Application of Steel Fiber Reinforced Lightweight Aggregate Concrete in Underground Mining

Several devices are used to provide support in an underground space. Wooden prop is generally employed for the purpose of passive secondary or short-term support of the mine roadway roof and sides. The wooden prop has various known usage limitation, including low strength, deterioration of wood in humid environment, poor ductility, and generally low service life. Substitution of the wooden prop with a prop made with a more suitable material could thus yield important advantages. In this study, lightweight aggregate concrete (LWAC) is proposed to be used as a prop material. Since lightweight aggregate has a relatively low ductility, steel fibers are used in this investigation to achieve enhanced ductility levels. Five mixtures of fiber reinforced lightweight aggregate concrete were considered with different steel fiber percentages and pumice lightweight aggregates produced in Iran. The density, compressive, tensile and flexural strength as well as the toughness index of different fiber reinforced lightweight aggregate concrete materials were measured in order to assess their potential as replacement for wood in prop production. The experimental results indicated that the density of lightweight aggregate concrete is higher than wood. Since the strength and toughness of LWAC is significantly more than those of wood, the weight of a LWAC element with the same strength turns out to be 22 percent less than the wood element. Hence, wooden prop may be replaced with lightweight aggregate concrete prop to achieve improved service life and ductility while reducing the weight of the prop

Shear resistance of channel shear connectors in plain, reinforced and lightweight concrete

This paper presents an experimental study on determining shear resistance of channel shear connectors in a solid concrete material slab under monotonic loading. The solid concrete slab is of different types of concrete including plain, reinforced and lightweight concrete. The channel shear connector length is varied as well. A series of push-out specimens were tested for this study. The results verified using channel shear connectors embedded in lightweight concrete in composite structures and shows that lightweight concrete has a slight effect on the ductility and load-displacement performance of the specimens. However, using reinforcement in concrete causes considerable increase in ultimate strength and ductility of channel shear connectors and using channels embedded in unconfined normal concrete has a brittle performance of them. In general, the channel shear connector showed a ductile behaviour.</p

Experimental assessment of angle shear connectors under monotonic and fully reversed cyclic loading in high strength concrete

An experimental study was performed to investigate the behaviour of angle shear connectors embedded in high strength concrete (HSC) slab. Eight push-out specimens were tested covering various geometries of angle shear connector. On top of the experimental study, the accuracy of the available equations to estimate the load capacities of angle connectors is also evaluated for the angles embedded in HSC. The results show inadequate ductility behaviour for the angle shear connectors embedded in HSC. Nonetheless, the angle connectors exhibited good behaviour in the case of strength degradation under cyclic loading. All specimens experienced the angle fracture type of failure and showed a very low strength degradation (0.1%-1.4%) when they were subjected to low cyclic fatigue loading. This study also concludes that the current available equations estimated the shear capacity of angle connectors embedded in HSC either are conservative or overestimate the ultimate capacity.</p