Determination and modelling of bond properties of synthetic macro-fibres in concrete

Bond behaviour of a synthetic macro-fibre in concrete is the object of this research. The bond strength and stiffness are the parameters characterising the bonding mechanism that determines the efficiency of the reinforcing material. However, there is no general methodology developed to evaluate fibre efficiency. There also exists neither a straightforward procedure to estimate the bond quality of a synthetic macro-fibre nor a reliable numerical model to simulate the bond behaviour of such fibres. In this work, the bond mechanisms of 40 mm long synthetic macro-fibres are investigated using pull-out tests: 16 concrete cubes were made for that purpose. One type of synthetic macro-fibre available at the market is considered. In each test sample, three fibres were inserted perpendicular to the top and two side surfaces; two bonding lengths (10 mm and 20 mm) were used. A gripping system was developed to protect the fibres from local damage. A physically non-linear finite element model of the pull-out sample was developed. A bond model was proposed to simulate deformation behaviour of the fibres. Article in English. Betono ir sintetinio makroplaušo sukibties savybių nustatymas ir modeliavimas Santrauka Šio tyrimo objektas – sintetinio makroplaušo sukibties elgsena betone. Sukibties stiprumas ir standumas yra parametrai, apibūdinantys sukibties mechanizmą, kuris lemia armatūrinės medžiagos efektyvumą. Tačiau nėra bendros metodikos, kuria būtų galima įvertinti plaušo efektyvumą. Taip pat nėra nei paprasčiausios sintetinio makroplaušo sukibties kokybės įvertinimo procedūros, nei patikimo skaitmeninio modelio, kuris imituotų tokių plaušų sukibties elgesį. Šiame darbe 40 mm ilgio sintetinių makroplaušų sukibties mechanizmai tiriami atliekant ištraukimo bandymus. Tam buvo pagaminta 16 betono kubelių. Išbandoma viena iš rinkoje esančių sintetinių makroplaušų rūšių. Kiekviename bandinyje trys plaušai buvo įgilinami statmenai viršutiniam ir dviem šoniniams paviršiams. Buvo naudojami du įgilinimo ilgiai (10 mm ir 20 mm). Sukurta įtvirtinimo sistema, apsauganti plaušus nuo vietinių pažeidimų. Buvo sukurtas fiziškai netiesinis iš betono ištraukiamų plaušų baigtinių elementų modelis, pasiūlytas sukibties modelis, siekiant imituoti plaušų elgseną deformuojantis. Reikšminiai žodžiai: sintetiniai plaušai, ištraukimas, bandymas, sukibties elgsena, skaitmeninis modeliavimas

Investigation and Improvement of Bond Performance of Synthetic Macro-Fibres in Concrete

Strength and stiffness are the key parameters characterising the bond performance of fibres in concrete. However, a straightforward procedure for estimating the bond parameters of a synthetic macro-fibre does not exist. This study employs pull-out tests to investigate the bond behaviour of synthetic macro-fibres. Two types of macro-fibres available in the market were investigated. A gripping system was developed to protect the fibres from local damage. The experimental campaign consisted of two stages. At the first stage, 32 concrete specimens were manufactured for performing 96 pull-out tests (three fibre samples were embedded in each cube perpendicular to the top surface and two sides). Two types of macro-fibres with either 10 or 20 mm embedment length were tested. The obtained load–displacement diagrams from pull-out tests demonstrate that the bond performance (characterised by the strength and deformation modulus) of the “top” fibres is almost 20% weaker than fibres positioned to the side surfaces. At the second stage, one type of macro-fibre was chosen for further experimentation of the feasibility of improving the bond performance through the use of colloidal silica or steel micro-fibres. This investigation stage employed an additional 36 concrete specimens. The use of steel micro-fibres was found to be an efficient alternative. The success of this solution requires a suitable proportioning of the concrete

Investigation and Improvement of Bond Performance of Synthetic Macro-Fibres in Concrete

Strength and stiffness are the key parameters characterising the bond performance of fibres in concrete. However, a straightforward procedure for estimating the bond parameters of a synthetic macro-fibre does not exist. This study employs pull-out tests to investigate the bond behaviour of synthetic macro-fibres. Two types of macro-fibres available in the market were investigated. A gripping system was developed to protect the fibres from local damage. The experimental campaign consisted of two stages. At the first stage, 32 concrete specimens were manufactured for performing 96 pull-out tests (three fibre samples were embedded in each cube perpendicular to the top surface and two sides). Two types of macro-fibres with either 10 or 20 mm embedment length were tested. The obtained load–displacement diagrams from pull-out tests demonstrate that the bond performance (characterised by the strength and deformation modulus) of the “top” fibres is almost 20% weaker than fibres positioned to the side surfaces. At the second stage, one type of macro-fibre was chosen for further experimentation of the feasibility of improving the bond performance through the use of colloidal silica or steel micro-fibres. This investigation stage employed an additional 36 concrete specimens. The use of steel micro-fibres was found to be an efficient alternative. The success of this solution requires a suitable proportioning of the concrete.This article belongs to the Special Issue Advanced Composites: From Materials Characterization to Structural Application (Second Volume)This project has received funding from the European Regional Development Fund (Project No. 01.2.2-LMT-K-718-03-0010) under grant agreement with the Research Council of Lithuania (LMTLT). The APC was funded by Vilnius Tech