Cement Specimens Research Articles

Enhanced bone cement for fixation of prosthetic joint utilizing nanoparticles

Bone cement is commonly utilized to secure prosthetic joints in the body because of its robust fixation, stability, biocompatibility, and immediate load-bearing capability. However, issues such as loosening, leakage, and insufficient bioactivity can lead to its failure. Therefore, improving its mechanical, physical, and biological properties is crucial for enhancing its efficiency. This study examines the impact of incorporating four different nanomaterials—Titanium Dioxide (TiO2), Magnesium Oxide (MgO), Calcium Phosphate (Ca3(PO4)2), and Alumina Oxide (Al2O3)—into bone cement on its mechanical, physical, and biological properties. TiO2 and Al2O3 nanoparticles are selected to enhance the compression strength of bone cement, thereby preventing loosening. Magnesium Oxide (MgO) and Ca3(PO4)2 nanoparticles are chosen to improve cell adhesion and reducing the risk of cement leakage. Five specimens were prepared: the first with 100% pure bone cement powder, the second with 98% pure bone cement powder and modified with 2% MgO and TiO2, and the remaining three with 95% pure bone cement powder and modified with 5% varying ratios of MgO, TiO2, Ca3(PO4)2, and Al2O3. Compression, tensile, hardness, and bending strengths were assessed to determine improvements in mechanical properties. Setting temperature, porosity, and degradation were measured to evaluate physical properties. Cell adhesion and toxicity tests were conducted to examine the surface structure and biological properties. The results demonstrated that the modified specimens increased compression strength by 8.14%, tensile strength by 3.4%, and bending strength by 4.96%. Porosity, degradation, and setting temperature in modified specimens increased by 3.24%, 0.64%, and 5.17% respectively pure bone cement values. Cell adhesion in modified bone cement specimens showed normal attachment when scanned with FE-SEM. All of the tested modified specimens showed no toxicity, except for specimens with 2% Al2O3 that showed 25% toxicity which could be averted by employing antibiotics.Graphical

Effect of squeeze motion on the tribo-performances of molybdenum disulfide powder lubricated textured cemented carbide specimens

Purpose This study aims to improve the lubrication performance of molybdenum disulfide powders at textured surface of cemented carbide materials, a squeeze motion of vibration assistance method was introduced and investigated. Design/methodology/approach Surface texture was fabricated on YT15 cemented carbide samples using a laser marking machine. After that, a tribological experiment was carried out on a self-built friction testing machine under different amplitude and frequency of squeeze motion conditions. Moreover, a simulation model was also established to verify the principle of squeeze motion on the lubrication performance improving of MoS2 particles at textured interfaces. Findings Analysis results indicated that surface texture on test sample can increase the storage ability of solid lubrication particles, and the lubrication film at the contact interface is more easily formed due to the reciprocating action. Squeeze motion can improve the storage ability of it due to an intermittent contact, which provides an opportunity for MoS2 particles infiltration, and then a more uniform distribution and load-bearing properties of force chain are also established and formed simultaneously. Thus, a better tribological performance at the contact interface is obtained. Originality/value The main contribution of this work is to provide a reference for the molybdenum disulfide powder lubrication with textured surface of cemented carbide materials. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0166/

Turning Waste into Treasure: Utilizing Environment-Pollutant Graphite Tailings as Photocatalyst for Photocatalytic Building Materials

Graphite tailings, as solid waste residuals from graphite extraction and refinement, pose serious risks to the surrounding ecological environment and the safety of residents’ lives. However, it is desirable but challenging how to rationalize the utilization of graphite tailings and further to develop their functionality. Herein, we demonstrate a "turning waste into treasure" strategy: capitalizing on the characteristics of graphite tailings in visible light absorption and rich metal catalytic sites, graphite tailings are employed as photocatalysts and fine aggregates to manufacture photocatalytic building materials, achieving sustainable use. Tailings powder from Luobei, Heilongjiang Province is selected as the photocatalyst, we discover that it exhibits photocatalytic degradation capability for methylene blue (MB) in water under visible-light irradiation: the degradation rates reach 70% within one hour and near-complete degradation within two hours, accompanying good recyclability. Structural analysis reveals that the graphite tailings are enriched with Fe2O3 and TiO2. They are capable of forming type-II heterojunction that enable efficient charge separation and transfer processes, transmitting photogenerated electrons to the active catalytic site to accomplish the photocatalytic degradation of MB. Moreover, other tailings, such as those from Jixi, also achieve photocatalytic degradation of MB, and cement specimens made with graphite tailings also bespoke photocatalytic degradation performance. This work is to provide solutions for the reuse of graphite tailings in the field of functional building materials, and to explore the feasibility of transforming graphite tailings from industrial solid waste to photocatalytic building materials.

Experimental study on creep characteristics of cemented coal gangue backfill under uniaxial compression

ABSTRACT The uniaxial compression creep test is used to study the cemented coal gangue backfill body specimens with different cement-sand ratios (1:4,1:6,1:8, respectively). Through the processing and analysis of the creep curve, we discussed the influence of different cement-sand ratios, stress load and loading time on the strain, creep rate and long-term strength of the backfill body. These studies have revealed the creep law of the backfill body and obtained accurate conclusions. The results show that: (1) Different proportions of cemented coal gangue backfill body under the action of the set step by step axial loading stress, the strain is positively correlated with the change of loading stress. (2) With the increase of axial stress, the instantaneous deformation of cemented coal gangue backfill with three kinds of cement–sand ratio increases with the decrease of cement–sand ratio under the same axial stress. (3) With the increase of the axial stress of the three kinds of cement–sand ratio cemented coal gangue backfill body, the strain rate of the deceleration creep speed and the constant creep stage increases, and the duration of the deceleration creep stage increases. The average creep strain rate of the three kinds of cement–sand ratio cemented coal gangue backfill materials before entering the accelerated creep stage is determined. (4) Using an improved steady-state creep rate inflection point method, the long-term strength of three kinds of cement–sand ratio of cemented coal gangue backfill is determined, and it is concluded that the long-term strength decreases with the decrease of cement–sand ratio, which is positively correlated.

Evaluation of Radiation Rates and Health Hazards from Different Cement Types in Pakistan

The raw materials of cement contain radioactive elements that come from natural sources. Members of the decay chains of uranium, thorium, and potassium radioisotope 40K are the primary sources of this radioactivity. The natural radionuclide concentration levels in cement differ greatly depending on different geographic areas. To estimate the radionuclides concentration in cement specimens from twelve diverse Pakistani companies, gamma-ray spectroscopy analysis was used in the study. 226Ra, 232Th, and 40K had activity concentration levels ranging from 18.08 to 43.18 Bq/kg, 16.73 to 23.53 Bq/kg, and 14.24 to 315.22 Bq/kg, respectively. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) threshold for the 226Ra was surpassed by five of the studied samples. The indoor and outdoor dose rates as well as different radiological health hazard indices were also examined. The Indoor Absorbed Dosage (Din) for some of the samples exceeded the permissible limit. These samples also had a high Indoor Effective Lifetime Cancer Risk (ELCR) factor, which makes them unsafe for interior construction purposes. The outdoor dosages as well as the hazard indices were well within the permitted ranges. The outdoor ELCR factor is low for all the cement brands, which makes them safe for exterior construction purposes. The findings were compared with published data from other countries around the globe. Finally, a thorough statistical analysis was performed and Pearson’s Correlation Coefficient (r) exhibited a very strong correlation between the different outdoor and indoor radiological health hazard indices.

Studying of Mechanical Behavior of Waste Materials Modified Cement Mortar

Large-scale environmental problems have been triggered by ceramic tiles from demolished buildings and animal bone waste. Therefore, optimizing their potential for reuse and recycling is an important goal of sustainable solid waste management. The primary objective of this study is to evaluate the feasibility of partial replacement of the fine aggregates in cement mortar with a combination of natural animal bone powder and industrial waste materials which is wall tiles ceramic powder. This study measures thermal and mechanical characteristics. Recycling construction waste is one of many ways to deny waste material from entering landfills and create new eco-friendly material that reduces energy consumption in buildings. Modified mortar cement specimens with 5% up to 25% mixtures were combined using a 1:3 ratio and a 0.5 W/C ratio to see how the ratios would affect the material’s properties. The addition of a superplasticizer boosted the cement mortar’s workability and compressive strength. The compressive strength, flexural strength, density, and thermal conductivity were evaluated for each mortar mixture ratio. Results showed that compared to regular cement mortar, cement mortar combined with 20% bone and ceramic powder wastes reached the optimal replacement percentage. Compressive strength increased by 54% and flexural strength by about 67%. At the 28-day mark, thermal insulation was lowered by 25%.It is concluded from this study that it is possible to use bone waste as a natural material with ceramic waste as an industrial material to modify the insulation and mechanical properties of cement mortar.

Incorporating concrete waste as additive in acidic fermentation–A novel approach for enhanced biohydrogen production and concrete mass reduction

Acidic fermentation (AF) of organic waste/wastewater generates valuable byproducts, including hydrogen, volatile fatty acids, and ethanol; however, its sensitivity to pH drops limits the stability and efficiency of the process. A reversal process, the acidic chemical treatment of concrete waste (CW) to recycle its aggregates, generates calcium hydroxide, which can serve as buffering agent. Meanwhile, integrating both processes can introduce a sustainable win-win approach, which is the aim of this study. To assess this approach, a series of batch AF experiments were conducted at 50 °C and pH 5.5, using glucose as the substrate. Cementitious specimen (1.5 × 1.5 × 0.8 cm) was supplemented to each 200 mL-fermenter. Unamended fermenters, with and without additional NaHCO3-buffering, were used as controls to compare with the amended ones. Introducing cementitious specimens to AF increased H2-production by 2-fold and 1.7-fold compared to controls with and without NaHCO3-addition, respectively, after three consecutive feed-cycles. The surface analysis of incorporated specimen confirmed the Ca, Al, Mg, and Si leaching. The AF efficiency and resulting cementitious mass reduction were further assessed at different organic loads and specimens’ volume, surface area, and porosity (by changing water-to-cement [W/C] ratio). Increasing the organic load from 10 to 20 g-glucose/L resulted in lower H2-production, higher specimen mass reduction (up to ∼32%), and higher Ca2+ release (up to 2 g/L); however, no significant effect was observed when using specimens with higher W/C ratio or surface area. Moreover, the presence of cementitious specimens significantly influenced the microbial composition, leading to notable developments in the abundant genera Thermoanaerobacterium and Bacillus. This study presents a novel approach to sustainably enhancing AF process using CW as both an additive and a treatable substance, with reusable aggregates as a byproduct. It provides valuable insights for optimizing the process and guiding future practical applications. This includes considering various concrete compositions, adjusting organic load conditions, and evaluating long-term stability in larger-scale systems.

Masking ability of CAD-CAM resin-matrix ceramics with different translucencies and thicknesses combined with four cement shades against varying background colors when facing veneer restorations

BackgroundTo evaluate the comprehensive effect of translucency, thickness, cement shades, and background color on the masking ability of resin-matrix ceramic veneer restorations.MethodsResin-matrix ceramic specimens with 2 translucencies (LT, HT) and 3 thicknesses (0.5, 1.0, and 1.5 mm) were made of Upcera Hyramic (A2 shade). Cement specimens were made of Variolink N in 4 shades (yellow, white, transparent, and bleach XL). Five background specimens were made of IPS Natural Die Material in 5 shades (ND1, ND2, ND3, ND4, and ND5). Color coordinates of 120 subgroups (n = 5) of combined specimens composed of different ceramic, cement, and background specimens were obtained using a spectroradiometer. Color difference (ΔE00) compared with a 4-mm thick specimen of LT and HT ceramics was calculated and four-way ANOVA was used for statistical analysis (α = 0.05).ResultsTranslucency, thickness, cement shade, background color, and their interaction had significant effects on ΔE00 (p < 0.001). ΔE00 values of HT groups were always higher than that of LT groups and were greater than 1.8 against all background colors. ΔE00 values of LT groups could be achieved to be less than 1.8 with appropriate thickness and cement shade. ΔE00 value decreased with increasing ceramic thickness. The effect of cement shade on ΔE00 had no obvious regularity, but ΔE00 values of bleach XL cement shade group were always lower than other cement shade groups under ND3 and ND5 background color.ConclusionsThe masking ability of CAD-CAM resin-matrix ceramics can be simultaneously affected by translucency, thickness, cement shade, and background color. Resin-matrix ceramics with low translucency has a better masking ability than that with high translucency. The masking ability of CAD-CAM resin-matrix ceramics increase with increasing thickness. Cement shade has less impact on the final color of resin-matrix ceramic restorations.

Efficient sealing of cemented sheath: An oil-responsive self-healing latex with toughness enhancement for cement composites

The integrity of the cemented sheath is important to the safe exploration of oil and gas resources. Sealing failure of cement sheath will result in formation fluid channeling and pressure carryover in the annulus. The both toughening and oil-responsive self-healing latex (TOS) was prepared to achieve efficient sealing of cemented sheath, and prolong its service life. The structure and oil swelling behavior of TOS, its toughening and self-healing effects on hardened cement paste (HCP) were analyzed by comprehensive characterizations. Results demonstrated that TOS possessed excellent stability and an oil swelling rate of 1235 %. Cement specimens by curing 28d containing 8 % TOS exhibited a 27.8 % increase in flexural strength, a 48.7 % reduction in elasticity modulus and a 33.8 % reduction in brittleness coefficient. The addition of TOS can effectively improve the toughness of cement. The average pore size of specimens containing 8 % TOS admixture decreased to 9.17 nm. This indicates that TOS enhanced the structural density of cement materials. The crack about 103μm in the cracking specimens with 8 % TOS was almost healed, and the corresponding permeability was reduced 99.1 % after curing in oil. Adsorption and film formation of TOS can resist the cracking of cement sheath, and the oil swelling expansion of film in cement matrix can repair the cracked structure.

Assessment of Dual-Cure Resin Cement Properties of Microhardness and Water Sorption/Solubility through Various Shades of Monolithic Zirconia

ABSTRACT Background: It is important to evaluate the physical properties of dual-cure resin cement in different shades of monolithic zirconia because such an understanding is necessary for its clinical application. Materials and Methods: For this in vitro study, 60 specimens of dual-cure resin cement were prepared and grouped into three sets (n = 20) according to monolithic zirconia shade: light, medium, and dark. Two-millimeter-thick discs of each shade were used as substrates for curing the resin cement. A Vickers hardness tester was employed for measuring microhardness, while ISO 4049 standards were followed for examining water sorption and solubility. Measurements were recorded at 24 hours, baseline, and 1 week after curing. Results: The highest mean value of microhardness (85 HV) was observed in the light shade zirconia group, whereas medium and dark shades exhibited average values equal to 80 HV and 75 HV, respectively. The dark shade showed maximum water sorption among other groups with a mean value of 35 μg/mm³, followed by medium (30 μg/mm3) and light (25 μg/mm3) shades. In relation to solubility, the dark shade also had the highest value, which was approximately 3.5 μ/mm3, while the medium shade showed around 2.5 μg/mm3 and the light shade exhibited nearly 1.5 μg/mm3. Conclusion: Microhardness and water sorption/solubility are significantly affected by the shade variation of monolithic zirconias combined with dual-cured resins. Lighter shades result in higher microhardness and lower water absorption and solubility, leading to better performance and longer lifespan.

Sulfate resistance of alkali-activated flyash-slag-lime concrete: comparative study of drying-wetting cycles and conventional exposure

Abstract Sulphate resistance of concrete is a crucial parameter for design of offshore structures. Of late alkali-activated materials are been given due consideration for infrastructure projects. In this context, the present study aims to assess the sulphate resistance of Alkali-Activated Concrete (AAC) with ternary blend of flyash-Ground Granulated Blast furnace Slag (GGBS) and limestone as the principal binder. The first phase of the study includes the optimization of ternary AAC mix with the inclusion of limestone as a potential binder to popularly used flyash slag blends. The inclusion of 5% limestone powder into the binder matrix is found to have beneficial effect on the mechanical properties of the ternary blended AAC. Further, an increase in the limestone powder content is not found to influence mechanical properties positively. The AAC mix with 5% limestone of total binder content was therefore selected for further evaluation of sulphate resistance. The sulfate resistance is evaluated under the alkaline media by subjecting AAC specimens to constant immersion and alternative drying and wetting cycles. The mechanical characteristics and mass reduction of the exposed samples were tested and compared with the conventional Ordinary Portland Cement (OPC) specimens. Evaluations were conducted over periods of 30, 45, 120, and 365 days of exposure. Scanning Electron Microscopy (SEM), and Energy Dispersion Spectroscopy (EDS) were also used to determine the surface morphology and mineral composition of samples after 365 days of exposure periods. The Flyash-Slag-Lime AAC exhibits denser morphology in comparison to OPC-based concrete, which in turn offers enhanced sulphate resistance.

Energy evolution and damage deformation behavior of cemented broken coal specimen under triaxial compression condition

Coal is a major energy source, and deep coal mining often leads to fractured coal around roadways. Grouting is a common method used to reinforce fractured rock masses, where the slurry encases coal particles, forming a cemented broken coal (CBC) body. The content of coal particles (CP) significantly affects the energy characteristics of CBC specimens. To investigate this, a series of triaxial compression tests and triaxial unloading tests were conducted on CBC specimens with varying CP contents. The results indicate that as CP content increases, both peak strength and cohesion decrease, while the internal friction angle increases in both tests. In the triaxial unloading tests, specimens with higher CP content showed tensile-shear failure. Additionally, energy trends during damage were similar in both tests. In triaxial compression tests, dissipated energy increased with CP content, while in the triaxial unloading test, it initially rose and then fell. During the unloading phase of the triaxial unloading tests, the CBC specimen with 40 % CP content exhibited the most significant change in energy increment and its rate. Analysis of damage and deformation characteristics indicated that damage, deformation, and dilation were effectively restrained in CBC specimens with 40 % CP content during unloading.

The preparation and axial compressive properties of 3D-printed polymer lattice-reinforced cementitious composite columns

Research on the mechanical properties of 3D-printed lattice-reinforced cementitious materials is becoming increasingly widespread. The bending and compression performances of such materials have been studied from the perspectives of the lattice preparation materials, structural forms, gradient design, and cement-based material types. The extant research has primarily focused on the bending performance of lattice-reinforced specimens, while little research has been conducted on the compressive properties. In addition, the reinforcing effect of the lattice on cementitious materials under lateral constraints has not been considered. This article investigates the compressive performance of cement mortar reinforced by 3D-printed spiral lattices or skin structures with different volume reinforcement ratios (different grid constraint layers). Multi Jet Fusion (MJF) technology was used to print four types of spiral lattices, and six specimens, including a control group, were prepared. The experiment considered the performance differences of polymer-reinforced mortars with different volume reinforcement ratios, bonding performance, and skin reinforcement. The load, displacement, stress, strain and other data of the specimen were measured, and combined with the full field strain measured by DIC technology, the strength, energy absorption performance, ductility, elastic modulus, constraint effect, deformation mechanism, and failure mode of the specimen were comprehensively analyzed. The experimental results indicate that 3D-printed spiral or skin lattices can improve the ductility and energy absorption capacity of cementitious materials. However, the elastic modulus of the raw materials used to reinforce the structure is lower than that of cementitious materials, which will reduce the compressive strength and elastic modulus. In addition, the lateral deformation constraint effect of the lattice or skin structure on the cement mortar under axial compression is not significant. All cementitious specimens were found to exhibit the shear failure of the inclined section under axial compression. This article reveals that 3D printed spiral lattices can improve the deformation ability of cementitious composite materials under compression, providing new ideas for the ideal replacement of stirrups and the development of building energy conservation and emission reduction.

Effect and mechanisms of surface treatment using nano titanium dioxide on the permeability of cementitious materials

Corrosive media typically penetrate the interior of cementitious materials through porous structures, causing corrosive damage. Strengthening the surface structure of the substrate is an effective method for enhancing the durability performance of such a material. This study investigates the effects of different concentrations of a nano titanium dioxide suspension (NTS) used for the surface treatment of cement specimens after 24 h of molding and the influence of this treatment on the impermeability of the substrate surface. The results indicate that at 28 d of hydration, water absorption by the 1 % NTS-treated specimens decreases by 45 %, and the resistance to chloride-ion penetration increases by 32.7 % with respect to that of the control group. Furthermore, results of the microscopic tests indicate that when NTS surface treatment is conducted on hardened cementitious materials, NTS provides nucleation sites to enhance the degree of cement hydration, fill minuscule voids, promote the dispersed growth of hydration products, optimize the surface pore structure, and increase the density of the microstructure, thereby improving the impermeability of the substrate surface. This study is expected to provide innovative ideas for the future utilization of nanomaterials for strengthening surface structures and enhancing the durability performances of cementitious materials.

Synthetic Clay Application to Reduce the Segregation of Barite-Based Oil-Well Cement.

In the oil and gas industry, cement segregation is a significant concern that can have disastrous consequences, such as the failure of cement. The change of hardened cement's properties is observed, resulting in a decrease in its strength and an increase in its permeability. Therefore, providing some solutions to prevent this is crucial. The objective of this study is to assess the efficacy of synthetic clay in mitigating the problem of segregation in cement having barite. Six concentrations of synthetic clay were used to prepare six heavy-weighted cement samples with a high density of 18 lb/gal using the barite weighting material. The approaches of density distribution and nuclear magnetic resonance (NMR) were employed to characterize the heterogeneity in the hardened cement samples with the aim of identifying the potential of cement segregation. Then, the optimum concentration of the synthetic clay was selected and its effects on the rheological, strength, petrophysical, and elastic properties were evaluated and compared with the properties of the base cement (without synthetic clay). The results showed that 0.4% by weight of cement (BWOC) synthetic clay was the optimum concentration, which yielded the minimum cement segregation as represented by a 61% reduction in the density variation compared to the control specimen. The results obtained from the NMR technique validated the findings of the density distribution method, indicating that the porosity distribution of the synthetic clay cement with a concentration of 0.4% BWOC exhibited uniformity across its top, middle, and bottom sections, with a slight deviation window, while the porosity distribution of the control cement specimen displayed noticeable variation. Moreover, the synthetic clay had better properties than the control cement specimen. For example, the rheological properties were improved as represented by a 22% reduction in plastic viscosity and 42 and 11% increase in the yield point and gel strength, respectively. Compared to the base cement, the compressive and tensile strength were increased by 39 and 43%. The synthetic clay decreased the permeability and porosity by 73 and 24%, respectively. The synthetic clay enhanced the elastic properties as represented by a 1.5% reduction in Young's modulus and a 1.3% increase in Poisson's ratio compared to the base cement sample.

Investigation on Strength and Flexural Behavior of PVA Fiber-Reinforced and Cemented Clayey Soil

Adding cement to soft soils may lead to brittle behavior and the occurrence of sudden damage. Methods to further improve the tensile and flexural properties of cemented clay are noteworthy topics. This paper mainly focuses on the effect of cement and moisture content on the strength and flexural properties of cemented clay reinforced by PVA fiber. The selected clayey soil was a kaolin with cement content of 5%, 10%, and 15% and moisture content of 50%, 56%, 63%, and 70%. The results show that the incorporation of 0.6% fiber can effectively improve the deformability of cemented clay in unconfined compression tests (UCS). The strengthening effect of fiber, as seen in the peak strength and post-peak strength of UCS, was significantly related to cement content. As the water content increased, the compressive strength of the fiber-reinforced cemented clay decreased, but its load-bearing capacity enhanced. When the cement content was 15%, the splitting tensile strength of fiber-reinforced cemented specimens increased by 11% compared to cemented soil, but the deformability of the specimens became poor. In the cement-content interval from 5% to 10%, the bending toughness was significantly improved. Sufficient cement addition ensures the enhancement of PVA fibers on strength and flexural properties of cement-stabilized clayey soil.

Impact of Manual Addition of Vancomycin to Polymethylmethacrylate (PMMA) Cements.

(1) Background: The addition of antibiotics to bone cements is a common practice in the treatment of periprosthetic joint infections. In revision cases, the amount and type of antibiotic is often insufficient and additional antibiotics must be added. The addition, however, changes the product itself, and the surgeon becomes the "manufacturer" of the bone cement. PMMAe wished to clarify whether the admixture of antibiotics changes the mechanical stability of the bone cements used and if the added antibiotics were still functional and released in sufficient quantities. (2) Methods: We compared two industrially manufactured vancomycin-containing PMMA cements; the low-viscous VancogenX® (TECRES, Sommacampagna, Italy) and the high-viscous Copal® G+V (Heraeus Medical GmbH, Wehrheim, Germany), with two PMMA cements loaded with aminoglycosides, to which 2.0 g of vancomycin (Hexal CT1631) were manually added-the high-viscous Smartset® GHV and the medium-viscous Antibiotic Simplex with Tobramycin (antibiotic Simplex® T). Test specimens of the bone cements were used to determine mechanical stability (bending strength and bending module), and the release of the antibiotics was determined by HLPC and modified Kirby-Bauer assays. (3) Results: All tested bone cements showed an initial high release within the first hours. Repeated testing after 24 h showed a reduced efficacy of VancogenX® and Smartset® GHV in Kirby-Bauer assays. Long-time release over days showed a release of functional antimicrobial active ingredients over this period of time in anti-microbial assays, but no activity of VancogenX® from day 21 onward. No significant differences in the ISO bending modules could be detected, but in contrast to the bending module, the ISO bending strength was substantially reduced by 10-15 mPal in comparison to both cements of the reference group. The Simplex®T met just the ISO 5833; the Smartset® GHV did not after adding vancomycin. (4) Conclusions: In conclusion, the manual addition of 2 g of vancomycin to 40 g of PMMA powder is recommended for the treatment of methicillin-resistant staphylococci. Vancomycin is released over a period of 42 days with concentrations above the MIC for typical staphylococci. The mechanical properties of the PMMA just met, or did not fulfill, ISO mechanical specification. Copal® G+V showed a better elution than VancogenX® over time.

Effect of in situ CO2 mixing of cement paste on the leachability of hexavalent chromium (Cr(VI))

In situ CO2 mixing technology is a potential technology for permanently sequestering CO2 during concrete manufacturing processes. Although it has been approved as a promising carbon capture and utilisation (CCU) method, its effect on the leachability of heavy metals from cementitious compounds has not yet been studied. This study focuses on the effect of in situ CO2 mixing of cement paste on the leaching of hexavalent chromium (Cr(VI)). The tank leaching test of the CO2 mixing cement specimen resulted in a Cr(VI) cumulative leaching of 0.614 mg/m2 in 28 d, which is ten times lower than that of the control mixing specimens. The results in thermogravimetric analysis indicated that a relatively significant amount of CrO42− is immobilised as CaCrO4 during the CO2-mixing, and a higher Cr–O extension is observed in the Fourier transform infrared spectra. Furthermore, a portion of the monocarboaluminate is inferred from microstructural analyses to incorporate CrO42− ions. These results demonstrate that in situ CO2 mixing is beneficial not only in reducing CO2 emissions, but also in controlling the leaching of toxic substances.

Relative permeabilities for two-phase flow through wellbore cement fractures

Multiple fluids are likely to exist in fractures and flow paths associated with leaky wellbores, including liquids (e.g., crude oil) and gases (e.g., gas exsolved from liquid). These fluids occupy and move through different portions of the pore spaces within the fractures depending on many factors, including fluid properties, fracture size, and the amount of the different fluids. Upward leakage of any phase, through the fracture, can contaminate water-bearing formations, create hazardous surface conditions, and compromise the functionality of the wellbore. Early signs of wellbore leaks may be expressed by anomalous pressure behavior at surface monitoring points on cavern storage wells. These pressure anomalies are difficult to interpret, necessitating knowledge of the factors that affect the multiphase flow in fractures and porous media. These parameters are critical to modeling multiphase flow in fractures. This insight can guide further diagnosis and maximize leak remediation. Our study focuses on the relationship of the liquid–gas relative permeabilities for representative variable-aperture wellbore cement fracture. To obtain the relative permeability of each phase, two-phase flow tests were conducted where both fluids were flowing simultaneously through a fractured wellbore cement specimen under a range of factors, namely (1) aperture size, (2) capillary numbers, and (3) viscosity ratio. The flow experiments were conducted under a range of confining stresses and flow velocities, using nitrogen gas and silicone oils (of different viscosities) in a specially designed pressure vessel. The sum of gas and oil relative permeabilities were found to be less than one under all conditions, which indicates that the presence of one phase affects the permeability of the other phase, and vice versa. Since the gas phase flow conditions include a significant inertial flow component in addition to viscous flow, the inertial flow coefficients at different saturation states are presented. The factors affecting the relationship between the relative permeabilities are discussed in detail. A new mathematical model for estimating the relative permeability of wellbore cement fracture is presented and experimentally validated.

Compressive Strengths of Cube vs. Cored Specimens of Cement Stabilized Rammed Earth Compared with ANOVA

Cement-stabilized rammed earth (CSRE) is a variation of the traditional rammed earth building material, which has been used since ancient times, strengthened by the addition of a stabilizer in the form of Portland cement. This article compares the compressive strength of CSRE determined from specimens cored from structural walls and those molded in the laboratory. Both types of specimens underwent a 120-day curing period. The tests were conducted on specimens with various grain sizes and cement content. An analysis of variance (ANOVA) was performed on the obtained results to determine whether it is possible to establish a conversion factor between the compressive strength values obtained from laboratory-molded cubic samples and those from cored samples extracted from the CSRE structure. The study revealed that the compressive strength of CSRE increases significantly over the curing period, with substantial strength gains observed up to 120 days. The results indicated no statistically significant difference in the mean unconfined compressive strength (UCS) between cubic and cored specimens for certain mixtures, suggesting that a shape coefficient factor may not be necessary for calculating CSRE compressive strength in laboratory settings. However, for other mixtures, normal distribution was not confirmed. These findings have implications for the standardization and practical application of CSRE in construction, highlighting the need for longer curing periods to achieve optimal strength and the potential to simplify testing protocols.