Potential use of waste tire rubber as aggregate in cement concrete - A comprehensive review

The utilisation and reuse of waste tire rubber in concrete can reduce the consumption of raw materials, which leads to economic efficiency and sustainable development of the construction industry. In this review, we conclude the major achievement of crumb rubber concrete (CRC) in nearly 5 years, discuss and analyse its fresh concrete properties, mechanical properties, durability and other properties. Results show that utilising the hydrophobic nature of rubber particles and appropriate admixture can increase slump and improve the workability of concrete. Concrete incorporating crumb rubber (CR) particles decreases the fresh density, and it decreases linearly with the increase in the CR content. The mechanical properties of concrete generally decrease as the CR content incorporated increases. However, the compressive and flexural strength of CRC, which is slightly above that of natural aggregate concrete (NAC), is limited to fine CR size that replaces sand and optimum CR replacement level (CR content from 0% to 10% increases the compressive strength by 2%, and the flexural strength is increased by 7%-21% in mixes with 10%-20% CR). CRC has higher water absorption and permeability than NAC. Nevertheless, small amounts of rubber replacement level (2.5%-7.5% CR) and mixing different rubber particle sizes can reduce the water absorption of concrete. CRC exhibits high freeze-thaw resistance, electrical resistance, abrasion resistance and resistance to sulfuric and sulfate attack when incorporating proper CR content at concrete mixes. The depth of chloride-ion penetration of CRC decreases with low CR content (up to 27.3% of reduction for CR content of 5%) but increases when the CR content exceeds 20%. A clear advantage of CRC is favourable thermal and acoustic insulation. The mechanical properties and durability of CRC can be improved by adding treated CR particles, fibres and supplementary cementing materials. Further research is needed to improve the weak bonding in the interfacial transition zone between CR aggregates and cement paste, thereby increasing the mechanical properties and durability of CRC. Discussions in this paper can provide new knowledge and information on the applications of green and sustainable CRC. (C) 2019 Elsevier Ltd. All rights reserved.