Fiber Reinforced Concrete 1994

This paper reports the results of a pilot study of punching shear tests of six small scale slabs (690 x 690 x 80 mm, 27 x 27 x 3 in), four of which reinforced with 3-D carbon fiber fabric and the remaining two reinforced with No. 3 bars for comparison. Crack patterns, load-deflection response, and ultimate load capacity are discussed. The carbon fiber reinforced concrete (CFRC) slabs showed more cracks and more ductile behavior before reaching the ultimate load than the conventionally reinforced slabs.

4098
Balaguru, P. N.
"CONTRIBUTION OF FIBERS TO CRACK REDUCTION OF CEMENT COMPOSITES DURING THE INITIAL AND FINAL SETTING PERIOD"
ACI Materials Journal, May-Jun 1994, Vol. 91, No. 3, pp 280-288.

The contribution of steel, synthetic, and cellulose fibers to the shrinkage-crack reduction potential of cement composites during the initial and final setting period and its evaluation are presented in this paper. The primary variables of the investigation were: fiber types, matrix composition, and test methods. Fiber type consisted of steel and nonmetallic (synthetic and cellulose) fibers with lengths varying from a fraction of an inch to 2.4 in. (1 to 60 mm). For steel fibers, three fiber lengths of 1.2, 2.0, and 2.4 in. (30, 50, and 60 mm) were investigated at volume contents of 75 and 100 lb/yd3 (45 and 60 kg/m3). The nonmetallic fibers were made of cellulose, nylon, polyethylene, polypropylene, or polyester. Cellulose and polyethylene fibers were in the pulp form (microfibers) with lengths in the order of a few mm and diameters in microns. Polypropylene fibers were evaluated both in the pulp form and in relatively longer lengths of 0.75. (19 mm). The longer polypropylene fibers were fibrillated. Nylon and polyester fibers were made of single filaments with lengths varying from 0.75 to 2.0 in. (19 to 50 mm). The matrix consisted of cement mortar with various cement-sand ratios, concrete containing coarse aggregates, and lightweight concrete. In the case of test methods, the primary variables were specimen thickness and plane dimensions of the test panels. Results indicate that both steel and synthetic fibers make a definite contribution to shrinkage crack reduction during the initial and final setting periods. The microfibers (pulp form) are more effective in rich cement mortar, whereas the longer fibers, 0.75 in. (19 mm) long, are more effective in lean mortars and concrete. None of the test methods available in the published literature are suitable for standardization in the present form. The primary drawbacks of the test methods are: (1) the attempt to induce cracks in plain matrixes at normal temperature, humidity, and wind velocity; and (2) the possible errors that can occur in the measurement of crack area.

4099
Banthia, N. and Trottier, J-F.
"CONCRETE REINFORCED WITH DEFORMED STEEL FIBERS, PART I: BOND-SLIP MECHANISMS"
ACI Materials Journal, Sept-Oct 1994, Vol. 91, No. 5, pp 435-446.

Bond-slip characteristics were investigated for three deformed steel fibers bonded in concrete matrixes with different strengths. Fibers were aligned at 0, 15, 30, 45, and 60 deg with respect to the loading direction, and complete load-versus-slip curves were obtained. It was found that the bond-slip characteristics of fibers aligned with respect to the loading direction were significantly superior to those for inclined fibers. Inclined fibers supported smaller peak pullout loads and absorbed less pullout energy than the aligned fibers. A high-strength matrix often caused brittle failures of fiber and matrix, and led to reductions in the energy-absorption capability. The paper provides interpretations of the bond-slip curves based on various micromechanical processes in the matrix and fiber, and identifies the conditions that lead to a brittle response. The bond-slip information generated in this study for the various deformed fibers will be correlated to the actual behavior of fiber reinforced concrete in the second part of this paper.

4100
"FIBER REINFORCED CONCRETE: DEVELOPMENTS AND INNOVATIONS"
Papers Presented at the ACI Conventions in Boston, March 1991, and in Dallas, November 1991; Ed. by James I. Daniel and Surendra P. Shah; American Concrete Institute, Detroit, MI, 1994, viii, 318 pp. (ACI SP-142)

Fiber reinforced concrete is made primarily of hydraulic cements, aggregates, and discrete reinforcing fibers. This does not include a provision for concretes reinforced with continuous meshes, woven fabrics, or continuous fiber networks. Fifteen papers address some of the following topics: Comparison of Shrinkage Cracking Performance of Different Types of Fibers and Wiremesh; Toughness of Slurry Infiltrated Fibrous Concrete (SIFCON); Durability Characteristics of Cellulose Fiber Reinforced Cement Composites; Flexural Behavior of Carbon Fiber Reinforced Cement Composite; Influence of Test Control on the Load-Deflection Behavior of FRC; Ultra High Performance Reinforced Concrete; Analytical Deflection Evaluation of Partially Prestressed Fiber Reinforced Concrete Beams.

4101
Hackman, L. E., Farrell, M. B., and Dunham, O. O.
"ULTRA HIGH PERFORMANCE REINFORCED CONCRETE"
in Fiber Reinforced Concrete: Developments and Innovations; Papers presented at the ACI Conventions in Boston, March 1991, and in Dallas, November 1991; Ed. by James I. Daniel and Surendra P. Shah; American Concrete Institute, Detroit, MI, 1994, pp 235-247. (ACI SP-142)

An innovative technique for reinforcing concrete to achieve extremely high flexural strengths was developed. This technique utilizes a steel fiber mat instead of short, discrete steel fibers. The mat configuration is preplaced for infiltration with a concrete slurry to yield a composite with flexural strengths approaching ten times that of conventional concrete. Applications include high performance bridge decks, earthquake resistant structures, nuclear waste containment, military applications and other innovative uses where flexural strength is at a premium. Stainless steel mats or other advanced alloys can be provided where corrosion resistance or high temperature strength is required.

4102
Hsu, L. S. and Hsu, C-T. T.
"STRESS-STRAIN BEHAVIOR OF STEEL-FIBER HIGH-STRENGTH CONCRETE UNDER COMPRESSION"
ACI Structural Journal, Jul-Aug 1994, Vol. 91, No. 4, pp 448-457.

A series of compression tests was conducted on 3 x 6-in. (75 x 150 mm) cylindrical specimens using a modified test method that gave the complete stress-strain behavior for high-strength steel-fiber concrete with or without tie confinements. The volume fractions of steel fiber in the concrete were 0, 0.5, 0.75, and 1 percent, respectively. Empirical equations are proposed herein to represent the complete stress-strain relationships of high-strength steel-fiber concrete with compressive strength exceeding 10,000 psi. Various parameters were studied and their relationships were experimentally determined. The proposed empirical stress-strain equations have been compared to actual cylinder tests under axial compression and were found to be in good agreement.

4103
Malhotra, V. M., Garette, G. G., and Bilodeau, A.
"MECHANICAL PROPERTIES AND DURABILITY OF POLYPROPYLENE FIBER REINFORCED HIGH-VOLUME FLY ASH CONCRETE FOR SHOTCRETE APPLICATIONS"
ACI Materials Journal, Sept-Oct 1994, Vol. 91, No. 5, pp 478-486.

Investigations at CANMET have led to the development of polypropylene fiber reinforced, high-volume fly ash concrete for shotcreteing rock outcrops. This type of concrete has a very low water-to-cementitious material ratio, fly ash content greater than 50 percent of the cementitious material, and contents of fibers up to 5 kg/m3 of concrete. The workability of the concrete is maintained by the use of high dosages of superplasticizers. This paper presents the results of CANMET investigations dealing with the development of this type of concrete. The test results show that polypropylene fiber reinforced, high-volume fly ash concrete has satisfactory workability and strength characteristics. It also has very low permeability, low drying shrinkage, adequate ductility, and toughness characteristics.

4104
Richard, P. and Cheyrezy, M. H.
"REACTIVE POWDER CONCRETES WITH HIGH DUCTILITY AND 200-800 MPA COMPRESSIVE STRENGTH"
in Concrete Technology: Past, Present, and Future, Proceedings of V. Mohan Malhotra Symposium, held Mar 21-23, 1994 at the ACI Annual Convention in San Franscisco, CA; Ed. by P. Kumar Mehta; American Concrete Institute, Detroit, MI, 1994, pp. 507-518. (ACI SP-144).

The use of ultra-high-strength concrete for the construction of some types of structural members can be considered if non-brittle behavior is achieved. This paper introduces Reactive Powder Concretes (RPC) which exhibit ultra-high-strength and high ductility at the same time. Compared to conventional concretes, the ductility estimated in terms of fracture energy is increased by one to two orders of magnitude, while the compressive strength values are in the range of 200 to 800 MPa.

4105
Rizkalla, S. H. and Tadros, G.
"A SMART HIGHWAY BRIDGE IN CANADA"
Concrete International, Jun 1994, Vol. 16, No. 6, pp 42-44.

This paper describes the construction details of the first experimental bridge in Canada, in which six precast prestressed concrete bulb-tee girders were prestressed using two different types of carbon fiber reinforced plastic (CFRP) tendons. A system of structurally integrated optical sensors was also incorporated to monitor the behavior of the tendons during construction. The two-span continuous skew bridge of 75 and 63 ft (22.83 and 19.23 m) spans has a total of thirteen precast pre-tensioned girders. Continuity of the bridge was achieved by using post-tensioned steel tendons in precast girders, extended along the entire length of the bridge.

4106
Rossi, P.
"STEEL FIBER REINFORCED CONCRETES (SFRC): AN EXAMPLE OF FRENCH RESEARCH"
ACI Materials Journal, May-Jun 1994, Vol. 91, No. 3, pp 273-279.

A methodology to study the mix design and mechanical behavior of SFRCs is proposed. This methodology is based on two general principles: the optimization of a SFRC (including the choice of fiber to use, the percentage to incorporate, and the formulation of the matrix) depends on the industrial application, and the study of its mechanical behavior must clearly distinguish the influence of the fibers on the scale of the material and on the scale of the structure. An example of the application of the approach is proposed; it concerns SFRCs for reinforced concrete structures. The main results concerning this type of application can be summarized in the following: the minimum percentage of fibers needed is around 1 percent by volume; the composition of the matrix is completely modified, and the quantity of the cement paste and water-cement ratio (w/c) increases; the compressive and uniaxial tensile strengths decrease compared to those of a normal concrete. The replacement of stirrups by SFRCs is considered from the viewpoint of French regulations. It is shown that the application of these regulations to the dimensioning of SFRC structures with respect to shear force leads to an operative result. An alternative approach to these traditional regulations that would develop powerful numerical models is needed. An example of this type of model is presented.

4107
Saadatmanesh, H.
"FIBER COMPOSITES FOR NEW AND EXISTING STRUCTURES"
ACI Structural Journal, May-Jun 1994, Vol. 91, No. 3, pp 346-354.

Fiber composite materials have been used in a variety of industries, such as aerospace, automotive, shipbuilding, chemical processing, etc., for many years. Their application in civil engineering, however, has been very limited. Their high strength-to-weight ratio and excellent resistance to electro-chemical corrosion make them attractive materials for structural applications. This paper presents an overview of some of the applications of non-metallic, fiber composites in concrete construction.

4108
Shin, S. W., Oh, J. G., and Ghosh, S. K.
"SHEAR BEHAVIOR OF LABORATORY-SIZED HIGH STRENGTH CONCRETE BEAMS REINFORCED WITH BARS AND STEEL FIBERS"
in Fiber Reinforced Concrete: Developments and Innovations; Papers presented at the ACI Conventions in Boston, March 191, and in Dallas, November 1991; Ed. by James I. Daniel and Surendra P. Shah; American Concrete Institute, Detroit, MI, 1994, pp 181-200. (ACI SP-142)

This paper reports an investigation on the behavior of high-strength concrete beams (with concrete compression strength equal to 11,600 psi or 80 MPa) with or without steel fiber reinforcement, to determine their diagonal cracking strength as well as nominal shear strength. Experimental data on the shear strength of steel fiber reinforced high-strength concrete beams are currently scarce to non-existent. Twenty-two beam specimens were tested under monotonically increasing loads applied at mid-span. The major test parameters included the volumetric ratio of steel fibers, the shear-span-to-depth ratio, the amount of longitudinal reinforcement, and the amount of shear reinforcement. It was found that steel fiber reinforced high-strength concrete beams effectively resist abrupt shear failure. Such beams exhibit higher cracking loads and energy absorption capabilities than comparable high-strength concrete beams without fibers. Empirical prediction equations are suggested for evaluating the diagonal cracking strength as well as nominal shear strength of steel fiber reinforced high-strength concrete beams.

4109
Tan, K. H., Paramasivam, P., and Tan, K. C.
"INSTANTANEOUS AND LONG-TERM DEFLECTIONS OF STEEL FIBER REINFORCED CONCRETE BEAMS"
ACI Structural Journal, Jul-Aug 1994, Vol. 91, No. 4, pp 384-393.

In this study, the instantaneous and long-term deflections of reinforced concrete beams with steel fibers were studied. Deflections were monitored on 14 steel fiber reinforced concrete (SFRC) beams, five of which were tested monotonically to flexural failure and the others subjected to various levels of sustained loading. An analytical method following the ACI approach is proposed for the prediction of both the instantaneous and long-term deflections of the beams. The method accounts for the enhanced cracking load and the beam stiffness, as well as the creep and shrinkage restraints due to fibers. The predictions of the method were compared with the test results of the present study and those available in the literature. In general, good agreement between the predicted and experimental values was obtained, particularly in the service load range.

4110
Vares, S.
"FROST RESISTANCE OF STEEL FIBRE HIGH STRENGTH CONCRETE"
Nordic Concrete Research, 1994, Publication No. 15, pp 75-88.

The main objective of this work was to investigate the influence of Dramix steel fibres on the microstructure of steel fibre reinforced concrete (SFRC) and the influence of the microstructure on frost resistance. This work is part of the investigation "Fibre-reinforced high-strength concrete" by Vares & Hakkinen, 1993. The frost resistance of SFRC with 2% and 4% steel fibres was determined, after subjecting the concretes to 100 and 200 freeze-thaw cycles, by comparing changes of strength, toughness and microstructure with those of specimens stored in water. No serious damages to the SFRC microstructure was observed after 200 freeze-thaw cycles.