Barrett Byrd Associates

Plant supervisor Julian Doxey and his two mobile asphalt granulators tour the country’s coating plants, quarries and road reconstruction sites to turn previously unwanted products into useful construction materials. Mike Water reports

Reusing coated stone to produce recycled asphalt is one of those rare developments which produces environmental benefits at the same time as being financially more attractive. The financial benefits come from reducing costs of disposing of material at landfill, as well as providing a cheap and ready source of aggregate. Environmental gains also include saving on road movements by heavy lorries taking planings away for low grade applications and bringing material to site to replace it.

RMC Aggregates’ recycling division has been impressed enough by the double whammy to buy a second Ammann mobile asphalt granulator to keep pace with the growing market demand to recycle asphalt for use in base and binder course road materials. In addition to crushing already used asphalt, the granulators are also used to pulverise bricks, concrete blocks and glass.

Both mobile crushers are the responsibility of RMC recycling supervisor Julian Doxey, who has worked with the first granulator since it was purchased nearly five years ago.

Julian has been with RMC for over 20 years and was an obvious choice to operate and later supervise the first of the company’s mobile crushers. He began his career working in sand and rock quarries in Derbyshire before moving on to a coating plant in North Yorkshire. He is an experienced operator of heavy plant and is a highly regarded fitter, often being called out to fix faulty machinery.

Recent outings for the mobile crushers include a stint in a Cornish quarry, where one was used to crush glass bottles, and on a road recycling job in Cambridgeshire.

In July Julian used a crusher to recycle thousands of tonnes of asphalt beside a large RMC coating plant at Dagenham in Essex.
“The granulator has been crushing both material produced locally that has not quite met the required specification as well as surplus asphalt returned from site. Once crushed, coated stone is fed back into our asphalt plant to produce recycled material,” says Julian.

Asphalt cannot be fed into the mobile crusher when hot, so warm material ready for reprocessing is stockpiled to cool. Stockpiled macadam tends to solidify, so any large blocks of asphalt are broken into more manageable pieces using a hydraulic breaker or an excavator.

A loading shovel loads carefully weighed asphalt material into the mobile granulator, where a swinging hammer impactor provides the crushing action. The asphalt is reduced in size to particles of no larger than 40mm and any oversize material – of which there is little – is fed back into the crusher.

“The crushing action sheers the binder matrix around aggregate particles within the asphalt while leaving the aggregate coated, which helps fresh bitumen to bind the recycled material together,” Julian adds.

Working the machine is usually a one man operation, but two men are needed to set up the plant and pack it away on completion of works. Julian is currently training a new operator who will be carefully monitored and supervised for their first couple of months.

“Operatives must undergo comprehensive training, even if they have previous mobile crushing experience, as few other crushers are configured like these two.”

He adds that treating the machinery with respect has become second nature, and he hopes that other operators will follow his lead. “I take a great deal of pride in looking after the mobile crushers, not least because the condition of machinery entrusted to someone is a reflection on the person responsible for them.”

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