TWISTED STEEL FIBER-REINFORCED CONCRETE FOR ENHANCED FLEXURAL STRENGTH AND DUCTILITY

Abstract

Abstract The present invention provides a method for reinforcing concrete using twisted steel fibers (TSF) to enhance tensile, flexural, and shear strength. Each TSF is constructed from two helically twisted steel wires, resulting in a fiber that maximizes bond strength and pull-out resistance within the concrete matrix. The method involves incorporating TSF at specific dosages into the concrete mix, achieving a uniform distribution that improves load-bearing capacity and reduces failure risks. The helical shape of the fibers provides mechanical interlock, transforming the failure mechanism to require more energy, which significantly increases structural performance. This fiber-reinforced concrete is ideal for load-bearing applications, offering a cost-effective alternative to traditional rebar. The method also includes a stress-block approach to accurately design and calculate the structural capacity of TSF-reinforced elements. TSF concrete offers improved durability, ductility, and resistance to multi-directional stresses, making it suitable for beams, slabs, pavements, and other critical structures. The figure associated with the abstract is Fig.1

Specification

Description:4. DESCRIPTION

Technical Field of the Invention

This invention relates to construction materials, specifically to fibre-reinforced concrete. More particularly, it focuses on a twisted steel fibre (TSF) design and its integration within concrete to enhance flexural strength, ductility, and overall structural integrity.
Background of the Invention

Concrete has long been the preferred material in construction due to its affordability, compressive strength, durability, and availability. However, despite these advantages, conventional cement concrete exhibits significant limitations in tensile strength and ductility. This inherent brittleness restricts its effectiveness in applications where tensile loads are expected. To address this, the concept of Reinforced Cement Concrete (RCC) was developed, where steel reinforcement bars (rebars) are embedded within the concrete to absorb tensile stresses. Although effective, RCC requires careful placement of steel, which is time-consuming, labor-intensive, and costly. Additionally, the design philosophy of RCC often neglects the concrete in the tension zones, reducing material efficiency.

In pursuit of a more effective solution, Fiber Reinforced Concrete (FRC) was introduced. FRC incorporates various fiber types-such as steel, glass, synthetic, and natural fibers-into the concrete matrix to improve tensile strength, crack resistance, and ductility. Fibers within the concrete matrix can bridge micro cracks, prevent crack propagation, and contribute to enhanced durability. However, despite these benefits, conventional FRC has limitations. The fibers often suffer from poor bond strength within the matrix, leading to inadequate load transfer between the concrete and fibers. Additionally, many fiber types lack the necessary stiffness and strength to contribute significantly to load-bearing applications, especially under flexural or shear stress.

Among the various types of fibers explored for FRC, steel fibers have shown the most promise due to their inherent strength and stiffness. Nonetheless, traditional steel fibers also face challenges with bond strength and resistance to pull-out forces under loading. Conventional straight steel fibers can slip out of the concrete matrix relatively easily, especially under high loads, limiting their ability to contribute to structural integrity in critical stress zones. To counteract these issues, researchers have experimented with various steel fiber shapes and surface profiles, such as hooked, crimped, or twisted profiles, to improve bond strength and frictional resistance. However, these approaches have not fully optimized the performance potential of fiber-reinforced concrete in flexural, tensile, and shear applications.

This invention addresses these challenges by introducing a novel Twisted Steel Fiber (TSF), specifically designed to maximize bond strength, load distribution, and structural efficiency within the concrete matrix. Unlike traditional straight or mildly deformed fibers, the TSF in this invention possesses a unique helical twist along its length, which significantly improves its interaction with the surrounding concrete. When embedded in the matrix, the TSF's helical profile creates frictional interlock and mechanical resistance, greatly enhancing its ability to resist pull-out under load. Each twist in the fiber effectively "locks" the fiber within the concrete, preventing premature slippage and ensuring that tensile forces are effectively transferred between the matrix and the reinforcement.

Brief summary of the Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

The primary objective of this invention is to provide a twisted steel fibre (TSF) for concrete that significantly improves bond strength and pull-out resistance, ensuring effective load transfer and reducing slippage.

Another key objective is to enhance the tensile and flexural strength of concrete, allowing for higher structural resilience and durability without the need for traditional rebar.

Another key objective is to o achieve uniform reinforcement within the concrete matrix, improving performance under complex loading and reducing failure risks.

Another key objective is to enable precise calculation of structural capacity with stress-block parameters tailored for TSF-reinforced concrete, aiding in more accurate design of load-bearing members.

According to an aspect of the present invention, a novel Twisted Steel Fibre (TSF) designed to reinforce concrete, enhancing its tensile strength, flexural capacity, and ductility. Unlike conventional straight or hooked steel fibres, the TSF in this invention is characterized by a unique helical profile. Each TSF fibre is formed from two thin steel wires twisted together into a single fibre, approximately 20 mm in length and 0.5 mm in diameter, creating a rigid yet flexible reinforcement with a highly effective mechanical interlock within the concrete matrix.

In accordance with the aspect of the present invention, the primary innovation of the TSF design is the twist pattern, which maximizes the bond strength between the fibre and the surrounding concrete. When concrete undergoes stress, such as bending or shear, the TSF fibres resist pull-out more effectively than conventional fibres due to their twisted shape. Each twist functions as a micro-anchor, which "locks" the fibre within the concrete and prevents slippage under load. This mechanism fundamentally changes the failure behaviour from a simple pull-out to a torsional or untwisting failure, which requires substantially more energy to occur. As a result, concrete reinforced with TSF exhibits superior resistance to cracking, increased load-carrying capacity, and improved structural resilience.

In accordance with the aspect of the present invention, a method of incorporating TSF into concrete, achieving a uniform distribution of fibres throughout the matrix. The recommended dosage of TSF varies according to the grade and intended application of the concrete. For example, a dosage of 0.45% TSF by volume has been found to deliver optimal improvements in tensile and flexural performance in M20 grade concrete. When uniformly mixed, the TSF fibres align randomly within the concrete, providing reinforcement in all directions, which is particularly beneficial in applications where multi-directional stresses are anticipated.

In accordance with the aspect of the present invention, the TSF-reinforced concrete exhibits notable improvements in several critical performance parameters:
• Tensile Strength: The addition of TSF fibres significantly increases the tensile strength of concrete, particularly in low-to-medium strength grades. For M20 concrete, a 0.45% dosage of TSF increases tensile strength by approximately 156% compared to standard concrete.

• Flexural Strength: TSF's helical profile also enhances flexural performance by increasing the concrete's resistance to bending loads. This improvement is quantified through moment resistance coefficients, which rise with increasing TSF dosage, demonstrating the effectiveness of TSF in carrying bending moments.
• Shear Strength: TSF-reinforced concrete provides enhanced resistance to shear stresses, a crucial factor in preventing brittle failure under load. The twisted fibres add frictional resistance, enabling the concrete to resist shear forces more effectively.

In accordance with the aspect of the present invention, a method for calculating structural capacity using TSF in reinforced concrete. By establishing stress-strain models for TSF concrete in both compression and tension, stress-block parameters are derived to facilitate accurate design of flexural members such as beams and slabs. This approach allows for the design of concrete structures with higher load-bearing capacities and ductility while reducing dependency on traditional steel reinforcement.

In accordance with the aspect of the present invention, a cost-effective and practical solution for enhancing concrete performance in a wide range of structural applications. The TSF design reduces the need for rebar, simplifies construction, and provides a more efficient alternative to conventional reinforcement methods. TSF-reinforced concrete is ideal for structural components subjected to flexural and tensile loads, including beams, columns, slabs, and other critical elements in infrastructure, residential, and commercial construction.

Further objects, features, and advantages of the invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.

Brief Summary of the Drawings

The invention will be further understood from the following detailed description of a preferred embodiment taken in conjunction with an appended drawing, in which:

Fig. 1 illustrates the flowchart representing the method for enhancing concrete performance using twisted steel fibers (TSF), in accordance with an exemplary embodiment of the present invention.

Detailed Description of the Invention

The detailed description of the invention presents a comprehensive view of an automated system designed to revolutionize the production of short news videos, primarily for consumption on digital platforms such as social media. The invention significantly automates the production process, integrating advanced technological components that streamline operations from the capturing of footage to the editing and publishing stages.

According to an exemplary embodiment of the present invention, a novel Twisted Steel fibre (TSF) for reinforcing concrete, aiming to improve its structural performance, particularly in terms of tensile strength, flexural capacity, and ductility. The TSF design addresses key limitations of traditional reinforced and fibre-reinforced concrete by enhancing bond strength, increasing load resistance, and improving ductility in concrete structures. The invention includes a unique twisted fibre configuration, methods for integrating TSF into concrete, and comprehensive calculation methods for designing structural elements using TSF-reinforced concrete.

In accordance with the exemplary embodiment of the present invention, the Twisted Steel Fiber (TSF) is designed to achieve maximum bonding with the concrete matrix and prevent slippage during loading. Each TSF fiber is constructed from two thin steel wires twisted along a helical axis, forming a single fiber with a total diameter of 0.5 mm and a length of 20 mm. This helical configuration creates a "locking" mechanism within the concrete, with each twist providing frictional resistance that significantly enhances the fiber's pull-out resistance. The unique helical shape of the TSF offers multiple benefits: it increases the fiber's lateral surface area, resulting in enhanced mechanical bonding and frictional resistance within the concrete matrix, and it ensures that stresses are carried uniformly in all directions when embedded in the matrix. This uniform stress distribution is particularly beneficial for structural elements subjected to multi-directional loads. Additionally, the twist pattern reduces slippage and prevents pull-out failure, as each twist in the fiber provides an interlock with the surrounding concrete, which transforms a simple pull-out failure into a torsional or untwisting mode that requires greater energy to occur.

In accordance with the exemplary embodiment of the present invention, the inclusion of TSF in concrete mixtures fundamentally enhances the mechanical properties of the concrete, especially in terms of tensile, shear, and flexural strengths. The tensile strength of TSF-reinforced concrete (TSFRC) increases significantly due to the fiber's ability to act as reinforcement within the concrete matrix. For example, in M20 grade concrete, a 0.45% dosage of TSF by volume has demonstrated a 156% increase in tensile strength, rising from approximately 4.9 MPa to 10.7 MPa. In addition to tensile strength, the TSF fibers contribute to improved flexural capacity, with the moment of resistance for TSFRC beams increasing in proportion to the fiber dosage. For instance, the moment resistance coefficient for M20 concrete improves from 0.297 (with no fiber) to 1.56 (at a 0.45% fiber content). TSFRC also shows enhanced resistance to shear forces, which is crucial for preventing brittle shear failure in structural elements. With the twisted fiber design, concrete achieves greater shear capacity, enhancing the overall stability and safety of the structure.

In accordance with the exemplary embodiment of the present invention, the method of incorporating TSF into concrete ensures optimal performance through uniform fiber distribution. The base concrete mix consists of Portland cement, fine and coarse aggregates, water, and TSF fibers, which are thoroughly blended to maintain even distribution throughout the matrix. The fiber dosage varies depending on the grade of concrete and specific structural applications. For example, a 0.45% dosage by volume is ideal for achieving maximum tensile and flexural performance in M20 concrete. The TSF fibers are added to the wet concrete mix to achieve a random orientation, which provides reinforcement in multiple directions and improves structural performance in applications with multi-directional stresses.

In accordance with the exemplary embodiment of the present invention, this invention also introduces a specialized method for calculating the structural capacity of TSF-reinforced concrete elements. For structural designs, stress-block parameters are derived based on the stress-strain models specific to TSFRC. These parameters consider the contributions of TSF within both the compressive and tensile zones of the concrete matrix, allowing for accurate calculations of load-bearing capacity in flexural members such as beams and slabs.

In accordance with the exemplary embodiment of the present invention, the stress-block approach uses experimentally derived stress-strain curves for TSFRC, which provides limiting moment coefficients based on the depth of the beam section, the grade of concrete, and the fiber dosage. Using these parameters, the moment of resistance of a TSFRC beam section can be calculated, providing accurate structural design tailored to specific load-bearing requirements. Additionally, Finite Element Analysis (FEA) conducted through software like ANSYS validates the stress-strain behavior and structural performance of TSFRC. The FEA results closely align with experimental data, confirming the reliability and real-world applicability of TSF for structural applications.

In accordance with the exemplary embodiment of the present invention, the twisted steel fiber of this invention offers several advantages over traditional reinforcement and existing fiber types. TSF-reinforced concrete reduces the need for conventional rebar, providing a cost-effective alternative that also reduces construction time and labor costs. The TSF fibers improve concrete ductility, allowing structural elements to withstand higher deformation without catastrophic failure, thereby enhancing durability and sustainability in construction practices. Additionally, the TSF design enables more efficient construction by simplifying the concrete pouring process, as reduced or minimized rebar usage streamlines assembly and preparation.

In accordance with the exemplary embodiment of the present invention, the enhanced properties of TSFRC make it ideal for a wide range of structural applications. In load-bearing elements, such as beams, columns, and slabs in buildings, bridges, and infrastructure projects, TSFRC provides increased load-carrying capacity and resilience. For thin-walled structures, the high tensile strength and reduced thickness enabled by TSFRC make it suitable for applications like architectural panels and structural facades. TSFRC's durability and tensile strength also make it well-suited for high-stress surfaces, such as pavements, industrial flooring, and factory floors. Additionally, precast concrete products, such as panels and pipes, gain durability and load resistance through TSF reinforcement, reducing the need for maintenance and repair.

Referring to Fig.1, The process begins by gathering the required concrete components, including Portland cement, aggregates, and water. Twisted steel fibers (TSF) are then introduced into the concrete mixture, with each fiber constructed from two helically twisted steel wires, resulting in a total diameter of approximately 0.5 mm and a length of 20 mm. The appropriate dosage of TSF is set, typically between 0.3% and 0.5% by volume, depending on the concrete grade and specific structural requirements. This mixture is then thoroughly blended to ensure an even distribution of fibers, facilitating uniform reinforcement throughout the concrete matrix. The helical shape of each fiber provides mechanical interlock within the concrete, enhancing bond strength and resistance to pull-out. Once mixed, the TSF-reinforced concrete is evaluated to confirm improvements in tensile strength, flexural capacity, and shear resistance. Structural calculations are performed using a stress-block approach to accurately determine the load-bearing capacity of TSF-reinforced elements. Finally, the TSF concrete is applied in structural components such as beams, slabs, and columns, enhancing load-bearing capacity and durability.
, Claims:5. CLAIMS
I/We Claim
1. A method for enhancing the tensile, flexural, and shear performance of concrete, comprising the steps of:
a. Incorporating twisted steel fibers into a concrete mix, wherein each fiber is constructed from two steel wires twisted together to form a helical shape, each wire having a diameter of approximately 0.25 mm, resulting in a fiber length of about 20 mm and a total diameter of approximately 0.5 mm;
b. Mixing the twisted steel fibers uniformly within the concrete matrix to create a fiber-reinforced concrete with improved bonding and pull-out resistance, whereby the helical twists in the fiber provide mechanical interlock with the surrounding concrete; and
c. Adjusting the dosage of twisted steel fibers to optimize tensile and flexural properties of the concrete according to the desired grade, thereby improving the overall structural performance of the concrete.

2. The method as claimed in claim 1, wherein the twisted steel fibers are incorporated into the concrete mix at a dosage ranging from 0.3% to 0.5% by volume, depending on the grade and application of the concrete.

3. The method as claimed in claim 1, wherein the helical shape of the twisted steel fibers increases the lateral surface area of the fibers, enhancing frictional resistance and improving bonding with the concrete matrix.

4. The method as claimed in claim 1, wherein the twisted steel fibers are mixed into M20 grade concrete at a dosage of 0.45% by volume to achieve an increase in tensile strength of at least 150% compared to standard concrete.

5. The method as claimed in claim 1, wherein the helical profile of the twisted steel fibers enables a significant increase in the moment resistance coefficient of the concrete, improving flexural strength in load-bearing applications.

6. The method as claimed in claim 1, wherein the twisted steel fibers enhance the shear resistance of the concrete, reducing the risk of brittle shear failure under load.

7. The method as claimed in claim 1, further comprising the step of mixing the concrete formulation to achieve a uniform distribution of twisted steel fibers, providing reinforcement in all directions and enhancing the concrete's performance under multi-directional stresses.

8. The method as claimed in claim 1, wherein the twisted configuration of the steel fibers transitions the concrete's failure mechanism from a pull-out mode to a torsional or untwisting failure mode, requiring higher energy for fiber displacement.

9. The method as claimed in claim 1, further comprising the use of a stress-block calculation approach to determine the structural capacity of a concrete element reinforced with twisted steel fibers, taking into account the enhanced stress-strain characteristics provided by the fibers.

10. The method as claimed in claim 1, wherein the fiber-reinforced concrete is used to construct structural elements such as beams, columns, or slabs, enhancing load-bearing capacity, durability, and resistance to flexural and tensile stresses.

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