC) with low water-cement ratios (w/c ≤ 0.4), where chemical self-desiccation lowers pore relative humidity by 40%, compared to just 1% in traditional concretes (w/c ≈ 0.5). Standard American Society for Testing and Materials (ASTM) C1608 tests, using 10 mm thick water-immersed specimens, show large shrinkage because the half-time of water ingress is many decades, unable to offset shrinkage-causing self-desiccation. The present experiment, using a laser microscopy-topography technique, proves the opposite—expansion, evidenced by measuring the length changes of water-immersed HPC shards 0.5 mm thick in which the diffusion halftime, only about one hour, allows continuous resaturation of pores, canceling self-desiccation. The faster diffusion (halftime of one hour) enables continuous pore resaturation, preventing shrinkage. When sealed with paraffin oil, the shards self-desiccate and shrink. These findings align with studies since 2015, showing that models excluding hydration expansion cannot fit test data across various specimen sizes and sealing conditions. The results suggest that standardized ASTM tests for the so-called chemical shrinkage in modern concretes with very low water-cement ratios are misleading and need revision.

Science & Technology - Other Topics↗
DOE OSTI2019

Monitoring and Repair of Cement-Geomaterial Interfaces in Borehole and Repository Scenarios

The failure of subsurface seals (i.e., wellbores, shaft and drift seals in a deep geologic nuclear waste repository) has important implications for US Energy Security. The performance of these cementitious seals is controlled by a combination of chemical and mechanical forces, which are coupled processes that occur over multiple length scales. The goal of this work is to improve fundamental understanding of cement-geomaterial interfaces and develop tools and methodologies to characterize and predict performance of subsurface seals. This project utilized a combined experimental and modeling approach to better understand failure at cement-geomaterial interfaces. Cutting-edge experimental methods and characterization methods were used to understand evolution of the material properties during chemo-mechanical alteration of cement-geomaterial interfaces. Software tools were developed to model chemo-mechanical coupling and predict the complex interplay between reactive transport and solid mechanics. Novel, fit-for-purpose materials were developed and tested using fundamental understanding of failure processes at cement-geomaterial interfaces.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Self-Healing Polymer-Modified Cements for Ambient-Temperature Applications

We present two novel polymer-modified cement formulations which can self-heal cement microfractures at ambient temperature. The polymers used are either commercially available boric acid gel (BAG) or a synthesized polymer MBA-BDA. This report summarizes the progress of developing polymer-modified cement formulations. The polymers used are either commercially available or synthesized in house. Results show two formulations (commercial boric acid gel BAG and as-synthesized polymer MBA-BDA), both with potential to bring about room-temperature self-healing to conventional cement.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Belite Cement, and Concretes; Novel Low-Energy Approaches to Making Concrete Extremely Durable (Final Report)

This award allowed the University of Kentucky to demonstrate a number of key objectives. The focus of the project was on creating a belite cement, and concrete, that demonstrated a greatly reduced CO 2 demand for manufacture and enabling the development of extremely durable concrete. The accomplishments of the developed technology includes the following, as compared to Ordinary Portland cement: 2x greater compressive strength; 10x greater corrosion resistance; 35 – 50% less estimated clinker and mill energy use; 15 – 20% less estimated cement manufacturing cost; 35% more estimated clinker capacity; 25 – 30% less estimated cement CO 2 footprint.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Cement Plant TEA/LCA

This presentation was prepared for the 2024 Carbon Management Project Review Meeting. The slides summerize recent NETL systems analysis work examining the application of carbon capture systems at cement plants. This includes a 2023 NETL report titled "Analysis of Carbon Capture Retrofits for Cement Plants" and a 2024 NETL authored journal article titled “The Impact of Cement Plant Air Ingress on Membrane-Based CO2 Capture Retrofit Cost”. The slide deck also highlights ongoing NETL techno-economic analysis and lifecycle assessment work on capture from cement plants & other industrial capture projects.

Homsy, Sally↗