Lindetorpsvï¿½gen 7, Stockholm, Sweden
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Nygen 910 is added to asphalt mixtures to make it possible to use a higher proportion of recycled asphalt while also contributing to quality in the end product.
Orust is the fourth biggest island in Sweden, situated just over 70kms north of Gothenburg. Two of the island’s roads needed to be renovated in the summer of 2016. They both have a width of six metres and an average traffic flow of 1500 vehicles per day.
Client the Swedish Transport Administration wanted a work solution that was environmentally friendly and cost efficient. It chose warm mix asphalt in order to reduce energy consumption and greenhouse gas emissions, the mix containing a relatively high proportion of recycled asphalt.
A softening agent was needed for the hard binding agent in the asphalt arisings following milling of the original asphalt. The agent chosen was Nygen 910. Softening old asphalt enables it to regain most of the properties that it has lost through ageing.
This means that asphalt producers can incorporate larger volumes of recycled asphalt into their mixtures without any loss of quality. Together with Nynas’ laboratory, contractor Svevia confirmed the correct blend percentage to meet the client’s requirements for the change in viscosity from tank to laying on the road.
Work started at the end of April 2016 with milling and the contract was completed by the middle of June. Some 6600t of aggregate in total was needed for the base course and 4000t for the surface course. According to the job specification, soft bitumen had to be used. Hardness was not to exceed V12000 (V = viscosity) and the viscosity change was not to double.
Nygen 910 was added early on to the asphalt arisings, as at the time there was no ideal point for inserting the agent during the asphalt production process. The arisings were then stored for two weeks.
It was permissible to use 50% recycled asphalt in the bound base course and 20% in the surface course. Afterwards, Svevia’s Production Manager confirmed that the contractor achieved an exceptionally workable asphalt mixture with Nygen 910.
Asphalt production took place using a mobile steam turbo unit. In such a unit, the aggregate is heated by spraying in overheated water vapour. The steam is then mixed with the binding agent. This eliminates any risk of overheating the asphalt mixture.
In other words, a steam turbo unit enables careful heating and reduced ageing of the binding agent. It also takes up little space which makes it possible to compress operations, minimising transport requirements.
LOCATION Orust, north of Gothenburg in Western Sweden
ASSIGNMENT New base and surface course
CLIENT Swedish Transport Administration
Date April-June 2016