Fracture energy of natural fibre reinforced concrete

2013 ◽  
Vol 40 ◽  
pp. 991-997 ◽  
Author(s):  
I. Merta ◽  
E.K. Tschegg
Author(s):  
Ana Caroline Da Costa Santos ◽  
Paul Archbold

Fibre-reinforced concrete (FRC) is widely employed in the construction industry, with assorted fibre types being used for different applications. Typically, steel fibres give additional tensile strength to the mixture, while flexible fibres may be used in large sections, such as floor slabs, to control crack width and to improve the handling ability of precast sections. For many reasons, including durability concerns, environmental impact, thermal performance, etc, alternatives to the currently available fibres are being sought. This study examines the potential of using basalt fibres, a mineral and natural material, as reinforcement of concrete sections in comparison to steel fibres and plain concrete mix. Mixes were tested containing 0.5% and 1.0% of basalt fibres measuring 25mm length, 0.5% of the same material with 48mm length and steel fibres measuring 50mm by 0.05%, 0.1%, 0.15% and 0.2% of the concrete volume. For the mechanical performance analysis, the 3-point bending test was led and the fracture energy, Young’s modulus and tensile strength in different moments of the tests were calculated. When compared to the control mixtures and the steel-fibre-reinforced concrete, the mixes containing basalt had a reduction in their elastic modulus, representing a decrease in the concrete brittleness. At the same time, the fracture energy of the mixtures was significantly increased with the basalt fibres in both lengths. Finally, the flexural strength was also higher for the natural fibre reinforced concrete than for the plain concrete and comparable to the results obtained with the addition of steel fibres by 0.15%.


2012 ◽  
Vol 19 (4) ◽  
pp. 373-380 ◽  
Author(s):  
Fuat Köksal ◽  
Yuşa Şahin ◽  
Ahmet Beycioğlu ◽  
Osman Gencel ◽  
Witold Brostow

AbstractIn this study, we worked to estimate the fracture energy of steel fibre-reinforced concrete (SFRC) according to the water/cement ratio (w/c), tensile strength of steel fibre, steel fibre volume fraction and flexural strength of concrete sample as inputs using the Mamdani-type fuzzy inference system (FIS). In the study, the values obtained from the model and experimental divided three groups (each group has six experimental results) according to the w/c ratios to evaluate the fuzzy logic (FL) model approximate reasoning ability. As a result, the Mamdani-type FIS has shown a satisfying relation with the experimental results and suggests an alternative approach to evaluate the fracture energy estimation using related inputs.


The demerits of plain concrete are its lesser tensile strength, not significant ductility and poor resistance to cracking. Due to propagation of internal micro cracks in plain concrete causes decrease in tensile strength, hence leads concrete to brittle fracture. Addition of fibres behaves like crack arrester and enhances the dynamic properties of concrete. In India natural fibres such as bamboo, coir, jute, sisal, pineapple, banana, ramie etc are high available. Jute is a useful natural fibre for concrete reinforcement due to its easy availability and low cost. In this research, the experiments related to Jute fibre reinforced concrete (JFRC) are done by taking different fibre percentage and the compressive strength and modulus of rapture value observed. This JFRC can replace plain concrete and wood in many cases for example in door and window panels, inclined roof slabs, partition walls etc


2021 ◽  
Author(s):  
Hesham Othman

The next generation of concrete, Ultra-High Performance Fibre Reinforced Concrete (UHP-FRC), exhibits exceptional mechanical characteristics. UHP-FRC has a compressive strength exceeding 150 MPa, tensile strength in the range of 8-12 MPa, and fracture energy of several orders of magnitudes of traditional concrete. The focus of this research is to investigate and analyze the advantage of using UHP - FRC in impact resistance structures. To achieve these goals, two experimental testing programs and major numerical investigations have been conducted. The material experimental investigation has been conducted to determine the effects of strain rate on UHP - FRC. Two parameters are investigated, namely: compressive strength (80, 110, 130, and 150 MPa); and steel fibre content (0, 1, 2, and 3%). Experimental results showed that the rate sensitivity decreases with the increase in the compressive strength ; and the dynamic enhancement of tensile strength is inversely proportional to the fibre content. The structural impact testing program focuses on the dynamic response of full - scale reinforced concrete plates as well as generating precise impact measurements. Twelve reinforced plates with identical dimensions are tested under high-mass low-velocity multi-impacts. The investigated parameters include: concrete type (NSC, HSC, and UHP - FRC), fibre volume content, and steel reinforcement ratio. The results showed that the use of UHP -FRC instead of NSC or HSC is able to change the failure mode from punching to pure flexural; and UHP -FRC containing 3% fibre has superior dynamic properties. For plates with identical steel reinforcement, the total impact energy of UHP-FRC plate containing 3% fibres is double the capacity of UHP - FRC plate containing 2% fibres , and 18 times the capacity of NSC plate. A three-dimensional finite element analysis has been performed using ABAQUS/Explicit to model multi-impacts on RC plates and the applicability is verified using existing experimental data. Concrete damage plasticity (CDP) model is adapted to define UHP - FRC. The CDP constitutive model parameters for the new material are calibrated through a series of parametric studies. Computed responses are sensitive to CDP parameters related to the tension, fracture energy, and expansion properties. The analytical results showed that the existing CDP model can predict the response and crack pattern of UHP - FRC reasonably well.


2020 ◽  
Vol 309 ◽  
pp. 240-245
Author(s):  
Martin Tipka ◽  
Jitka Vašková

The paper deals with possible ways of defining the material model of fibre reinforced concrete as a material for structural design. The material model is a tool that can be used to describe response of material to the applied load. It usually includes several different parameters: strengths, ultimate deflections, deformation modules, fracture energy, etc. The paper deals with the problematic phases of tests that are necessary to create a material model, but which may not always provide relevant data. Due to the nature of the material (a fibre reinforced composite with a relatively brittle matrix), it is necessary to analyse separately the behaviour of the material before and after cracks when creating the material model.


1994 ◽  
Vol 21 (1) ◽  
pp. 89-100 ◽  
Author(s):  
Cheng Yan ◽  
Sidney Mindess

The bond between epoxy-coated reinforcing bars and concrete under static, high strain rate, and impact loading was studied for plain concrete, polypropylene fibre reinforced concrete, and steel fibre reinforced concrete. The bond stress, slip, crack development, the bond stress–slip relationship, and the fracture energy during the bond-slip process were investigated experimentally. The results were compared with those for uncoated reinforcing bars. It was found that for epoxy-coated rebars, the bond resistance decreased, in terms of the maximum local bond stress and the average bond stress; wider cracks developed during the bond process; and the fracture energy during bond failure decreased. It was also found that the influence of epoxy coating on the bond behaviour for push-in loading was much more significant than for pull-out loading. However, steel fibre additions at a sufficient content, and higher concrete strength, can mitigate the above effects to a considerable degree. Polypropylene fibres were much less effective in this regard than steel fibres. Key words: epoxy-coated rebars, bond, fibre concrete, strain rate, impact steel fibres, polypropylene fibres, concrete, high strength concrete.


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