A sustainable life-cycle approach to designing pavements
A sustainable lifecycle approach to designing pavements
To the naked eye, most roads appear alike. But from a design and engineering perspective, each road is unique.
Road surfaces, usually referred to by engineers as pavements, are remarkably varied in their composition. The longevity and sustainability of a road depends on many things, such as what it is made of, and what function it serves.
It may surprise you to know that pavements account for about 30 per cent of Australia’s total road construction and maintenance costs. With such large amounts of money in play, and safety a key concern, we need to get it right.
Traditionally, pavement design has aimed to meet immediate and specific cost criteria whereas broader economic questions and issues surrounding sustainability are given much less attention.
However, a multi-dimensional design process, which takes a lifecycle approach, is changing the face of pavement engineering.
Ensuring a better return on investment
The lifecycle approach is a good example of reverse engineering. If we can first understand what it is the public needs from a particular road, and also keep sustainability top of mind, we can appropriately calibrate durability and other performance measures, and plan for how and when maintenance should be carried out.
There are a number of important questions to be built into the process. How will the pavement respond over time to pedestrian and vehicle use? How rough, cracked and deformed might the pavement surface become? And when is it truly necessary for maintenance to be completed? Safety, of course, remains a priority.
We also investigate how best to reuse existing materials and carefully consider which new materials to add to, or use as substitute for, traditional materials.
Where pavement upgrades or extensions may previously have involved removing existing asphalt layers and replacing it with the same amount of new product, we now can re-use the old asphalt planings and combine it with certain new materials to create what is essentially a recycled pavement layer. Polymers, plastics, glass, and other solid waste material now come into play.
Concrete pavements are also better understood and can have significant lifecycle benefits. Recycled crushed concrete is also now a widely used road building material that is essentially 100 per cent recycled.
Tailoring design to suit individual needs
Experience has shown that detailed modelling of how a pavement will behave in the long-term is essential to overall project success. Modelling considers how environment, transport volume, and other project specific inputs impact longevity and maintenance.
Each project will vary according to a client’s KPIs. These must be well understood to ensure client expectations are factored into the design.
Pavement surfaces remain the point of contact between the user and road infrastructure. The surface must be safe, comfortable, sustainable and cost effective. It’s a field that continues to develop – if solar panel roads have moved from science fiction to engineering fact, you can only wonder what might come next.