2: 4 (2012) 266-271 Alternative Ways of Reinforcing Cement Composites (original) (raw)
Related papers
Alternative Ways of Reinforcing Cement Composites
2012
This paper presents the results of laboratory research on concrete beams with alternative types of reinforcement, assuming a constant volume of fibers. As the reinforcement of the cement matrix, two types of macro-fibres, namely steel and polypropylene fibres, were used. In addition, traditional beam reinforcement in the form of aligned, smooth, and ribbed steel rods were tested. In the case of the long fibers-the steel bars were assumed to force the long fibers to adopt a certain position four rods at the corners of the cross section, two of which were in the tension zone and two in the compression zone. By introducing a slip sleeve in three stirrups to stabilize the transverse bars in the desired position, efforts were made to ensure the independent operation of each of the four rods. It was shown that the highest load-carrying capacity and the toughness of the composite, was obtained for concrete beams reinforced with ribbed steel rods. Unexpectedly, the beams with the polypropyl...
Composite Structures, 2015
The shear capacity of reinforced concrete beams strengthened with cement based composite materials (FRCM, Fabric Reinforced Cementitious Matrix) was investigated in the paper. The analysis refers to a FRCM system made by PBO (short of Polypara-phenylene-benzo-bisthiazole) fabric meshes with dry fiber strands disposed along two orthogonal directions bonded to concrete surfaces with a cement based mortar. A total of 9 reinforced concrete beams strengthened both in flexure and shear with PBO-FRCM have been tested varying both the shear strengthening configuration (continuous and discontinuous U-wrapped strips) and the PBO reinforcement ratio. The main issues focussed in the paper are: (i) the effectiveness of the PBO-FRCM system as shear strengthening system, (ii) the shear performance, including failure modes, of reinforced concrete beams strengthened in terms of the PBO, the internal transversal steel reinforcement (steel stirrups), the internal longitudinal steel reinforcements and the concrete strength, (iii) the interaction between transversal internal steel and external PBO-FRCM shear reinforcements and, by comparison with experimental results, (iv) the reliability of models found based on the Ritter-Morsch criteria failure to predict the shear capacity of PBO-FRCM strengthened reinforced concrete beams.
Experimental Analysis of Load Capacity in Beams with Reinforcement of Steel Fibers
2019
The use of steel fibers in the concrete is mainly aimed to increase the post-peak toughness, due to the adhesion of the fibers to the cementitious matrix and to improve brittle behavior of the concrete. However, since there are various types of steel fibers, it can be said that the main difference is the characterization of macrofibers and microfibers that generally serve to soften the macrofissuracao and microcracking, respectively. Within this context, this study aims to evaluate the use of microfiber (20kg/m³), macrofibers (20kg/m³) and hybridization (microfibre (10kg/m³) + macrofibers (10kg/m³)) entered into a concrete high strength (fck = 80 MPa) acting as reinforcement on the face pulled large armed beams (12x20x160 cm) high strength concrete, and in addition were examined: the flexural strength in non-armed small beams (10x10x35 cm), the compressive strength and modulus of elasticity on cylindrical specimens (20xO10 cm). All tests were compared to the reference concrete witho...
Composite rods as a steel substitute in concrete reinforcement
2007
The current work is concerning with the development of braided reinforced composites rods for concrete reinforcement, as a steel substitute. The research study aims to understand the mechanical behaviour of composite rods reinforced by a fibrous structure -core reinforced braided fabric. Several samples of braided reinforced composite rods were produced. Polyester fibres were used to produce the braided fabric; several types of fibres, and several combinations of fibres, were used as braided fabric core reinforcement; and polyester resin was used as polymeric matrix. The mechanical properties of braided reinforced composite rods have been evaluated under tensile. The objective was to identify the type of fibre, or combination of fibres, to be used as braided fabric core reinforcement, in order to produce composite rods with mechanical properties similar to those of steel rebars.
In recent years using the polymer materials in strengthening and retrofitting the concrete elements is on the developing process. Fiber-reinforced polymers (FRP), have emerged as an alternative solution to traditional materials for strengthening and retrofitting structures, especially in existing structures which need to up build or to change the destinations. In attempt to increase strength and ductility of reinforced concrete (RC) load bearing elements through confining systems the FRP membranes have become a familiar solution. Extensive studies (experimental, finite element modeling and analytical modeling) were carried out on the analysis of confining effect in case of concentrically loaded RC columns. This paper investigates the prospect of strengthening deficient square columns and cycle columns with carbon fiber-reinforced polymer(CFRP) jackets. In both cases output results will compare with the etalon specimen (without strengthening). Currently, the study of RC columns confined with composite materials will be focused in centric compression, because the eccentric compression is relatively new and limited. FRP confinement systems are less effective under eccentric loading compared to concentric. Experimental program on testing the performance of centric loaded RC columns externally strengthened with CFRP membranes was carried out and results are presented in this paper.
International Journal of Cement Composites and Lightweight Concrete
The effects of a combination of conventional steel reinforcement and steel fibre reinforcement on the flexural behaviour of concrete were investigated. It was found that the strength aria ductility improvements brought about by the addition of fibres alone were much less than those which could be achieved by using conventional reinforcement. However, the combination of fibres and conventional reinforcement increased the flexural strength of the beams by 32-55% compared to beams reinforced only with steel bars. Higher postcracking rigidity was also obtained by the combined reinforcement. There was an increase in the number of cracks, but a decrease in their length and width.
Polyolefin Fibres for the Reinforcement of Concrete
Alkenes
Given that concrete has limited tensile strength, it has been necessary to combine its properties with the use of steel bars. This resulted in the arrival of reinforced concrete which was the main solution used in structures in the last century. Partial or even full substitution of steel bars for fibres would not only allow the cost of a structure to be reduced but also provide certain improved properties. Modern fibre-reinforced concrete (FRC) now permits reduction or substitution of steel bars that has given rise to the commonly named structural FRC. Advances in the plastic industry during the last three decades have allowed the production of macro-polymer fibres as an alternative to steel fibres due to their chemical stability and lower weights for analogous residual strengths. After 30 years of research and practice, polyolefin-based macro-fibres have offered additional advantages such as safe handling, low pump wear and reduction in weight when transported and stored. This chapter provides an overview of the properties and structural capacities of polyolefin fibre-reinforced concrete (PFRC). Furthermore, the respective codes and test methods are examined. Moreover, the results obtained for structural design and the mechanical properties, found both in the literature and in practice, are supplied and discussed.
Structural Performance of Concrete: Exploring the Limits of Steel Fiber Reinforcement
International Journal for Multidisciplinary Research, 2024
Concrete is one of the most extensively utilized construction materials today. Its popularity stems from its ready availability, ease of moulding into various shapes, cost-effectiveness, and high compressive strength. Despite these advantages, concrete is known for its low tensile strength and poor performance in harsh conditions, which is a significant drawback for any construction material. To mitigate these weaknesses, concrete is typically combined with steel reinforcement. Steel fibers are added to concrete to improve the structural properties, particularly tensile and flexural strength. Plain, straight and round fibers were found to develop very weak bond and hence low flexural strength. In this research, steel binding wires were used as steel fibers which are locally available at very cheap cost. Steel fibers were added in different percentage i.e. 0%, 0.5 %, 1%, 1.5%, 2%, 2.5% and 3%. The primary focus of the research was to calculate compressive and tensile strengths of various samples and determine the maximum amount of Steel fibers that can provide the maximum strength. To achieve this, cubes and cylinders were cast and tested using a Universal Testing Machine for their compressive and tensile strengths. The findings indicated a slight increase in compressive strength, while the addition of steel fibers resulted in a more significant increase in tensile strength.