I would like to respond to the numbers game and the "science" that the Portland Cement Association has initiated as reported in Tudor Van Hampton's article "Concrete Goes to College" (ENR 1/23/p. 8).
First, Congress is not in the business of selecting materials for roadbuilding. Nor should it be. If congressmen were to dig into life-cycle cost analysis (LCCA) as presented by Massachusetts Institute of Technology's Concrete Sustainability Hub (CSH), funded by PCA, they would find the idea of asphalt pavement costing double that of concrete pavement ludicrous.
Notice that the CSH has used theoretic estimations of futures pricing for commodities to predict pavement LCCA. That's not sound science. A supply-and-demand study must be based on factual evidence and not probable estimates. In addition, the study should start accurately.
For instance, the 34.4% of asphalt pavement costs CSH researchers assigned to liquid binder is much more than the 7.8% that the Federal Highway Administration assigns in reality. Only 7 of 38 state departments of transportation responding reported initial life cycles of asphalt pavements at less than 15 years, thus the CSH assumed a way-too-short timeline for starting repairs on asphalt roads. And it left out the value of using recycled products, which is a hallmark of the asphalt industry today.
Second, concrete pavements pose a hazard to the environment no matter what they cost in dollars. A Ministry of Transportation for Ontario study showed a concrete pavement over a 50-year period has a carbon footprint of 1,610 tonnes of CO2e/kilometer. You can refer to Van Hampton's article to see an excellent breakdown of where the most emissions are exuded. Add in the fact that the fly-ash product PCA members add to their production might be declared a hazardous material in the near future and you have a nightmare in the making for concrete workers.
In that same Ontario study, conventional asphalt's 50-year life-cycle produced only 500 tonnes/kilometer, and a "perpetual" long-life asphalt pavement produced only 463. That kind of science is hard to beat.
My bias toward asphalt is backed by good, independent science and an excellent national association. I invite you to check in with the National Asphalt Pavement Association at www.asphaltpavement.org, and I thank you for a chance to update the "concrete curriculum."
Editor, The AsphaltPro MagazineCape Coral, Fla.