Performance-based Testing Methodology for Concrete Durability

This report presents an overview of performance based testing methodology for concrete durability and work currently underway jointly at Queens University Belfast and Heriot Watt University, Edinburgh, to undertake this research under a EPSRC funded project (EP/G02152X/1). EN206-1 superseded BS 5328 on 1st December 2003 and allows designers and producers to use a wide range of cements and aggregate types for a variety of exposure conditions. In this new standard, the durability of concrete is specified in terms of the constituent materials of concrete, properties of fresh and hardened concrete, limitations for concrete composition, specification of concrete, delivery of fresh concrete, production control procedures, conformity criteria and evaluation of conformity and verification of these properties. Within this, six basic forms of exposure is also specified, namely XO (no risk of corrosion), XC (Corrosion induced by carbonation), XF (Freeze / thaw attack), XS (Corrosion induced by chlorides from seawater), XD (Corrosion induced by chlorides other than from seawater) and XA (Chemical attack). According to EN206-1, the performance method adopted should be based on satisfactory experience with local practices in local environments from data obtained from an established performance test method for the relevant mechanism, or using appropriate proven predictive models. Therefore, the methods that may be used include those methods based on:- · long-term experience of local materials and practices and on detailed knowledge of the local environment. · approved and proven tests that are representative of actual conditions and have approved performance criteria. · analytical models that have been calibrated against test data representative of actual conditions in practice. The concrete composition and the constituent materials should be closely defined to enable the level of performance to be maintained. In order to determine the best methods for assessing concrete durability for performance, it is important to review those methods which have been developed and used in Queens University Belfast and Heriot Watt University to test for permeability, diffusion and absorption as well as electrical methods used to assess if the performance criteria have been achieved in structures using non-destructive testing methods. Prior to specifying durability performance testing methods, a review of previous projects where limits on permeability, diffusion, electrical resistivity etc, are presented along with the various durability tests used to assess these limits. The examples given are from a number of projects in the UK, Ireland and Europe of varying complexity and size. Due to the relatively small number of such examples in the UK and Ireland, the need for the research presented here is further justified. The proposed experimental work for the EPSRC project is presented which includes a breakdown of the concrete samples, tests and details of a new marine exposure site on the Northwest coast of Ireland. Based on the findings of this experimental work and the numerical calibration using the ClinConc model, development of a methodology for testing the concrete durability to assess the performance limits set will be determined. Through this work, the performance methods adopted will satisfy the EN206-1 guidelines above

Performance Monitoring of Cover-Zone Concrete

The concrete cover-zone is a major factor governing the degradation of concrete structures as it provides the only barrier to aggressive agents which initiate corrosion of the reinforcement. Knowledge of the protective qualities of cover-zone concrete is critical in attempting to make predictions as to the in-service performance of the structure with regard to likely deterioration rates for a particular exposure condition and compliance with specified design life. To this end, a multi-electrode array was used to study the surface 50mm of concrete specimens thereby allowing a detailed picture of the response of the covercrete to the changing environment. In the current work, CEM I, CEM II/B-V and CEM III/A cements were used and comprised field studies representing a range of exposure conditions

Comparison of surgical times of various total knee replacement techniques and assessment of learning curve of robotic total knee replacement: a retrospective study

Background: This study aims to compare the operating times of manual, computer-assisted and robotic- assisted TKA and to calculate the learning curve for image-less robotic-assisted TKA (RATKA). Methods: This retrospective observational study, conducted at the Centre of Excellence, Bone, Joint and Spine, Meitra Hospital, Kozhikode, Kerala, India, focused on patients aged 60 and above undergoing total                                                                       knee replacement for stage 4 osteoarthritis. The study included 75 consecutive cases of manual, computer- assisted, and robotic-assisted unilateral total knee arthroplasties performed between May 2021 and September 2022 (18 months). Data was collected from the hospital records. Results: The surgeon transitioned from learning to proficiency phase of RATKA after 14 cases. In the robotic learning phase, the overall operative time was 113.14 minutes (±8.96), significantly longer than the robotic proficiency phase's average of 98.24 minutes (±2.98) and that of CATKA (99.57±10.700 minutes) and manual TKAs (97.01±7.17 minutes). No statistically significant difference was observed in the global operative time between the proficiency phase RATKAs and the CATKA and manual groups (p=0.139). Conclusions: By optimizing techniques and modifying workflow, one can swiftly overcome the initial learning curve of RATKA and achieve operating times comparable to manual TKA. To enhance efficiency and productivity, the study proposes a revised workflow modifying various rate limiting surgical steps

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030