Using the efflorescence mechanism of portland cement to obtain a shiny calcium carbonate surface

This study presents a novel curing strategy to produce a smooth and shiny surface on Portland cement paste by controlling efflorescence. The proposed methodology consists of curing fresh cement paste in contact with a smooth, polystyrene mold, which modifies the boundary conditions at the cement–mold interface by limiting evaporation and promoting local moisture retention during early hydration. Although direct exposure to the atmosphere is restricted, carbon dioxide from the environment can still diffuse through the cement pore network and specimen edges. Under these conditions, calcium ion migration toward the interface is facilitated, leading to the controlled precipitation of a thin, calcium carbonate–rich surface layer. The surface and bulk evolution of the cement paste were investigated after 7, 14, and 28 days of curing using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface gloss measurements, and compressive strength testing. The analyses reveal the formation of a uniform near-surface region enriched in calcium-containing phases, while the bulk phase assemblage remains dominated by typical hydration products. Quantitative gloss measurements show an increase in surface reflectivity with curing time, reaching approximately 57 ± 1.3 gloss units after 28 days. Compressive strength results indicate that the formation of the shiny surface layer does not adversely affect the mechanical performance of the material. Overall, the results indicate that under the proposed curing conditions, controlled efflorescence could be harnessed as a surface engineering approach to obtain visually uniform and chemically stable surfaces without the use of additives or post-processing treatments

Investigating Iosipescu shear properties of laser powder bed fusion 316L stainless steel via digital image correlation technique

Laser Powder Bed Fusion (LPBF) has been widely adopted for producing stainless steel 316L components with complex geometries; however, despite extensive research on its tensile performance, the shear behavior of LPBF 316L remains insufficiently characterized. Reliable shear properties are crucial for structural components operating under multiaxial loading, yet experimental data enabling accurate calibration of multiaxial yield and failure models are still scarce. In this study, the tensile and shear responses of LPBF 316L were systematically investigated through standard uniaxial tensile testing and Iosipescu shear testing, supported by full-field Digital Image Correlation (DIC). All specimens were fabricated using LPBF system, and their build orientations were precisely documented to account for anisotropy effects. Tensile tests yielded an ultimate tensile strength of approximately 650 MPa and an average elastic modulus of 197 ± 32 GPa. Iosipescu shear tests demonstrated a maximum shear stress of 621 MPa, revealing a notably close relationship between shear strength and tensile strength. The experimentally measured shear modulus was also consistent with the tensile-derived value through classical elastic relations. The combined results deepen our understanding of LPBF 316L mechanical behavior, especially the coupling between tensile and shear responses. The findings further highlight the importance of integrating shear data into design procedures, multiaxial stress assessments, and material databases for additively manufactured stainless steels. Overall, this study provides a robust experimental foundation for improving structural integrity assessments and advancing the design of LPBF 316L components subjected to complex loading

Structural performance analysis of steel piled offshore platforms under environmental loads

Steel pile foundations used in offshore structures must be able to maintain their structural integrity and safety throughout the structure's service life under environmental effects such as waves, currents, and wind. In this context, this study conducts a detailed investigation of the structural performance of a steel-piled offshore platform under environmental wave loads with different return periods. Within the scope of the analysis, the behavior of a typical platform pile group was modeled and analyzed using the Sesam Genie software under wave loads with 1-year (operating), 100-year (extreme), and 10,000-year (abnormal) return periods, considering four different soil units (ZU1, ZU2, ZU3, and ZU4). The analysis determined the maximum internal forces acting on the piles (axial forces, lateral forces, and moments) as well as the maximum displacement values at the pile tips, which ranged between 0.012 m and 0.054 m depending on the load direction and return period. Furthermore, the maximum utilization factor (UF) for each pile was calculated, varying between 0.22 and 0.49, and compared against the minimum safety factors specified in the ISO 19902 standard. It was found that in all scenarios, the maximum utilization factors of the piles remained below the respective safety limits, and the horizontal displacements at the pile tips were within acceptable engineering levels. Unlike many previous studies focusing on single piles, this study systematically evaluates group pile behavior in layered soil conditions, providing more realistic insights into offshore foundation performance. In conclusion, this study highlights the importance of concurrently evaluating soil properties and environmental loads for the structural safety of steel pile foundations and contributes to the multifaceted engineering parameters that must be considered during the design phase

Mechanical properties assessment of recycled brick aggregate concrete using demolition waste from century-old masonry buildings in Nepal

This study explores the potential of recycling bricks from dismantled old buildings into brick aggregates and utilizing them as coarse aggregates in recycled brick aggregate concrete. Nepal, being susceptible to seismic events, generates large amounts of construction debris, with bricks being a major portion of this, which is mainly disposed of through landfilling. Additionally, the increasing use of reinforced cement concrete construction has been significant, which poses a toll on natural aggregate resources, resulting in the depletion of finite resources. To address these issues, this study focuses on recycling bricks as coarse aggregates in concrete. An experimental approach was adopted to determine properties of bricks and concrete ingredients, including cement, sand, brick aggregates, and coarse aggregates. The mechanical and physical properties of concrete, that is, compressive, split-tensile, and flexural strengths were studied by replacing natural coarse aggregates with recycled crushed brick aggregates at different percentages (0%, 10%, 20%, 30%, and 100%), denoted as B0%, B10%, B20%, B30% and B100%, respectively. Meanwhile, ultrasonic pulse velocity was performed to determine the quality of recycled brick aggregate concrete. With respect to the control mix (B0%), percentage decrease in compressive strength, tensile strength, and flexural strength for B10% and B100% are 0.72% and 28.26%, 4.68% and 25.16%, and 2.95% and 7.58%, respectively. From the ultrasonic pulse velocity, all mixes except B100% had excellent quality as per Indian Standards. Results highlight that recycled brick aggregate seems suitable up to 30% replacement, considering the strength decrement in compressive and flexural strengths relative to the control mix

Seismic hazard and risk analyses of historical masonry structures in Kocaeli, Türkiye

Protection of masonry structures is among the most important building groups around the world. Generally constructed of heavy materials such as stone and brick, these structures are highly seismically vulnerable. In large earthquakes, masonry structures that have not received adequate engineering services are usually heavily damaged or destroyed. To prevent damage to these structures, seismic hazard and risk analyses must first be conducted correctly. This study investigates the seismic hazards and risk distributions of historical masonry structures in Kocaeli, Türkiye. As a preliminary step, information and document collection studies on historical masonry structures were conducted in Kocaeli, Türkiye. Then, a detailed building inventory data set was prepared. Following that, a probabilistic seismic hazard assessment for the investigation area was conducted considering the different attenuation relationships. In the seismic hazard analyses, the hazard maps, hazard curves and response spectra were prepared based on the inventory data set at select reference points. After that, the seismic risk analyses were conducted to determine the structure distribution based on damage levels for the structures in the data set considering different fragility curves. Accordingly, historical masonry structures in Kocaeli province close to the North Anatolian Fault (NAF) Line have high hazard curves and spectrum values, whereas structures on the Black Sea coast have low values. According to the hazard maps obtained as a result of the analyses, Kartepe, Darica, Gölcük, and Başiskele districts have a high estimated hazard distribution, while Kandira has a lower estimated hazard distribution. Further, when the risk assessment is carried out by looking at the distribution of building groups based on damage levels, it was determined that towers, aqueducts, residential structures, and dome structures are the highest priority risk structures, respectively

Optimal metaheuristic design of CFRP wrapping for enhancing the shear capacity of reinforced concrete columns

Reinforced concrete (RC) columns are prone to brittle shear failure under lateral loads like earthquakes, especially in older structures. Carbon fiber reinforced polymer (CFRP) wrapping effectively enhances shear capacity, ductility, and energy dissipation. This study optimizes CFRP jacket design to increase shear strength while minimizing material volume per meter of column. The objective function includes the number of layers (n), strip width (Wf), spacing (Sf), and thickness (tf), following ACI 440.2R-2017 and ACI 318-05 constraints on strain, shear contribution, and capacity. Three metaheuristic algorithms—JAYA, Teaching-Learning-Based Optimization (TLBO), and Flower Pollination Algorithm (FPA)—were used to solve the nonlinear problem in MATLAB with randomized populations, 100–500 iterations, and 30 independent runs. Analyses for 100–500 kN shear demands (20%–100% increases) yield valid designs. Low shear demands typically require minimal CFRP, often a single layer with moderate strip width and large spacing. Higher demands required more intensive reinforcement through increased layer count and reduced spacing, with width adjustments as needed to satisfy code constraints. FPA achieved the lowest CFRP volumes due to its Lévy-flight global search, TLBO produced the most stable results with low variability, and JAYA offered the fastest computation. Increasing iteration count and population size improved convergence in all algorithms, yielding solutions closer to the optimum. Results confirm that metaheuristics enable economical, reliable CFRP retrofitting, promoting sustainability. Future work could include multi-objective optimization for cost and constructability

The predictive impact of perioperative hypofibrinogenemia on re-exploration in cardiac surgery: Insights from a single-center analysis

Background: Postoperative bleeding in cardiac surgery is a serious complication associated with increased morbidity, mortality, and healthcare costs. The objective of this study was to identify independent risk factors for re-exploration due to bleeding in patients undergoing cardiac surgery, with a particular emphasis on the predictive role of perioperative hypofibrinogenemia.Methods: In this single-center retrospective observational cohort study, a total of 593 consecutive adult patients who underwent cardiac surgery between January 1, 2025, and June 30, 2025, were retrospectively reviewed. The primary endpoint was surgical re-exploration for bleeding within 48 hours postoperatively. Demographic characteristics, comorbidities, laboratory parameters, surgical variables, and postoperative complications were recorded. Variables found to be significant in univariate analysis were further analyzed using multivariate logistic regression. The threshold value of postoperative fibrinogen for predicting re-exploration risk was calculated.Results: The overall re-exploration rate was 15.6%. Approximately 10% of cases were urgent surgeries. Independent risk factors identified in multivariate analysis were female sex (OR=2.7; p=0.001), age ≥65 years (OR=2.0; p=0.011), body mass index (BMI) outside the normal range (OR=2.7; p=0.002), preoperative fibrinogen <1.5 g/L (OR=3.7; p=0.007), and postoperative fibrinogen <1.5 g/L (OR=2.7; p=0.012). The ROC analysis for postoperative fibrinogen was statistically significant (AUC=0.691; 95% CI 0.629–0.752; p<0.001). The optimal cut-off was 2.06 g/L (Youden index=0.346), with 79.8% sensitivity and 54.8% specificity. Patients undergoing re-exploration had significantly longer ICU stays (p<0.001) and higher mortality rates (p<0.001).Conclusions: The risk of re-exploration in cardiac surgery is increased in association with female sex, advanced age, abnormal BMI, and particularly perioperative hypofibrinogenemia. A preoperative fibrinogen level <1.5 g/L emerged as the strongest predictor. These findings suggest that close monitoring of fibrinogen and early replacement strategies may play a critical role in reducing re-exploration rates

Perioperative factors associated with severe early postoperative pain after single-level lumbar discectomy: A retrospective cohort study

Background: Lumbar disc herniation is a frequent cause of radicular low back pain, and lumbar discectomy remains one of the most commonly performed spinal procedures when conservative treatment fails. Despite advances in surgical technique and perioperative management, postoperative pain—particularly during the early postoperative period—remains clinically relevant. Severe pain within the first 24 hours after surgery may delay mobilization, increase opioid requirements, and complicate recovery. However, perioperative factors associated with severe early postoperative pain following elective single-level lumbar discectomy remain incompletely understood.Methods: This retrospective cohort study included adult patients undergoing elective single-level lumbar discectomy under general anesthesia. Postoperative pain intensity was assessed using the maximum numeric rating scale score recorded within the first 24 hours. Severe pain was defined as a score ≥7. Demographic, operative, and analgesic variables, including operative duration, intraoperative opioid exposure (fentanyl equivalents), multimodal analgesia, and rescue opioid use, were analyzed. Univariable and multivariable logistic regression analyses identified factors independently associated with severe early postoperative pain.Results: Among 322 patients, 78 (24.2%) experienced severe early postoperative pain. Longer operative duration (adjusted odds ratio 1.38 per 10-minute increase), higher intraoperative opioid exposure (adjusted odds ratio 1.29 per 50 microgram increase), absence of multimodal analgesia (adjusted odds ratio 0.46), and post-anesthesia care unit rescue opioid administration (adjusted odds ratio 3.12) were independently associated with severe pain within the first 24 hours.Conclusions: Severe early postoperative pain after single-level lumbar discectomy is common and is influenced by perioperative factors. Optimizing multimodal analgesia and limiting intraoperative opioid exposure may improve outcomes

Walking the tightrope: Anaesthesia for fragile hearts and overactive glands in elderly hip surgery

Anesthetic management of elderly patients with ischemic heart disease, dilated cardiomyopathy with severe left ventricular dysfunction, and hyperthyroidism undergoing bipolar hemiarthroplasty presents unique challenges. Hyperthyroidism can exacerbate cardiac conditions, increasing perioperative risks. Preoperative optimization involves achieving euthyroid status using antithyroid medications and beta-blockers to control heart rate. A comprehensive cardiovascular evaluation is essential to manage heart failure and maintain hemodynamic stability. Severe pulmonary arterial hypertension further complicates anesthetic management due to increased perioperative morbidity and mortality. These patients are at higher risk for complications such as myocardial infarction and respiratory failure during anesthesia and surgery. Intraoperatively, regional anesthesia techniques may be preferred to minimize cardiovascular stress. Close monitoring of pulmonary pressures and ventricular function is crucial during the perioperative period. Postoperative care should focus on vigilant monitoring for potential complications, including thyroid storm, cardiac events, and exacerbation of pulmonary arterial hypertension. A multidisciplinary approach involving anesthesiologists, cardiologists, pulmonologists, and surgeons is essential to enhance surgical outcomes in such high-risk patients. In this case report, we present the combination of lumbar and sacral plexus blocks that we applied as the sole anesthesia method in a high-risk patient with multiple comorbidities undergoing bipolar hemiarthroplasty surgery

Failed labour epidural analgesia: mechanisms, risk factors and stepwise management: Guideline-based review

Bacgkround: Epidural analgesia is the most widely used neuraxial technique for labour pain management; however, inadequate or failed analgesia remains a frequent and clinically relevant problem. This review aims to summarise the mechanisms and risk factors associated with failed labour epidural analgesia and to present a stepwise management approach aligned with current European Society of Anaesthesiology and Intensive Care (ESAIC) guidance.Methods: A review of clinical guidelines, observational studies and interventional trials addressing labour epidural failure, breakthrough pain and rescue strategies was performed.Results: Failed labour epidural analgesia is a multifactorial condition involving catheter-related issues such as suboptimal insertion depth, migration, unilateral or patchy block and unintended catheter placement, in addition to maternal, obstetric and operator-related factors. Effective management requires structured reassessment of pain characteristics, labour progression, sensory block level, catheter position and infusion parameters. Stepwise rescue strategies, including catheter manipulation, patient repositioning and adjustment of local anaesthetic dosing, may restore analgesic efficacy. Persistent inadequacy necessitates timely senior review and early consideration of catheter re-siting or alternative neuraxial techniques.Conclusions: Early recognition and structured, stepwise management are essential for the effective treatment of failed labour epidural analgesia. Adherence to evidence-based guidelines, optimization of technical practice and appropriate organisational support may reduce failure rates and improve maternal outcomes