Experimental evaluation of using pyrolyzed carbon black derived from waste tires as additive towards sustainable concrete

Waste tires (WTs) are one of the most critical environmental problems worldwide. Since the WTs cannot be landfilled or burned, innovative solutions and proper solid waste management are needed. Therefore, several methods have been proposed for WTs treatment. Among these methods, the pyrolysis process is considered the most favorable. Pyrolysis is a process of converting WTs in absence of oxygen into pyrogas, fuel oil, and a by-product, which is pyrolyzed carbon black (PCB). To introduce the idea of eco-friendly and sustainable concrete, it is proposed to use PCB as an additive in concrete structures. In this experimental investigation, PCB samples are obtained from a local pyrolyzed WTs plant. Several concrete properties are investigated considering different mixes of different weight percentage ratios of PCB to cement (PCB/c); 0% (control sample), 3%, 3.5%, 4%, 4.5%, 5%, 7%, and 10%. Typically, fixed amounts of cement, water, sand, aggregate, and superplasticizer are prepared following international preparation standards, and then, mixed with the aforementioned PCB/c ratios. Afterward, an array of mechanical tests are performed investigating properties enhancements. These tests are slump, compressive strength, and abrasion resistance, along with water absorption. Results show a noticeable increase in the compressive strength for tested samples of 29.3 and 38.4 MPa were obtained at a ratio of 4% for 7 and 28 days, respectively. This is combined with a slight reduction of slump results; however; slump values are still within standard limits for most of the mixes. In addition, abrasion resistance results suggest a vital improvement in the PCB/c mixes. Also, water absorption measurements reflect enhancement of concrete mixes up to a specific percentage of PCB. Amongst tested PCB/c ratios, the study highlights the optimal value to be between 3% and 5%. In addition, a multi-level framework on the impact of institutional pressures on the adoption of PCB as an additive to cement has been addressed to rationalize and raise awareness towards the applicability of such a feasible approach. Thus, the overall results reflect the promising horizons of using PCB as an improving additive material in concrete mixes.