Investigation of the Bond between Concrete Substrate and ECC Overlays

WOS: 000333451000020Rigid concrete overlays have been used for smoothing damaged surfaces and/or restoring or improving the mechanical capacity of bridge decks for many years. However, engineered cementitious composites (ECCs), which demonstrate superior ductility with high strength and improved durability characteristics, are an attractive alternative to conventional overlay materials if a strong mechanical bond is formed between the overlay and the substrate material. An experimental study was performed to evaluate the bond strength between ECC overlay and an ordinary concrete substrate with smooth and rough surface textures. Microsilica concrete (MSC), generally used as an overlay material, was also prepared as a control mixture. ECC and MSC overlay mixtures were cast over the concrete substrate to determine bonding performance. Slant shear and splitting prism tests were performed with MSC and two ECC mixtures. The experimental results show that when ECC is used as an overlay material, bond strength is significantly increased compared to MSC. Under compression loading (slant shear test), the bond-strength properties of layered ECC substrate concrete cylinder specimens were greater than the strength of substrate concrete with compressive strength of around 30MPa. However, in the case of layered MSC substrate concrete cylinder specimen, failure consistently occurred at the interface.Scientific and Technical Research Council (TUBITAK) of Turkey [MAG-112M035]; Gaziantep University Scientific Research Centre [MF.10.09]; Feyzi AKKAYA Scientific Activates Supporting Fund (FABED) Young Investigator Research AwardThe authors gratefully acknowledge the financial assistance of the Scientific and Technical Research Council (TUBITAK) of Turkey provided under project MAG-112M035, Gaziantep University Scientific Research Centre provided under project MF.10.09, and Feyzi AKKAYA Scientific Activates Supporting Fund (FABED) Young Investigator Research Award

High-early-strength ductile cementitious composites with characteristics of low early-age shrinkage for repair of infrastructures

Reduced performance in concrete infrastructures is mainly caused by the formation of cracks, which may arise due to deteriorating mechanisms during service life. In most cases, reduced performance calls for urgent repairs to the degraded section. Therefore, it is highly desirable to develop dimensionally stable, ductile repair materials that can attain adequately high strength in a limited amount of time, compensate for significant deformation due to mechanical and environmental loadings, and prevent early-age shrinkage cracks. In this paper, the performance of such a material (high-early-strength engineered cementitious composites, HES-ECC, with very low early-age shrinkage capacity) was investigated by studying mechanical properties and dimensional stability. Composites were produced with different water to cementitious materials and slag to Portland cement ratios. In order to enhance composite properties in terms of ductility and early-age shrinkage characteristics, saturated lightweight aggregates replaced sand in the mixtures. The experimental results show that the majority of HES-ECC mixtures developed in this study attained compressive strength values of more than 20.0 MPa and minimum flexural strength of 6.0 MPa within 6 h. Moreover, the HES-ECC mixtures exhibited strain-hardening behavior with strain capacities comparable to normal strength ECC, as well as substantially reduced autogenous shrinkage strain, both of which are unlikely to trigger the formation of cracks in tension at early ages. The integration of these conflicting parameters suggests that HES-ECC can easily meet the need for fast and durable repairs.Scientific and Technical Research Council (TUBITAK) of Turkey (MAG-112M035); Turkish Academy of Sciences, Young Scientist Award program; Feyzi AKKAYA Scientific Activates Supporting Fund (FABED) Young Investigator Research Awar

BOWEL OBSTRUCTION: IMAGING AND EMERGENCY MEDICAL MANAGEMENT

<p><i><strong>Introduction: </strong>Bowel obstruction develops when the regular flow of intraluminal contents is obstructed. Obstruction can occur in the small or large bowel, which can be either functional or mechanical. In nearly 80% of cases of mechanical intestinal obstruction, the small bowel is involved. Ischemia, which aggravates up to 42% of intestinal obstructions, considerably raises bowel obstruction-related mortality. Twenty percent of admissions involving "surgical abdomens" are due to bowel obstructions. Radiology is crucial for confirming the diagnosis and determining the root of the problem. Emergency management of bowel obstruction often comprises aggressive fluid resuscitation, bowel decompression, analgesic and antiemetic therapy when clinically necessary, and early surgical consultation.</i></p><p><i><strong>Aim of the Study: </strong>The purpose of this review is to familiarise radiology residents and other practitioners with the imaging findings indicative of intestinal blockage and to highlight problems necessitating emergency surgical intervention. The evaluation will concentrate on radiography and CT., which are the two most often utilized imaging techniques for suspected intestinal obstruction.</i></p><p><i><strong>Methodology:</strong>The review is a comprehensive research of PUBMED since the year 1997 to 2021</i></p><p><i><strong>Conclusion:</strong>Understanding the treatment of patients with small and large bowel obstruction is crucial for colon and rectal surgeons. For the majority of suspected intestinal blockages, computed tomography is typically the most suitable and accurate diagnostic imaging modality. Plain radiography and contrast imaging/fluoroscopy are two additional frequently used imaging modalities. Ultrasonography and magnetic resonance imaging are less often used imaging modalities. No matter the imaging modality employed, the interpretation of imaging should follow a methodical, systematic approach to guarantee diagnostic accuracy.</i></p><p><i><strong>Keywords:</strong>Bowel obstruction, small bowel obstruction, large bowel obstruction, imaging, computed tomography, abdominal radiography, contrast enema, small bowel follow-through, Ultrasound, magnetic resonance imaging, emergency treatment, etc.</i></p&gt