Properties of Steel Fiber Reinforced Concrete Using Either Industrial or Recycled Fibers from Waste Tires

Currently, more than 2.5 million tires are discarded each year in Bogota, Colombia, and 1.2 million of them are not properly disposed, producing a huge environmental problem. As a possible solution, previous studies have assessed the performance of steel fibers recovered from recycled post-consumer tires as reinforcement of concrete. However, engineers in Colombia are still uncertain to use this type of recycled material, since the concrete and the dosages used in reported studies were obtained mostly from different construction practices and materials in countries other than Colombia. The aim of this paper is to show and discuss the results of a research intended at evaluating the mechanical response of concrete reinforced using recycled steel fibers from waste tires in Bogota, Colombia. The testing campaign of the study comprised 45 axial compression and splitting tension tests on cylinders, and 14 bending tests on concrete slabs reinforced using nominal fiber dosages of 15, 30 and 60 kg/m(3)of steel fibers obtained from used tires. For comparative purposes, the study included also the test on 21 cylinders and 12 beams made of concrete reinforced using industrial steel fibers, with the same nominal dosages used for the recycled steel fibers. Based on measured response, preliminary design equations are proposed to estimate the mechanical properties of concrete reinforced using recycled steel fibers. It is also checked whether the obtained results fulfil the requirements specified by ACI-318 and NSR-10 building codes when steel fibers are used as minimum shear reinforcement of concrete beams.