Tensile Strength Of Fibre Reinforced Concrete Research Articles

Investigation of pull-out and mechanical performance of fibre reinforced concrete with recycled carbon fibres

This paper presents the pull-out bonding behaviour and mechanical performance of recycled carbon fibre (rCF) reinforced concrete based on the recent investigation of fibre reinforced concrete (FRC) with rCF recovered from pyrolysis. Single fibre pull-out tests have been carried out to identify the apparent interfacial shear strength of different types of rCF and virgin carbon fibre (vCF) to identify the fibre matrix connection. Furthermore, a series of tests have been carried out to identify the workability, compressive strength and tensile strength of FRC. Besides rCF, also vCF and steel fibre were used for fabrication of FRC test specimens. rCF have shown the same adhesion behaviour and strength like vCF. Furthermore, the use of unsized or acrylate-based sized rCF creates an adhesion between fibre and matrix material. During the pull-out tests, the failure does not occur as an adhesive crack between fibre and cement matrix, but as a cohesive crack in the cement matrix. The mechanical performance of FRC with rCF was compared with mortar and FRC with vCF and steel fibres. The results of compressive test conducted for FRC with vCF and rCF indicated that the influence of vCF and rCF on the compressive strength of FRC was insignificant. On the other hand, the results of tensile test conducted for FRC with vCF and rCF indicated that the tensile strength of FRC with rCF was at least 14.9% greater than that of FRC with vCF.

Efficacious application of data-driven machine learning models for predicting and optimizing the flexural tensile strength of fiber-reinforced concrete

In the literature, a limited number of studies have utilized the random forest (RF) technique to model the flexural tensile strength (FTS) of steel fiber reinforced concrete (SFRC). This study established modeling of the FTS of SFRC containing mono-fibrous (exclusively crimped and hooked) systems. A comprehensive database of 193 records was used from 18 published studies (including 30 documents sampled by authors). Machine-learning numerical models were developed and evaluated. Partial dependence plots were constructed to visualize the relationship between the model parameters and rank the parameters based on their importance. It has been found that the RF model can be rationally used to predict and optimize the FTS of SFRC, as most of the predicted–tested results were close to the ± 80% accuracy range. The model showed of underestimation nature for SFRC with high FTS values. The Gini index-based importance analysis showed that the fiber’s content and tensile strength had the highest significance among the other variables. A drastic increase in the FTS by an increase in the fibrous dosage was achieved. However, no major SFRC’s tensile strength enhancement for dosages was more than 1.5%, while its optimum diameter was 0.5–0.7 mm. The results also illustrated that the effect of the fiber’s length is quite similar to that of the fiber content. However, no significant increase can be achieved by increasing the fiber’s length from 40 to 60 mm.

Applicability of Large-Scale Direct Tension Specimens to Quantify Tensile Strength of Fiber-Reinforced Ultra-High-Performance Concrete

Abstract In this study, a large-scale direct tension specimen (minimum cross-sectional area of 11,000 mm2) was developed to determine its ability to quantify tensile behaviors of fiber-reinforced ultra-high-performance concrete. Direct tension specimens were successfully mixed and molded using readily available equipment in a typical construction materials laboratory. Results from large-scale direct tension tests were compared with results from commonly used indirect methods (i.e., splitting cylinder strength and double punch testing). At early ages, direct tensile specimens had a 0 % failure rate and recorded coefficient of variation values of 6.2 %. Computerized tomography scans from several sections within a large-scale specimen showed sufficiently random fiber orientation, particularly within the desired fracture region. Altogether, this effort showed that large-scale direct tension specimens were successfully able to quantify tensile strength of fiber-reinforced concrete; however, the effects of fiber orientation and boundary conditions on postcracking tensile strength of large-scale specimens need to be further evaluated in future efforts.

Inverse analysis-based model for the tensile behaviour of fibre-reinforced concrete with manufactured and waste tyres recovered fibres

The urgency of finding green solutions within the construction industry encouraged, in latest years, the adoption of sustainable materials for structural concrete. One of the most up-and-coming proposal is the use of recycled steel fibres, to complement or possibly replace traditional steel reinforcement. Nevertheless, the contribution of the fibres on the mechanical performance of concrete is still uncertain and requires further investigation. This study is aimed at providing an analytical model for the tensile response of concrete reinforced with manufactured steel fibres and recycled steel fibres recovered from waste tyres. The proposed model features several parameters ruling the cracking strength, the post cracking behaviour and the residual tensile strength of fibre-reinforced concrete. The parameters in the analytical model were calibrated by numerical simulation of toughness tests on specimens with different types and contents of fibres in the mixture. A satisfactory simulation of experimental load-crack tip opening displacement curves was obtained, with numerical-vs-experimental curve scatter lower than 10%. However, the variability of experimental results hindered obtaining an accurate blind simulation of additional tests selected from the literature. On the other hand, a clear correlation between the parameters ruling the cracking strength-to-residual strength ratio and fibres amount was identified for both recycled and manufactured fibres. The outcome of this study showed that the proposed model can be used in simplified design approaches, to account for the fibres’ type and content in the evaluation of tensile response of fibre reinforced concrete.

Neural network-aided prediction of post-cracking tensile strength of fibre-reinforced concrete

Structural fibres are an effective method to improve concrete post-cracking tensile strength (fctR). Currently, the characterization of this property is mainly performed experimentally. This is a source of uncertainties at design stages, which hinders the development of new fibre type and/or optimization of those currently existing. This paper presents a multilayer perceptron neural network to predict fctR of fibre-reinforced concrete (FRC) subjected to the Barcelona Test. The optimal architecture of the predictor is obtained by evaluating 9216 configurations of input dimension and number of hidden layers and neurons. The generalization performance is assessed using repeated random sub-sampling validation with 50 iterations. The final model can predict with high accuracy the fctR of FRC for different cracking stages. A parametric analysis is performed to prove coherence between the results predicted by the model and the established understanding of the FRC behaviour. Finally, numerical expressions are provided as an alternative tool to traditional testing to predict the residual strength of the Barcelona Test for pre-design and quality control purposes based on fibre dosage, concrete strength, specimen type and height and fibre geometric characteristics. These type of approaches are found to be necessary for boosting the development of the FRC technology.

Investigation on mechanical properties of fiber reinforced concrete

Concrete has high compression strength but low tensile strength. Therefore fibers are added to enhance the tensile strength. South Kalimantan is one of Indonesia’s largest wetlands, and the banana tree is common in this area. After harvesting, they are accumulated or be burned, causing pollution. Utilizing banana tree waste as fiber in the concrete minimizes it. This paper investigated the effect of banana fiber length and percentage of fiber by volume fraction on the compressive of mortar, tensile, and compressive concrete strength. The correlation between the compressive and tensile strength was further established. The percentage of fiber used in this research was 0.1%, 0.2%, and 0.3%, and the length of the fiber was 7cm and 15cm. The results showed that the addition of banana fiber significantly improved the mechanical properties of mortar and concrete. The compressive strength of mortar with a fiber length of 7cm was higher than 15cm. The higher percentage of fiber causes the lower compressive strength of mortar. The compressive strength of fiber-reinforced concrete was 27.9 MPa, and the ordinary concrete was only 17.91 MPa. The tensile strength of fiber-reinforced concrete was 6.96 MPa, while the ordinary concrete was just 1.93 MPa.

PROPERTIES OF THE STEEL-FIBER-REINFORCEDCONCRETE WITH DISPERSED REINFORCING WIRE FIBER FROM TECHNOGENIC WASTE

The article presents the results of theoretical and, most importantly, experimental studies of some properties of steel-fiber-reinforcedconcrete reinforced with dispersed reinforcement from industrial wastes, namely, ITEX steel wire fiber from SPA INNOTECH from spent steel ropes, a large number of which are used as raw materials for fiber production, has accumulated in the region with the mining industry (East Kazakhstan region). The result of the research was indicators of tensile strength of fiber-reinforced concrete during bending of samples, characteristics of crack resistance, and impact strength indicators of fiber-reinforced concrete reinforced with fiber from industrial waste. Knowing and demonstrating these characteristics will make it possible to more effectively ensure the possibility of selling a new product on the building materials market. This publication has been carried out as part of the sub-project Technology for Manufacturing Fiber from Technogenic Wastes, funded by the Government of the Republic of Kazakhstan and the World Bank, Project for Stimulating Productive Innovations.

Computational Model of the Tensile Strength of Fiber-Reinforced Concrete

We propose a model of deformation and fracture of a composite based on the cement matrix (fiber-reinforced concrete) in tension. The model takes into account the presence of microcracks and pores in the structure of the material and the presence of reinforcing fibers. The computational formulas are proposed for the evaluation of the tensile strength of fiber-reinforced concrete. We analyze the influence of porosity and the volume content of reinforcing fibers on the strength of the composite. The experimental investigations and calculations reveal a noticeable increase in the tensile strength with the volume content of the fibers. The theoretical predictions are in good agreement with the experimental data.

Strength of hollow circular steel sections filled with fibre-reinforced concrete

The strength of hollow circular steel sections filled with normal-strength plain concrete and fibre-reinforced concrete (FRC) was evaluated. First, the case of centrally loaded composite members was considered and the bearing capacity of the columns was calculated using the methods proposed by a European code (EC4) and an American code (LRDF). Some expressions in these codes were validated for the case of FRC by adapting experimental data to introduce the mechanical properties of the FRC. To do this, experimental results of standard tests on FRC (compression and splitting tension) were used as well as data on circular steel columns filled with 2% FRC by volume with different types of fibres (steel, polyolefin). Second, the moment - axial force diagrams for composite members, taking into account the residual tensile strength of FRC, were calculated, showing the advantages of using FRC compared with plain concrete for filling hollow steel sections.Key words: fibre-reinforced concrete, hollow steel columns, composite members, steel fibres, polyolefin fibres.

A New Test Method for Fiber-Reinforced Concrete

Abstract It has long been recognized that the principal benefit gained by using fiber reinforcement in portland cement concrete is a conversion of the material from brittle to relatively ductile behavior. The apparent ductility, or toughness, is primarily related to the improved tensile strength of fiber-reinforced concrete (FRC) especially and even after significant matrix cracking has occurred. However, the methods used to measure tensile strength and toughness of FRC have been, at best, elaborate and controversial. A practical and much needed testing methodology for fiber-reinforced concrete has been developed and adopted as an ASTM standard. It was conceived from the need to have a test that is relatively simple and inexpensive to conduct and is yet capable of assessing the tensile strength of cracked FRC. The test method, ASTM C 1399, and an interlaboratory testing program conducted to help formulate a precision statement for the new methodology is discussed.

Uniaxial tensile strength of early age fibre concretes

This study deals with the determination of uniaxial tensile strength of concretes reinforced withA-fibres (slag-basalt fibres) and glass-fibres at the age of 0,3 and 6 hours. For the determination of the tensile strength of fibre-reinforced concrete in its early age of setting and hardening a method was applied which was developped for the investigation of plain concretes.