Comparative study on properties of kerb concrete made from recycled materials and related carbon footprint

Kerbs play an important role in providing structural support to the road. The compressive strength of concrete is often the only design consideration. Premature kerb failure is common indicating that only considering compressive strength in design may not be sufficient. Flexural/bending strength, deflection capacity, impact resistance, water absorption/sorption, abrasion resistance, and freeze-thaw resistance can also be important. The use of recycled products in concrete has been an active area of research in recent years and concrete produced from recycled concrete aggregate (RCA) and tyre-derived aggregate (TDA) could be a cleaner and more sustainable alternative to conventional concrete. In this study, ten different concrete mixes were developed for a target strength of 25 MPa and tested for mechanical and durability properties. Significant variations in the mechanical properties of different concrete were observed despite all concrete having similar compressive strength. The addition of TDA was found to improve flexural strength, deflection, and abrasion resistance properties, however, it led to inferior impact resistance and higher shrinkage compared to control concrete. A carbon footprint analysis showed that the use of 100% RCA (replacing natural aggregates) could drastically reduce the carbon footprint of concrete. For concrete with TDA aggregate, some environmental benefits of recycling TDA may get offset by the additional binder requirement to achieve the desired compressive strength.