Steel Fiber Reinforced Lightweight Concrete Research Articles

Mechanical Behavior of Steel Fiber-Reinforced Lightweight Concrete Exposed to High Temperatures

The mechanical characteristics of steel fiber-reinforced lightweight concrete (SFLWC) under high temperatures are studied in this paper. Different concrete matrices, including all-lightweight concrete (ALWC) and semi-lightweight concrete (SLWC), and different steel fibers with hooked ends and crimped shapes are considered as objects. In addition, normal-weight limestone aggregates concrete (NWC), no-fiber ALWC, and SLWC were tested after high-temperature treatment as a control group. The temperature effects on the splitting tensile strength, ultrasonic pulse velocity, compressive stress–strain curve, elastic module, peak strain, and axial compressive strength of the SFLWC were investigated. The results showed that, with increasing exposure temperature, both the axial compressive strength and the elastic modulus decreased, while the axial peak strain has a certain increase, and hence the stress–strain curves were gradually flattened. The toughness of all the concretes increased first and then reduced with increasing temperature, while the specific toughness of all the concretes increased with the increase in temperature. Compared with NWC and SLWC, ALWC had a better capacity to resist high temperatures, especially temperatures > 400 °C. Adding steel fibers can improve the capacity of energy absorption, specific toughness, and residual splitting tensile strength of lightweight concrete (LWC) before and after it is exposed to high temperatures. Based on a regression analysis, a segmented constitutive equation for LWC and SFLWC under uniaxial compression was derived from fitting the experimental findings, and the fitting curve agrees well with the test results.

Structural Performance of Steel Fibre Reinforced Lightweight Concrete Frames Subjected to Lateral Load

Masonry infilled Reinforced Concrete (RC) framed structure is the utmost common kind of building in which, RC frames contribute in resisting lateral forces. Due to heavy mass and rigid construction, the RC framed buildings performs unfortunate under lateral forces. Practice of Lightweight concrete (LWC) is superlative because the dead load of concrete is massive. Low density materials are chosen in LWC, reduces the mass of the building thus decreasing the influence of lateral forces. However, LWC having a lesser modulus of elasticity has a more rapidly develops the cracks in the RC members. In this investigation, pumice is a naturally available material of volcanic source, has low density, which creates it ideal for production of LWC, likewise steel fibres are employed as an additive to enhance the energy absorption ability and to reduce the possibility of development of the cracks. In the present paper the structural behaviour of Lightweight RC framed structures realized by using steel fibres and subjected to lateral forces, In this study, four RC frames viz., F1-NWC (Control), F2- NWCF (with 1% Vf of steel fibres), F3-LWC (with 20% substitute of coarse aggregate instead of pumice aggregate) and F4-LWCF (with 20% substitute of coarse aggregate instead of pumice aggregate and 1% Vf of steel fibres) were casted and tested under in-plane horizontal loading, which are designed according to Indian Standard (IS) code IS 456 (2000). It was observed that the behaviour of F4-LWCF significantly better in comparison to other frames in various parameters such as load carrying capacity, displacement, ductility, stiffness and energy dissipation.

Experimental investigation on bond of reinforcement in steel fibre-reinforced lightweight concrete

Bond behaviour of reinforcement is crucial parameter for load bearing reinforced concrete members. Many parameters like anchorage of reinforcement, lap splices, deflection or tension stiffening are influenced by the bond properties. It is well known that the ductility of bond can be improved by steel fibres. In this context almost innumerable experiments were performed for investigation of bond in normal weight concrete. However, the bond behaviour of reinforcement in steel fibre-reinforced lightweight concrete (SFRLWC) has received much less attention. For this reason, an experimental program dealing with bond in SFRLWC has been started at HTWK Leipzig/Germany. Main parts of the investigation were pull-out tests with various bar sizes and application of different steel fibre-reinforced lightweight and normal weight concretes. The paper reports the details of experimental investigations and evaluates the test results. As one of the most important outcomes that can be noted is that there is pronounced effect of bar size and steel fibre amount on bond properties in general. But those effects are more pronounced for SFRLWC in comparison to normal weight concrete with and without steel fibres.

Flexural and Shear Resistance of Steel Fiber–Reinforced Lightweight Concrete Beams

In the present paper an analytical model is proposed that is able to determine the shear resistance of lightweight reinforced concrete beams with longitudinal bars, in the presence of reinforcing steel fibers. The model is based on the evaluation of the resistance contribution resulting from beam and arch actions. For the resistance contribution of main bars in tension, the residual bond adherence of steel bars and the crack spacing of reinforced concrete (RC) beams in the presence of fibers are considered. The contribution in terms of postcracking resistance in the tension zone of the beams is also included. The model was verified on the basis of experimental data available in the literature and is able to include the following variables in the resistance provision: diameter and number of steel bars, depth to shear span ratio, resistance of materials and fiber characteristics, crack spacing, tensile stress in main bars, residual bond resistance, postcracking tensile resistance, and size effects. Finally, some of the more recent analytical expressions able to predict the shear resistance of fibrous concrete beams are mentioned and a comparison is made with experimental data.

Mechanical properties of steel fibre reinforced lightweight concrete with pumice stone or expanded clay aggregates

This paper presents basic information on the mechanical properties of steel fibre-reinforced light-weight concrete, manufactured using pumice stone or expanded clay aggregates. Results are presented for standard compressive tests and indirect tensile tests (splitting tests on cylinder specimens and flexure tests on prismatic beams using a three-point loading arrangement) under monotonically increasing or cyclically varying loads. The influence of steel fibres and aggregate types on modulus of elasticity, compressive and tensile strength and post-peak behaviour is evaluated. Test results show that compressive strength does not change for pumice stone aggregates, while an increase is observed for expanded clay; tensile strength and fracture toughness are significantly improved for both pumice stone and expanded clay. The results also show that with both expanded clay and pumice stone lightweight aggregates a suitable content of fibres allows one to obtain performances comparable with those expected from normal weight concrete, the important advantage of lower structural weight being maintained.

Impact resistance of steel fibre reinforced lightweight concrete

Resistance to impact and other suddenly applied loads is now recognised as one of the significant properties of fibre reinforced cementitious materials. Until recently there has, however, been no simple and practical test method to measure this property of fibre concrete and to evaluate the effectiveness of the different types of fibres in enhancing the impact strength of fibre concrete. More recently ACI Committee 544 has developed such a method, and this test is currently being considered for inclusion as an ASTM standard. This paper reports on the application of this test method to determine the impact resistance of structural lightweight concrete reinforced with steel fibres. It is shown that the test can effectively assess the impact resistance of plain and fibre concrete, and that it is able to distinguish the differences due to fibe shape and fibre geometry.