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Road raw material depot: How we recycle concrete roads

Resource-conserving renovation of the A2 southern motorway

The reuse of construction materials plays a key role in sustainable road construction - for example in asphalt recycling or the recycling of concrete roads. On the southern motorway in Austria, STRABAG is renovating an eleven-kilometre-long concrete carriageway and is not only recycling concrete and asphalt to a high degree, but also sand for the first time thanks to adapted regulations. The project shows how integrated construction material recycling works in practice and is promoted by partnership models.

What is a concrete road?

A concrete road - also known as a concrete carriageway or concrete road surface - is a road whose carriageway surface is made of concrete. It is mainly used where the traffic load is particularly high, for example on busy motorways, lorry parks or industrial areas.

Even if the installation of a concrete pavement is more complex than an asphalt pavement, concrete carriageways offer some decisive advantages: they are particularly resilient, durable, low-maintenance and - thanks to their light-coloured, light-reflecting surface - highly visible at night or in bad weather.

How does the recycling of the concrete road on the A2 motorway work?

To recycle the concrete road on the A2 motorway, the carriageway is first removed. This leaves concrete, asphalt and rock, which are transported to a mobile crushing plant not far from the construction site. The crushing plant crushes the material, which is then reused in the sub-base concrete and base courses. The material - 325,000 tonnes in total - is thus completely returned to the cycle. This is hardly ever done on this scale in Austria - and is therefore a real statement in favour of the circular economy in road construction! This saves around 13,500 lorry journeys, which not only reduces material consumption but also greatly minimises CO₂ emissions.

Bird's eye view of the building materials broken up for road renovation

Recycling on the south motorway:

Local material cycle: 325,000 tonnes of road demolition waste are processed and reused on site.
Recycled asphalt: 40,000 tonnes of asphalt with a recycled content of 70 percent are used.
More flexible regulations: Amended regulations mean that sand (aggregates 0 to 4 mm) can be recycled for the first time.

New rules, more recycling

On the A2 motorway, the STRABAG project team is recycling sand for the first time due to an adjustment in the regulations - specifically, aggregates from zero to four millimetres. Previously, sand that was separated from the road rubble could not be reinstalled and in many cases had to be landfilled.

Every grain of sand counts! What seems tiny at first can have a big impact in the masses - especially when it is reused. You can find out more about how STRABAG uses recycled building materials sensibly here.

Bird's-eye view of a highway road rehabilitation project

We are also increasing recycling in other areas: in the asphalt layer that is applied between the cement-stabilised base layer and the concrete layer above - also known as the clean layer - we use asphalt with a recycled content of 70 percent. This is almost four times higher than is usual on Austrian motorways. As a rule, the proportion here is 20 per cent.

The project impressively demonstrates how construction material recycling can be a success. When regulations become more flexible and clients trust our expertise, resource conservation in road construction becomes common practice.

Florian Weber
Technical Division Manager STRABAG

What role do partnership models play in sustainable road rehabilitation?

Partnership models are an important lever for protecting resources in construction projects. The renovation on the A2 is being carried out using the "Early Contractor Involvement light (ECI)" contract model, which meant that we were involved in the planning process at an early stage and were able to review and optimise the project together with ASFINAG and make it as efficient as possible.

Early coordination helps to avoid planning errors. If adjustments have to be made at a later stage, these are often associated with additional costs, material consumption and CO₂ emissions. Early and trusting cooperation favours the targeted introduction of sustainable solutions.

Factsheet:

A2 Road renovation

pdf ∙ 12 MB