Anwar Khitab

1. The construction industry is one of the largest consumers of natural resources and a significant contributor to global carbon emissions. The production of cement, a key binder in concrete, is pa...

The recent past has shown that rubberized cementitious composites, despite their potential benefits such as improved ductility, impact resistance, and utilization of waste rubber, exhibit reduced workability and mechanical strength. This performance degradation is attributed to the lower density and higher elastic nature of rubber particles, which hinder compaction efforts and induce voids. Also, the hydrophobic nature of rubber particles repels water molecules and gives rise to pores. Present research focuses on improving the workability and strength of rubberized composites by using waste materials like silica fumes and fly ash and adding polypropylene fibers. A 1:4 cement-sand mortar was prepared as a control specimen. A systematic study was conducted in which the ingredients were added incrementally. First, 5% of the sand was replaced with crumb rubber. In the next group of samples, silica fume and fly ash were included as extra materials in the cement, replacing 2.5% of the cement's weight. Subsequently, a water reducer was introduced. Finally, in the last set of specimens, polypropylene fibers were added at a rate of 0.1% by volume of mortar. The results revealed that the incorporation of crumb rubber reduced the 28-day compressive strength from 8.5 MPa to 4.55 MPa, corresponding to a strength loss of 46%. The proposed modifications reduced this strength loss to only 7.4%, resulting in a 28-day compressive strength of 7.9 MPa. Similarly, the flow value increased from 80 mm to 100 mm after the incorporation of supplementary cementitious materials. It is concluded that the careful incorporation of supplementary cementitious materials and synthetic fibers can improve the mechanical strength and workability of rubberized mortar.