Performance enhancement of rubberised concrete via surface modification of rubber: A review

Adding rubber to concrete not only facilitates handling of waste rubber and reduces consumption of natural raw materials but also improves certain properties of concrete. However, due to the hydrophobic nature of rubber, the hydraulic phase migrates out of the rubber and causes a weak interfacial transition zone between the rubber and cement matrix. Moreover, compared with the modulus of elasticity of natural aggregates, that of the rubber aggregates is much lower than that of the surrounding cement matrix. As load is applied to rubberised concrete, stress concentration is formed around the rubber aggregates, thereby resulting in crack formation and strength reduction. Therefore, modifying the rubber surface is an effective method to improve the interface bonding between the rubber aggregates and cement matrix. Physical and chemical rubber modifications are two common methods for enhancing the bond between rubber and cement matrix, which is beneficial for improving the mechanical properties and durability of rubberised concrete. This paper reviews the published methods for modifying rubber aggregates to enhance the performance of rubberised concrete and points out their advantages and disadvantages. The rubber pre-coated with cementitious materials and treated with sodium hydroxide solution, silane coupling agent and sulphuric acid solution show promising results. The combined treatment methods are remarkable in improving mechanical properties. At present, the cost and environmental impact of various treatment methods have not been considered, but these areas should be considered when selecting low-cost and highly efficient methods, which are essential for the extensive application of rubberised concrete in engineering. (C) 2019 Elsevier Ltd. All rights reserved.