Some properties of sustainable lightweight concrete incorporating rubber and fibers from waste tires recycling

Waste tire disposal continues to increase an environmental concern in world regions. Disposing of used tires is a significant environmental problem faced by most regions, especially in urban areas of Iraq. Recycling rubber tire waste contributes to solve the issues mentioned above by using recovered materials such as crumbled rubber and steel fibers to make a new type of sustainable concrete. This research used Recycled Tire Steel Fiber (RTSF) to study its effect on high strength lightweight concrete containing tire rubber aggregate. The ultrasonic pulse velocity (UPV), water absorption, static modulus of elasticity, thermal conductivity, and flexural toughness of all prepared concrete mixes were tested. Several trial mixes with various rubber waste contents (10, 15, and 20% for coarse aggregate as 5, 10, and 15 % for fine aggregate) as volume substitution to natural coarse or fine aggregate were carried out. The selected lightweight concrete mixtures is with 20% and 15% volume replacement of rubber to coarse and fine aggregate respectively. Also, this selected mixture was reinforced with different volume fractions of recycled tire steel fibers of 0.5%, 0.75, and 1%. The results illustrate that the inclusion of RTSF enhances the UPV of concrete with rubber tire aggregate, and high strength lightweight concrete with 50 MPa-compressive strength or more that can be produced. The improvement in UPV, static modulus of elasticity, and flexural toughness were 22%, 12.7%, and 1114%, respectively, for the lightweight concrete reinforced with volume fraction of 1% compared to the reference mixture.