Development of Crumb Rubber Concrete for Practical Application in the Residential Construction Sector – Design and Processing

Extensive research has been carried out on crumb rubber concrete (CRC) in the past 10 years due to its potential as a sustainable and environmentally friendly material. Nevertheless, the practical use of this concrete class in the concrete industry to date has been very limited. This research is a part of a project that focuses on developing CRC for practical use in residential construction. The design and processing of CRC at three grades (20 MPa, 25 MPa, and 32 MPa) was carried out and the performance was investigated and compared with conventional concrete at the same strength levels. The study included three stages namely; selecting effective rubber particle size, designing and adjusting concrete mixes, and testing recommended mixes for practical applications. The slump, compressive strength, tensile strength, flexural strength, modulus of elasticity, shrinkage, creep, rubber pre-treatment effect and mixing order effect were measured. The results showed that within the crumb rubber size range used (0.15–2.36 mm) increasing the rubber particle size decreases the compressive strength losses. Compared to conventional concrete, the presence of 20% rubber as sand volume replacement decreased the 7-day/28-day strength ratio by values that ranged between 9% and 20%. CRC exhibited similar or lower shrinkage values, but higher creep strains compared to those of conventional concrete. The rubber pre-treatment enhanced the concrete slump, but no significant effect on compressive strength was observed. When the rubber was added together with water at the beginning without being premixed, the workability was low; however, when rubber was added and mixed dry or wet with the other materials, the CRC workability was enhanced.