International Concrete Abstracts Portal

SP142 Fiber reinforced concrete is concrete made primarily of hydraulic cements, aggregates, and discrete reinforcing fibers. This definition does not include a provision for concretes reinforced with continuous meshes, woven fabrics, or continuous fiber networks. To address all potential types of fiber reinforced concrete, ACI has produced "Fiber Reinforced Concrete Developments and Innovations." Fifteen papers address: - Comparison of Shrinkage Cracking Performance of Different Types of Fibers and Wiremesh - The Effect of Low Addition Rates of Polypropylene Fibers on Plastic Shrinkage Cracking and Mechanical Properties of Concrete - Toughness of Slurry Infiltrated Fibrous Concrete (SIFCON) - Tensile and Compressive Strengths of Polypropylene Fiber Reinforced Concrete - Durability Characteristics of Cellulose Fiber Reinforced Cement Composites - Carbon Fiber Reinforced Cements: Structures, Performance, Applications and Research Needs - Flexural Behavior of Carbon Fiber Reinforced Cement Composite - Shear Capacity of Fiber Reinforced Concrete Based on Plasticity of Concretes: A Review - Influence of Test Control on the Load-Deflection Behavior of FRC - Shear Behavior of Laboratory-Sized High Strength Concrete Beams Reinforced with Bars and Steel Fibers - Behavior of Fiber Reinforced High Strength Concrete Under Direct Shear - Ultra High Performance Reinforced Concrete - Constitutive Modeling of Fiber Reinforced Concrete - Analytical Deflection Evaluation of Partially Prestressed Fiber Reinforced Concrete Beams - Dynamic Tension Fatigue Performance of Fibrous Concrete Composites

Compares load-deflection responses obtained using deflection control and crack-mouth opening displacement (CMOD) control. CMOD control provides a more stable response in the immediate post-peak regime of the load-deflection response than deflection control. The differences in the responses recorded using these two types of test control are more pronounced for the more brittle mixes. Results reported and discussed in this paper were obtained using third-point loading in flexure. Deflection controlled tests were performed using manual control on a stiff million-lb-capacity machine. This is similar to the manner in which most commercial laboratories perform deflection controlled tests on concrete specimens. CMOD controlled tests were conducted using a servo-controlled machine. Normal and lightweight aggregate concrete mixes were evaluated with polymeric fiber loadings of 1, 2, 3, and 4 lb/yd 3 (0.6, 1.2, 1.8, 2.4 kg/m 3). Overall load-deflection response and material toughness values are compared and discussed. Beams reinforced with low volume contents of polymeric fibers typically exhibit a sharp drop in load carrying capacity after first crack. The shape of the load-deflection response in the initial portion of the softening regime is important for toughness computations, particularly for the smaller ASTM indices, such as I 5 and I 10. Since the type of test control and the level of post-peak stability provided by the test set-up influence the shape of the load-deflection response in this regime of interest, there are questions regarding the objectivity of toughness indexes computed at small limiting deflections.

Partially prestressed beams contain both prestressed and non-prestressed reinforcement. Addition of steel fibers results in an increase in first crack moment and flexural strength and a decrease in deflection and reinforcement stresses. This paper presents an analytical method to compute the deformation of partially prestressed beams made with fiber reinforced concrete. A computer program was developed to evaluate the theoretical moment-curvature and moment-deflection relationships. It uses the linear and nonlinear stress-strain relationships of the composite materials. Strain compatibility concept is incorporated to obtain the stresses in concrete, prestressed steel, and non-prestressed steel. The cracking moment and the nominal flexural strength are also computed. The method can analyze prestressed sections of rectangular, T, I, and box shapes. The analytical predictions of the proposed method agree well with experimental results.

It is well recognized that fiber reinforced concrete (FRC) exhibits a number of superior properties relative to plain concrete, such as improved strength, ductility, impact resistance, and failure toughness. These advantageous features of FRC can lead to novel structural applications, for which standard design and analysis procedures must be supplemented by numerical modeling (for example, the finite element method). This, in turn, makes necessary the development of satisfactory constitutive models that can predict the behavior of FRC under different load conditions, both monotonic and cyclic. In this paper, a constitutive model for FRC is developed loosely within the theory of mixtures. For plain concrete, an anisotropic, strain-based, continuum damage/plasticity model with kinematic and isotropic damage surfaces is developed. To represent the effect of the fibers, a simplified model that accounts for the tensile resistance of the fibers and the enhanced tensile resistance of the plain concrete is proposed. The predictions of the FRC constitutive model are compared to data from laboratory tests of steel fiber reinforced concrete (SFRC) specimens under uniaxial and biaxial loadings.

This research was specifically designed to test concrete in direct tension. Concrete prism specimens measured 4 x 4 x 16 in. in length. The specimens were first tested under monotonic loading conditions to determine ultimate stress-strain relationships. Samples were also tested under low-frequency high cyclic loading conditions to simulate concrete fatigue. Fibrous concrete containing steel, polypropylene, and composite fiber reinforcement made up the test groups. A closed-loop hydraulic test machine was used to develop a testing procedure to measure the monotonic and cyclic tension responses of fiber reinforced concrete. This procedure proved successful in determining the stress-strain relationship and cyclic behavior of the fiber reinforced concrete. The concrete evaluation included monitoring concrete in the plastic state. Concrete temperature, slump, air content, mix design, and mixing time were carefully controlled. The long-term concrete curing period lasted 150 days. The testing of cured samples included mechanical testing, statistical treatment evaluation, and scanning electron microscope analysis. The fiber reinforced concrete and composite fiber specimens provided substantial performance improvement when compared to the plain concrete specimens.