Crumb rubber has been used in spray seal binders in Australia since the 1970s, and is continuously being explored across the country by producers and contractors alike as a cost-effective maintenance treatment.
As a material derived from end-of-life tyres, crumb rubber boasts a number of environmental benefits as a recycled product – benefits that are being realised across the Australian roads and infrastructure sector.
SAMI Bitumen has been leading technological innovations in the sector for nearly 40 years, and has established itself as a staunch player in the national bitumen market. One of its most recent accomplishments has been the development of its long-haul S45R crumb rubber binder, which overcomes traditional challenges around material transportation across long distances and is helping increase the uptake of the sustainable material.
The binder has been specially formulated so that it remains more storage stable during prolonged heating and transport from the factory to the point of use. SAMI’s Technical Services Manager Iulian Man says previously, the use of preblended crumb rubber binder was limited to a short distance from the point of manufacture.
“SAMI’s new crumb rubber binder technology allows the preblended binder to be transported over thousands of kilometres without any degradation or settlement problems. This was proved again more recently with the use of SAMI’s S45R binder on two large rural reseal contracts in Queensland and Western Australia,” Mr. Man explains.
Approximately 1500 tonnes of S45R binder was supplied to Colas’ spray sealing crew for a project in the Western Region of Queensland – located over 1000 kilometres away from SAMI’s Brisbane plant.
“The typical transport and heating time for each delivery to the work site was 27 hours. No problems were experienced with rubber settlement in the road tankers or changes in the binder properties at the point of use,” he says.
Similarly, 5000 tonnes of S45R was supplied to Boral for a reseal contract in the Goldfields region near Kalgoorlie and Esperance from SAMI’s Freemantle binder plant in Western Australia without any problems.
Mr. Man says the use of preblended long haul crumb rubber binder is a win-win for all stakeholders, from the surfacing contractor to the asset owner and the environment. “The supply of preblended crumb rubber modified binder over long distance negates for the need to carry out field blending at the point of use,” he says.
“Contractors also prefer to use crumb rubber modified binder because it improves the early stone retention in the newly constructed spray seal.”
This means that the new spray sealed surface can be swept and opened to traffic much sooner compared with other binder types, reducing the risk of stone wipe-off. The natural rubber and polymer in the tyres are very effective for improving the elastic properties of the bitumen, which is good for sealing cracks in the pavement. The carbon black in the rubber is an antioxidant, which helps improve the durability of the binder, providing a much longer life to the seal.
SAMI’s General Manager Sebastien Chatard says there are also big benefits to the environment in reusing the rubber from end-of-life tyres. SAMI’s crumb rubber binder, for instance, is produced from rubber buffings recovered from used truck tyres.
“In 2018 this amounted to 658,000 equivalent passenger car tyres being saved from ending up in landfills,” he says. “Australia generates about 56 million equivalent passenger car tyres per annum. So, SAMI is doing its bit by helping to reuse the rubber in these tyres to modify the properties of the bitumen.
“By reusing the rubber from end-of-life tyres we are reducing the demand for importing more expensive polymers to modify bitumen, providing a more durable and longer lasting road surfacing and keeping old tyres out of landfills.”