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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 OSTI2024

On the Flow of a Cement Suspension: The Effects of Nano-Silica and Fly Ash Particles

Additives such as nano-silica and fly ash are widely used in cement and concrete materials to improve the rheology of fresh cement and concrete and the performance of hardened materials and increase the sustainability of the cement and concrete industry by reducing the usage of Portland cement. Therefore, it is important to study the effect of these additives on the rheological behavior of fresh cement. In this paper, we study the pulsating Poiseuille flow of fresh cement in a horizontal pipe by considering two different additives and when they are combined (nano-silica, fly ash, combined nano-silica, and fly ash). To model the fresh cement suspension, we used a modified form of the power-law model to demonstrate the dependency of the cement viscosity on the shear rate and volume fraction of cement and the additive particles. The convection–diffusion equation was used to solve for the volume fraction. After solving the equations in the dimensionless forms, we conducted a parametric study to analyze the effects of nano-silica, fly ash, and combined nano-silica and fly ash additives on the velocity and volume fraction profiles of the cement suspension. According to the parametric study presented here, larger nano-silica content results in lower centerline velocity of the cement suspension and larger non-uniformity of the volume fraction. Compared to nano-silica, fly ash exhibits an opposite effect on the velocity. Larger fly ash content results in higher centerline velocity, while the effect of the fly ash on the volume fraction is not obvious. For cement suspension containing combined nano-silica and fly ash additives, nano-silica plays a dominant role in the flow behavior of the suspension. The findings of the study can help the design and operation of the pulsating flow of fresh cement mortars and concrete in the 3D printing industry.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Self-re-adhering alkali-activated cement composite and its ability to mitigate corrosion of carbon steel in 300 °C hydrothermal environment

Cement-steel interface is a weak point of cement sheath integrity under the environments of high-temperature geothermal wells. This paper presents carbon steel (CS) adherence behaviors of 300 °C-autoclaved alkali-activated Calcium-Aluminate-Cement (CAC)/fly ash F (FAF) (Thermal Shock Resistant Cement, TSRC), granulated blast furnace slag (GBFS)/SiO 2 , and Ordinary Portland Cement (OPC)/SiO 2 blends. The composites’ ability to preserve the bond under the conditions of thermal shock (TS) and strong acid attack (pH 0.6 H 2 SO 4 /brine at 90 °C) as well as their ability to recover the damaged bond and provide steel corrosion protection after additional short-time 5-day curing at 300 °C were evaluated. GBFS/SiO 2 sheath underwent catastrophic failure in the first TS cycle; OPC/SiO 2 lost 78 % and TSRC 51 % of the bond strength in 6 cycles. Only TSRC-CS bond survived 30 days of strong acid exposure; OPC/SiO 2 bond failed after 18 days and GBFS/SiO 2 after 20 days. Addition of micro-glass fibers (MGF) to TSRC further improved its bond strength and CS corrosion protection. Samples of TSRC-CS cured for 30 days at 300 °C before the bond damage recovered 49 % of the damaged bond strength after additional short-time curing. The CS protected by the re-adhered TSRC showed low corrosion rate of 0.13 mm/year (TSRC-MGF), 0.2 mm/year (TSRC) vs. 0.64 mm/year for OPC/SiO 2 protected CS.

15 GEOTHERMAL ENERGY↗

DOE OSTI2021

An insight on the effect of sodium and silicon on microstructure and crystallography of high alumina cements

In the present study the influence of minor elements (Na{sub 2}O and SiO{sub 2}) on the mineralogy, chemistry and microstructure of High Alumina Cements (HACs) has been investigated. HACs have several advantages respected to Ordinary Portland Cement (OPC) but the shortage of Al-rich raw materials represents a limiting factor: re-use of Al-rich waste as raw material represents a solution but it will add minor elements to the raw meal that could change HACs properties. For the first time, four commercial HACs, doped with sodium and silicon, and one synthetic HAC, only highly doped in sodium, were studied through a multidisciplinary approach by combining conventional and unconventional analytical techniques. Results highlighted that (i) sodium and silicon were mainly incorporated in a sodium-rich phase (Na-phase, NCA{sub 2}, Na{sub 1.9}CaAl{sub 3.9}Si{sub 0.1}O{sub 8}), (ii) no minor phases such as gehlenite and/or mayenite occurred, and (iii) CA (CaAl{sub 2}O{sub 4}) and CA{sub 2} (CaAl{sub 4}O{sub 7}) revealed a limited ionic substitution.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Accelerated carbonation and structural transformation of blast furnace slag by mechanochemical alkali-activation

Alternative cements and production routes are necessary to offset the considerable global CO 2 emissions of Portland cement production. The combination of alkali-activation and mechanochemical milling in a CO 2 rich atmosphere is a promising green direction for synthesizing cementitious material as it upcycles hazardous material (slag) while capturing wt% of CO 2 during synthesis. We investigate the resulting structural transformations incurred during synthesis and hydration using a suite of characterization techniques including solid-state 27 Al, 29 Si, and 13 C NMR. The local aluminosilicate network structure of the processed clinker is best described by a melilite-type structure. Upon hydration, the network polymerizes to form a calcium, sodium aluminosilicate hydrate gel. The synthesis route also creates various metastable carbonates and bicarbonates from captured CO 2 and alkali-additives that transform into stable carbonate phases like calcite, aragonite, and gaylussite, after hydration. These findings indicate accelerated carbonation reactions occur during clinker production and demonstrates novelty as a green cement technology.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Tailoring Cementitious Materials Towards Value-Added Use of Large CO 2 Volumes

Hydraulic cements with alternative chemistries were developed for large-volume and value-added use of carbon dioxide. The hydraulic cements were processed using the energy-efficient mechanochemical technique at room temperature and atmospheric pressure. Carbon dioxide was captured directly from combustion emissions during processing. For this purpose, mechanochemical processing of hydraulic cements was accomplished under a flow of combustion emissions prior to the release of emissions to the atmosphere. The process removed a significant fraction of carbon dioxide from combustion emissions. The hydraulic cements captured carbon dioxide at about 10% of their weight. Two hydraulic cement chemistries were developed, and their mechanochemical processing was successfully scaled-up. The characteristic feature of one chemistry was its relatively low (near-neutral) pH where the integration of carbon dioxide yielded clear value. The second cement chemistry was based on alkali activation of industrial wastes. This chemistry could make value-added use of carbon dioxide, but it had to be refined to control the pH drop caused by CO 2 integration. These two cements render binding effects upon hydration by forming a combination of stable carbonates and aluminosilicates or phosphates. Efforts to develop cement chemistries based solely on carbonates were not successful. The mechanochemical process was found to integrate carbon dioxide into the alternative cement chemistries in the form of disordered and metastable carbonates. During hydration reactions, the disordered/metastable carbonates are either transformed into stable carbonate phases with desired binding efforts, or carbonates get integrated into the primary inorganic binders (hydrates). When compared with mechanochemical processing in pure carbon dioxide, mechanochemical processing in combustion emissions produced hydraulic cements with improved engineering properties. The mechanochemical process was scaled-up, and its variables as well as the raw materials formulations were optimized for implementation at pilot scale. Scale-up was found to enhance the carbon capture potential and the engineering qualities of the resulting hydraulic cements. This was because scale-up raises the intensity of mechanical energy input to raw materials. Certain mechanochemical phenomena cannot be induced, irrespective of the cumulative mechanical energy input, unless the intensity of impact is raised above a minimum level that cannot be achieved in laboratory-scale implementation of the process. Due to this effect, the duration of the mechanochemical process as well as its energy demand could be reduced significantly (by an order of magnitude) upon transition from laboratory to pilot scale, with the hydraulic cements produced at pilot scale offering engineering properties that were superior to those realized in laboratory-scale mechanochemical processing. The hydraulic cements produced at pilot scale via mechanochemical processing under a flow of combustion emissions were thoroughly characterized. They were found to meet standard requirements for ‘General Use’ hydraulic cements. They were compatible with the industrial-scale concrete production and construction practices that are used with the currently prevalent hydraulic cements. The new hydraulic cements with integrated carbon dioxide were found to offer distinct advantages over the currently prevalent Portland cement in terms of net carbon footprint and energy content. The combined raw materials and energy costs of the new hydraulic cements are competitive, and major cost savings can be realized because of the simplified production process that significantly lowers the capital investment in cement production plants. Mechanochemical processing of the new hydraulic cements under a flow of combustion emissions can be implemented using some existing components of cement manufacturing plants; this facilitates adoption of the technology by the cement industry.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Analysis of Carbon Capture Retrofits for Cement Plants

This PowerPoint presentation summarizes the cost and performance results of the techno-economic analysis of carbon capture retrofits at representative cement plants, published in early 2023, titled “Analysis of Carbon Capture Retrofits for Cement Plants.” The analysis report used as a basis for slide contents was developed by NETL in partnership with the Portland Cement Association.

Hughes, Sydney↗

DOE OSTI2025

Electrochemical Production of Calcium Hydroxide from Calcium Carbonate [Poster]

Cement production involves the decomposition of limestone (calcium carbonate) at high temperatures (~900°C) to produce CaO, a major constituent in Portland cement (60-70%). Our unique approach will eliminate the high temperature process and introduce a low-temperature electrochemical process to produce Ca(OH) 2 which can be converted into CaO through dehydration process. This program will allow SRNL to become a leading organization in an open and unexplored field that addresses many of the technical challenges.

36 MATERIALS SCIENCE↗

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 OSTI2024

Decarbonized cement blends

Various embodiments include cementitious compositions with low levels of embodied greenhouse gas emissions, in particular carbon dioxide, as a result of its production and/or use compared to conventional cementitious materials, such as portland cement. Various embodiments include any cementitious material or materials with low embodied carbon, as well as any material produced using this cement.

Benck, Jesse D.↗

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 OSTI2022

Production of α' H -belite-CSA cement at low firing temperatures

A global increase in population creates a need for infrastructure development to stimulate economic growth and improve quality of life. Concrete plays a significant role in this development due to its availability and mechanical strength. Ordinary Portland cement (OPC) has been the most utilized binder in the construction industry since its formulation. However, OPC production has an enormous energy demand and generates large quantities of CO 2 . This research investigates the production of a clinker, containing mainly the hydraulically activated alpha'H-belite polymorph and calcium sulfoaluminate (ye'elimite or C4A3$\acute{S}$), at a lower firing temperature, using a combination of fluoride and boron oxide. This novel clinker addresses the problem of creating high strength cements at extremely low firing temperatures of 1000–1050 °C (a decrease of 450–500 °C as compared to OPC, and a decrease of 200–250 °C as compared to calcium sulfoaluminate (CSA) cement). This clinker reduces CO 2 emissions from energy consumption and by producing phases with lower limestone requirements. The combination of lower firing temperatures and clinker phases that require lower limestone requirements provide a means to reduce CO 2 emissions.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Graphene Oxide Nanoribbons for High Early-Strength Cement Concrete

Longitudinal oxidative unzipping of the outer walls of multiwalled carbon nanotubes (MWCNTs) yields graphene oxide nanoribbons (GONRs), which exhibit greater open surface area and functional edge content than MWCNTs. This paper presents a study of the nano-amendment of Portland cement concrete with GONRs in concentrations between 0.05% (in weight of cement, wt%) and 0.0005 wt%, thus up to two orders of magnitude lower than that reported as lower-bound in the archival literature. The dispersibility in aqueous solution as a function of GONR concentration and oxygen weight content (O%) was assessed through dynamic light scattering (DLS) and zeta potential analysis. The results indicated that less effective suspensions were obtained for 0.05 wt% of GONRs and 22.7 O%. Therefore, GONR water suspensions with 30-40% O% were used to manufacture 50 mm × 100 mm cylindrical concrete specimens. After 7 days of curing, results from uniaxial compression tests using four specimens per configuration (MWCNT concentration and O%) showed that the incorporation of GONRs resulted in an average increase in compressive strength up to 45%. Consistent with the DLS and compression test results, SEM micrographs showed well-dispersed GONRs together with accelerated and preferential formation of calcium silicate hydrates (C-S-H) for all GONR concentrations. The results indicate, for the first time, that the incorporation of very small concentrations (as low as 0.0005 wt%) of well-dispersed GONR amendments can significantly enhance the early-age concrete strength. However, such enhancement became insignificant after 28 days of curing.

cement↗

DOE OSTI2025

Analcime-wairakite formation during experimental cement-bentonite alteration at 200–300 °C

Engineered barrier system materials in nuclear waste repositories may undergo hydrothermal alteration in response to groundwater saturation and heating events over their long operational timescales. Hydrothermal interactions between engineered materials (e.g., bentonite buffers, cements, waste canister materials) and the host rock environment may drive alteration processes that affect the advantageous properties of some barrier materials. However, such alteration will also promote the formation of zeolites, hydrothermally formed minerals that may themselves act to isolate radionuclides. Understanding the environmental conditions that control radionuclide-sorbing properties of zeolites, such as Si/Al ratio or Na content, will be valuable for assessing the changing properties of engineered barrier materials in the case of an in situ heating event. Here, we present experimental work characterizing the formation of zeolites during hydrothermal interactions between generic clay and cement barrier materials, with a focus on the analcime-wairakite zeolite series, which has known radionuclide sorption and exchange properties. We present the results of hydrothermal experiments combining uncured ordinary Portland cement powder with steel and Wyoming bentonite in the presence of Opalinus clay and a synthesized Opalinus clay groundwater to simulate water-saturated conditions in an argillaceous rock repository. The experiments were conducted isothermally at 200 or 300 °C for 8 to 24 weeks. In contrast to analogous studies that did not include cement reactants, we observed the formation of analcime-group minerals in all experiments. The addition of cement resulted in lower Si/Al ratios in the zeolites compared to similar studies that did not include cement. The presence of cement as a reactant was interpreted to promote analcime formation at 200 °C. At 300 °C, we observed higher calcium and silica concentrations in the aqueous solutions as well as increased wairakite formation and decreased analcime formation compared to the experiments at 200 °C. These results show a fully realized analcime-wairakite solid solution that falls between Si/Al = 2 (ideal) and a trend of analcime minerals that have increasing Si/Al ratios with increasing Na/(Na+Ca). Our results show predictable relationships between the Si/Al ratio and the analcime-wairakite content under hydrothermal conditions and illustrate that repository material interactions may promote the formation of zeolites in the analcime-wairakite solid-solution series during heating events in the subsurface.

58 GEOSCIENCES↗

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 OSTI2021

Simulation of hardened cement degradation and estimation of uncertainty in predicted failure times with peridynamics

Modeling the degradation of cement-based infrastructure due to aqueous environmental conditions continues to be a challenge. In order to develop a capability to predict concrete infrastructure failure due to chemical degradation, here we created a chemomechanical model of the effects of long-term water exposure on cement paste. The model couples the mechanical static equilibrium balance with reactive–diffusive transport and incorporates fracture and failure via peridynamics (a meshless simulation method). The model includes fundamental aspects of degradation of ordinary Portland cement (OPC) paste, including the observed softening, reduced toughness, and shrinkage of the cement paste, and increased reactivity and transport with water induced degradation. This version of the model focuses on the first stage of cement paste decalcification, the dissolution of portlandite. Given unknowns in the cement paste degradation process and the cost of uncertainty quantification (UQ), we adopt a minimally complex model in two dimensions (2D) in order to perform sensitivity analysis and UQ. We calibrate the model to existing experimental data using simulations of common tests such as flexure, compression and diffusion. Then we calculate the global sensitivity and uncertainty of predicted failure times based on variation of eleven unique and fundamental material properties. We observed particularly strong sensitivities to the diffusion coefficient, the reaction rate, and the shrinkage with degradation. Also, the predicted time of first fracture is highly correlated with the time to total failure in compression, which implies fracture can indicate impending degradation induced failure; however, the distributions of the two events overlap so the lead time may be minimal. Extension of the model to include the multiple reactions that describe complete degradation, viscous relaxation, post-peak load mechanisms, and to three dimensions to explore the interactions of complex fracture patterns evoked by more realistic geometry is straightforward and ongoing.

36 MATERIALS SCIENCE↗

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 OSTI2021

Mechanisms dominating thixotropy in limestone calcined clay cement (LC3)

Limestone calcined clay cement (LC3) is a green binder with great practical importance for the cement industry. Growing application has increased the need to understand the mechanisms governing its thixotropy for better control of workability. While formation of C-S-H bridges is understood to dominate the thixotropy of ordinary Portland cement, LC3 paste displayed unique thixotropy properties. In this study, focused beam reflectance measurement, zeta potential, 1H nuclear magnetic resonance relaxometry and micro X-ray computed tomography were used to track the colloidal interaction and hydration extent within LC3 paste. Results showed that flocculation due to the negative surface charge and water affinity of calcined clay appears to be the dominating factor. This leads to a reduction of water available to contribute to fluidity of the paste and, in turn, governing the development of thixotropy over time. In addition, the dilution effect due to high clinker substitution diminishes thixotropy growth with time.

36 MATERIALS SCIENCE↗