Search Results (248)

Backfilling materials are commonly employed materials in mines for filling mining waste, and the strength of the consolidated backfill formed by the binding material directly influences the stability of the surrounding rock and production safety in mines. The traditional approach to obtaining the strength of the backfill demands a considerable amount of manpower and time. The rapid and precise acquisition and optimization of backfill strength parameters hold utmost significance for mining safety. In this research, the authors carried out a backfill strength experiment with five experimental parameters, namely concentration, cement–sand ratio, waste rock–tailing ratio, curing time, and curing temperature, using an orthogonal design. They collected 174 sets of backfill strength parameters and employed six population optimization algorithms, including the Artificial Ecosystem-based Optimization (AEO) algorithm, Aquila Optimization (AO) algorithm, Germinal Center Optimization (GCO), Sand Cat Swarm Optimization (SCSO), Sparrow Search Algorithm (SSA), and Walrus Optimization Algorithm (WaOA), in combination with the CatBoost algorithm to conduct a prediction study of backfill strength. The study also utilized the Shapley Additive explanatory (SHAP) method to analyze the influence of different parameters on the prediction of backfill strength. The results demonstrate that when the population size was 60, the AEO-CatBoost algorithm model exhibited a favorable fitting effect (R² = 0.947, VAF = 93.614), and the prediction error was minimal (RMSE = 0.606, MAE = 0.465), enabling the accurate and rapid prediction of the strength parameters of the backfill under different ratios and curing conditions. Additionally, an increase in curing temperature and curing time enhanced the strength of the backfill, and the influence of the waste rock–tailing ratio on the strength of the backfill was negative at a curing temperature of 50 °C, which is attributed to the change in the pore structure at the microscopic level leading to macroscopic mechanical alterations. When the curing conditions are adequate and the parameter ratios are reasonable, the smaller the porosity rate in the backfill, the greater the backfill strength will be. This study offers a reliable and accurate method for the rapid acquisition of backfill strength and provides new technical support for the development of filling mining technology. Full article

Sustainability in the construction sector has become a fundamental objective for mitigating escalating environmental challenges; given that concrete is the most widely used man-made material, extending its service life is therefore critical. Among durability concerns, magnesium sulfate (MgSO₄) attack is particularly deleterious to concrete structures. Therefore, this study investigates the short- and long-term performance of concrete produced with copper slag (CS)—a massive waste generated by copper mining activities worldwide—employed as a supplementary cementitious material (SCM), together with recycled coarse aggregate (RCA), obtained from concrete construction and demolition waste, when exposed to MgSO₄. CS was used as a 15 vol% cement replacement, while RCA was incorporated at 0%, 20%, 50%, and 100 vol%. Compressive strength, bulk density, water absorption, and porosity were measured after water curing (7–388 days) and following immersion in a 5 wt.% MgSO₄ solution for 180 and 360 days. Microstructural characteristics were assessed using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis with its differential thermogravimetric derivative (TG-DTG), and Fourier transform infrared spectroscopy (FTIR) techniques. The results indicated that replacing 15% cement with CS reduced 7-day strength by ≤10%, yet parity with the reference mix was reached at 90 days. Strength losses increased monotonically with RCA content. Under MgSO₄ exposure, all mixtures experienced an initial compressive strength gain during the short-term exposures (28–100 days), attributed to the pore-filling effect of expansive sulfate phases. However, at long-term exposure (180–360 days), a clear strength decline was observed, mainly due to internal cracking, brucite formation, and the transformation of C–S–H into non-cementitious M–S–H gel. Based on these findings, the combined use of CS and RCA at low replacement levels shows potential for producing environmentally friendly concrete with mechanical and durability performance comparable to those of concrete made entirely with virgin materials. Full article

To address the limitations of traditional hardened concrete road surfaces in coal mine tunnels, which are prone to damage and entail high maintenance costs, this study proposes using modular concrete blocks composed of fly ash and coal gangue as an alternative to conventional materials. These blocks offer advantages including ease of construction and rapid, straightforward maintenance, while also facilitating the reuse of substantial quantities of solid waste, thereby mitigating resource wastage and environmental pollution. Initially, the mineral composition of the raw materials was analyzed, confirming that although the physical and chemical properties of Liangshui Well coal gangue are slightly inferior to those of natural crushed stone, they still meet the criteria for use as concrete aggregate. For concrete blocks incorporating 20% fly ash, the steam curing process was optimized with a recommended static curing period of 16–24 h, a temperature ramp-up rate of 20 °C/h, and a constant temperature of 50 °C maintained for 24 h to ensure optimal performance. Orthogonal experimental analysis revealed that fly ash content exerted the greatest influence on the compressive strength of concrete, followed by the additional water content, whereas the aggregate particle size had a comparatively minor effect. The optimal mix proportion was identified as 20% fly ash content, a maximum aggregate size of 20 mm, and an additional water content of 70%. Performance testing indicated that the fabricated blocks exhibited a compressive strength of 32.1 MPa and a tensile strength of 2.93 MPa, with strong resistance to hydrolysis and sulfate attack, rendering them suitable for deployment in weakly alkaline underground environments. Considering the site-specific conditions of the Liangshuijing coal mine, ANSYS 2020 was employed to simulate and analyze the mechanical behavior of the blocks under varying loads, thicknesses, and dynamic conditions. The findings suggest that hexagonal coal gangue blocks with a side length of 20 cm and a thickness of 16 cm meet the structural requirements of most underground mine tunnels, offering a reference model for cost-effective paving and efficient roadway maintenance in coal mines. Full article

Long-chain imidazolium-based ionic liquids (ILs) possess a broad-spectrum biological activity and are considered promising antifouling agents for protective coatings. A new hydrophobic IL, 1-dodecyl-3-methylimidazolium dodecylbenzenesulfonate (C₁₂C₁IM-DBS), has been synthesized, and a modified epoxy coating material containing 10, 20, and 30 wt% of this IL was prepared by dissolution of C₁₂C₁IM-DBS in commercial DER 331 epoxy resin, followed by a curing phase with diethylenetriamine. Infrared analysis revealed physicochemical interactions between the hydroxyl groups of the resin and the IL. Spectrophotometric studies showed no release of C₁₂C₁IM-DBS after 30 days of exposure of the modified coatings to water. The plasticizing effect of the IL on the epoxy resin was established by differential scanning calorimetry analysis. The introduction of 10 and 20% C₁₂C₁IM-DBS into DER 331 reduced its glass transition temperature from 122.8 °C to 109.3 and 91.5 °C, respectively. The hardness of epoxy resin decreased by approximately 26% after the introduction of the IL. Moreover, DER 331/C₁₂C₁IM-DBS coatings on steel substrates showed significantly improved impact resistance compared to neat resin. The antibiofilm efficiency of DER 331/C₁₂C₁IM-DBS coatings was evaluated by assessing the capability of two biofilm-forming model strains, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa PA01, to form attached biofilms on the surface. The IL effectively inhibited S. aureus surface-associated biofilm development even at the lowest content of 10%. On the contrary, an approximately 50% inhibition of biofilm metabolic activity was detected for DER 331/C₁₂C₁IM-DBS coatings containing 20% and 30% of the IL. Overall, the results of this study indicate that the hydrophobic IL C₁₂C₁IM-DBS is an efficient modifying additive for epoxy resins, which can significantly improve their operational properties for various industrial applications. Full article

Considering the harsh marine environment characterized by dry–wet cycles, freeze–thaw action, chloride penetration, and sulfate attack, four optimized ultra-high-performance concrete (UHPC) mix designs were developed. Durability was assessed via electric flux, dry–wet cycles, and rapid freeze–thaw tests to evaluate the effects of curing methods, aggregate types, and mineral admixtures on key durability indicators, including chloride ion permeability, compressive strength loss, and mass loss. Scanning electron microscopy (SEM) examined microstructural changes under various conditions. Results showed that curing method significantly affected chloride ion permeability and sulfate resistance. High-temperature curing (70 ± 2 °C) reduced 28-day chloride ion electric flux by about 50%, and the compressive strength loss rate of specimens subjected to sulfate attack decreased by 2.7% to 45.7% compared to standard curing. Aggregate type had minimal impact on corrosion resistance, while mineral admixtures improved durability more effectively. Frost resistance was excellent, with mass loss below 0.87% after 500 freeze–thaw cycles. SEM analysis revealed that high-temperature curing decreased free cement particles, and mineral admixtures refined pore structure, enhancing matrix compactness. Among all mixtures, Mix Proportion 4 demonstrated the best overall durability. This study offers valuable insights for UHPC design in aggressive marine conditions. Full article

Background: Local audits of Helicobacter pylori (H. pylori) prescriptions and outcomes are necessary to assess guideline awareness among clinicians and treatment effectiveness. Aims: The aims were to investigate first-line prescriptions and effectiveness over a 10-year period in Ireland and evaluate the influence of the 2017 Irish consensus guidelines on these trends. Methods: Data were collected at e-CRF AEG-REDCap from the European Registry on H. pylori management (Hp-EuReg) and quality reviewed from 2013 to 2022. All treatment-naïve cases were assessed for effectiveness by modified intention-to-treat (mITT) analysis. Multivariate analysis was also performed. Results: Data from 1000 patients (mean age 50 ± 15 years; 54% female) were analyzed. Clarithromycin (C) and amoxicillin (A) triple therapy represented 88% of treatments, followed by sequential C, A, and metronidazole (M) therapy (4.3%) and triple C + M (2.7%). Bismuth quadruple therapy was prescribed in 1.7% of cases. Treatment durations of 14, 10, and 7 days accounted for 87%, 4.5%, and 8.5% of prescriptions, respectively. High-, standard-, and low-dose proton pump inhibitors (PPIs; 80 mg, 40 mg, and 20 mg omeprazole equivalent b.i.d.) were used in 86%, 0.9%, and 13% of cases, respectively. The overall eradication rate was 80%, while it was 81% for triple C + A. Good compliance and high-dose PPI were associated with higher overall mITT eradication rates (OR 4.5 and OR 1.9, respectively) and triple C + A eradication rates (OR 4.2 and OR 1.9, respectively). Overall eradication rates increased from 74% pre-2017 to 82% (p < 0.05) by the end of 2022. Similarly, the triple C + A eradication rates increased from 76% to 83% (p < 0.05). Conclusions: While first-line treatment effectiveness improved in clinical practice over time, cure rates remain below 90%. Alternative first-line strategies are required in Ireland. Full article

The construction industry generates large amounts of waste and high CO₂ emissions, especially from cement production. Sustainable alternatives, such as geopolymers, help reduce these impacts by promoting eco-friendly materials. This study aimed to develop geopolymer mortar using ignimbrite (IG) residues from the Arequipa region, Peru, combined with metakaolin (MK). The raw materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) to assess the chemical composition, structure, and morphology. Geopolymeric mortars were synthesized with varying MK/IG ratios while maintaining a fixed fine sand proportion. An activating solution of 9 mol/L NaOH was used with different liquid-to-solid ratios. Geopolymers cured at room temperature for 28 days exhibited lower compressive strength than those dried at 50 °C for 48 h or sequentially at 50 °C for 48 h followed by 90 °C for 12 h. The highest IG-content mixture achieved a compressive strength of 18 MPa, while the MK-based geopolymer reached 12 MPa, both under high-temperature curing. An increase in the SiO₂/Al₂O₃ molar ratio was also associated with improved mechanical performance, reinforcing the influence of precursor composition on geopolymerization. These results highlight the potential of regional ignimbrite for the production of geopolymer mortar, promoting sustainable and innovative building materials. Full article

Background: There are very few studies in literature concerning the bonding between 3D-printed resin posts and the core build-up material. This study aimed to evaluate and compare the adhesion of 3D-printed and milled resin posts to composite resin core build-up material following different surface treatments. Methods: Three types of resin posts were utilized in this study: ready-made glass-reinforced fiber post (3M ESPE, Germany), milled PEEK POST (Bredent, Germany), and 3D-printed resin post (CROWNTEC, Saremco Dental AG, Switzerland). Each type of post was categorized into three groups based on surface treatments: C: untreated surfaces; SB: Air abrasion with 50 μm aluminum oxide particles was applied to the posts’ surfaces.; HO: the posts’ surfaces were immersed in 30% H₂O₂ for 5 min. A dual-cured composite resin (Grandio DC; VOCO) was utilized for core build-up in each group to evaluate adhesion through the push-out bond strength test. The modes of failure were analyzed, and the surface morphology of the post was characterized using SEM. Data were analyzed using a two-way analysis of variance (ANOVA) along with Tukey’s test. Results: The two-way ANOVA indicated a significant effect for surface treatment (F = 583.54, p < 001), post type (F = 79.96, p < 0.001), and their interactions (F = 265.74, p < 0.001). Regarding 3D-printed resin post, 30% H₂O₂ for 5 min recorded the highest statistically significant bond strength value (13.11 ± 1.61) compared to other groups. Regarding the milled PEEK post, the air particle abrasion recorded the highest statistically significant value (23.88 ± 1.66) compared to other groups. Adhesive failure was the predominant failure type, with an occurrence rate of 70.35%. Mixed failure was noted in 24.07% of the cases, with a significant prevalence in the PEEK post within the air particle abrasion group (58.3%). Cohesive failure was noted in 5.54% of cases, with a significant prevalence in the air particle abrasion group, occurring at rates of 16.6% in the resin fiber post group and 33.3% in PEEK posts. Conclusions: Air particle abrasion significantly improved the push-out bond strength of milled PEEK posts, but it did not have a similar effect on the 3D-printed resin posts. The application of 30% H₂O₂ for 5 min to 3D-printed resin post enhanced the adhesion to core build-up material. The manufacturing method of posts, the surface treatments utilized, and their interactions affect the interfacial bond strength between posts and the composite resin core build-up material. Full article

Winter concrete construction in cold regions faces significant challenges due to extreme subzero temperatures, and the harsh environment presents new requirement for cement-based materials to resist this hostile external condition. To address this gap, this study proposes gradient Joule heating (GJH) curing for steel-fiber-reinforced high-performance concrete (SFR-HPC) in subzero environments (−20 °C to −60 °C). Compared to room-temperature (RT) curing, GJH enabled specimens at −20 °C to −50 °C to achieve equivalent mechanical properties within a short curing duration; the compressive strength of the specimens cured at such low environmental temperature still reached up to that of the specimen cured by RT curing. Moreover, the compressive strength of the specimens cured at −60 °C retained >60 MPa despite reduced performance. Specifically, the specimens cured at −20 °C, −30 °C, −40 °C, and −50 °C for 2 days exhibited compressive strengths of 75.8 MPa, 79.2 MPa, 77.6 MPa, and 75.4 MPa, respectively. FTIR/XRD confirmed that the specimens cured by GJH showed hydration product integrity akin to RT-cured specimens. Moreover, it should be noted that early pore structure deteriorated with decreasing temperatures, but prolonged curing mitigated these differences. These results validate GJH as a viable method for in situ HPC production in extreme cold, addressing critical limitations of conventional winter construction techniques. Full article

This study investigates the coupled effects of waste rock-to-tailings ratio (WTR) and curing temperature on the pore structure and mechanical performance of cemented tailings waste rock backfill (CTRB). Four WTRs (6:4, 7:3, 8:2, 9:1) and curing temperatures (20–50 °C) were tested. Low-field nuclear magnetic resonance (NMR) was used to characterize pore size distributions and derive fractal dimensions ($D_a$, $D_b$, $D_c$) at micropore, mesopore, and macropore scales. Uniaxial compressive strength (UCS) and elastic modulus (E) were also measured. The results reveal that (1) the micropore structure complexity was found to be a key indicator of structural refinement, while excessive temperature led to pore coarsening and strength reduction. $D_a$ = 2.01 reaches its peak at WTR = 7:3 and curing temperature = 40 °C; (2) at this condition, the UCS and E achieved 20.5 MPa and 1260 MPa, increasing by 45% and 38% over the baseline (WTR = 6:4, 20 °C); (3) when the temperature exceeded 40 °C, $D_a$ dropped significantly (e.g., to 1.51 at 50 °C for WTR = 7:3), indicating thermal over-curing and micropore coarsening; (4) correlation analysis showed strong negative relationships between total pore volume and mechanical strength ($R$ = −0.87 for ${\mathsf{\delta }}_a\mathrm{v}\mathrm{s}.\mathrm{U}\mathrm{C}\mathrm{S}),$ and a positive correlation between $D_a$ and UCS (R = 0.43). (5) multivariate regression models incorporating pore volume fractions, $T_2$ relaxation times, and fractal dimensions predicted $\mathrm{U}\mathrm{C}\mathrm{S}$ and E with R² > 0.98; (6) the hierarchical sensitivity of fractal dimensions follows the order micro-, meso-, macropores. This study provides new insights into the microstructure–mechanical performance relationship in CTRB and offers a theoretical and practical basis for the design of high-performance backfill materials in deep mining environments. Full article

This study demonstrates the conversion of agricultural and industrial waste into construction materials by developing ultra-high-performance concrete using cold-bonded sesame ash and waste glass aggregates. The primary focus of this study was sustainability and waste valorization in self-curing concrete systems. This study focuses on many aspects of producing cementless concrete with superior short- and long-term properties, incorporating an innovative artificial aggregate premanufactured using sesame ash and waste glass. Prepacking technology of casting was used. A self-curing additive is used to reduce the energy required for curing. In cold-bonded aggregates (CBAs), the aggregate content ranged from 10 to 50% of the total sand volume. Polyethylene glycol was used as an internal curing agent to evaluate the mechanical properties of the concrete, including the compressive strength and tensile strength at different ages. The durability characteristics of the concrete were also analyzed in terms of its resistance to sulfates, chloride ion penetration, and performance at elevated temperatures of 300 and 600 °C. Microscopic analyses were conducted by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). The results showed a significant improvement in the mechanical and durability performance, especially at 30%, which resulted in the highest compressive strength of 147.2 MPa at 90 days. This is an 11.93% increase compared with that of the reference mix. The tensile strength was also improved by 14.5% at the same replacement ratio. The mix containing 30% manufactured aggregate demonstrated the best thermal resistance, retaining the highest percentage of residual strength at both 300 °C and 600 °C, as well as superior sulfate impact resistance, with a strength reduction factor of 39.5%. When the replacement ratio was increased to 50%, the chloride penetration resistance improved significantly by 41% compared with that of the reference mix. FTIR, TGA, and DSC analyses also demonstrated enhanced silicate polymerization and increased carbonate formation, contributing to the improved chemical stability and density of the concrete matrix. Full article

This study presents the synthesis of chitosan nanoparticles (CSNPs) using a microfluidic device. Microfluidic rapid mixing enables fast nucleation for small-sized nuclei, but a high PDI value like 0.956 shows uncontrollable growth of small nuclei, resulting in the formation of larger and more variable aggregates at room temperature. High temperatures play a key role in controlling the growth of CSNPs to enhance uniformity. Temperatures of 40 °C and 50 °C promote controlled interactions among small nuclei, while increasing the temperature to 80 °C further accelerated the curing process, suitable for synthesizing CSNPs with various sizes. At 80 °C, size regulation can be achieved by changing the TPP concentration, which controls surface curing and affects the size as well. These results emphasize the impact of elevated temperature and precise TPP concentration for product quality control and modulation in CSNPs’ synthesis. Full article

The utilization of steam-cured steel slag fine aggregate concrete (SC) faces challenges in accurately predicting its stress–strain relationship. The mechanical properties of steam-cured SC and its stress–strain relationship have been systematically investigated through combined tests and machine learning (ML) approaches. The results showed that steam curing at 50 °C greatly increased the peak stress and ductility of SC. Specimens, the steel slag fine aggregate (SA) content of which was 40% by volume, and which were subjected to steam curing at 50 °C, exhibited superior mechanical and deformation properties. The prediction performance of three ML models—random forest (RF), backpropagation neural network (BPNN), and support vector regression (SVR)—was compared based on the test data. The analysis results revealed that the RF model achieved optimal performance (R² = 1.00), whereas the SVR model underperformed overall. Through the transfer validation method, it was found that the BPNN model, after parameter optimization, demonstrated a superior generalization ability in cross-mix-proportion predictions. It exhibited satisfactory prediction stability for steam-cured SC with an untrained mix proportion. In contrast, the RF model tended to overestimate peak stress. The theoretical reference for realizing the comprehensive utilization of steel slag in precast concrete components has been provided. Full article

Epoxy resins (ERs) are esteemed for their mechanical robustness and adhesive qualities, particularly in steel bridge deck applications. Nonetheless, their intrinsic brittleness limits broader utility. This study addresses this limitation by modulating ER crosslink density through adjustments in curing agent concentration, incorporation of hyperbranched polymers (HBPs), and optimization of curing conditions. Employing a multi-objective optimization strategy, this research aims to enhance toughness while minimizing strength degradation. Non-isothermal curing kinetics, realized using the differential scanning calorimetry (DSC) method, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), tensile testing, and thermogravimetric analysis (TGA), were employed to investigate the effects of curing agent and HBP content on the curing reaction, mechanical properties, and thermal stability, respectively. Response surface methodology facilitated comprehensive optimization. Findings indicate that both curing agent and HBP contents significantly influence curing dynamics and mechanical performance. Curing agent content below 40% or above 50% can induce side reactions, adversely affecting properties. While a curing agent content exceeding 45% or an HBP content exceeding 5% improves the toughness of ER, these increases concurrently reduce mechanical strength and thermal stability. The study identifies an optimal formulation comprising 45.21% curing agent, a curing temperature of 60.45 °C, and 5.77% HBP content. Full article

In recent years, there has been a notable concern about the production of cementitious composites due to its high cement consumption and the corresponding carbon footprint. This has led to significant progress within the construction sector in integrating various waste materials as cement alternatives into cementitious composites. In this study, a sustainable high strength fiber reinforced mortar (HS-FRM) was designed with ceramic powder (CP) and metakaolin (MK) materials as partial replacements of the conventional HS-FRM by up to 80%. Magnetized water (MW) was used in the proposed HS-FRM as mixing water and replaced the normal tap water (TW) for producing a more sustainable and higher strength cementitious product. The HS-FRM was cured using four different curing methods, namely, tap water, seawater, air, and sunlight. Fresh, mechanical, durability, and microstructure characteristics were measured and analyzed for the proposed HS-FRM. The results showed that CP can enhance the slump of HS-FRM by up to 50% (achieved at 40% CP), while MK showed the same or less slump (by up to 33%) than that of the conventional HS-FRM. Using up to 80% of either CP or MK in the HS-FRM continuously decreased its 28-day compressive strength by up to 78% or 83%, respectively. The HS-FRM cured in tap water exhibited the highest compressive strength compared to the other curing conditions. The use of MW improved the workability of the HS-FRM by up to 225% and the compressive strength by up to 13%. The microstructure analyses interpreted the reported variation in the HS-FRM compressive strength and showed that using MW in the HS-FRM revealed a dense structure with an adequate bond between the fiber and the matrix with a relatively low number of micro-cracks and pores compared when using TW. The XRD analysis showed higher peaks of Q, C, and L with the presence of MW compared to mixtures made with TW. Full article