Effect of fibre reinforcement on the crack width profile and internal crack pattern of conventionally reinforced concrete beams (original) (raw)
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Influence of Fibre Reinforcement on the Long-Term Behaviour of Cracked Concrete
RILEM Bookseries, 2016
The influence of fibre reinforcement on the long-term behaviour of cracked concrete is analysed in this work by means of a creep test. Nine concrete mixes were prepared (7 SFRCs and 2 conventional RCs) based on two basic mix designs. Concretes type I were conceived for structural precast applications and concretes type II reproduce a general purpose. Fibre dosages and conventional reinforcements were varied to represent a wide spectrum of post-peak flexural responses. In all cases with fibre reinforcement steel fibres were used. Conventional RC specimens were reinforced with two steel rebars. In addition to the variables of mix design of concrete, there are two significant variables related to the creep test: the pre-crack opening level (CMODpn) and the stress level (Ic) sustained during the test. Creep tests were performed by applying a constant flexural load on notched pre-cracked specimens and controlling crack opening evolution. Some of the specimens developed a sudden increase of crack opening deformations during the creep test. Creep coefficients and Crack Opening Rates were calculated and analysed. Creep coefficients show significant dependence on the analysed variables. The results of this experimental campaign show that creep of SFRC specimens may be similar to a traditional RC.
European Journal of Environmental and Civil Engineering, 2018
In the present experimental work, 28 reinforced concrete beams were manufactured and tested in bending under 2 concentrated loads. The beams, which were made in high strength concrete and in ordinary concrete for comparison purposes, had different quantities of fibres, with two aspect ratios. During the testing, a special attention was given to the monitoring of flexural cracking in terms of width, spacing and length, using a digital camera and Gom-Aramis software for the analysis of the recorded images. The measured crack widths were compared with theoretical values predicted by three major universal design codes for reinforced concrete, namely the American ACI 318, the British Standard 8110, the Eurocode 2, and by the technical document of Rilem TC 162-TDF. In the present experimental work, an amendment of the Rilem model, taking into consideration the three important parameters, namely the quantity of fibres, their orientation factor and their aspect ratio, is proposed. The predicted values of the crack width obtained by the modified Rilem model were compared with the test values and assessed against other experimental data on fibre-reinforced concrete beams taken from the literature. The results show that the modified Rilem model is fairly reliable in predicting the crack width of fibre-reinforced concrete.
New Procedure to Evaluate the Post-Crack Behavior of Fiber-Reinforced Concrete
Transportation Research Record: Journal of the Transportation Research Board, 2019
This study attempted to identify the challenges in testing and characterization of the post-crack behavior of structural fiber-reinforced concrete (FRC) for use in pavements. The benefits and challenges associated with three different FRC testing methods, ASTM C1550, C1399, and C1609 were discussed and compared. Two new parameters, post-crack toughness, and post-crack performance (PCP) index were proposed to characterize the post-crack behavior of FRC. These parameters are a function of the fibers’ contribution and are minimally influenced by the properties of the non-fiber ingredients of concrete such as aggregates, cement, and water. A laboratory study conducted on 10 different types of FRCs validated the applicability of the two proposed new parameters. Transportation agencies can use the PCP index to shortlist effective fibers and post-crack toughness to determine fiber dosage. The study found that fibers with irregular cross-section or geometry and high lateral stiffness provid...
1999
Durability studies are carried out by subjecting FRC-beams to combined mechanical and environmental load. Mechanical load is obtained by exposing beams to 4-point bending until a predefined crack width is reached, using a newly developed test setup. Exposure to a concentrated chloride solution is used as environmental load. The chloride penetration is characterized both qualitatively (UV-test) quantitatively (chloride profile) and by microscopy. The test programme involves three different concrete qualities. Both steel fibres and polypropylene fibres are used in the concrete beams as well as main reinforcement. The effect of the cracks, the fibres and the concrete quality on the chloride penetration is studied.
IJRASET, 2021
This The influence of fibre reinforcement on crack propagation in concrete was studied. Thirty-five double torsion specimens, made with three types of fibres (fibre glass , straight steel fibres and deformed steel fibres) were tested. The variables were the fibre volume and size of the fibres. The test results indicated that the resistance to rapid crack growth increased somewhat with increasing fibre content up to about 1.25%-1.5% by volume. The degree of compaction had an enormous effect on the fracture properties .The fracture toughness increased with fibre content up to about 1.25% by volume, and then decreased , due to incomplete compaction. It was found that in this test geometry, fibres did not significantly restrain crack growth. It was also observed that once the crack had propagated down the full length of the specimen, the system changed from a continuous system to a discontinuous system, consisting of two separate plates held together by the fibre reinforcement. Different types of fibres did not significantly affect the fracture toughness.
More efficient and industrialised construction methods are both necessary for the competitiveness of in-situ concrete and essential if the construction industry is to move forward. At present, the expenditure on labour (preparation and dismantling of formwork, reinforcing, and casting and finishing of concrete) almost equals the cost of material. Fibre-reinforced concrete (FRC) extends the versatility of concrete as a construction material, offers a potential to simplify the construction process and, when combined with self-compacting concrete, signifies an important step towards industrial construction. However, a barrier to more widespread use of FRC has been the lack of general design guidelines which take into account the material properties characteristic of FRC, i.e. the stress-crack opening (sigma-w) relationship. The presented work has been focused on FRC, showing a strain-softening response, and the interrelationship between material properties and structural behaviour. Thi...
Engineering Structures, 2020
The inclusion of fibres into concrete is now an accepted method of controlling crack widths. Several recently released design guidelines and codes of practice contain provisions which allow designers to predict the instantaneous crack widths in reinforced concrete members (containing fibre reinforcement) subjected to flexure. Most of these models have been developed for steel fibres, despite non-steel fibres representing a significant proportion of the fibres available in the marketplace. The current paper examines the results of flexural tests on 53 sets of beams reinforced with steel bars and fibre reinforced concrete. The specimens contained a wide range of fibre types, including steel, polypropylene, aramid, glass, basalt & PVA fibres. An assessment of available codified expressions for crack width estimation has been compared to measured crack widths presented herein. Despite satisfactory results, improved comparisons may be obtained by using the residual tensile strength of fibres at crack widths substantially smaller than is normally used, and by considering alternative expressions for the bond strength between steel reinforcing bars and fibre-concrete than are presently used in code models. 2. Experimental program The majority of test data used in this study were derived from tests
Effect of the Notch-to-Depth Ratio on the Post-Cracking Behavior of Steel-Fiber-Reinforced Concrete
Materials, 2021
Concrete barely possesses tensile strength, and it is susceptible to cracking, which leads to a reduction of its service life. Consequently, it is significant to find a complementary material that helps alleviate these drawbacks. The aim of this research was to determine analytically and experimentally the effect of the addition of the steel fibers on the performance of the post-cracking stage on fiber-reinforced concrete, by studying four notch-to-depth ratios of 0, 0.08, 0.16, and 0.33. This was evaluated through 72 bending tests, using plain concrete (control) and fiber-reinforced concrete with volume fibers of 0.25% and 0.50%. Results showed that the specimens with a notch-to-depth ratio up to 0.33 are capable of attaining a hardening behavior. The study concludes that the increase in the dosage leads to an improvement in the residual performance, even though an increase in the notch-to-depth ratio has also occurred.
International Journal of Concrete Structures and Materials
Improvement in fracture behaviour of fibre-reinforced concrete (FRC) due to the inclusion of various types and combinations of fibres is widely reported. The fracture behaviour of FRC needs to be fully understood for the optimum use of these fibres in structural elements. Fracture behaviours of synthetic fibre-reinforced concrete (SynFRC), hybrid fibre-reinforced concrete (HFRC) and steel fibre-reinforced concrete (SFRC) are investigated in this study using digital image correlation (DIC) technique. This work focuses on improvement in the structural performance of FRC through a comprehensive study of the change in the crack length, crack opening and fracture process zone (FPZ) due to different fibres addition and their combinations. Three distinct fibre dosages of 0.50%, 0.75%, and 1.00%, of macro-polyolefin fibres, hooked end steel fibres and their hybrid combination are regarded as research parameters. Test outcomes indicate that HFRC offers higher post-cracking resistance when co...