U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
|This report is an archived publication and may contain dated technical, contact, and link information|
Publication Number: FHWA-RD-96-112
This guide describes the current technology in specifying, proportioning, mixing, placing, and finishing of steel fiber reinforced concrete (SFRC). Much of the current conventional concrete practice applies to SFRC. The emphasis in the guide is to describe the differences between conventional concrete and SFRC and how to deal with them. Guidance is provided in mixing techniques to achieve uniform mixtures, placement techniques to assure adequate compaction, and finishing techniques to assure satisfactory surface textures. Sample mix proportions are tabulated. A listing of references is provided covering proportioning properties, refractory uses, shotcrete technology, and general information on SFRC.
Eight high-strength concrete beams with different fiber contents and shear span-depth ratios were tested to study the influence of fiber addition on ultimate load, crack propagation, flexural rigidity, and ductility. The addition of steel fibers enhanced the strength and increased the ductility and flexural stiffness of the tested beams. A semi-empirical equation is proposed to estimate the effective moment of inertia of simply supported high-strength fiber reinforced concrete beams. The estimated deflections using this equation agree well with the experimental values. At ultimate conditions, the length of the plastic hinge developed was found to be proportional to the fiber content.
This study investigated the workability and the behavior under compression, splitting tension, flexure, and shear of fiber reinforced high strength semilightweight concrete. Silica fume and high-range water-reducing admixtures were used to obtain the high strength. The lightweight aggregate used was made of expanded shale. The primary independent variables were fiber content and fiber length. Study results showed that the silica fume can be successfully used to obtain high strength. The brittleness of silica fume concrete can be overcome by using fibers. The addition of fibers provides a significant increase in Young's modulus, splitting tensile strength, and shear strength. Strength increase is also considerable under flexure. In all cases, fibers provide substantial improvement in ductility.
Controlled material evaluation projects are being conducted by the Ohio Department of Transportation to analyze steel fiber reinforced micro-silica modified concrete and steel fiber reinforced superplasticized dense concrete as potential thin-bonded overlay material candidates. Both SFR-MSC and SFR-SDC effectively combine the beneficial attributes of several modern concrete admixtures to adequately transform the brittle matrix of conventional non fibrous portland cement concrete mix into a more isotropic ductile composite. Extensive research has formulated various engineering properties for SFRC. The characteristics of a desirable bridge deck overlay material alternative are listed and discussed, and the details of ODOT's program and its review are described.
The effect of silica fume on the properties of synthetic fiber-reinforced concrete was assessed. Two fiber types were used: fibrillated polypropylene fibers and polyethylene- terphalate polyester fibers. Various fiber volume fractions were examined. Fiber volumes ranged from 0 to 0.6%, and fiber length was 12 mm (1/2 in.). Silica fume was used as partial replacement of portland cement on an equal-mass basis at 0, 5, 10, and 25%. The fresh mixtures were tested for slump, inverted slump cone time, and air content. The hardened concrete material was tested for compressive and flexural behaviors as well as impact resistance. Rapid chloride permeability was also measured. The purpose of the experimental investigation was to assess the suitability of synthetic-fiber silica-fume concrete for application in bridge-deck overlays and other applications for which the mechanical properties and permeability are important. The results indicate that silica fume is useful in improving the effectiveness of fiber reinforcement of concrete and reducing its permeability.
An experimental research investigation of the fresh and hardened material properties of the fibrillated polypropylene fiber reinforced concrete is reported. Fiber lengths were 1/2 and 1/4 inch, and volume fractions were 0.1, 0.3, and 0.5%. Fiber effects on concrete properties were assessed. Properties studied were slump, inverted slump cone time, air content, compressive and flexural behaviors, impact resistance and rapid chloride permeability, and volume percent of permeable voids. An innovative method of characterizing the flexural behavior of fibrillated polypropylene fiber concrete was proposed. The new method was dependent on the post-peak flexural resistance of concrete. For impact resistance and flexural behavior, it was concluded that 1/4-inch-long fibers were more effective than 1/2-inch-long fibers for volumes of 0.3% or less, while 1/2-inch-long fibers were more effective for 0.5% volume.
Brown, V. L. and Bartholomew, C. L.
"FRP DOWEL BARS IN REINFORCED CONCRETE PAVEMENTS"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, pp. 813-829. (ACI SP-138)
In reinforced concrete pavements, dowel bars are typically used to transfer the load across the transverse joint from one pavement slab into the adjoining slab. Steel dowels have been used almost exclusively in these applications in the past. Because the bars cross construction joints, they are particularly susceptible to corrosion from the salts used for ice control. Corrosion can cause the dowel bars to fail or to freeze in the joint, resulting in pavement distress. As a solution to this problem, it would appear practical to fabricate the dowels from a material which is more resistant to corrosion from roadway salts than steel. This paper presents the initial results from an investigation into the feasibility of substituting fiberglass reinforced plastic (FRP) dowel bars for steel bars in reinforced concrete pavements. FRP dowels are compared with steel dowels, both theoretically using a Friberg analysis and also experimentally through laboratory tests with scaled model slabs. It is concluded that the use of FRP dowels is feasible, provided that dowel diameters are increased approximately 20 to 30 percent.
The use of short pitch-based carbon fibres (0.5 percent by weight of cement, 0.189 volume percent (vol percent) of concrete), together with a dispersant, chemical agents and silica fume, in concrete with fine and coarse aggregates resulted in a flexural strength increase of 85 percent, a flexural toughness increase of 205 percent, a compressive strength increase of 22 percent, and a material price increase of 39 percent. The slump was 102 mm (4 in) at the optimum water/cement ratio of 0.50. The air content was 6 percent, so the freeze-thaw durability was increased, even in the absence of an air entrainer. The aggregate size had little effect on the above properties. The optimum fibre length was such that the mean fibre length decreased from 12 mm before mixing to 7 mm after mixing, which used a Hobart mixer. The drying shrinkage was decreased by up to 90 percent. The electrical resistivity was decreased by up to 83 percent.
"FIBER-REINFORCED-PLASTIC REINFORCEMENT FOR CONCRETE STRUCTURES"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, xiii, 977 pp. (ACI SP-138)
The 55 papers contained in the volume represent the most comprehensive compilation to date of fiber reinforced plastics (FRP) research, design, and application information. A comparison of the papers provides an insight into the different approaches in the use and development of FRP reinforcement within the research communities of Europe, Japan and North America. This symposium volume is significant because substantial portions of the extensive Japanese papers provide an insight to both the magnitude of the technical work being conducted in Japan and the organization of the Japanese research program. The editors summarized the most important points in a synopsis covering seven topical areas: material properties, creep-rupture, ductility, durability, reinforcement form, fire resistance, and the Japanese national project.
Iyer, S. L.
"ADVANCED COMPOSITE DEMONSTRATION BRIDGE DECK"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, pp. 831-852. (ACI SP-138)
A 30 ft. span 17 ft. wide bridge was constructed in Rapid City, South Dakota in the summer of 1991 to demonstrate the application of graphite and fiberglass cables for prestressing bridge decks. The bridge was designed by consultants and built by local contractors with the technology developed at South Dakota School of Mines and Technology. This paper deals with the construction phase, testing, and monitoring of the bridge from September 1991-December 1992. Post tension bonded method was used for prestressing the bridge deck in the transverse direction, whereas non-prestressed reinforcement was used in the longitudinal direction as distributors. The thickness of the slab was 7 in. and was supported by three longitudinal girders. One third of the bridge was prestressed with S-2 glass cables while the second one-third was prestressed with graphite cables and the last one-third was prestressed with steel cables. Special anchorages were used for prestressing the cables. Electrical and slip gages were used to monitor the stresses in the cable and the deck. After the deck bridge was constructed, it was loaded for static and dynamic loading before it was opened for traffic. The test methods and quality control for cables used for the bridge deck, including design guidelines for using new materials for bridge decks, were discussed. The actual test data for the bridge was compared with the design data and found to be very comparable in this project. The bridge project demonstrates the feasibility of using advanced composite cables for prestressing bridge decks. The information gained through design, construction, and monitoring this bridge will help provide guidelines for the design and construction of future bridges.
Mufti, A. A., Jaeger, L. G., Bakht, B., and Wegner, L. D.
"EXPERIMENTAL INVESTIGATION OF FIBRE-REINFORCED CONCRETE DECK SLABS WITHOUT INTERNAL STEEL REINFORCEMENT"
Canadian Journal of Civil Engineering, Jun 1993, Vol. 20, No. 3, pp 398-406.
The concrete deck slabs of slab-on-girder bridges subjected to concentrated loads develop an internal arching system provided that certain conditions of confinement of the concrete are met. Because of this arching system, the deck slab, being predominantly in compression, fails in punching shear rather than in flexure. This is an investigation of the feasibility of fiber-reinforced concrete decks that are entirely devoid of steel. Through tests on a small number of half-scale models, it has been established that fiber reinforced concrete slabs with inexpensive nonferrous fibers is indeed feasible, provided that the top flanges of the steel girders are connected just below the deck by transverse steel straps and the concrete deck is joined to the girders and diaphragms by shear connectors. The straps and shear connectors together provide the restraint necessary for development of the internal arching system in the slab, while the fibers control cracking due to the effects of shrinkage and temperature in the concrete. This paper describes the exploratory model tests and presents their results.
MECHANICAL BEHAVIOR OF HIGH PERFORMANCE CONCRETES, VOLUME 6: HIGH EARLY STRENGTH FIBER REINFORCED CONCRETE Naaman, A. E., Alkhairi, F. M., and Hammoud H.
Strategic Highway Research Program, National Research Council, Washington, D. C., 1993, xix, 297 pp. (SHRP-C-366)
This study provides an extensive database and a summary of a comprehensive experimental investigation on the fresh state and mechanical properties of high early strength fiber reinforced concrete (HESFRC). The control high early strength (HES) concrete used for fiber addition and the resulting HESFRC are defined as achieving a target minimum compressive strength of 5 ksi (35 MPa) in 24 hours, as measured from 4 x 8-in. (100 x 200-mm) cylinders. Fresh HESFRC properties tested include air content, workability (by the inverted slump test), temperature, and plastic unit weight. Tests on the mechanical properties include compressive strength, elastic modulus, flexural strength, splitting tensile strength, and fatigue life. Sixteen different combinations of parameters were investigated; the variables were the volume fraction of fibers (1% and 2%), the type of fiber (steel, polypropylene), the fiber length or aspect ratio, and the addition of latex or silica fume to the mix. Optimal mixes that satisfied the minimum compressive strength criterion, and showed excellent values of modulus of rupture, toughness indices in bending, and fatigue life in the cracked state, are identified. Potential applications in construction, repair, and rehabilitation of transportation structures are suggested.
Noritake, K., Mukae, K., Kumagai, S, and Mizutani, J.
"PRACTICAL APPLICATIONS OF ARAMID FRP RODS TO PRESTRESSED CONCRETE STRUCTURES"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, pp. 853-873. (ACI SP-138)
Aramid FRP rods, which are a composite of reinforced aramid fibers (brand name Technora©) were developed by Sumitomo Construction Co., Ltd. and a textile maker, Teijin Co., Ltd. Corrosion-free FRP rods are used in various fields, and the aramid FRP rods have been gaining attention for their use in prestressed concrete tendons. Aramid FRP rods have high tensile strength and excellent chemical resistance. They are manufactured from aramid fibers and vinylester resin using a pultrusion process. The physical properties of aramid FRP rod were determined experimentally. The use of Aramid FRP rod as prestressed concrete tendons requires a high bond performance with grout or concrete, and a special anchoring system also had to be developed. Studies carried out in response to these requirements confirmed that aramid rods could make viable prestressed concrete tendons, and a pre-tensioned road bridge (L = 12.5 m), a post-tensioned road bridge (L = 25.0 m), a ground anchor and a prestressed concrete berth were constructed by using the aramid FRP rods. This paper describes the practical applications of the aramid FRP rods.
Okamura, H., Kakuta, Y., Uomoto, T., and Mutsuyoshi, H.
"DESIGN CONCEPT FOR CONCRETE MEMBERS USING CONTINUOUS FIBER REINFORCING MATERIALS"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, pp. 549-559. (ACI SP-138)
As fibers made of materials such as glass, carbon, aramid and vinylon have very high resistance to corrosion, more and more attempts are being made to utilize continuous fiber reinforcing materials (CFRM) in reinforced and prestressed concrete structures instead of the ordinary steel. However, CFRM are composite materials composed of millions of fibers and binding material, and have little plastic behavior. The mechanical behavior of reinforced concrete using CFRM is quite different from conventional reinforced concrete. As of now, there is no general agreement relating to the methodology to be adopted in design or testing methods of such fibers. Realizing this problem, the Concrete Committee of the JSCE (Japan Society of Civil Engineers) organized a subcommittee on CFRM in 1989. The following results have been published as the committee report in 1992: (1) Design Concept for Concrete Members Using CFRM, (2) Test Methods for Durability of CFRM, (3) Concept for Durability of CFRM, and (4) A State-of-the-Art Report on CFRM for Concrete Structures. This paper describes the design concept for concrete members using CFRM.
Rostasy, F. S.
"FRP TENSILE ELEMENTS FOR PRESTRESSED CONCRETE -- STATE OF THE ART, POTENTIALS AND LIMITS"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, pp. 347-366 (ACI SP-138)
Fiber reinforced plastics (FRP) are new materials for structural engineers. Hence, an overview on the important properties of fibers, matrix resins and composite elements becomes necessary to show the assests and drawbacks of FRP and to illustrate their potentials and limits. Besides several other fields, the prestressing of concrete seems to become a promising field of application of FRP. In prestressed concrete construction the high strength and good corrosion resistance of FRP can be optimally utilized. In such an application FRP can compete with prestressing steel especially in cases where the corrosion protection of the prestressing steel becomes expensive or remains tarnished by residual risks. The post-tensioning of concrete requires anchorages with a high mechanical efficiency. The main avenues of development are discussed and the necessary future research is outlined.
Santoh, N., Kimura, H., Enomoto, T., Kiuchi, T., and Kuzuba, Y.
"REPORT ON THE USE OF CFCC IN PRESTRESSED CONCRETE BRIDGES IN JAPAN"
Proceedings of the International Symposium on Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, held Mar 28-31, 1993, Vancouver, Canada; Ed. by Antonio Nanni and Charles W. Dolan; American Concrete Institute, Detroit, MI, 1993, pp. 895-911. (ACI SP-138)
In this paper the characteristics of CFCC including mechanical properties, fatigue, relaxation, and anti-corrosive properties are described. Examples of actual bridges in which CFCC has been used as a reinforcement material are shown. The investigation of these characteristics and the results of such tests as adhesion with concrete, anti-fatigue characteristics, anti-alkali characteristics, relaxation, and temperature cycle tests confirmed that CFCC is a material suitable for tension applications in PC bridges.
The effects of polypropylene fibers and construction operations on the plastic shrinkage cracking of concrete slabs were investigated. Statistical methods of experimental design and analysis were used to derive statistically reliable conclusions. Polypropylene fibers, at relatively low fiber volume fractions, were observed to reduce substantially the total area and maximum crack width of slab surfaces subjected to restrained plastic shrinkage movements. The rate of screeding of the fresh concrete surface was also a critical factor (particularly in plain concrete). Slower screeding rates led to reduced plastic shrinkage cracking.
Soroushian, P., Tlili, A., Alhozaimy, A., and Khan, A.
"DEVELOPMENT AND CHARACTERIZATION OF HYBRID POLYETHYLENE FIBER REINFORCED CEMENT COMPOSITES"
ACI Materials Journal, Mar-Apr 1993, Vol. 90, No. 2, pp 182-190.
This paper deals with the optimization of the combined use of two different fiber types in cementitious matrixes. The two fiber types were a high modulus polyethylene fiber and a fibrillated polyethylene pulp. The details of the study are described, and it is noted that in the case of impact resistance, the positive effect of each fiber was pronounced in the presence of the other fiber type. For flexural strength and toughness, the combined use of polyethylene fiber and pulp produced desirable results as long as the amounts incorporated were below certain limits. The negative effects of fibers on compressive strength were less pronounced when the two fiber types were used in combination. The interactions between polyethylene fiber and pulp in deciding the specific gravity, volume of permeable pores, and water absorption capacity of cementitious materials were either negligible or only moderately significant.
Experimental and modeling studies were performed on two types of fibers, polypropylene and steel fibers, in conjunction with or without conventional stirrups. In general, fibers proved to be more effective in high-strength concrete than in normal strength concrete, increasing both ultimate load and overall ductility. For specimens with steel fibers, significant increases in ultimate load and ductility were observed. With polypropylene fibers, a lower increase in ultimate load was obtained when compared to the increase due to steel fibers. Ductility of the polypropylene fiber specimens was greater than that of the steel fiber reinforced specimens. In tests with combinations of fibers with stirrups, slight increases in ultimate load with major improvements in ductility were noted in comparison to the values for plain concrete specimens with conventional stirrups.