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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Graphene nanoplatelets reinforced cement as a solution to leaky wellbores reinforcing weak points in hydrated Portland cement with graphene nanoparticles improves mechanical and chemical durability of wellbore cements

In this work, to improve the performance of wellbore cement under subsurface environments, graphene nanoplatelets (GNPs) were added in various percentages to Class-H cement slurry. Microstructural characterization of cement slurries cured at 90 °C and 95% RH indicates that GNP modifies the microstructure of hydrated cement by reinforcing pore spaces. As a result, the mechanical properties, such as Young's modulus and axial peak stress, obtained from high temperature triaxial compression tests are significantly improved based on different percentages of added GNPs. Furthermore, the hydrated 1 × 2 inch GNP- Portland cement cores tested under simulated deep wellbore conditions of high-temperature and high pressure (HTHP), appear to have a ductile-like behavior, when compared to a typical brittle nature of Portland cement pastes. From our observations and published data on graphene resistance to fracture, GNP addition to cement is evidently enhancing the flexibility of cement. These improvements would reduce the risks associated with wellbore cement deterioration and a consequent leakage in fossil fuel production, geothermal energy production, CO 2 storage as well as long-term sealing materials in plugging and abandonment of all wellbores at the end of their service life.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Influence of multi-species solute transport on modeling of hydrated Portland cement leaching in strong nitrate solutions

The differences between the predictions of Fickian diffusion and Nernst-Planck electro-diffusion based reactive transport models are investigated in the context of an important practical problem – leaching of Portland cement in strong nitrate porewater solutions under saturated conditions. Numerical results are presented for three distinct porewater solutions: deionized water, ammonium nitrate solution, and diluted porewater from a cementitious low-activity nuclear waste form. Solute concentrations predicted by the two transport models show significant differences: as much as a factor of two for ammonium nitrate leaching and as much as a factor of four for waste form leaching; whereas, negligible differences are observed for deionized water leaching. The major conclusion is that Fickian diffusion may be accurate enough for deionized water leaching, but electro-diffusion should be considered in the reactive solute transport modeling of ammonium nitrate decalcification and in the degradation modeling of cementitious materials exposed to nuclear waste form solutions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Insights into the physical and chemical properties of a cement-polymer composite developed for geothermal wellbore applications

To isolate injection and production zones from overlying formations and aquifers during geothermal operations, cement is placed in the annulus between well casing and formations. Wellbore cement can fracture due to chemical and physical stress. A polymer-cement (composite) with self-healing properties, stable at high temperatures, was recently developed by our group. Here we present data on the elemental distribution, mineral composition, internal microstructure, and tensile elasticity of this composite and how it compares to cement without polymer (control cement). Entrapped air porosity was similar between control cement (0.44% by volume) and composite (0.22% by volume). Total voids increased with polymer content in the cement (10% and 25% composite), and polymer was found to fill most of these voids. Polymer appears to act as a (cement hydration) retarder increasing the amount of unhydrated silicate minerals in the matrix. Tensile elasticity was improved for composites as compared to control cement, suggesting that the composite materials perform better under mechanical stress. Density-functional calculations reproduce the drop in Young’s modulus by about 60% observed experimentally when polymer is added to the cement. In addition, calculations indicate that the bonding interactions between the cement and polymer remain stable over the range of strain studied.

Rod, Kenton A. (ORCID:0000000318189094)↗
DOE OSTI2017

Hydrated Ordinary Portland Cement as a Carbonic Cement: The Mechanisms, Dynamics, and Implications of Self-Sealing and CO 2 Resistance in Wellbore Cements

This report analyzes the dynamics and mechanisms of the interactions of carbonated brine with hydrated Portland cement. The analysis is based on a recent set of comprehensive reactive-transport simulations, and it relies heavily on the synthesis of the body of work on wellbore integrity that we have conducted for the Carbon Storage Program over the past decade.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Structural and chemical changes from CO2 exposure to self-healing polymer cement composites for geothermal wellbores

Wellbore cement is subjected to a number of mechanical, thermal and chemical stress regimes over its lifetime. Therefore, next generation wellbore cement formulations need to be evaluated in conditions relevant to these environments. In this work, we investigate the mechanism of the alteration of a novel self-healing polymer-cement composite recently reported by our group after exposure to a CO2-rich environment by using synchrotron based X-ray Fluorescence (XRF) and X-ray absorption near edge structure (XANES) and scanning electron microscopy coupled with energy dispersive spectroscopy. Results showed that chemical alteration of the polymer-cement follows the rim carbonation mechanism, similar to conventional cement although carbonation takes place to a lesser extent in polymer-cements despite the higher porosity. Along with detailed mechanistic insights on carbonation in polymer-cement composite, the performance of these in CO2-rich environment is further studied using standard compressive strength analysis.

Elbakhshwan, Mohamed↗
DOE OSTI2021

Cement stress and microstructure evolution during curing in semi-rigid high-pressure environments

The process of cement slurry curing into a solid has a direct effect on the initial state of stress in a composite concrete and steel structure. Failure models for critical infrastructure and wellbores could benefit from measurements of this initial stress because it greatly influences structural performance. Here, we present measurements of the initial stress state (total stress, effective stress, and pore pressure) of multiple cement formulations cured under a high-pressure of 40 MPa within a semi-rigid steel pipe. Our results show that cements cured in this restrained environment exhibit dense microstructures with low permeability (nano-Darcy), develop an anisotropic stress state greater than zero and less than the curing pressure, and undergo a staged curing process where hydration and mechanical behaviors evolve from a slurry into a pre-stressed porous medium. Both drained and undrained scenarios were investigated, revealing a feedback from the semi-rigid boundary towards improved cement performance.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Enabling phase quantification of anhydrous cements via Raman imaging

The phase composition of Portland cements is typically determined using conventional techniques like X-ray Diffraction (XRD) Rietveld analysis, optical microscopy point counting, and electron microscopy. However, these techniques have several limitations that may affect their accuracy in certain sample-specific scenarios. Here, we report a highly accurate phase quantification of 11 different types of commercial, anhydrous cements using a new and complementary technique: Raman imaging. Specifically, for the 4 principal phases, composition from our extensive data (250,000 Raman spectra per sample, error < 0.71%) and those obtained from XRD Rietveld and supplier data have high coefficients of determination (R{sup 2} > 0.98, mean deviation <2%). Additionally, we also quantify 8 secondary phases present in cement clinkers (gypsum, anhydrite, bassanite, syngenite, dolomite, calcite, quartz, and portlandite) with a high degree of confidence, thereby demonstrating that Raman imaging is a highly versatile tool for anhydrous phase quantification in a broad variety of cements.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Experimental and modeling study of calcium carbonate precipitation and its effects on the degradation of oil well cement during carbonated brine exposure

Decalcification of cement in solutions of carbonated brine is important to a host of engineering applications, especially in subsurface service environments where cementitious materials are frequently utilized as engineered barriers for wellbore seals, as well as shaft and drift seals and waste forms for nuclear waste disposal. Analysis of leaching simulations and experiments shows that, depending on solution compositions (dissolved CO{sub 2} concentration, pH, Ca ion concentration), calcite precipitation occurring during leaching of cement in contact with carbonated brine can have a significant impact on cement reactivity, in some instances leading to complete arrest of reactivity via calcium carbonate ''pore-clogging''. We present modeling and experimental results that examine the range of solution conditions that can lead to pore-clogging. Analysis of the results shows that distinct regimes of leaching behavior, based on pH and pCO2, can be used to form a framework to better understand the occurrence of pore-clogging.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Geochemical narrowing of cement fracture aperture during multiphase flow of supercritical CO2 and brine

For carbon capture and storage operations, wells are used as a necessary conduit for injecting CO2 at depth, but they can also act as leakage conduits if the cement seals are compromised. The specific objective of this research was to investigate the nature of self-healing of a fracture within cement under multiphase flow of CO2 and brine, and to compare this to a newly developed model. This was accomplished through a laboratory investigation, flowing reacting supercritical CO2 and brine through a cement fracture with multiphase flow. The influent end of the fracture was degraded as evidenced by the formation of cracks across the surface. At the effluent end of the fracture, the initial aperture of 137 µm was reduced to 50 µm. This reduction by 87 µm was similar to results from a recently developed model tested in this study, which predicted an aperture reduction of 80 µm. Our results demonstrated that the model accurately predicted the reactions which occurred in this multiphase flow system.

wellbore, cement, fracture, multiphase-flow, super↗
DOE OSTI2021

On the use of limestone calcined clay cement (LC3) in high-strength strain-hardening cement-based composites (HS-SHCC)

Highlights: • Use of LC{sup 3} slightly reduces flowability and shortens the setting time of fresh matrices. • Highly polymerized C-A-S-H gel and abundant ettringite benefit flexural strength of LC{sup 3}-matrices. • Use of LC{sup 3} enhances the bond strength between fiber and high-strength matrix. • LC{sup 3}-based HS-SHCC yields similar flexural performance as the composite with Portland cement. High-strength strain-hardening cement-based composites (HS-SHCC) demonstrate excellent mechanical and durability properties. However, high cement content typical to HS-SHCC results not only in high carbon footprint, but also in excessive hydration heat and severe autogenous shrinkage. In this investigation, Limestone Calcined Clay Cement (LC{sup 3}) was used to produce sustainable HS-SHCC. The LC{sup 3} substitution resulted in higher energy consumption during mixing and in shorter setting times of the fresh, plain matrices. Although the LC{sup 3} substitution slightly reduced the compressive strength, the formation of highly polymerized C-A-S-H gel and abundant ettringite benefited the flexural strength of the plain matrices. Additionally, single-fiber pullout experiments showed that the use of LC{sup 3} led to increased fiber-matrix bond strength and pullout energy. Finally, the replacement of Portland cement by LC{sup 3} resulted in HS-SHCC with similar mechanical performance to the reference composite, indicating a high potential for using LC{sup 3} in high-performance cement-based composites.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Atomic Origins of the Self-Healing Function in Cement–Polymer Composites

Motivated by recent advances in self-healing cement and epoxy polymer composites, we present a combined ab initio molecular dynamics and sum frequency generation (SFG) spectroscopy study of a calcium-silicate-hydrate/polymer interface. On stable, low-defect surfaces, the polymer only weakly adheres through coordination and hydrogen bonding interactions and can be easily mobilized towards defected surfaces. Conversely, on fractured surfaces, the polymer strongly anchors through ionic Ca-O bonds resulting from the deprotonation of polymer hydroxyl groups. In addition, polymer S-S groups are turned away from the cement/polymer interface, allowing for the self-healing function within the polymer. The overall elasticity and healing properties of these composites stem from a flexible hydrogen bonding network that can readily adapt to surface morphology. The theoretical vibrational signals associated with the proposed cement-polymer interfacial chemistry were confirmed experimentally by SFG spectroscopy.

ab initio molecular 8 dynamics↗
DOE OSTI2018

Toward understanding barnacle cementing by characterization of one cement protein-100kDa in Amphibalanus amphitrite

Barnacles, as major fouling organisms, have attracted more attentions. It is no doubt that the study on cement proteins is required to illustrate the mechanism of barnacle cementing. A cement protein defined as Aa-cp100k was characterized from Amphibalanus amphitrite in this study. The amino acid sequence of Aa-cp100k was shown a high similarity to other three barnacles including Megabalanus rosa (Mr-cp100k), Tetraclita japonica formosana (Tj-cp100k) and Pollicipes pollicipes (Pp-cp100k). Moreover, the localization of Aa-cp100k in the vacuoles of cyprid β secretory cells and the adult cement gland cells by immunofluorescence microscopy, indicating that Aa-cp100k existed in both cyprid and adult barnacle. Aa-cp100k from basal plate could be dissolved in urea buffer without high concentration of dithiothreitol (DTT), different from that in Megabalanus rosa, implying diverse possible roles of cp100k in cementing.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Eco-efficient cements: Potential economically viable solutions for a low-CO2 cement-based materials industry

The main conclusions of an analysis of low-CO{sub 2}, eco-efficient cement-based materials, carried out by a multi-stakeholder working group initiated by the United Nations Environment Program Sustainable Building and Climate Initiative (UNEP-SBCI) are presented, based on the white papers published in this special issue. We believe that Portland-based cement approaches will dominate in the near future due to economies of scale, levels of process optimisation, availability of raw materials and market confidence. Two product-based approaches can deliver substantial additional reductions in their global CO{sub 2} emissions, reducing the need for costly investment in carbon capture and storage (CCS) over the next 20–30 years:1.Increased use of low-CO{sub 2} supplements (SCMs) as partial replacements for Portland cement clinker. 2.More efficient use of Portland cement clinker in mortars and concretes. However, other emerging technologies could also play an important role in emissions mitigation in the longer term, and thus merit further investigation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Iron speciation in blast furnace slag cements

Slag-containing pastes and concretes were analysed by element-specific synchrotron-based techniques to determine the speciation of iron on crushed materials through spatially resolved micro-spectroscopic studies. The investigated cement samples were hydrated either in the laboratory, or exposed to river or sea water. Metallic iron, along with minor proportions of iron sulphide and magnetite was detected in the laboratory sample. Iron sulphide, goethite, and siliceous hydrogarnet were discovered in the blended slag cements hydrated in contact with river water for up to 7 years. In contrast, no Fe(0) was observed in blended concretes exposed to sea water. Instead, iron sulphide, iron(II)-hydroxide and -oxide, hematite, magnetite, siliceous hydrogarnet, and goethite were detected as well as ilmenite (FeTiO{sub 3}) in the aggregates. The strong acceleration of Fe oxidation in samples exposed to sea water and the long-term passivation observed in the other samples indicate comparable processes as those occurring on steel bars.

36 MATERIALS SCIENCE↗