Downer paves way for better roads

Downer New Zealand, which started life as the Public Works Department in 1870, has invested $15million to improve the quality of roads in the country.
Half of that investment has gone into upgrading its bitumen storage and blending facility in Totara St, Mount Maunganui, with new emulsion and polymer plants.
Downer's other bitumen facilities in Bluff and Lyttelton have also been upgraded with the emulsion plants.
The $7.5 million Mount plant, featuring state-of-the-art equipment from Denmark's ENH Engineering A/S, was opened by Tauranga MP Simon Bridges in front of 82 guests from New Zealand's roading fraternity.
Cos Bruyn, Downer New Zealand chief executive, told guests that the company was investing in the most up-to-date plant - and training its staff on the latest technology - to deliver safe and sustainable products for the road-surfacing industry.
At the Mount, Downer is now producing stronger polymer modified bitumen (PMB) that significantly lengthens the life of a road surface.
Tauranga-based John Vercoe, Downer's technical manager of bitumen supply, said around New Zealand it's not unusual for cracks to start appearing in roads after five to seven years; with PMB the fatigue life will go beyond 20 years.
The automated polymer plant at the Mount is the only one of its kind in the country. The polymer, fed into hoppers, and the bitumen, pumped through, are combined in a blending tank and then milled - so the polymer is evenly dispersed through the bitumen.
The PMB is then sent to the storage tanks, which have dedicated stirrers and a hot oil heating system - the mixture has to be kept at temperatures of 170-180C.
Mr Vercoe, a polymer chemist, provides the different recipes for the bitumen mix. "The polymer plant has a continuous process and control system, and the tolerances [for the mix] are extremely tight, down to very small percentages."
A rubber polymer from Asia is mainly used for the bitumen mix, but Downer is also importing an even tougher plastic polymer from the US to be used for harder-wearing surfaces, at ports, airports, freight terminals, and rail and log yards.
The constant traffic of heavy machinery, such as straddle carriers at the ports, soon ruts the pavement and plastic polymer, mixed with bitumen, gives the surface longer life.
The PMB is 20-25 per cent more expensive but it saves on maintenance costs. Mr Vercoe said the demand was strong.
"The polymer has grown out of sight for us," he said. "We've done more in the first four months than the whole of last year. Clients are convinced they are getting better value with a specialty product."
Mr Vercoe said the demise of rail had led to increased wear and tear on New Zealand roads. "In the 1950s, 60s and 70s, the road structure was fine and could adequately handle the traffic.
"But today the roads are being pounded to death by the increased weight and sheer number of commercial traffic.
"We need higher performing materials to get more life out of the roads," he said.
Downer has also found a way to spray the bitumen on to roads at a lower temperature and thus improve the safety for construction workers and the public.
The bitumen is mixed with water containing chemicals, including surfactants, and milled in the emulsion plant at the Mount, reducing the heat to between 70 and 90C.
At present, bitumen is applied to the road at temperatures of between 160 and 170C and kerosine is added as a cutter. It can be an explosive mixture.
"We are taking a lead in the industry and pushing the emulsion hard," said Mr Vercoe. "The chemistry is tricky to do - like fat, bitumen hates water - but we've found a way to spray [water-based] bitumen safely at much lower temperatures and without kerosine present."
Downer handles about 65,000 tonnes of bitumen a year, half of it imported and the remainder shipped from The New Zealand Refinery Company at Marsden Point.
With the Mount upgrade, Downer has the ability to receive 35,000 tonnes in one shipment. "It has given us more flexibility, and the company has made a major commitment to putting investment into regional areas," said Mr Vercoe.
Downer, listed on the Australian sharemarket, employs more than 21,000 people in Australia, New Zealand, the Asia Pacific region and the UK. At the start of this year, it had $20 billion work in-hand.
It provides engineering and infrastructure management services to customers operating in minerals and metals, oil and gas, power, infrastructure, telecommunications and water, as well as roading.