Special asphalt in Castricum: In close cooperation with the municipality

If you look at the map of Castricum, you can notice it immediately: the road that connects the railway and the roundabout on the Oranjelaan in Castricum is not very long. Nevertheless, the redesign and asphalting of this road was a complex process because of the great variation in the asphalt mixtures and foundations.

The reason for the redevelopment of the Oranjelaan was the need for a traffic-safe environment for cyclists and local residents. No superfluous luxury, with a large school around the corner and a bus stop, railway and nursing home in the street. In addition to improving road safety, two other aspects were of key priority: sustainability and a close cooperation.

“The environmental goals from the Climate Agreement are reflected in municipal policy,” says Marco van Beek, Project Leader at the municipality of Castricum. “We are continuously looking for ways to translate and apply these goals. Within the municipality of Castricum, we like to think innovatively. This is why we always look for ways to reduce the impact of asphalt on the environment by using sustainable asphalt mixtures. In this project, we sat down with Ballast Nedam Road Specialties and a sustainability and asphalt mixture expert from DIBEC to create the best mixture.”

Thinner and more durable - with the same strength

Ballast Nedam carries out asphalting work for the municipality of Castricum within a framework contract. We have based the collaboration within this refurbishment project on this basic agreement. “We thought: what if we consider and design the entire construction from scratch?” says Thomas Snelderwaard, Project Manager at Ballast Nedam Road Specialties. “It started with an inventory. What do we have in-house? And what calculations can we make? DIBEC has calculated the pavement constructions on durability and lifespan based on the desired principles.”

For this project, the choice was made for a CO2-saving paving construction that does not affect the lifespan. The asphalt chosen is in line with the ambitions of the municipality and scores high on sustainability due to the reuse of various materials. “We replaced the sand foundation with hydraulic mixed granulate,” says Thomas. “The sand released is reused within the municipality. Also, we can apply a thinner asphalt package because DIBEC has calculated with a load-bearing foundation and more stable asphalt mixtures. As a result, we only need a layer thickness of 120 millimeters in total. That is a big difference, because according to the municipality's research, no less than 170 millimeters of asphalt would be needed here. In short, a huge reduction of CO2 by using fewer raw materials.”

The underlayer mixture consists of almost 100% recycled materials, thanks to the recycling of old asphalt and the use of other materials from the same chain. “We only had to add a little bit of new materials and binder to this to create a new underlayer mixture,” says Thomas. “And we actually do the same in the top layer. Traditionally, a maximum of 30% is recycled in top layer mixtures, but we even work here with 65% old asphalt in the mixture. We guarantee quality through extensive testing. The asphalt has the same life expectancy and functionality as the traditional mixture.”

 

Special red asphalt on the bike paths

A highlight of the redesign is the new cycle path that frames the road on both sides. A new mixture has been developed for these cycle paths, in which the old red asphalt is reused. Ballast Nedam and DIBEC extensively investigated whether the asphalt was suitable for this. The result? A first in the Netherlands. This method saves red pigment, red stone chips and bitumen. That is a good starting point, since we don't have to extract an extra oil product from the ground. The environmental impact and CO2 emissions have been reduced by more than 50% during the production of this red asphalt mixture compared to a new mixture.

A large part of the new cycle paths has become less red since the redevelopment and tends more towards red-brown. This is due to the reuse of the old asphalt and the use of black binder. Thomas: “This means that the old asphalt returns in exactly the same place. This way of working will be the future.”

However, the brighter color can still be found in certain parts of the bicycle paths. At these places, such as the roundabout, cyclists pass car traffic and it is important for road safety that the bicycle paths are extra well marked. That is why we mixed red pigment and white binder in these places. Although this results in less profit at a sustainability level, it also makes for an even safer traffic situation.

Redesign from a triangle

The old bus stop has disappeared and now offers plenty of space for greenery. In the autumn we will plant more than twenty trees and 300m2 of perennials will be placed on the large roundabout. In addition, old tiles in the footpath have been reused and LED lamps have been installed.

Marco looks back: “We have actively sought close cooperation on this project. As client, contractor and consultant, we formed a triangle and we have come up with something beautiful that exactly answered our question. We are very happy with the result: a sustainable approach and a road that is safer and can last for years. "We'll make it a great project," we said at the start. Well, it worked.”