Papers by Keyword: Steel Fibre Reinforced Concrete (SFRC)

Abstract: The effect of fibre reinforcement on Load Induced Thermal Strains (LITS) has not yet been significantly investigated up to now. Creep is becoming a key research topic only in the last few years. A semi-empirical model able to take into account both the thermo-mechanical damage associated to coarse aggregates and the thermo-chemical damage induced in the matrix and calibrated on the basis of the main results on plain concrete available in the scientific literature is presented. Some tests in uniaxial compression on Fibre Reinforced Concrete (FRC) cylinders characterized by a long age – 11-years-old – have been investigated and compared with the model to highlight fibre effects, if any. The uniaxial compressive strength at 28 days of the SFRC was 75 MPa; the specimens after 11 years showed a compressive strength exceeding 110 MPa. A strong increase of SLS residual strength was observed in post-cracking tension due to the long aging, while ULS residual strengths weakly increased. The cylindrical specimens were exposed to a maximum temperature of 200°C and 400°C and loaded with two load thresholds corresponding to 20% and 40% of the compressive strength detected at 28 days of aging, that means about 12.5% and 25% of the 11-years-old specimens. Two paths were investigated: pre-heated specimens up to 200°C or 400°C, then loaded with a compression stress equal to 0.2f_c,28 and 0.4f_c,28; and pre-loaded specimens up to 0.2f_c,28 and 0.4f_c,28 and then heated up to 200°C or 400°C. The duration of each test did not exceed 12 hours. Two main fibre effects were observed: a significant reduction of irreversible strains when the specimens were loaded and then heated and cooled and a different evolution in LITS passing from 200°C to 400°C, characterized by a significant reduction of the expected deformation.

Abstract: Currently, manufacture of steel fibre reinforced concrete (SFRC) takes place in concrete mixer truck for floors mostly of industrial halls. This technology is suitable for low dosages of fibres (about 20kg/m³), which is determined by uncrossable price of deposited concrete (400 – 600 crowns/m² for the floor in thickness from 150 to 200 mm). Totally realistic premise in future is, that SFRC will be used for load-bearing SFRC structures of aboveground objects. In this case, production of SFRC must take place in concrete plants at higher weight doses than 40 kg/m³ of fibres, to achieve the characteristics of SFRC, which bring effects to SFRC structures. In the paper, there are presented two examples of the production of SFRC in concrete plants. There is specified manufacturing process of production of SFRC in mixers with forced circulation, which is necessary to comply, in order to achieve a homogenous fresh fibre concrete and to minimize wear of machinery.

Abstract: This paper describes the experimental results on compressive and flexural behavior of alkali-activated slag (AAS) concrete reinforced with hooked end steel fiber. Two different fiber volume fractions of 0.5 and 1.0% were used for AAS concrete and Ordinary Portland cement (OPC) concretes were also mixed for comparison. Test results indicated that compressive and flexural performance of AAS concretes with water-to-binder (W/B) ratio of 0.55 are equivalent to those of OPC concrete. The addition of steel fiber to AAS concrete improves more compressive and flexural performance than those of steel fiber reinforced concrete.

Abstract: This paper provides experimental results on the seismic performance of four concrete infill wall elements with test variables of vertical slits and hooked end steel fiber reinforcing. 1/3-scale infill wall elements with height-to-length ratio of 0.55 were manufactured and tested up to failure. Four walls (CIW-N and-S, SCIW-N and-S) are similar to each other except presence of steel fiber reinforcement and vertical slits with the width of 40 mm. All specimens had the same rectangular cross-section of 1,100 mm x 50 mm, with wall panel height of 600 mm. The experimental results showed that concrete infill wall element with vertical slits exhibited more stable hysteretic behavior than solid infill wall element. This phenomenon is remarkable for steel fiber reinforced concrete infill wall element. Inclusion of vertical slits on the normal concrete and steel fiber reinforced concrete infill wall element improve the ductility and energy dissipation capacity but decrease the load-carrying capacity and stiffness of infill walls.

Abstract: Uniaxial dynamic compression tests were carried out on the triaxial testing machine to investigate the effect of noncyclic variable amplitude load. The characteristic of steel fiber concrete and differences among static uniaxial loading testing and dynamic uniaxial testing were studied systematically. It is shown that both the strain and the stress are directly proportional to the cycle frequency. Meanwhile, as the cycle amplitude increases, the irreversible plastic deformation increases gradually. And increasing the strain ranges, the stress strain curve becomes sparser. The comparison tests indicate that the peak stress relies on the loading modes. Under noncyclic variable amplitude load, the peak stress is higher than that of the static uniaxial load testing and the dynamic uniaxial testing, but the peak stress of the type corresponding to different frequency shows no evident difference.

Abstract: Through low cycle reverse tests of three steel fiber reinforced concrete coupled shear walls, the crack pattern, bearing capacity, stiffness and displacement are analyzed. Test results show that the bearing capacity, yielding stiffness and the anti-crack performance of the coupled shear walls are generally improved by adding steel fibers to reinforced concrete coupling beams, and the stiffness degeneration is also reduced to a certain degree. More cracks are induced by steel fibers bridged the main crack, which can make the shear wall consume more energy.

Abstract: Steel fiber reinforced concrete is a new type of composite material developed rapidly in recent years. It is widely used in various types of engineering construction field with its good crack resistance, flexural toughness and impact resistance. Meanwhile, Steel fiber reinforced concrete has high tensile strength and fracture toughness, fatigue resistance, and forming pouring easy，for variety of complex stress position of the structure. This paper provides something for this new concrete materials in the project of the building structure design and construction, through the introduction of the main performance of steel fiber reinforced concrete.

Abstract: By the method of experiment and simulation of numerical value, destructive effect of SFRC under strong impact load is studied, the destructive effect of numerical value simulation is well matched with the experimental result, it is analyzed that the destructive effect of SFRC explosion is affected by the main factor of the content of steel fiber in SFRC, and effects not only on the destructive parameter of SFRC, but also on its form and compress destructive coefficient K_a.

Abstract: The effects of aggregate size and fiber volume fraction on the flexural behavior of 70MPa high strength steel fiber-reinforced concrete (SFRC) were investigated in this work. Test variables consist of fiber volume fraction (0, 1 and 2 %) and maximum aggregate size (8, 13 and 20 mm). The prism for flexural test was 100 x 100 x 400 mm and was tested under four points loading. Flexural toughness index was measured using ASTM C 1018 procedure. Test results indicated that the addition of steel fiber to 70MPa high strength concrete improves flexural and post-cracking behaviors. This phenomenon is remarkable for SFRC mixture with higher fiber content and smaller aggregate size. Also, the flexural toughness of high strength SFRC depends primarily on fiber content. The maximum aggregate sizes were secondary in importance.

Abstract: Three 1/3-scale squat steel fiber reinforced concrete (SFRC) shear walls with height-to-length ratio of 0.55 were manufactured and tested up to failure. Two walls (SFRC-SS and-LS) are similar to each other except the height (230 and 460mm) of vertical slits with the width of 40mm. For comparison, solid wall (SFRC-NS) was made. All specimens had the same rectangular cross-section of 1,100mm x 50mm, with wall panel height of 600mm. The experimental results showed that squat SFRC shear walls with vertical slits exhibited more stable hysteretic behavior than a solid SFRC shear wall. Vertical slits on the squat SFRC shear walls improve the ductility and energy dissipation capacity but decrease the load-carrying capacity and stiffness of squat SFRC walls.