Page 114 - New Trends in Eco efficient and Recycled Concrete

88 New Trends in Eco-efficient and Recycled Concrete

The shortage of natural resources, such as sand, also pushes for the reuse of by-
products as fine aggregates. Waste rubber as a partial or full replacement of the fine
aggregate fraction in construction materials not only reduces the demand for extrac-
tion of natural raw materials, but also saves landfill space.
This chapter aims to review research which has been carried out on the effect of
partial or full replacement of fine aggregates in traditional mortars and concrete
based on Portland cement binder, with waste rubber as the main property of
cement-based materials.

4.2 Waste rubber aggregate characterisation

4.2.1 Chemical properties
Chemical compositions of waste rubber mainly depends on the origin of the waste
material. Sienkiewicz et al. (2017) show that there are eight types of natural
rubber and 30 types of high-quality synthetic rubber, and various chemical com-
pounds are used to vulcanise them. Rubber from tyres is generally composed of
different types of rubber, such as textile cords, fabric belts, and vulcanised rubber.
Styrene Butadiene rubber is a widely used polymer in the tyre industry. Carbon
black, zinc oxide, natural rubber and sulphur, etc., are also often added. Jusli
et al. (2014) examined the chemical properties of waste rubber tyre granules by
using X-ray fluorescence to establish its chemical composition. The energy
dispersive X-ray (EDX) analysis showed that the main elements in waste tyre
rubber granules are carbon, zinc, silicon, magnesium and calcium. The X-ray
fluorescence (XRF) apparatus was used based on the procedure stated in BS ISO
29581-2 to determine the chemical composition of tyre rubber granules as shown
in the Table 4.1.

Table 4.1 Chemical composition of waste rubber tyre granules
(Jusli et al., 2014)

Chemical composition Percentage (%)
SBR 48.0
Carbon black 47.0
Extender oil 1.9

Zinc oxide 1.1
Stearic acid 0.5
Sulphur 0.8
Accelerator 0.7
SBR, styrene butadiene rubber.