Green Manufacturing of UHPFRC Made with Waste Derived from Scrap Tires and Oil Refineries

Ultrahigh-performance fiber-reinforced cement-based composite (UHPFRC) made with waste derived from scrap tires and oil refineries was tested in this study. The UHPFRC sample exhibited a maximum compressive strength of about 189 MPa at the end of 28 days. Steel fibers were recovered from scrap tires and were added up to 3% by volume in the UHPFRC samples. Such additions reduced cement flow by 11% but improved compressive strength by 21%. The equilibrium catalyst particles (ECAT) disposed of by oil refineries were used in amounts of up to 15% by weight as a replacement for cement in such UHPFRC samples. These aluminosilicate materials are spherical in shape and have a porous microstructure, which was found to reduce the cement flow by absorbing more free water onto their surfaces. They also reduced the heat and strength developments at early stages. However, the total cost of the final cement-based mixture and associated CO2 emissions were reduced by up to 7% and 15% due to the inclusion of the ECAT particles. These findings help to optimize the ECAT and recovered steel fibers in the UHPFRC mix design, and such waste valorization strategies can help achieve the goal of becoming carbon neutral.