Cement Porosity Research Articles

Response Surface Design Models to Predict the Strength of Iron Tailings Stabilized with an Alkali-Activated Cement

Tailing storage facilities are very complex structures whose failure generally leads to catastrophic consequences in terms of casualties, serious environmental impacts on local biodiversity, and disruptions in the mineral supply. For this reason, structures at risk must be reinforced or decommissioned. One possible option is its reinforcement with compacted filtered tailings stabilized with binders. Alkali-activated binders provide a more sustainable solution than ordinary Portland cement but require an optimization of the tailing–binder mixture, which, in some cases, can lead to a substantial experimental effort. Statistical models have been used to reduce the number of those experiments, but a rational design methodology is still lacking. This methodology to define the right mixture for a required strength should consider both the mixture components and in situ conditions. In this paper, response surface methods were used to plan and interpret unconfined compression strength test results on an iron tailing stabilized with alkali-activated binders. It was concluded that the fly ash content was the most important parameter, followed by the liquid content and sodium hydroxide concentration. From the obtained results, several statistical models were defined and compared according to the definition of a strength prediction model based on a mixture index parameter. It was interesting to observe that models with the porosity cement index still provide reasonable adjustment even when different tailings’ water contents are considered.

Tensile strength and porosity of regolith-based cement with human hair

Tensile strength and porosity of regolith-based cement with human hair

Antimicrobial Regimens in Cement Spacers for Periprosthetic Joint Infections: A Critical Review.

Antibiotic-loaded cement spacers (ALCSs) are essential for treating periprosthetic joint infections (PJIs) by providing mechanical support and local antibiotic delivery. The purpose of this review is to comprehensively examine the various types of spacers utilised in the management of periprosthetic joint infections (PJIs), including both static and articulating variants and to analyse the fundamental principles underlying spacer use, their clinical benefits, the selection and administration of antimicrobial agents, appropriate dosages, and potential adverse effects. Articulating spacers, which allow joint mobility, often yield better outcomes than static ones. Spacer pharmacokinetics are vital for maintaining therapeutic antibiotic levels, influenced by cement porosity, mixing techniques, and the contact area. Antibiotic choice depends on heat stability, solubility, and impact on cement's mechanical properties. Mechanical properties are crucial, as spacers must withstand physical stresses, with antibiotics potentially affecting these properties. Complications, such as tissue damage and systemic toxicity, are discussed, along with mitigation strategies. Future advancements include surface modifications and novel carriers to enhance biofilm management and infection control.

Hydration of Portland cement in the presence of triethanolamine and limestone powder: Mechanical properties and synergistic mechanism

The study systematically examined the hydration and strength development patterns within ordinary Portland cement (OPC) when triethanolamine (TEA) and limestone (LS) powder were introduced, with a particular emphasis on unraveling their synergistic effects. The findings reveal that 0.02 % TEA addition has a beneficial impact on the early strength of OPC while diminishing later strength. However, the co-incorporation of LS powder effectively eliminates the detrimental effect of TEA on later strength while maintaining the growth of strength. In addition, the concurrent addition of TEA and LS powder reduces the overall cement porosity as well as modulates the pore size distribution, increasing the proportion of non-harmful pores. Through monitoring the hydration process of the OPC, a notably positive synergistic effect between TEA and LS powder is revealed. Firstly, the complexation of TEA indirectly enhances the dilution impact of LS powder, leading to a substantial enhancement in early cement hydration. Secondly, the nucleation effect of LS powder effectively counteracts the inhibitory influence of TEA on C3S, thus eliminating the associated drawbacks. Most significantly, the synergistic effect between TEA and the chemical effect of LS powder accelerates the hydration of C3A and C4AF while preserving ettringite, ultimately resulting in reduced porosity of the samples.

Use of confocal microscopy to measure the porosity of cement containing sulfocalcic binder: A comparative study

This work proposes an effective methodology for measuring the porosity of mixed hydraulic binders applying image analysis (IA) with confocal microscopy (CM). CM offers a certain simplification of sample preparation compared to the standard procedure EN 480-11, as the steps of sample staining and pore masking are eliminated. A set of cement and a hydraulic clinker-free sulfocalcic binder pastes was prepared with various aeration. Total air content, micro air content and the air pore spacing factor according to EN 480-11 standard were determined for hardened pastes using measuring chords. Subsequently, a new simple Surface porosity evaluation for IA methodology using CM was proposed and results were compared with the standard evaluation. The results of both IA evaluations achieved high agreement and the new porosity Surface evaluation was found to be promising for the determination of total air content. Porosity values measured by both IA methods were further compared with MIP.

Advancing thermochemical storage: synthesis and characterization of cement-based composite materials

Thermal Energy Storage (TES) is crucial for sustainability of the energy sector, yet the development of cost-effective, robust materials remains a significant challenge. This study aims at exploring the synthesis and thermal characterization of cement-based composites for seasonal thermochemical energy storage, with the goal to harness the high energy density of hygroscopic salts while mitigating their limitations. We investigate composites with several cement matrices to improve salt-cement compatibility. Furthermore, we investigate the possible incorporation of porous low-cost compounds to enhance porosity and improve economic aspects. As far as the characterization aspects are concerned, we show experimental adsorption isotherms at different temperatures to estimate key material properties like isosteric heat and water uptake, along with the relevant figures of merit such as energy density. Our research leverages on adjustable porosity and affordability of cement as a host matrix for the ‘active phase’. We studied two synthesis approaches: traditional dry impregnation and an in-situ technique suitable for cements. The in-situ method, being straightforward and reproducible, permits greater control over salt content. Preliminary cost analysis positions these composites competitively in the market. Although we are still at sub-optimal stage, potential cost reduction of some less popular cement matrices suggests an opportunity for improvement.

Design and Analysis of Composite Biomaterial Bone Graft Plate

The mixing technique was applied in this study to enhance the strength performance of the cement. The addition of 3% by weight of hydroxyapatite (HA) nanoparticles were mixed with 97% polymethyl methacrylate (PMMA) acrylic polymer, which has a nano size to serve as the matrix material. The surface roughness and continuous porosity of the bone cement were found to be slightly increased by the incorporation of nanoparticles, which enhanced bone-implant osseointegration and ingrowth. Atomic force microscopy (AFM) analysis revealed that the addition of hydroxyapatite (HAp) nanoparticles resulted in a surface roughness value (Sa) of 16.25 nm, which is similar to that of natural bone. The energy-dispersive X-ray spectroscopy (EDS) mapping results discover precentor material and uniform distribution. The Sample exhibited promising results in the antibacterial test, showing efficacy against bacteria both with and without sterilization, confirming its antibacterial properties. The mechanical tests conducted on the sample, including tensile, compression, bending and Vickers hardness tests, yielded favorable results and indicated that the sample is suitable for its intended application. In the theoretical works the design of the bone, screw, and bone plate was conducted using SolidWorks, followed by an analysis using ANSYS under both axial and bending load conditions. The theoretical analysis revealed that the safety factor was less than 1 when an axial load of 13 N was applied and a bending load of 2 N was applied, indicating that the structure may not be able to withstand these loads safely. Under both ambient and physiologically relevant conditions in the human body, HA and PMMA have demonstrated to be excellent choices for enhancing the clinical performance of bone cement. This, in turn, can lead to increased longevity of implants, decreased patient risk, and lower healthcare costs

High-performance cementitious composites containing nanostructured carbon additives made from charred coal fines.

Carbon-based nanomaterials, such as carbon nanoplatelets, graphene oxide, and carbon quantum dots, have many possible end-use applications due to their ability to impart unique mechanical, electrical, thermal, and optical properties to cement composites. Despite this potential, these materials are rarely used in the construction industry due to high material costs and limited data on performance and durability. In this study, domestic coal is used to fabricate low-cost carbon nanomaterials that can be used economically in cement formulations. A range of chemical and physical processing approaches are employed to control the size, morphology, and chemical functionalization of the carbon nanomaterial, which improves its miscibility with cement formulations and its impact on mechanical properties and durability. At loadings of 0.01 to 0.07wt.% of coal-derived carbon nanomaterial, the compressive and flexural strength of cement samples are enhanced by 24% and 23%, respectively, in comparison to neat cement. At loadings of 0.02 to 0.06wt.%, the compressive and flexural strength of concrete composites increases by 28% and 21%, respectively, in comparison to neat samples. Additionally, the carbon nanomaterial additives studied in this work reduce cement porosity by 36%, permeability by 86%, and chloride penetration depth by 60%. These results illustrate that low-loadings of coal-derived carbon nanomaterial additives can improve the mechanical properties, durability, and corrosion resistance of cement composites.

Effect of mineral admixtures on the calcium leaching resistance of porous cement stabilized macadam

Porous cement stabilized macadam has a good drainage property, but the loss of strength due to calcium leaching can significantly reduce its road performance. The effect of the dosage of fly ash, silica fume, and slag powder on the calcium leaching resistance of porous cement stabilized macadam base material was investigated using the accelerated leaching method with 4 mol/L ammonium chloride. The results show that calcium leaching occurs simultaneously at multiple contact points between the internal cement paste and the leaching solution, and the leaching depth has exceeded the average thickness of the layered cemented paste within 3d. The dissolution of CH crystals and the decalcification of C-S-H gel increase the porosity of cement and reduce the strength of the base material. Volcanic ash reaction of silica fume and fly ash as well as slag powder by alkali excitation and sulfate excitation will consume CH and generate low alkalinity C-S-H gel with better dissolution resistance, which can reduce calcium leaching and delay the loss of strength. The optimum dosages of fly ash, silica fume, and slag powder are 20%, 15%, and 30%, respectively, and their optimum dosages can be estimated on the assumption that the mineral admixtures completely consume CH.

Experimental Study on the Evolution Law of the Mechanical and Pore Characteristic Parameters of Set Cement under High- and Ultra-High-Temperature Treatments

Cement has been widely used as a structural material in many underground projects, and these projects often face high- or ultra-high-temperature environments, leading to the deterioration of the mechanical, porosity, and permeability properties of set cement, thereby increasing the risk of instability of underground structures. In response to this, two new temperature-resistant cement slurry systems were designed. Experiments were conducted on the changes in porosity and permeability of set cement after thermal treatment using low-field nuclear magnetic resonance technology (NMR), visual studies of pore and crack development were carried out using the argon-ion polishing field emission scanning electron microscopy (FE-SEM) and computed tomography (CT) methods. The research results show that as the thermal treatment temperature continued to rise, the compressive strength first increased (25 °C–200 °C) and then decreased (200 °C–600 °C). The porosity of the set cement first decreased (25 °C–115 °C) and then increased (115 °C–600 °C), and the penetration first slowly increased (25 °C–400 °C) and then rapidly increased (400 °C–600 °C). Visualization experiments were conducted on micro-cracks and the pore distribution of the set cement under high- and ultra-high-temperatures, which proved the evolution law of these characteristic parameters. The research results have vital reference significance for the protection of the structural stability of cement components when encountering high-temperature environments.

Assessing the mechanical properties of a cemented sand focusing on experimental and theoretical studies

The incorporation of cement to improve soil properties and attract the re-use of locally available materials has become a part of current geotechnical engineering projects. Its applicability varies from construction of pavement base layers, slope protection for earth dams, to support layer for shallow foundations. Unconfined behaviour might be used to evaluate the basic mechanical properties and efficiency of the cemented soils. The proposed relationship between porosity () and volumetric cement content (Civ), presented as porosity cement index (/Civ), was shown to play an important role in the initial shear stiffness (G0), tensile (qt) and compressive (qu) strength of cemented materials. This research aims to assess these parameters through experimental investigation and modelling predictions. Bender elements testing were carried out to assess the maximum initial shear stiffness (G0) prior to specimens testing, and assessing G0 evolution during cement hydration, focusing on the anisotropic/isotropic behaviour established during specimen moulding. Results show a good correlation between experimental and numerical data. It was also observed that cementation isotropises G0 during curing.

Application of cellulose nanocrystals in 3D printed alkali-activated cementitious composites

With the rapid development of concrete 3D printing for construction projects, it is crucial to produce sustainable 3D-printed cementitious composites that meet the required fresh and hardened properties. This study develops sustainable 3D-printed cementitious composites of ordinary portland cement and alkali-activated materials using cellulose nanocrystals (i.e., green natural nanomaterials). The extrudability and buildability of the alkali-activated slag-fly ash mixtures were improved and the extrusion pressure was reduced by ~ 35 % by increasing the cellulose nanocrystals content (up to 1 %) suggesting their viscosity-modifying properties in alkali-activated materials. The inclusion of cellulose nanocrystals improves the overall mechanical performance (8–20 % increase) and reduces the porosity of ordinary portland cement and heat-cured alkali-activated samples. Further, the addition of cellulose nanocrystals (up to 0.30 %) in sealed-cured alkali-activated samples improves their flexural strength by 20 %. The ordinary portland cement sample with cellulose nanocrystals densifies the microstructure and has an approximately 25 % increase in the degree of hydration at inner depths indicating cellulose nanocrystals' internal curing potential. The developed 3D-printable alkali-activated composites with cellulose nanocrystals can provide an overall reduction in the environmental impacts by eliminating/reducing the need for chemical admixtures to improve material consistency and stability, and replacing 100 % of portland cement.

Using Functionalized Micron-Sized Glass Fibres for the Synergistic Effect of Glass Ionomer on Luting Material.

This laboratory experiment was conducted with the objective of augmenting the mechanical properties of glass ionomer cement (GIC) via altering the composition of GIC luting powder through the introduction of micron-sized silanized glass fibres (GFs). Experimental GICs were prepared through the addition of two concentrations of GFs (0.5% and 1.0% by weight) to the powder of commercially available GIC luting materials. The effect of GF in set GIC was internally evaluated using micro-CT while the mechanical attributes such as nano hardness (nH), elastic modulus (EM), compressive strength (CS), and diametral tensile strength (DTS) were gauged. Additionally, the physical properties such as water solubility and sorption, contact angle (CA), and film thickness were evaluated. Reinforced Ketac Cem Radiopaque (KCR) GIC with 0.5 wt.% GF achieved improved nH, EM, CS, and DTS without affecting the film thickness, CA or internal porosity of the set GIC cement. In contrast, both GF-GIC formulations of Medicem (MC) GIC showed the detrimental effect of the GF incorporation. Reinforcing KCR GIC with 0.5 wt.% silanized GFs could improve the physical and mechanical attributes of luting material. Silanized GF, with optimal concentration within the GIC powder, can be used as a functional additive in KCR GIC with promising results.

Minimizing the particles settling of ilmenite weighted oil well cement using laponite

Cementing operations are fundamental undertakings during the drilling and completion of oil and gas wells, ensuring zonal isolation and structural stability within the wellbore. Ilmenite serves as a dominant weighting material for high-density cement. However, challenges associated with its particle settling have arisen, reporting the potential for various complications within the cement sheath. In this context, the present study used laponite, a synthetic layered clay, to address the issue of particles settling in ilmenite-weighted oil well cement under high pressure and high-temperature curing conditions. The investigation extended to comprehensively assessing the consequences of incorporating laponite on the cement's rheological, mechanical, and petrophysical properties. Varied concentrations of laponite were employed and compared against the base cement, devoid of laponite. A total of six high-density cement samples of 18 ppg at different concentrations of laponite were prepared under a high pressure of 3000 psi and a high temperature of 294 °F. Findings from this work revealed that an optimal laponite concentration of 0.3% by weight of cement (BWOC) appeared to be the most effective. Adding laponite to the cement led to an impressive 83% reduction in particle settling within ilmenite-weighted cement. This deduction was confirmed through the direct density variation method and NMR measurements. Moreover, the inclusion of laponite yielded favorable outcomes in the rheological aspects of oil well cement. Laponite-based cement showed a 40% reduction in plastic viscosity and a 31.5% and 14.5% increase in yield point and gel strength, respectively, compared to the base cement formulation. Mechanically, laponite had a tangible positive impact, evidenced by a 95% and 131% increase in compressive and tensile strengths, respectively and a 16% reduction in Young's modulus, all relative to the base cement sample. Significantly, laponite's role extended to pore space optimization, leading to a decline in cement porosity by 2% and a 25% reduction in permeability.

On the Flow of CO2-Saturated Water in a Cement Fracture

Cement fractures represent preferential leakage pathways in abandoned wells upon exposure to a CO2-rich fluid. Understanding fracture alteration resulting from geochemical reactions is critical for assessing well integrity in CO2 storage. This paper describes a mathematical model used to investigate the physical and the chemical changes in cement properties when CO2-saturated water is injected into a wellbore. This study examines the flow of a solution of CO2-saturated water in a two-dimensional fractured cement. In this approach, a micro-continuum equation based on the Darcy–Brinkman–Stokes (DBS) equation is used as the momentum balance equation; in addition, reactive transport equations are used to study the coupled processes of reactant transport and geochemical reactions, and the model for cement porosity alteration and fracture enhancement. This paper focuses on the effects of cement porosity, fracture aperture size, and surface roughness. Mineral dissolution and precipitation mechanisms are also considered. Our simulations show that smaller initial fracture apertures tend to a high mineral precipitation self-sealing. However, a complete sealing of the fracture is not observed due to the continuous flow of CO2-saturated water. The calcite precipitation mechanism of a rough fracture (random zigzag shape) differs from that of a smooth/flat fracture surface.

Study of microstructural changes in blast-furnace cement hardened by repeated dry and wet curing at high temperatures

In ordinary hardened cement, the pore structure changes with microstructural changes due to repeated dry and wet cycles. However, the calcium-silicate-hydrate (C-S-H) produced in blended cement is different from that of ordinary cement because blast furnace slag and fly ash are used in blended cement. In this study, microstructural changes in ordinary cement and hardened blast-furnace cement, which have different compositions of C-S-H, due to repeated dry and wet cycles at high temperatures, were analyzed by solid-state nuclear magnetic resonance (NMR) for structural changes in the products, and by time domain NMR and mercury intrusion porosimetry for changes in moisture and pore structure in the hardened cement. As a result, it was confirmed that the degree of coarsening of capillary porosity in blast-furnace cement was lower than in ordinary cement due to drying and repeated dry-wet cycles. This is believed to be because the aluminum contained in the blast furnace slag of the blast-furnace cement, which is present in the interlayer, improves the resistance of the C-S-H layer to compaction, resulting in less change in the pore structure. This study is expected to contribute to fundamental research on hardened cement in the future.

Numerical Simulation of Hydrogen Diffusion in Cement Sheath of Wells Used for Underground Hydrogen Storage

The negative environmental impact of carbon emissions from fossil fuels has promoted hydrogen utilization and storage in underground structures. Hydrogen leakage from storage structures through wells is a major concern due to the small hydrogen molecules that diffuse fast in the porous well cement sheath. The second-order parabolic partial differential equation describing the hydrogen diffusion in well cement was solved numerically using the finite difference method (FDM). The numerical model was verified with an analytical solution for an ideal case where the matrix and fluid have invariant properties. Sensitivity analyses with the model revealed several possibilities. Based on simulation studies and underlying assumptions such as non-dissolvable hydrogen gas in water present in the cement pore spaces, constant hydrogen diffusion coefficient, cement properties such as porosity and saturation, etc., hydrogen should take about 7.5 days to fully penetrate a 35 cm cement sheath under expected well conditions. The relatively short duration for hydrogen breakthrough in the cement sheath is mainly due to the small molecule size and high hydrogen diffusivity. If the hydrogen reaches a vertical channel behind the casing, a hydrogen leak from the well is soon expected. Also, the simulation result reveals that hydrogen migration along the axial direction of the cement column from a storage reservoir to the top of a 50 m caprock is likely to occur in 500 years. Hydrogen diffusion into cement sheaths increases with increased cement porosity and diffusion coefficient and decreases with water saturation (and increases with hydrogen saturation). Hence, cement with a low water-to-cement ratio to reduce water content and low cement porosity is desirable for completing hydrogen storage wells.

An experimental study on the impact of prosthesis temperature on the biomechanical properties of bone cement fixation

PurposeTo investigate the effect of the femoral component and tibial plateau component temperature on the strength of cement fixation during total knee arthroplasty (TKA).MethodsFemoral prosthesis, tibial plateau prosthesis, and polypropylene mold base were used to simulate TKA for bone cement fixation. Pre-cooling or pre-warming of femoral and tibial plateau components at different temperatures (4 °C, 15 °C, 25 °C, 37 °C, 45 °C), followed by mixing and stirring of bone cement at laboratory room temperature (22 °C), were performed during research. The prosthesis and the base adhered together, and the bone cement was solidified for 24 h at a constant temperature of 37 °C to verify the hardness of the bone cement with a push-out test.ResultsThe push-out force of the femoral prosthesis after fixation was higher than that of the tibial plateau prosthesis, and with the increase of the prosthesis temperature, the push-out force after fixation of the bone cement also increased linearly and the porosity of the prosthetic cement in the tibia and femur decreased as the temperature increased.ConclusionWithout changing the mixing temperature and solidification temperature, the fixation strength of the femoral prosthesis is higher than that of the tibial plateau prosthesis. Properly increasing the temperature of the prosthesis can increase the push-out force of the fixation strength.

Incorporation of synthetic water-soluble curcumin polymeric drug within calcium phosphate cements for bone defect repairing.

Modified macroporous structures and active osteogenic substances are necessary to overcome the limited bone regeneration capacity and low degradability of self-curing calcium phosphate cement (CPC). Curcumin (CUR), which possesses strong osteogenic activity and poor aqueous solubility/bioavailability, esterifies the side chains in hyaluronic acid (HA) to form a water-soluble CUR-HA macromolecule. In this study, we incorporated the CUR-HA and glucose microparticles (GMPs) into the CPC powder to fabricate the CUR-HA/GMP/CPC composite, which not only retained the good injectability and mechanical strength of bone cements, but also significantly increased the cement porosity and sustained release property of CUR-HA in vitro. CUR-HA incorporation greatly improved the differentiation ability of bone marrow mesenchymal stem cells (BMSCs) to osteoblasts by activating the RUNX family transcription factor 2/fibroblast growth factor 18 (RUNX2/FGF18) signaling pathway, increasing the expression of osteocalcin and enhancing the alkaline phosphatase activity. In addition, in vivo implantation of CUR-HA/GMP/CPC into femoral condyle defects dramatically accelerated the degradation rate of cement and boosted local vascularization and osteopontin protein expression, and consequently promoted rapid bone regeneration. Therefore, macroporous CPC based composite cement with CUR-HA shows a remarkable ability to repair bone defects and is a promising translational application of modified CPC in clinical practice.

Fatty Alcohol Polyoxyethylene Ether Sodium Sulfate–Modified Cement to Improve the Bonding and Sealing of Cement to Oil-Wet Casing or Formation Surface in Shale Gas Wells

Summary In shale gas wells, oil-based mud (OBM) changes the casing and rock surface wettability during drilling. It negatively affects the bonding and sealing of cement sheaths with casing or formation rock. Although the spacer is widely used in primary cementing, the casing and formation rock surface are wetted by OBM or oil phase due to poor displacement. For this work, a novel oleophilic cement slurry modified by fatty alcohol polyoxyethylene ether sodium sulfate (AES) was investigated to decrease the negative effect of OBM- or oil-wetted surface. The contact angle of nonpolar solvent 1-bromonaphthalene on the cement surface decreased from 35° to 8°, showing an ideal oleophilic property. The hydraulic isolation capacity; microstructure of the cement-casing or cement-rock interface; and the pore structure, hydration, and mechanical property of AES-modified cement were investigated by interfacial hydraulic isolation test device, computed tomography (CT), mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), thermogravimetric analyses (TGAs), and mechanical test. The results showed that the oleophilic cement could directly bond with an oil- or OBM-wetted surface and significantly eliminate the microchannel and connected pores caused by the oil phase or OBM on the interface. The fluid channeling on the OBM-wetted cement-rock and casing interface was prevented, and the sealing pressure of the interface was increased from approximately 3 to 7 MPa/m (fluid channeling occurred) to higher than 275 MPa/s (fluid channeling did not occur), respectively. Besides, the hydration degree, porosity, and mechanical property of the oleophilic cement remained at the same level as the conventional cement, indicating that the AES has no adverse effect on cement hydration and properties. The findings of this study can contribute to the cement slurry design in shale gas well cementing to improve the interface bonding and sealing when poor displacement happens.