In recent years, significant advancements in the development of large-scale 3D printers and construction materials have been made to meet the demand for industrial scale 3D printing construction. It is significant to construct the buildings and structural components by using 3D concrete printing. Additive manufacturing (AM) main benefits are freedom of design, construction waste reduction, mass customization, and ability to manufacture the complex structures. The major issues including the optimization of printing material which possess the suitable properties for 3D concrete printing. However, this technology towards the green building construction seems to improve the conventional methods by reducing the requirement of human resource, high investment cost, and formworks. The research community's interest in 3D printing for architecture and construction has grown significantly over the last few years. This paper review the latest trend of research and state of the art technologies in 3D printing in building and construction by analyzing the publications from 2002 to 2022. Based on aforementioned analysis of publications, printing methods, concrete printing systems and influence of constituent’s materials and chemical admixtures on concrete material properties are briefly discussed. Finally, this paper discussed the challenges and limitations of current systems, as well as potential future work to improve their capability and print quality.
In recent years, significant advancements in developing large-scale 3D printers and construction materials have been made to meet industrial-scale 3D printing construction demand. Constructing the buildings and structural components using 3D concrete printing is significant. The main benefits of additive manufacturing (AM) are freedom of design, construction waste reduction, mass customization, and the ability to manufacture complex structures. The major issues include optimizing the printing material with suitable properties for 3D concrete printing. However, this technology for green building construction seems to improve conventional methods by reducing human resource requirements, high investment costs, and formworks. The research community's interest in 3D printing for architecture and construction has grown significantly over the last few years. As a result, there is a need to combine existing and ongoing research in this area to understand better current problems and their potential solutions based on future research work. This paper reviews the latest trend of research and state-of-the-art technologies in 3D printing in building and construction by analyzing the publications from 2002 to 2022. Based on the above-mentioned analysis of publications, printing methods, concrete printing systems, and the influence of constituent materials and chemical admixtures on concrete material properties are briefly discussed. The challenges and recommendations of 3DCP, including reinforcement, development of new materials, multi-nozzle combinations, life cycle assessment of 3DCP, and development of hybrid systems, are then examined. This paper concluded with a discussion of the limitations of existing systems and potential future initiatives to enhance their capability and print quality.
Introduction: Large bowel obstruction due to colorectal carcinoma occurs in up to 20% of the patients and usually2-4 accompanied by morbidity and mortality . Almost 25 % deaths occur post-operatively following surgery for colorectal cancers occur in1 those who initially present with obstruction . Usually elderly patients with associated co-morbidities presents with bowel obstruction.Objective: Find out the frequency of colorectal cancers in patients presenting with large bowel obstruction. Design: Prospective crosssectional study. Setting: Shaikh Zayed Hospital Lahore. Period: from 31st December 2010 to 31st December 2012. Materials &Methods: A total 20 patients were presented with large bowel obstruction with the age ranges between 40 to 70 years. All the 20 patientsunderwent routine haematological and biochemical tests. In these patients an abdominal x-ray in a supine or standing position was takenand dilated loops of bowel, air-fluid interfaces, or both was observed then Contrast radiography(Barium/gastrograffin) was done todefine the site and extent of the obstruction. An abdominal computed tomography scan was done to evaluate the extent of the disease.Colonoscopy was also carried out in the patients with colorectal cancers to find out the size and location of the tumor and biopsy taken bycolonoscope. Results: 12 patients out of 20 presented with large bowel obstruction were diagnosed to have a colorectal cancers and theage ranges from 60 to 70 years. The 8 patients were diagnosed to have a sigmoid colonic tumour and 4 patients were suffering from atumour of recto sigmoid junction. Whereas in rest of the 8 patients the large bowel obstruction was due to other benign causes likevolvulus and intussusception and age range was 50 – 60 years. 6 patients were suffering from sigmoid volvulus and remaining 2 hadcolo-colic intussusception. Conclusions: It is concluded that the major cause of the large bowel obstruction is the left sided colorectalcancers the tumours of recto sigmoid junction.
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