Walter Yu, P.E., LEED AP

Going Green... With Asphalt!

Asphalt, concrete and construction materials are not very exciting topics – but with a global recession taking place and promise of economic stimulus by the Obama Administration through shovel-ready construction projects, basic construction materials are becoming big news for manufacturers and suppliers looking to “green” their products.

In fact, the Transportation Research Board has started to focus on green road construction methods and materials, and they were much of the buzz at this year’s conference. Road construction has traditionally been far from environmentally-friendly – generating large amounts of green house gases in each phase of material mining, transport, production and installation.

However, with stimulus money for shovel-ready with incentives for green construction methods, the TRB and engineers are looking for ways to reduce environmental impact of these “old as dirt” technologies.

Roadways are constructed from either concrete or asphalt, depending on which is more economical. Concrete is  used for highways or bridge structures connecting other stretches of roadway. Asphalt is used more frequently on local roadways and longer stretches of highways – it is used to repair cracking and settling.

The production of cement for use in concrete creates green house gases during each step as mentioned above – small improvements such as specifying local quarries to mine the material, air emission requirements of trucking and engineering improvements to the processing of the cement could all potentially save emissions.

One project in Ft. Myers in Florida has experimented with a two-layer road paving project using “econoconcrete” – the road section is comprised of a top layer using conventional concrete and the bottom layer using recycled concrete from old roadway sections. So far, 12 of the 33 sections on the 6.5 mile project have surpassed performance expectations.

It’s not uncommon for some local governments in the EU to require 100% re-use of all old road-building materials in new road construction. As a result, engineers there have relied on specialized equipment and computer-controls to better manage the special care required in handling and re-installing recycled building materials.

One improvement to asphalt that may have wide-spread application is warm-mix asphalt (WMA’s), which requires a lower mixing temperature compared to hot-mix asphalt. Lower prep temperatures lower energy costs, save approximately 30% in fuel and emit 1/3 less dust and greenhouse gases into the atmosphere. Rest assured, these new mix designs will undergo thorough testing and be rolled out into use as their performance requirements allow.

WMA is off to a promising start: they are the new norm in much of Western Europe and 40 states in the US, including one project in Yellow Stone Park near the I-70.

And as I mentioned in my post on cleantech, innovation in technology often relies on government funding – green building included. These new mix designs and other methods are off to a promising start but will need continued support at the federal and local levels to gain popularity with the construction industry and the public.