ROAD MAINTENANCE: Shuttle Buggy: More Road Life and Less Road Maintenance
Recent Gauteng Business News
Johannesburg-based Osborn has unveiled a new equipment offering that could bring down South Africa's road maintenance costs by up to 90%. It is the Roadtec Â“Shuttle BuggyÂ”, a state-of-the-art material transfer vehicle that is used extensively by government roads departments worldwide to achieve consistently high quality asphalt surfaces.
With the country's pothole problem constantly making news, along with a multi-billion Rand road maintenance backlog, South Africa is in dire need of a solution like the Shuttle Buggy. Recognising the value of this revolutionary unit, Polokwane Surfacing has already purchased one, and, according to Peet Venter, product sales manager at Osborn, the Shuttle Buggy is set to revolutionise road building and maintenance in South Africa.
Osborn is a wholly-owned subsidiary of United States-based Astec Industries, and is now supplying and supporting exceptional Astec equipment Â– like the Shuttle Buggy - in the South African market, giving a world-class boost to the country's road maintenance capabilities, among other areas.
The Shuttle Buggy Does Away with Thermal Segregation on Roads
Venter explains that thermal segregation is one of the reasons that asphalt pavement surfaces fail prematurely. Another reason is aggregate size segregation, which is caused by the same movement of the delivery vehicle as thermal segregation. Â“Even new pavement can show segregation spots - both thermal and aggregate size segregation - caused in great part by the delivery truck.Â”
Offering an unrivalled solution to this problem, the Shuttle Buggy is a mobile silo and on-site mixer for hot mixed asphalt paving material. It is capable of unloading a truck at a rate of 907 tonnes per hour, and re-blending the material to a uniform temperature and stone size gradation. After mixing, the machine sends material to the paver at a rate of 544 tonnes.
The patented triple pitch auger technology is the key to the mixing action of the Roadtec Shuttle Buggy, Venter states. Â“Steel drag slat conveyor technology aids mixing and carrying of paving material. Rubber belts are a problem because of the heat of the paving material.Â”
The Shuttle Buggy stands between the delivery vehicle and the paver. It receives and remixes the hot material to make the temperature homogeneous. Â“By eliminating the effect of 'end of load' segregation, the Shuttle Buggy doubles the road life and dramatically reduces maintenance costs.Â” This claim by the supplier has been borne out in studies undertaken by the Washington State Department of Transport (WSDOT) in the USA. According to the Department's Dr Joe Mahoney, the use of the Shuttle Buggy has Â“had a huge impact on improving the quality of our hot mix asphalt. Before understanding the issues with cyclic differentials and how to solve them with the Shuttle Buggy, it was common in Eastern Washington to see a pavement last only six years or so (due to cyclic differentials). Following the research and implementation over several years, this construction related issue rarely occurs and we typically expect a performance life of 11 to 12 years in that part of the stateÂ”.
Flawless Performance by the Shuttle Buggy
Osborn's Venter notes that spot temperatures across the paved (asphalt) mat differing over 14Â°C are a major problem. Â“These spots will have higher air voids after compaction than the surrounding mix, thus providing a weak spot for the entire structure. These 'over 14Â°C' projects typically lasted only half as long as ones with uniform temperature. Spots over 7Â°C will increase the maintenance cost even if they do not halve the service life,Â” he stresses. Â“The more uniform the temperature, the lower the maintenance cost over the service life of the road. The temperature of the mat at compaction is not as important as the uniformity of temperature during compaction. By eliminating cold joints and all thermal segregation, ensuring consistent temperature and consistent density, the Shuttle Buggy ensures flawless performance of the asphalt pavement.Â”
It's not just in the USA that the Shuttle Buggy is making its mark. Spain, Ireland, Holland, Sweden, Norway, Australia, New Zealand, China and Russia have significant rewards for contractors using this vehicle, while many US States and Canadian Provinces have followed Washington StateÂ’s lead, Venter says. Â“The savings are real and proven. SpainÂ’s Ministry of Transport 'CEDEX' testing agency has data showing that over 5Â° C differing temperature will have a major negative effect on the service life of the road, and the use of a Shuttle Buggy can double this service life.Â”
The paver hopper can hold as much as 12 to 15 tons of mix, making the Shuttle Buggy's 23 tons into a system of 35 to 38 tons and allowing the paver to move without the delivery truck. The Shuttle BuggyÂ’s conveyor allows two pavers to work with one Shuttle Buggy, which is a feature exclusive to Roadtec, and provides for less trucks to back up traffic and quicker turn-around times for a truck to dump and go.
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