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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Relevant biochar characteristics influencing compressive strength of biochar-cement mortars

To counteract the contribution of CO 2 emissions by cement production and utilization, biochar is being harnessed as a carbon-negative additive in concrete. Increasing the cement replacement and biochar dosage will increase the carbon offset, but there is large variability in methods being used and many researchers report strength decreases at cement replacements beyond 5%. This work presents a reliable method to replace 10% of the cement mass with a vast selection of biochars without decreasing ultimate compressive strength, and in many cases significantly improving it. By carefully quantifying the physical and chemical properties of each biochar used, machine learning algorithms were used to elucidate the three most influential biochar characteristics that control mortar strength: initial saturation percentage, oxygen-to-carbon ratio, and soluble silicon. These results provide additional research avenues for utilizing several potential biomass waste streams to increase the biochar dosage in cement mixes without decreasing mechanical properties.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Using high pressure solutions of polyfluoroacrylate and CO 2 to Seal cement cracks for improved wellbore integrity

Polyfluoroacrylate (PFA) is a hydrophobic and oleophobic polymer that is soluble in high pressure carbon dioxide (CO 2 ). In this study, the ability of PFA-CO 2 solutions to greatly reduce the apparent permeability of split or cracked Portland cement cylindrical samples is assessed. The apparent permeability values of confined samples were determined before and after treatment with PFA-CO 2 solutions. In four tests, PFA-CO 2 solutions were continuously displacing pure CO 2 from the cracked cement and the decrease in apparent permeability due to PFA adsorption and wettability alteration was monitored. The lowest apparent permeability cracked cement sample (81 nD) was completely sealed with a very small amount of solution. Samples with initial apparent permeabilities of 89 μD and 29.4 mD exhibited 92% and 99% reductions in permeability, respectively, before the experiments had to be stopped because of the excessively large increase in pressure drop. A 50% reduction in apparent permeability was observed with a 3.80 mD sample. Four other split cement samples (bound together with tape) with an initial apparent permeability in the 9.0–70 mD range were removed from the core holder and immersed in a PFA-CO 2 solution for 24 h to allow for PFA adsorption. Then the PFA-CO 2 solution was depressurized, allowing for the deposition of additional PFA from the solution within the crack as the pressure fell below the cloud point pressure of the PFA-CO 2 solution. These four samples were then confined again in a core holder and apparent permeability reductions of 29–93% were observed. Finally, results from these eight experiments indicates that the more substantial reductions in the nD – mD apparent permeability of the cracked cement correlated to lower initial crack permeability, higher PFA concentration, and slower injection rate of the PFA-CO 2 solution into the crack.

58 GEOSCIENCES↗
DOE OSTI2022

Geopolymer Cements: Resistance-Engineered Sewer Infrastructure for Longevity using Innovative, Energy-efficient, Synthesis Techniques (RESILIENT)

The primary objective of this project was to engineer an ultra-acid-resistant low-calcium alkali-activated cement paste for wastewater infrastructure applications to address the critical need for concrete materials with enhanced sulfuric acid resistance compared to ordinary Portland cement (OPC) concrete. In this project, the first milestone was to benchmark the sulfuric acid (SA) resistance of OPC and metakaolin-based geopolymer cement pastes. The second milestone was to model, select, and evaluate the efficacy of metal cation additions on the SA resistance of geopolymer cements. The third milestone was to create synthetic metakaolin that performed similarly to natural metakaolin. The fourth milestone was to design, build, and test the efficacy of four abiotic and biotic nano seeding agents. The fifth and final milestone was to quantify the breakeven material cost requirements and estimated environmental lifecycle costs of the most durable geopolymer cement formulations.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Self-repairing cement polymer composites and processes of making and using same

Examples of novel self-repairing cement-polymer composites and processes of making and using are detailed that address various problems in prior art cements. These matrices, compositions and materials that are more mechanically robust, thermally stable and chemically resistant and demonstrate better bonding to various structures and materials, than other self-healing cements known in the prior art. When in place under preselected conditions (the formulation of the slurry can be modified for optimal effectiveness under various conditions) the organic, cross linking and cement forming portions within the slurry form interconnecting chemical bonds and cures to form a self-repairing and self-re-adhering cement polymer composite matrix in the receiving location.

Fernandez, Carlos A.↗
DOE OSTI2021

Producing cement clinker assemblages in the system: CaO-SiO2-Al2O3-SO3-CaCl2-MgO

Highlights: • Alinite formation conditions are optimised. • Ye'elimite and alinite cannot be simultaneously produced. • Ternesite and chlormayenite are compatible at 1150 °C. • Alite is formed at a reduced temperature of 1300 °C. • Wadalite and chlorellestadite can incorporate chloride in cement clinker assemblages. The cement industry is carbon-intensive, and the valorisation of industrial side-streams/residuals for use as alternative raw materials can enable the cement industry to reduce its carbon footprint as well as promote resource efficiency. Apart from key clinker ingredients such as CaO, Al{sub 2}O{sub 3}, and SiO{sub 2}, industrial residues can also contain MgO, CaCl{sub 2}, and SO{sub 3}. Therefore, this study investigates the formation of cement clinker assemblages in the system CaO-SiO{sub 2}-Al{sub 2}O{sub 3}-SO{sub 3}-CaCl{sub 2}-MgO at temperatures ranging between 1100 and 1300 °C. The production of a clinker composed mainly of alinite and ye'elimite is first attempted; it is found that these phases cannot be simultaneously produced. Ternesite is also not compatible with alinite under the conditions studied. Wadalite is compatible with both ye'elimite and ternesite, while ternesite is also compatible with chlormayenite at 1150 °C. Additionally, the low-temperature formation of alite was also observed with the presence of CaCl{sub 2} in the raw-material mix.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The intrinsic mechanical properties of hydromagnesite, Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O, a key phase of reactive MgO carbonate cement

To potentially enable CO 2 sequestration, reactive MgO carbonate cement is emerging as an alternative binder to Portland cement. Understanding the mechanical properties of its binding phase is critical for understanding the strength development and performing materials design for reactive MgO cement systems; however, the intrinsic mechanical properties of hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O), a key binding phase, remain unexplored. Here the present study utilized synchrotron-based high-pressure X-ray diffraction to determine the unit cell-scale, intrinsic mechanical properties of hydromagnesite for the first time. Up to hydrostatic loading of 7.7 GPa, the bulk modulus of hydromagnesite was determined as 59 GPa or 71 GPa fitted using the second-order or third-order Birch-Murnaghan equation of state, which we contextualize with binding phases in various cement systems. The experiment results are applicable in materials design of low-carbon concrete and valuable for the validation and calibration of atomistic models.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stimuli-responsive petroleum cement composite with giant expansion and enhanced mechanical properties

Shrinkage, as an inherent property of cement during the curing process, has been a concern in the oil & gas industry for centuries. Therefore, expansive cement has been studied for many decades, primarily through incorporation of expansive additives. Nevertheless, traditional expansive additives are not able to achieve the required expansive ratio or maintain a good mechanical property for the cement composite at extreme underground condition. Accordingly, a new generation of expansive additive, which not only has the required expansion, but also work at the downhole high temperature and high pressure environment, and maintain or even enhance the mechanical property, is highly desired. In this work, a high enthalpy storage shape memory polymer (SMP) as a new class of expansive additive is investigated. It is found that the cement composite achieves 1.4% circumferential expansion by only 6% by weight of SMP additives. The compressive strength and flexural strength are also enhanced at the same time, which is hardly achievable by other expansive additives with the same concertation. Good pumpability is also proved by rheological study. The mechanism controlling the enhanced properties is reveled through morphological study and element mapping analysis at the SMP/cement interface.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Self-Healing Cements with Improved Toughness at Casing and Formation Interfaces for Subsurface Applications (CRADA 530)

Over the three-year CRADA, Pacific Northwest National Laboratory (PNNL) advanced a new class of Molecular Velcro™ self-healing wellbore cements designed to improve the long-term integrity of wells used for geothermal energy production and carbon storage. Conventional wellbore cement can crack due to repeated mechanical loading, temperature swings, and exposure to aggressive subsurface fluids. Once cracks form, they can create leakage pathways, drive expensive remediation (“workovers”), and in extreme cases shorten well life. This project addressed that problem by developing polymer-modified cement systems that can autonomously re-seal cracks and better tolerate the extreme conditions experienced in subsurface wells, while remaining compatible with practical cementing operations.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

Hydrophobic Lightweight Cement with Thermal Shock Resistance and Thermal Insulating Properties for Energy-Storage Geothermal Well Systems

This study assessed the possibility of using polymethylhydrosiloxane (PMHS)-treated fly ash cenospheres (FCS) for formulating a thermally insulating and thermal shock (TS)-resistant cementitious blend with calcium aluminate cement. To prevent FCS degradation in an alkaline cement environment at high temperatures, the cenospheres were pre-treated with sodium metasilicate to form silanol and aluminol groups on their surface. These groups participated in a dehydrogenation reaction with the functional ≡Si–H groups within PMHS with the formation of siloxane oxygen-linked M-FCS (M: Al or Si). At high hydrothermal temperatures of 175 and 250 °C, some Si–O–Si and SiCH 3 bonds ruptured, causing depolymerization of the polymer at the FCS surface and hydroxylation of the raptured sites with the formation of silanol groups. Repolymerization through self-condensation between the silanol groups followed, resulting in the transformation of siloxane to low crosslinked silicon-like polymer as a repolymerization-induced product (RIP) without carbon. The RIP provided adequate protection of FCS from pozzolanic reactions (PR), which was confirmed by the decline in zeolites as the products of PR of FCS. Cements with PMHS-treated FCS withstood both hydrothermal and thermal temperature of 250 °C in TS tests, and they also showed improved compressive strength, toughness, and water repellency as well as decreased thermal conductivity. The lubricating properties of PMHS increased the fluidity of lightweight slurries.

15 GEOTHERMAL ENERGY↗
DOE OSTI2024

Wellbore cement alteration and roles of CO 2 and shale during underground hydrogen storage

To mitigate climate change and adopt renewable energy, energy storage is crucial and can be done in the form of hydrogen gas (H 2 ). Subsurface geologic reservoirs are positioned to store H 2 on the largest scales for the longest terms of all potential options. However, H 2 injection may boost reactions that consume hydrogen, generate undesired gases, and alter pore structures of geomedia. To explore the extent of H 2 -associated biotic reactions at a near wellbore location, four experiments were conducted under underground storage conditions with wellbore cement cores and, in most instances, shale samples submerged in synthetic formation brine. Post-reaction gas, aqueous, and solid phase samples were analyzed using olfactory screening and, later, gas chromatography (GC-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), and synchrotron micro-scale x-ray fluorescence (μ-XRF). Within a period of 16 weeks, hydrogen sulfide (H 2 S) was generated in systems containing both H 2 and shale. XRF mapping identified a zone enriched in iron(II) and reduced sulfur along the rim of cement cross sections that was largely associated with CO 2 -induced cement carbonation. Shale did not show noticeable alteration, but there is evidence it contributed to the initial inoculation of the system and provided nutrients for microbes via water-rock interactions. Here, this study considers both rock formations and wellbore cement not previously evaluated concurrently. Findings support understanding and modeling of H 2 -associated biogeochemical reactions during underground hydrogen storage.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Cement and concrete as carbon sinks: Transforming a climate challenge into a carbon storage opportunity

Cement and concrete, while traditionally recognized as the main contributors to anthropogenic CO 2 emissions, also have untapped capacity to serve as substantial and scalable carbon sinks. This perspective examines how engineered mineral carbonation can transform cement-based materials into functional carbon storage systems, generating both environmental and economic value. We review the fundamental mechanisms of CO 2 uptake in cementitious systems, highlighting current limitations in reaction kinetics, phase control, and durability under varying environmental conditions. Emphasis is placed on the utilization of alkaline industrial residues and emerging magnesium-based cements, which offer synergistic pathways for carbon sequestration and circular resource use. We further assess the performance trade-offs associated with CO 2 uptake and the feasibility of deploying these technologies on industrial scales. A strategic roadmap is proposed that integrates scientific innovation, regulatory alignment, and carbon accounting in the life cycle to accelerate the adoption of carbon-storing concrete. This perspective provides a comprehensive framework to advance cement and concrete as engineered carbon sinks and supports the transition to a climate-positive construction industry.

Carbon storage↗
DOE OSTI2021

Inhibition mechanisms of steel slag on the early-age hydration of cement

Steel slag inhibits the early-age hydration of cement. However, its mechanism is still unclear. In this paper, the early-age hydration kinetics and the evolution of the solid phases, aqueous species and microstructures in a cement-steel slag composite binder are investigated to explore how steel slag inhibits the early-age hydration of cement. Two novel phenomena are found: (1) steel slag slows the depletion of gypsum and reduces the formation of ettringite, and (2) steel slag significantly inhibits the precipitation of CH and CSH. The results show that the addition of steel slag increases the Ca concentration in the pore solution, reduces the supersaturation of the pore solution with respect to CH and inhibits the nucleation and growth of CSH. Based on the above results, the retardation mechanisms of steel slag on the initial setting of cement paste are explained.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Long-term cement hydration studies with isothermal calorimetry

The purpose of this study was to investigate for how long the thermal power of hydration can be measured with isothermal calorimetry, which is a general measurement technique with stable properties that, in many cases, can detect low rates of processes. Measurements were conducted for 365 days on cement paste with Portland cement, fly ash blended Portland cement and different water-to-binder ratios. The results showed that all the tested systems still produced a measureable signal after one year. The samples with Portland cement were also analyzed by XRD after 365 days, and phase composition calculations were made with GEMS. Together with the calorimetric results, these results were used to determine the degree of hydration by five methods, the results of which showed good agreement.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Influence of mixing on the generation of nanoparticles in cement systems

In this work, we study the effect of mixing intensity on the size and concentration of nanoparticles in quartz and cement systems. We vary the local shear rate in the studied suspensions induced by mixing by either changing solid volume fraction or mixing speed. Our results obtained on quartz, cement and quartz-cement suspensions provide a master curve relating the concentration of nanoparticles in the pore solution as a function of the local shearing conditions computed at a micromechanical level. Our results suggest, in accordance with literature, that high mixing intensity is at the origin of a detachment of nano-hydrates from the surface of cement particles. These nanoparticles can be stabilized and therefore detected in the pore-solution only in the presence of superplasticizers, which inhibit their agglomeration to other particles.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of anionic and nonionic surfactants on the dispersion and stability of nanoSiO2 in aqueous and cement pore solutions

It has been well recognized that the benefits and effectiveness of nanoparticles in cement-based materials could not be maximized if these are not well dispersed. To address this issue, in this study, different anionic (SDS and PCE) and nonionic surfactants (Tweens and Tritons) were used to disperse nanosilica (NS) in aqueous solution and cement pore solution. The results show that the dispersibility of NS in cement pore solution was improved, and the compressive strength of the cement-NS pastes increased linearly with critical micelle concentration (CMC) of nonionic surfactants. Among all surfactants studied, Triton X-405 led the paste to the highest increase in strength (33% at 1-day and 41% at 3-days) since it had the highest CMC. TEM and EDS analysis evidenced that this strength increase might be attributed to the nucleation of outer product CSH gel and its densification with calcite nanocrystals, attributed to Triton X-405 addition.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Mechanisms of internal curing water release from retentive and non-retentive superabsorbent polymers in cement paste

This paper examines the mechanisms of desorption within cement pastes for superabsorbent polymers (SAP) with different sorption kinetics: retentive and non-retentive (self-releasing). Despite the different behavior in solution, both SAP types mitigated the autogenous shrinkage of cement pastes. {sup 1}H NMR and X-ray tomography showed that the cavities formed by both SAP types were saturated until 9–11 h after mixing, while the entrained water in the cavities redistributed to the cement matrix afterwards. In particular, the non-retentive SAP might have rapidly released the absorbed water, but the released water stayed in the original cavities. Therefore, the behavior of the SAP in the pore solution may not completely determine their internal curing performance in cement pastes. In particular, the initial absorption that forms the solution-filled cavities might be more important than whether the SAP are able to retain the solution for extended periods of time or not.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Impact of limestone fineness on cement hydration at early age

This study compares the influence of two limestone fineness on strength development and cement hydration. The replacement of clinker by 20% of fine limestone (d{sub v,50} = 2 μm and SSA = 4,21 m{sup 2}/g) gives similar strength development to PC up to 7 days. Fine limestone enhances cement hydration and offsets the dilution effect caused by the decrease of clinker amount. The accelerating effect of the limestone was explained by a higher degree of undersaturation with respect to C{sub 3}S. The influence of coarse limestone (d{sub v,50} = 130 μm and SSA = 0,46 m{sup 2}/g) on cement hydration is limited to dilution effect. The combination of fine and coarse limestone was also studied. A linear correlation was obtained between strength and gel space ratio for all investigated systems. Furthermore, the results showed that despite the similarity of specific surface area, limestone is more effective than quartz for the enhancement of cement hydration.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Cement hydration kinetics study in the temperature range from 15 °C to 95 °C

The heat evolution during the hydration of cement was examined by multiple calorimetric methods: isothermal, oscillating isothermal, as well as temperature scanning tests in the temperature range from 15 °C to 95 °C. The apparent activation energy (E{sub a}) of several different types of cements were all found to decrease significantly with temperature. Type of additives and water to cement ratio had little influence on the temperature dependence of E{sub a}. The correlation between E{sub a} and temperature may be mathematically simplified to a step function, where E{sub a} is a nonzero constant below a critical temperature (T{sub cr}) and reduces to zero above that temperature. The proposed model of E{sub a} was combined with a scale factor model to simulate the influence of curing temperature on the hydration kinetics of cement with significantly improved accuracy compared to an earlier model.

36 MATERIALS SCIENCE↗