Valorization of Douala Car Tyres Steel Fibers Waste in Concrete at Cameroonian Coast: Effect of Lengths and Fibers Content

Abstract

In developing countries such as Cameroon, the sale and use of second-hand tyres from European and Asian countries is booming; most vehicle owners cannot afford new tyres. These tyres obviously have a very short life (less than 3 months) and end up in the wild or in fire, with for both cases, a serious environmental impact: this often means that these countries are the garbage of the West. In order to make a useful valorization of these wastes, this work makes a contribution by incorporating the steel fibers from worn-out tyres into concrete. The study showed the impact of fiber lengths and their proportion, in quantity, on the mechanical behavior of concrete. To do this, the concrete was reinforced with steel fibers from used tyres collected from tyre operators in Douala 5^th specifically in Ndogbong - Douala. The sand used in this work comes from the river Sanaga - Edéa. We made test pieces according to four fiber grades (0%, 0.4%, 0.6% and 0.8%) and three different lengths of steel fibers (2 cm, 3.5 cm and 5 cm), in accordance with previous works. Subsequently, three-points bending tests, compression tests, water absorption rate and density tests were carried out on concrete samples at 7, 14 and 28 days of cure. Test pieces of dimensions 40 x 40 x 160 (in accordance with EN 196) were used to determine the rate of water absorption, density and tensile strength by three points bending in a first step; then those of dimensions 40 x 40 x 80 (following the NF P 18-406 standard) allowed to determine the compressive strengths. Analysis have shown that the density of steel fiber reinforced concrete is higher than that of control concrete in all cases. The introduction of steel fibers into concrete reduces the rate of absorption of concrete. In addition, compared with the control concrete, the bending limits and compression stresses of the different proportions increased for all lengths and fiber contents.  However, it was observed that concrete specimens with a dosage of 0.6% steel fibers and a length of 2 cm (BFA2-6) had an optimum physical and mechanical properties and was more elastic.