{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,10]],"date-time":"2026-01-10T02:27:39Z","timestamp":1768012059312,"version":"3.49.0"},"reference-count":35,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2024,7,6]],"date-time":"2024-07-06T00:00:00Z","timestamp":1720224000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Ministry of Science and Higher Education of the Republic of Kazakhstan","award":["BR21882278"],"award-info":[{"award-number":["BR21882278"]}]}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Buildings"],"abstract":"<jats:p>The present study investigates the flow characteristics of fly ash-based (FA) geopolymers reinforced with polypropylene (PP) fibers during the extrusion process in three-dimensional printing. By applying the Herschel\u2013Bulkley rheological model, this research provides a sound theoretical basis to understand the flow behavior of these materials under various conditions. The Herschel\u2013Bulkley model describes the relationship between shear stress and the shear rate in non-Newtonian fluids, capturing yield stress and flow consistency. A combination of experimental and numerical techniques based on the Finite-Element Method (FEM) in COMSOL has been used in this study. The results of both experimental and simulation approaches are compared to examine the material behavior during extrusion. The experimental results indicate that PP fiber content significantly affects the rheological properties. Mixtures with high fiber content encountered issues such as high static yield. However, mixtures with moderate fiber content showed smoother extrusion processes, suggesting an optimal fiber addition range that balances mechanical properties and extrudability. The numerical simulations generally agreed with the experimental data up to a certain fiber content level, beyond which more complex interactions necessitate further model refinements. The investigation identified a 0.25% to 0.5% fiber content range that enhances performance without complicating the extrusion process, facilitating the production of properly printed structures.<\/jats:p>","DOI":"10.3390\/buildings14072068","type":"journal-article","created":{"date-parts":[[2024,7,8]],"date-time":"2024-07-08T04:52:49Z","timestamp":1720414369000},"page":"2068","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["RETRACTED: A Comparative Study of the Rheological Properties of a Fly Ash-Based Geopolymer Reinforced with PP Fiber for 3D Printing: An Experimental and Numerical Approach"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2637-9704","authenticated-orcid":false,"given":"Bakytzhan","family":"Sariyev","sequence":"first","affiliation":[{"name":"Department of Mechanical and Aerospace Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan 010000, Kazakhstan"}]},{"given":"Alisher","family":"Konysbekov","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan 010000, Kazakhstan"}]},{"given":"Assel","family":"Jexembayeva","sequence":"additional","affiliation":[{"name":"Faculty of Architecture and Civil Engineering, Gumilyov Eurasian National University, Kazhymukan Str. 13 r205, Astana 010008, Kazakhstan"}]},{"given":"Marat","family":"Konkanov","sequence":"additional","affiliation":[{"name":"Faculty of Architecture and Civil Engineering, Gumilyov Eurasian National University, Kazhymukan Str. 13 r205, Astana 010008, Kazakhstan"}]}],"member":"1968","published-online":{"date-parts":[[2024,7,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"131614","DOI":"10.1016\/j.conbuildmat.2023.131614","article-title":"3D Printed Concrete: A comprehensive review of raw material\u2019s properties, synthesis, performance, and potential field applications","volume":"387","author":"Jindal","year":"2023","journal-title":"Constr. 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