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The flexural behaviors and mechanism of wollastonite microfiber modified ultra-high performance concrete with steel fiber from micro to macro scale

Zeng Deming, Cao Mingli

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e32, 2022

EN

Wollastonite microfiber (WF) is a naturally occurring calcium silicate (CaSiO3) produced in fibrous form and often used in ceramic industry as a cheap and valuable mineral. It is tried to be applied in ultra-high performance concrete (UHPC) in this study with expectation to improve the flexural performance and compensate for the deficiencies of steel fiber in enhancing UHPC from micro scale. The effects of WF on the flexural behaviors of UHPC with or without steel fibers were explored. The bonding behaviors of steel fiber in WF-modified ultra-high performance concrete (WFMUHPC) under different curing conditions were researched combined with single fiber pull-out tests. The results showed that WFs could significantly resist and delay the formation of microcracks in UHPC. When WFs were added to UHPC with steel fiber, the flexural properties of concrete were significantly improved from micro to macro scale. Accelerated curing contributed to the flexural strengths but deteriorate the toughness of WFMUHPC with steel fiber. The presented load–deflection curves proved that WFs had a significant improvement of first crack load and there were post-peak curve gaps because of the reinforcing effect of WFs on the frictional sliding behavior of steel fiber. The results of X-ray diffraction and scanning electron microscope showed that WFs had the bridging and filling effect and improved the interfacial transition zone between WFs and matrix. Meanwhile, the combined effect between WFs and high temperature that WFs provided sites for hydration products from cement particles and active minerals including silica fume and fly ash further improved the flexural behaviors. Moreover, a flexural strength model established could accurately describe the reinforcing effect of WFs on this particular UHPC and was expected to provide guidance for practical engineering applications.

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Effect of polymer fibers on pore pressure development and explosive spalling of ultra-high performance concrete at elevated temperature

Zhang Dong, Chen Baochun, Wu Xiangguo, Weng Yiwei, Li Ye

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e187, 2022

EN

This paper investigated pore pressure development of ultra-high performance concrete (UHPC) included various polymer fibers, i.e., linear low-density polyethylene (LLDPE), ultra-high molecular weight polyethylene (UHMWPE), polypropylene (PP), polyester (PET), and polyamide (PA) fibers. Temperature and pore pressure were measured simultaneously at different depths of UHPC specimens subjected to one-dimensional heating. It was found that the PP and PA fibers prevented spalling of UHPC by enhancing moisture migration, which resulted in the development of pore pressure in the deeper region of the specimens. The moisture migration in UHPC with LLDPE fibers caused spalling of a layer of concrete in a deep region of specimen. UHMWPE fibers did not affect pore pressure development and spalling resistance of UHPC significantly, while with PET fibers, the pore pressure of UHPC raised sharply due to inadequate moisture migration, leading to spalling of a whole layer. Instead of melting polymer fibers and empty channels left, microcracks created by the fibers were responsible for releasing vapor pressure and spalling prevention. Fibers with high thermal expansion between 100 and 200 °C are recommended for spalling prevention of UHPC.

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Nowoczesne kierunki rozwoju technologii betonu

Kostrzanowska-Siedlarz A.

Magazyn Autostrady

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2017

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Nr 4

60--65

PL

W artykule przedstawiono aktualne osiągnięcia w dziedzinie technologii betonu oraz podjęto próbę analizy rozwoju kierunków technologii betonu. Czy w przyszłości będzie można wyobrazić sobie drogi bez konieczności napraw? Mosty, które przez cały okres użytkowania wyglądają jak nowo wybudowane i ostrzegają o niebezpieczeństwach oraz permanentnie monitorują ruch? A budowa będzie przebiegała w wydruku 3D z ograniczeniem całego tradycyjnego zaplecza budowy? Faktem jest, że jednoznaczne odpowiedzi na powyższe pytania są trudne, z uwagi na postęp badań nad różnymi technologiami betonu, ale mam nadzieję, że przedstawione w artykule informacje pozwolą na przybliżenie technologii i problemów badawczych podejmowanych na świecie.

EN

The article presents the latest achievements in the field of concrete technology and attempts to analyze the directions of the concrete technology development. Will it be possible to imagine a road with no need to repair in the future? Bridges that look like newly built for their entire lifetime, that warn about dangers and permanently monitor traffic? A construction using 3D printing without the whole traditional construction site facilities? The fact is that unambiguous answers to these questions are difficult due to the progress of the research on different concrete technologies, but I hope the information presented in this paper will allow to approach these technologies and research problems undertaken in the world.