A team of engineers in Australia has come up with a new recipe for a road construction material that draws on two huge sources of waste; discarded tires and building rubble. The blended material was shown to offer the strength and flexibility required to handle heavy traffic, while being made from entirely recycled products.
The work was carried out by engineering researchers at Melbourne’s RMIT University, who point to the monumental amount of waste generated by construction, renovation and demolition practices around the world as motivation, along with the billions of scrap tires that are discarded annually.
Building rubble that is crushed and processed can be repurposed as a building material called recycled concrete aggregate (RCA). This can then be integrated with other building materials to lessen their environmental footprint, or find special use in areas such as drainage or filtering applications.
Another area where RCA can carry some of the load is in road construction. More specifically, as the base layer that sits above the subgrade and sub-base layers and below the asphalt on top. The RMIT team was experimenting with additives that could improve its performance in this area, and through its experiments found that crumb rubber taken from scrap tires fits the bill nicely.
The team established that a makeup of 0.5 percent fine crumb rubber and 99.5 percent RCA ticks quite a few important boxes. Using special machinery to test its performance, the team found that it delivered the required amount of shear strength, while maintaining good cohesion between the two materials.
This recycled blend is the first to feature a mix of rubber and rubble precisely optimized to meet road engineering safety standards, according to the team. It does offer greater flexibility than conventional materials, which the team says should make it less prone to cracking, all while offering a greener approach to construction.
“Traditional road bases are made of unsustainable virgin materials – quarried rock and natural sand,” says lead researcher Dr Mohammad Boroujeni. “Our blended material is a 100-percent recycled alternative that offers a new way to reuse tire and building waste, while performing strongly on key criteria like flexibility, strength and permanent deformation. As we push towards a circular economy that can eliminate waste and support the continual use of resources, our recycled blend is the right choice for better roads and a better environment.”
The research was published in the journal Construction and Building Materials.
Source: RMIT