A study on the properties of concrete aggregate replacement in rubber cement

The automobiles industry has grown rapidly in the last three decades throughout the world and the increasing use of cars as the main mode of transport has brought a huge boom in car tyre production. This means that an enormous number of waste car tyres are left at the end of its life. Apart from domestic cars, a large number of tyres wastes are also generated from commercial and heavy goods vehicles. Producing rubberised concrete by utilising waste tyre rubber as an aggregate can prove to be an effective approach to massively reduce tyre waste.
In this study, the performance of concrete mixtures containing rubber as fine and coarse aggregate was investigated. Scanning electron microscopy (SEM), water absorption, density, compressive strength and non-destructive tests were performed using test specimen (w/c = 0.43) containing two types of rubber. Two mix designs were designed containing 10% of as-received rubber or cement paste treated rubber. The results of two mixtures have been compared with the control mix which is used as a reference. It was found that using 10% v/v of crumb rubber into concrete reduced 12% of compressive strength while only 2% reduction was observed when 5% crumb rubber with 5% chipped rubber coated with cement paste was utilised. Overall the results showed that the use of cement coated rubber in concrete gave favourable results when compared to the control.
The SEM observation for interfacial transition between cement, aggregate and rubber was also studied. It was observed that a strong interface bonding occurs between cement paste and aggregate, but a weak interface bonding is formed rubber, cement paste and aggregate.