International Concrete Abstracts Portal

SIFCON (slurry-infiltrated fiber concrete) is a type of fiber reinforced concrete construction in which formwork molds are filled to capacity with fibers and the resulting network is infiltrated by a cement-based slurry under vibration. The main objective of the paper is to investigate the compressive properties of SIFCON and to develop constitutive models to describe them. Primary focus is on the results of the experimental phase of the program. The experimental program consists of compression tests on 3 x 6 in. cylindrical specimens. Parameters under investigation include the following variables: four compressive strengths for the slurry (with and without fly ash and microsilica), three types of fibers (deformed, hooked, and crimped), orientation of fiber axis to direction of loading (normal and parallel), and the effect of mold walls (cored versus molded specimens). The instrumentation used comprises a servohydraulic testing machine with closed-loop control capability, a data acquisition system, data transfer devices, and data plotting. Results include the stress-strain response as well as strength, stiffness, and ductility properties. To model the descending branch of the stress-strain curve that exhibits a plateau value up to very high strains (10 percent), an analytical relationship with asymptotic behavior is proposed.

Article presents selected conclusions derived from a slurry-infiltrated fiber concrete (SIFCON) research program performed by a New Mexico research group under an Air Force contract. The selected conclusions discussed concern certain material properties of several SIFCON mixes tested under uniaxial, unconfined compression. The article concerns itself with the effect of varying the two parameters of water-cement and fly ash-cement ratios on the compressive strength.

Paper presents the results of an experimental investigation on the behavior of slurry-infiltrated fiber concrete (SIFCON) subjected to flexure, shear, and axial tensile loading. More emphasis was placed on the flexural behavior in which the specimens were subjected to static and high-amplitude cyclic loading. Four fiber lengths, namely, 30, 40, 50, and 60 mm, and four volume contents ranging from 4 to 12 percent were used. Fibers with hooked ends were used for the entire investigation. Effect of the addition of silica fume and sand to cement slurry was investigated by using a selective group of specimens made with 8 percent fiber content. Freeze-thaw studies were also conducted using prisms that had 8 percent fibers. The behavior in shear was studied using direct shear specimens. Properties in axial tension were investigated using four fiber contents of 50 mm long fibers. The results indicate that strengths of up to 10,000 psi (68.9 MPa), 4000 psi (27.6 MPa), and 2000 psi (13.8 MPa) can be obtained in flexure, direct shear, and axial tension, respectively. The composite is extremely ductile in all three modes of loading. Based on the tests conducted in flexure, addition of silica fume increases the strength. Sand can be added to the slurry without reducing the strength up to a certain cement-sand ratio. The ductility characteristics are not affected by the addition of either sand or silica fume.

Tests have shown that steel fibers increase the tensile strength of concrete and reduce the sudden failure in tension when bonding is adequate; impact resistance is also greatly increased. On a lesser scale, polypropylene fibers also increase the impact resistance of concrete. Compressive strengths of concrete containing either type of fiber are not increased. Since creep is a fundamental property of concrete, a test program was initiated to measure the effect of both steel and polypropylene fibers on plain concretes and on concretes containing silica fume. The addition of fibers, polypropylene or steel, increased substantially (20 to 40 percent) the creep of plain concrete and, to a lesser extent, the creep of concretes containing 5 to 10 percent silica fume. It was found that creep of concrete with or without fibers was decreased by at least 20 percent when 5 to 10 percent of cement was replaced by silica fume.

Theoretical analysis is used to predict bending properties of strain-softening materials from known stress-strain relationships in uniaxial tension and compression. Conversely, given the bending load-displacement relation, it is possible to predict the entire tensile strain-softening response. Bending properties of a polymer concrete have been obtained using the proposed theory and given stress-strain relationships. It is shown that the bending strength is higher than the tensile strength due to the strain-softening effect.