Photo: Mediafarm

Old technique gives roads new lease of life 

By stabilising road beds with quicklime, as the Romans used to do, there are huge savings to be made and environmental gains to be had.
New studies show that old style stabilisation of road beds makes for more economical and durable roads.

Quicklime is being used to stabilise large volumes of weak clay soil, cutting more than a million Danish kroner off the price of a kilometre of motorway, saving large amounts of raw materials and reducing the load on the environment by not transporting replacement soil.
Photo: Illu: Mediafarm
Adding material such as lime to the soil creates a rigid base for road surfaces.


Lack of dimensioning methods

"You might say we're familiar with the technique but it's only now that we have the right equipment and computational models. With the improved analysis models and methods to predict what will happen to the road's load-bearing capacity, we can build stronger roads at better cost and thus promote the spread of stabilised roads," says Christian Busch, senior specialist at COWI.

For the moment, COWI, together with the Danish Road Directorate, has conducted a lime stabilisation pilot study on part of the new motorway between Odense and Ringe on Funen.

The Directorate has conducted another trial on the future motorway between Ønslev and Sakskøbing on Lolland. These pilot projects are now being followed up with full-scale projects.

Soil takes on properties of sand

Stabilisation is achieved by utilising the materials in the soil to achieve the desired strength. By adding lime, cement, or fly ash to the soil, it takes on the characteristics of sand and binds together into a rigid base.

The appropriate stabilisation method and amount of additives are determined during the design phase with the help of lab trials. The effect is demonstrated in practice by implementing a trial section before work starts on construction.

By Christina Tækker, cht@cowi.com
Published: 26.04.2007