White concrete can replace grey 

New Danish tests indicate that the colour of white concrete is durable. This could lead to nicer looking and safer roads.
When COWI project manager Birit Buhr used to think of white concrete, in her mind's eye she saw images of white-walled Greek houses.

But no longer. For the first time in Denmark, she is taking part in tests to document the extent to which white concrete barriers can withstand the changeable Danish weather and how they stand up to installation on roads busy with traffic.

Testing is currently under way on white concrete barriers installed on the southern section of Copenhagen's busy motorway Ring Road 3.

Emphasises the architecture

The advantage of white concrete is that it emphasises the architecture. But the white colour also offers important practical benefits in terms of traffic safety, particularly in overcast and rainy conditions - as the entire team witnessed in broad daylight when testing luminous reflectance on four white concrete barriers and one grey barrier.

White reflected light

When the grey barrier became sprinkled with water it took on an almost black appearance, whereas the white became luminous and reflected the light.

All the indications are that white concrete barriers perform well. So well that when they are wet they reflect the light as much as traditional grey do when dry.

The results could well provide the impetus that popularises the use of white concrete, which at present is only rarely used for infrastructure purposes.

Indicate that the white colour lasts


"With our knowledge of the durability of white concrete," says Birit Buhr, "we would say that it is comparable with grey. Preliminary results also indicate that the white colour lasts – hence there would be no excessive maintenance costs. All this means that those who work with concrete can equally well choose white.

Traffic safety

"The most obvious use for white concrete is to enhance traffic safety by using it for kerbstones and traffic barriers. Aesthetically, it would give luminous reflectance in tunnels and make it much more inviting to drive through tunnels than traditional grey does."

Want to test white concrete on a bridge

The project is the result of collaboration between cement producer Aalborg Portland and COWI. Precast concrete factory Dragsholm Beton has produced the white concrete barriers and the Danish Road Directorate has financed the test installation.

The next aim for Birit Buhr is to test white concrete on a bridge so as to document durability and aesthetics in larger construction projects.

A visually material

"It is interesting for me to learn as much as possible about a new material," adds Birit Buhr. "The technological details, in particular, fascinate me. But I also think that white concrete is a more visually pleasing material."

By Christina Tækker, cht@cowi.com  
Published: 27.10.2004



FACTS 

White concrete

White concrete contains the same ingredients as grey. The white colour is achieved by burning the cement klinker at high temperatures.

White concrete contains no colour additives and it can be made chalk-white or off-white by mixing together different types of sand and coarse aggregates.

Facts about the project:

Aalborg Portland is gauging luminous reflectance, Dragsholm Beton has produced the white concrete barriers and the Danish Road Directorate has financed the test installation on Ring Road 3 near Copenhagen.

COWI provides documentation for durability properties and aesthetics of the white concrete barriers, as well as advising on follow-up on the measurements.