Search Results (281)

This scoping study assesses practical aspects of electrokinetic (EK) biocementation of clay soil underneath a railway embankment ahead of upscaled testing to include a reduced-scale field pilot as an intermediate step towards subsequent pilot embankment treatment. It considers suitable field setups and performs Life Cycle Analysis (LCA) of biocementation by biostimulation of carbonic anhydrase (CA)-producing bacteria compared to hydrated lime slurry, if both treatments were implemented electrokinetically. LCA analysis was conducted using SimaPro software (version 9.6.0.1) with Ecoinvent database and bench-scale laboratory testing data. Electroosmotic flow modelling was performed to instruct on suitable setups and for estimates of power consumption towards the field application of 30 m of railway embankment and foundation soil. LCA indicated a considerable reduction in global warming if CA biocementation is used (0.00823 kg CO₂ eq for biocement vs. 0.022136 kg CO₂ eq for lime), and resource usage (7.06 × 10⁻⁵ kg Cu eq compared to 8.47 × 10⁻⁵ kg Cu eq for lime). Biocementation was more water-consuming compared to lime, as it involved multiple chemical solutions. Terrestrial acidification, aquatic eutrophication, and ecotoxicity were slightly higher for biocement, possibly due to system boundaries and processes assumed for material production. Further sustainability improvements would be possible if waste materials (e.g., captured industrial CO₂) could be used. Field trials will be essential for validation, system optimisation, and advanced model calibration. Full article

As a response to aging of cultured urease-producing microorganisms, the blending method was examined to obtain the required carbonate production amount using the apparent viability (Rcv) based on previous research. As a result, a significantly higher carbonate content than the amount of CaCl₂ 2H₂O used was produced. Since this trend has been obtained in previous studies, it was judged that carbonate hydrate was formed. As a next step, a penetration test of soil–biocement–liquid (BCS) was conducted to investigate the properties and behavior of the BCS system, taking into account the microscopic properties of the BCS response. The depth distribution of carbonate content (C) was measured by the acid dissolution method of soil sampled from the specimen. It was assumed that the C-profile was formed by adsorption based on the diffuse double layer of microorganisms. It was shown that the amount of precursor-carbonate (precursor CPR), the optical density (OD) of viable bacteria, and the physical amount of soil adsorbed at that position can be estimated from C obtained at the various depths. In addition, the previously obtained formulas among CPR, viable OD, and Rcv shown are briefly explained in this paper. Full article

The cement industry, a major contributor to global CO₂ emissions, urgently requires sustainable solutions that maintain or enhance material performance. This study investigates the efficacy of Microbially Induced Calcite Precipitation (MICP) as a partial cement replacement strategy by incorporating two distinct microorganisms, the bacterium Bacillus subtilis (B1) and the fungus Aspergillus fumigatus (B2), into cement mortar. The experimental design involved a significant 30% reduction in total cement content compared to the control mix, with each microorganism added at a dosage of 5% by cement weight. Flexural performance was assessed via three-point bending tests at 7, 28, and 56 days. Microstructural and chemical analyses were conducted using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) to elucidate the underlying mechanisms. The results demonstrate that the incorporation of both microorganisms effectively compensated for the reduced cement content, with the A. fumigatus mix (B2) showing a marked enhancement in flexural behavior, achieving a 4.3% increase over the full-cement control mix at 56 days. This superior flexural performance is attributed to its hyphal scaffolding and crack-bridging effect, which contributes to improved toughness. XRD and XRF analyses confirmed the formation of additional biogenic calcium carbonate (CaCO₃) and provided qualitative insights into matrix densification. This study validates the use of A. fumigatus via the MICP technique as a structurally efficient and eco-friendly pathway to produce high-performance mortars with enhanced flexural properties and a substantially reduced carbon footprint, offering a critical alternative for sustainable cementitious materials. Full article

Recently developed bioactive and reinforced glass ionomer cement (GIC) formulations may offer improved resistance to acid and mechanical wear compared to conventional formulations. Yet, comparative evidence under simulated oral conditions remains limited. This study evaluated the effect of erosive and erosive–abrasive challenges on the surface properties of five GIC-based restorative materials: Riva Self Cure (RS), Zirconomer Improved (ZI), Fuji II LC (FII), Equia Forte HT Fil + Equia Forte Coat (EQ), and ACTIVA BioACTIVE Restorative (AC). Standardized specimens from each material were immersed in artificial saliva, citric acid, or citric acid combined with simulated brushing. Surface roughness (Ra and Rq, µm) was measured, followed by qualitative surface characterization using scanning electron microscopy (SEM). Both material type and treatment condition significantly affected Ra and Rq values, with a significant interaction (p < 0.001). Erosive and erosive–abrasive challenges significantly increased surface roughness for all materials (p < 0.001). AC consistently exhibited the lowest values across all conditions, while ZI and RS showed the highest roughness, particularly under erosive–abrasive challenge. FII and EQ demonstrated intermediate performance. SEM observations corroborated profilometric findings, revealing material-dependent degradation patterns. All materials showed increased roughness following erosive and erosive–abrasive exposure. However, AC showed a comparatively more favorable profile than the other materials. Full article

Microbially Induced Carbonate Precipitation (MICP) is a biochemical process that promotes the precipitation of calcium carbonate, mainly in the mineral form of calcite, using urease-producing bacteria. This method has numerous applications, particularly in the field of geotechnical engineering when it is adopted for soil improvement or for the consolidation of porous or cracked construction materials such as stone and concrete. One microfluidic platform made of polymethylmethacrylate (PMMA) was designed with multiple channels, and the minerals precipitated were visualized using an optical microscope. The precipitated mineral observed in all channels analyzed formed spherical mineral structures with a core and multiple external rings. The same spherical mineral structures were observed in the biocement layer precipitated on plates of the same material as that of the microfluidic platform and on limestone, following the same treatment protocol. SEM images of pieces of these layers, complemented with EDS and mineral analysis by XRD, have confirmed the existence of multiple layers of minerals with spherical structures, mainly vaterite, precipitated around a nucleation point. Overlapping minerals in both the confined microfluidic channels and the unconstrained plates indicate that overlap results from repeated injections rather than physical confinement. From the tests with the microfluidic devices, these studies revealed that crystallization depends on different factors, namely the size of the channels and the number of Sporosarcina pasteurii cells. The number of injections appeared to affect the number of rings precipitated around the inner core. Substrate effects on spatial distribution or adhesion may still exist but were not detectable in this study and require further investigation. The observation of similar mineralogical structures in both the microfluidic devices and the plates, particularly the limestone, demonstrates that microfluidic systems are effective tools for small-scale visualization of geological processes. Full article

The presence of lithobionts has historically been associated with biodeterioration, posing significant challenges to the conservation of culturally and historically significant stone heritage. This perception stems from abundant evidence of their role in biogeophysical processes, such as mechanical disruption of stone structures, and biogeochemical processes, which chemically alter stone composition through metabolic activity. These processes, while integral to natural systems, often accelerate the weathering and deterioration of heritage materials. Coupled with the aesthetic impact of lithobiont growth, frequently resulting in discoloration or obscuring of intricate details, such effects have justified the widespread removal of these organisms from heritage surfaces. However, recent research has revealed a far more nuanced picture. These communities can enhance biodiversity, contribute to the perceived authenticity of aged monuments, and, in some cases, form a biological layer that shields stone from pollutants and weathering forces. Moreover, developments in biomediated conservation approaches, such as biocementation and biocleaning, highlight their potential as sustainable allies in preservation. This dual role of lithobionts—both as friends and foes in preservation—is central to this review. This review focuses on how these organisms—with a particular emphasis on fungi, often perceived as enemies of conservation—may also serve as unexpected partners in safeguarding our stone heritage, emphasizing the need for case-by-case evaluation of active communities and their environmental context. Full article

Conventional polycarboxylate superplasticizers (PCEs) suffer from uncontrollable adsorption, characterized by rapid initial uptake and limited subsequent release, which causes pronounced slump loss, particularly at elevated temperatures where hydration accelerates and dispersion efficiency declines. To overcome these limitations, we developed a series of chitosan-based upper critical solution temperature (UCST) responsive superplasticizers (Thermo-PCE_x, UCST = 40–42 °C) capable of temperature -adaptive dispersion during cement hydration. A vinyl-functionalized chitosan macromonomer (uCS-g-T₈) was synthesized by reacting cetyl polyoxyethylene glycidyl ether with chitosan, followed by methacrylate modification, and then copolymerized with acrylic acid and isopentenol polyoxyethylene ether to yield Thermo-PCE_x with tunable sugar-to-acid ratios. The polymers exhibited clear UCST-type phase-transition behavior in aqueous solution. When incorporated into cement paste, Thermo-PCE_x enabled continuous fluidity enhancement at 25 °C (<UCST), with increases of 43.6%, 52.9%, 62.3% and 63.6%, after 180 min for x = 0.5, 1, 1.5 and 2, respectively. Adjusting dosage and composition further regulated setting time, improved rheological stability, and enhanced mechanical strength. These findings demonstrate a viable pathway for designing bio-based, temperature-responsive superplasticizers with self-adaptive dispersibility for sustainable cement technologies. Full article

To overcome the high cost, marine ecological risks of traditional coral sand reinforcement, and the insufficient mechanical performance of standalone Enzyme-Induced Carbonate Precipitation (EICP), this study proposes a novel soil improvement method integrating EICP with aluminum chloride hexahydrate (AlCl₃·6H₂O). The objectives are to identify optimal EICP curing parameters, evaluate AlCl₃·6H₂O’s enhancement effect, and reveal the synergistic micro-mechanism. Through aqueous solution, unconfined compressive strength, permeability, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and Scanning Electron Microscope (SEM) tests, this study systematically investigated the reaction conditions, mechanical properties, anti-seepage performance, mineral composition, and pore structure. The results demonstrate that EICP achieves the best curing effect under specific conditions: temperature of 30 °C, pH of 8, and cementing solution concentration of 1 mol/L. Under these optimal conditions, the unconfined compressive strength of EICP-solidified coral sand columns reaches 761.6 kPa, and the permeability coefficient is reduced by one order of magnitude compared to unsolidified samples. Notably, AlCl₃·6H₂O incorporation yields a significant synergistic effect, boosting the UCS to 2389.1 kPa (3.14 times standalone EICP) and further reducing permeability by 26%. Micro-mechanism analysis reveals that AlCl₃·6H₂O acts both by generating cementitious aggregates that provide nucleation sites for uniform calcite deposition and by accelerating the transformation of metastable aragonite and vaterite to stable calcite, thereby enhancing cementation stability. This study delivers a cost-effective, eco-friendly solution for coral sand reinforcement, providing practical technical support for marine engineering in environments like the South China Sea. By addressing the core limitations of conventional bio-cementation, it opens new avenues for advancing soil improvement science and applications. Full article

The aim of this study is to investigate the potential applications of pine cones as plant-based waste material in the construction industry. In order to achieve this target, the pine cone particles (PCP) are mixed with cement to create new lightweight concretes. Furthermore, pine tree resin (PTR), acting as a natural bio-polymer binder, is incorporated into selected samples to ascertain its potential as a binder. The pine cones are cut into particles of 2–4 cm, 0–2 cm, and ground into a powder. A series of critical tests is conducted on the novel produced samples, including thermal conductivity, specific heat, density, compressive strength, water absorption rate, and drying rate. The experiments show that thermal conductivity, specific heat capacity, and thermal expansion coefficient decrease as the weight ratio and size of PCP increase. The presence of PTR increases porosity, further decreasing thermal conductivity, specific heat, and thermal expansion coefficients for the majority of samples. The compressive strength values decrease with the presence of PTR and PCP. Regarding durability, the water absorption ratios remain below the critical 30% threshold, making the material suitable for internal applications or external facades protected by coating/plaster or as external coverings. Full article

To facilitate the large-scale recycling of phosphogypsum (PG) as a construction material and mitigate the environmental safety concerns associated with its stockpiling or discharge, this study proposes an innovative approach. The method employs modified (acid-treated) basalt fibers (MBF) synergistically combined with microbially induced carbonate precipitation (MICP) technology for PG solidification. This synergistic MBF–MICP treatment not only enhances the strength and further improves the toughness of the solidified PG but also effectively immobilizes heavy metals within the PG matrix. Bacterial attachment tests conducted on fibers subjected to various pretreatment conditions revealed that the maximum bacterial adhesion occurred on fibers treated with a 1 mol/L acid concentration for 2 h at 40 °C. However, MICP mineralization experiments performed on these pretreated fibers determined the optimal pretreatment conditions for mineralization efficiency to be an acid concentration of 0.93 mol/L, a treatment duration of 0.96 h, and a temperature of 30 °C. Unconfined compressive strength (UCS) tests and calcium carbonate content measurements identified the optimal reinforcement parameters for MBF–MICP-solidified PG as a fiber length of 9 mm and a fiber dosage of 0.4%. Furthermore, comparative analysis demonstrated that the UCS and toughness of MBF–MICP-solidified PG were superior to those of bio-cemented PG specimens treated with unmodified fibers or without any fiber reinforcement. It was found by scanning electron microscopy that there was an obvious phosphogypsum particle-fiber-calcium carbonate precipitation interface in the sample, and the fiber had a bridging effect. Finally, heavy metal leaching tests conducted on the solidified PG confirmed that the leached heavy metal concentrations were below the detection limit, complying with national discharge standards. Full article

Aim: This cross-sectional study aimed to evaluate and compare parents’ and children’s preferences for full-coverage restorative treatment options of primary molars, including stainless steel crowns (SSCs), zirconia crowns (ZCs), and BioFlx crowns. Additionally, the study evaluates the influence of providing a brief overview of the advantages and disadvantages of each full-coverage restorative treatment option on parental preference. Methods: The study was conducted at the pediatric dental clinics at King Abdulaziz University Faculty of Dentistry (KAUFD) in Jeddah, Saudi Arabia, from January to May 2024. Healthy Arabic-speaking children aged 6–12 years attending KAUFD for routine dental treatment, along with at least one parent who agreed to participate, were included. Three typodont models with a SSC, a ZC, and a BioFlx crown were prepared and cemented by an expert pediatric dentist. The participating children and their parents were simultaneously and independently shown the prepared typodont models and asked to indicate which treatment option they preferred most. Subsequently, a trained pediatric dentist presented a brief overview of the advantages and disadvantages of each treatment option to the parents. Then, parents were asked to re-evaluate their preferences. The threshold for significance was set at p < 0.05. Results: A total of 172 children and their parents were included. The most preferred full-coverage restorative treatment among children was SSC (39.0%), while among parents, ZC (60.5%) was the most preferred. After providing a brief overview, the most preferred option among parents was SSC (39.5%), with ZC and BioFlx crowns being equally preferred (30.2%). Significantly more children with no history of dental pain or discomfort (49.1%) (p = 0.023) or with a history of previous dental treatment involving SSC (40.2%) (p = 0.045) preferred SSC. The ZC was significantly more preferred by parents of female children (70.65%) (p = 0.027) and by parents of children with a history of dental treatment (60.6%) (p = 0.018). Conclusions: The study revealed that parental demands and expectations often differ from those of their children, leading to notable differences between children’s and parents’ preferences. After a brief overview, parental preference shifted from ZC to SSC, highlighting the importance of effective communication and education when making treatment decisions for pediatric patients. Full article

This study aimed to evaluate the effects of thermal cycling and restorative material type on surface roughness of material surfaces and dental interfaces using a non-contact profilometer. Ninety Class V cavities (2 mm × 4 mm × 2 mm in height, width, and depth) were prepared on extracted third molars and restored with four bio-interactive materials (Equia Forte, Cention-N, Activa BioActive Restorative, Fuji II LC) and one composite resin (Solare-X) (n = 18/group). After polishing (Optidisc), initial surface roughness (Sa, µm) was measured following 24 h immersion in distilled water. Measurements were performed at cement/material (400 × 1600 μm²), enamel/material (1600 × 400 μm²), and material surfaces (800 × 800 μm²). Samples underwent 10,000 thermal cycles (5–55 °C) to simulate aging, and roughness was re-measured. Data were analyzed with two-way repeated measures ANOVA and Tukey’s post hoc test (p < 0.05). Solare-X showed the lowest roughness, while Fuji II LC and Activa BioActive Restorative were smoother than Cention-N and Equia Forte (p < 0.01). All materials exhibited significant roughness increases after thermal cycling (p < 0.01). Cement/material and enamel/material interfaces consistently showed higher roughness than material surfaces (p < 0.01). Thermal cycling significantly increased surface roughness of all tested materials. Interfaces demonstrated greater roughness than material surfaces, indicating higher susceptibility to plaque retention and potential risk for long-term restoration success. Full article

The aim of the study was to investigate the synergistic effect of conditioned medium (CM) and two types of calcium phosphate biocements on the osteogenic properties of a composite material through rat bone marrow-derived mesenchymal stem cells (MSCs). Briefly, MSCs were cultured for 7 and 17 days in extracts derived from the two biocement types. These extracts were supplemented with 5% (v/v) of concentrated CM. The CM was obtained from rat bone marrow MSC cultures after a 48 h conditioning period. The results showed that the addition of CM had a significant positive impact on the osteoblastic differentiation of MSCs, particularly in the extracts from the tetracalcium phosphate/monetite/calcium sulfate hemihydrate biocement (designated as CAS cement) compared to the other tested cement extract (designated C cement). After 17 days of culturing, a notable increase in cell viability and alkaline phosphatase (ALP) activity, as well as the upregulation of osteoblastic-related gene expression, was found. This enhancement in osteogenic activity was likely driven by the growth factors and bioactive molecules present in the CM. The study concluded that supplementing the biocement extracts with only 5% of 10X concentrated CM is sufficient to significantly influence and improve the in vitro characteristics, cell behavior, gene expression, and synthesis of cell products. It was demonstrated that, especially in the CAS supplemented with CM (CAS + CM) extract system, the improvement in osteogenic properties was due to the synergistic effect between the higher concentration of calcium ions in extracts released from the calcium sulfate hemihydrate-containing cement and the bioactive molecules supplied by the CM. Full article

The use of food industry by-products in the production of construction materials is a great method to achieve sustainability and simultaneously reduce cement consumption. The present research analyzes the use of pomegranate seed cakes (untreated, oven-roasted, and microwave-treated), grape seeds, and black cumin seeds for 0–15% cement replacement. In addition, the focus is on the thermal pretreatment methods and their compatibility with the microstructure of the cement, especially microwave processing due to its rapid heating, low energy demand, and improved microstructural compatibility. The outcomes suggest that microwave-treated pomegranate seed cakes resulted in the highest workability stability, lowest slump loss, and most uniform distribution in the cement matrix in comparison to untreated and oven-roasted pomegranate seed cakes. Comprehensive mechanical tests (compressive, flexural, and splitting tensile strength) and microstructural analyses (SEM, EDS, FTIR, XRD, BET) were conducted on both raw additives and concrete specimens. Although mechanical performance decreases with increasing organic content, mixtures containing 3–5% bio-modifier provided a favorable balance between workability, strength retention, and microstructural development. Microwave pretreatment not only improved the surface morphology but also made the interface more reactive, and by consuming around 80–85% less energy than the oven roasting, it strengthened the sustainability feature of the process. In a nutshell, the research proves that low-energy thermal pretreatment of food-grade waste can result in functional, eco-efficient cementitious composites, and at the same time, the integration of food engineering principles into environmentally friendly construction material design will become inevitable. Full article

Background/Objectives: Ceramic and polymer-based abutments and crowns are increasingly used for esthetic implant restorations, but their mechanical reliability under functional loading remains unclear. This study aimed to evaluate the fracture strength of implant-supported restorations with different abutment–crown material combinations. Methods: Ninety titanium implants (4.1 × 15 mm; BEGO, Germany) were restored with nine combinations of CAD/CAM-fabricated abutment and crown materials (zirconia, lithium disilicate, and ceramic-reinforced polymer; crowns of zirconia, advanced lithium disilicate, and hybrid nanoceramic; n = 10 per group). Ti-base abutments were bonded and cemented following material-specific surface treatments and thermocycled 5000 times (5–55 °C). Fracture tests were performed under static vertical loading at 1 mm/min in a universal testing machine. Data were analyzed using two-way ANOVA and Tukey HSD (α = 0.05). Results: Fracture resistance differed significantly among groups (p < 0.001). The highest mean strength was obtained for zirconia abutment–zirconia crown restorations (1417 N), followed by lithium-disilicate abutment–zirconia crown (1349 N), whereas BioHPP abutment–Tessera crown showed the lowest (823 N). Hybrid composite (Cerasmart) crowns exhibited stable performance across abutments, while Tessera crowns showed lower resistance. BioHPP abutments produced only crown-level fractures (p = 0.004), indicating a more reparable failure mode. Conclusions: Zirconia-based combinations showed the highest fracture resistance and are suitable for posterior use. Clinicians should balance strength with esthetics when considering translucent materials like advanced lithium disilicate or hybrid ceramics. Long-term clinical studies are needed to confirm these results and guide material selection. Full article