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Beton zbrojony włóknami pozyskanymi ze zużytych maseczek ochronnych

Szpetulski Jacek, Stawiski Bohdan, Michalska Klaudia

Przegląd Budowlany

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2024

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R. 95, nr 1-2

92--95

PL

Produkcja odpadów medycznych na świecie jest bardzo duża, co przekłada się na zaśmiecenie środowiska. W ostatnim czasie produkcja odpadów medycznych została znacznie zwiększona z powodu przeciwdziałania wirusowi SARS-CoV-2, który wywołuje chorobę zwaną COVID-19 i przyczynił się do powstania pandemii. W celu zapobiegania zarażeniu się wirusem SARS-CoV-2 stało się powszechne używanie maseczek ochronnych, a tym samym na wysypiskach przybyło w ogromnym stopniu odpadów w postaci zużytych maseczek. Wychodząc naprzeciw ochronie środowiska zaproponowano metodę przetwarzania maseczek ochronnych, w sposób umożliwiający ich powtórne użycie do produkcji fibrobetonu. W artykule zaprezentowano wyniki badań wytrzymałości na ściskanie i na rozciąganie betonu zbrojonego włóknami pozyskanymi ze zużytych maseczek ochronnych składających się z warstw włókniny polipropylenowej. Wyniki badań betonu zbrojonego włóknami stanowiącymi 0,05% objętości mieszanki betonowej oraz 0,2% objętości mieszanki betonowej porównano z wynikami betonu referencyjnego.

EN

The production of medical waste in the world is very large, which translates into environmental pollution. Recently, the production of medical waste has been significantly increased due to the counteraction of the SARS-CoV-2 virus, which causes the disease called COVID-19 and contributed to the creation of the pandemic. In order to prevent infection with the SARS-Co-V-2 virus, it has become common to use protective masks, and thus a huge amount of waste in the form of used masks has arrived in landfills. To meet environmental protection, a method of processing protective masks was proposed in a way that allows their reuse for the production of fiber-reinforced concrete. The article presents the results of testing the compressive of concrete and the tensile strength of concrete reinforced with fibers obtained from used protective masks consisting of layers of polypropylene non-woven fabric. The test results of concrete reinforced with fibers constituting 0.05% of the concrete mix volume and 0,2% of the concrete mix volume were compared with the results of the reference concrete.

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Retrofitting of heat-damaged fiber-reinforced concrete cylinders using welded wire mesh configurations

Abadel Aref A.

Materials Science Poland

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2024

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Vol. 42, No. 2

52--69

EN

Fire damage poses a significant risk to reinforced concrete structures throughout their lifespan. Fire exposure influences the stress-strain properties and durability of concrete, despite its non-flammability. Therefore, the strengthening approach is an economic option for lengthening their lifespan. This paper aims to conduct an experimental investigation into retrofitting heat-damaged fiber-reinforced concrete cylinders using welded wire mesh (WWM) configurations. Four concrete mixes were investigated. In total, 48 concrete cylinders were tested under axial compression until failure. The primary variables considered in the testing program consisted of (i) the influence of various fiber types (steel fiber (SF), polypropylene (PP), and hybrid fibers (SF+PP)); (ii) exposure temperature (26°C and 600°C); and (iii) WWM strengthening. Exposure to a temperature of 600°C led to a significant reduction in the compressive strength, ranging from 23.7% to 53.3%, while the inclusion of fibers has a substantial effect on the compressive strength of concrete, regardless of fiber type, with an increased ratio reaching up to 34.7%. The finding also clearly shows that the strengthening of heat-damaged specimens with WWM jacketing resulted in a 38.8%, 4.9%, and 9.4% increase in compressive strength for SF, PP, and SF+PPF specimens, respectively, compared to unheated control specimens. The suggested approaches to strengthening, which involve the use of WWM jacketing with two layers, successfully restored and surpassed the initial concrete compressive strength of the specimens that were damaged due to exposure to high temperatures.

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The properties and application of composite materials on the example of concrete with addition of steel and synthetic fibres

Mazewska Marta

Modern Engineering

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2023

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1

1--5

EN

The properties of fibre reinforced concretes are currently the subject of many studies due to the possibility of using that type of material in various fields of building engineering. The fibre reinforced concretes are composite materials, that consist of a concrete matrix and fibers. There are applied many kinds of fibres, for example made of steel, polypropylene or glass. The addition of fibers to the concrete has a beneficial effect on many of its features, including increased impact strength, reduced shrinkage and it also improves concrete strength. The paper presents the possibilities of using reinforced concretes with the addition of steel and propylene fibres.

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Mechanical properties of concretes modified with steel fibers and polypropylene

Helbrych Paweł

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2022

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nr 71 (143)

56--63

EN

This paper presents the effect of the addition of steel and propylene fibers on the mechanical properties of floor concretes (compressive and tensile strengths in the bending test). The polypropylene fibers used in the tests (fibrillated and single fibers) are dosed in the amount of 0.5 kg/m3 to 2 kg/m3 , and the straight and hooked steel is dosed from 10 kg/m3 to 25 kg/m3 . It is shown that, after 28 days of maturation, the highest compressive strength is achieved by concretes containing the addition of 25 kg/m3 of hook-like steel fiber. In addition, the influence of the fiber content on the consistency of the concrete mix and workability is investigated. It was shown that the amount of steel fibers dosed in the tests, regardless of their shape, did not adversely affect the consistency and workability of the concrete mix. On the other hand, the addition of polypropylene fibers has a significant impact on the characteristics of the concrete mix. The addition of 2 kg/m3 of polypropylene fibers caused the change of consistency from S4 to S1/S2 and worsened the workability of the mixture. All of the tested series of the concrete are created using the same technology. The concrete production technology reflects the concrete production technology for flooring concretes.

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Real fracture toughness of FRC and FGC: size and boundary effects

Elakhras A. A., Saleem M. H., Sallam H. E. M.

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e99, 1--17

EN

The present dilemma is how to simulate the real crack in full depth (FD) fiber-reinforced concrete (FRC), FD FRC, to get the actual fracture toughness of such fibrous composites, i.e., through-thickness pre-cracks are inappropriate for such materials. To overcome this dilemma, a new technique was adopted to create a pre-matrix crack (MC) without cutting the fibers bridging the two surfaces of the pre-crack. The main objective of the present work is to study the size and boundary effects on the real fracture toughness of MC-FD FRC and functionally graded concrete (FGC). Forty-eight MC-FD FRC and MC-FGC beams with three different span to depth ratios L/d equal 4, 5, and 6, and three different beam depths of the same beam span have been tested under three-point bending. All beams have the same pre-MC length to beam depth ratio (ao /d) of 1/3. Hooked end steel fibers of 1% fiber volume fraction produced FRC. FGC beams consist of three equal layers, FRC layer at the tension side, normal strength concrete layer at the middle of the beam, and high strength concrete layer at the compression side. The applied load versus all beams' crack mouth opening displacement (CMOD) curves have been analyzed. The present load/ CMOD results showed that beams having constant L/d ratios are recommended to capture independent size effect parameters. The size effect law (SEL) and boundary effect model (BEM) are good candidates to predict the size effect. According to the maximum non-damaged defect concept, the SEL is more reliable in predicting MC FD FRC fracture toughness than BEM.