Where the Rubber Meets the Road: Why Chemomechanical Design of Materials is Critical to Sustainable Transportation Infrastructure
Krystyn Van Vliet, Ph.D. '02, Associate Professor, Department of Materials Science and Engineering
Description: Our conversations on sustainable transportation typically begin with a review of vehicle efficiencies, and end with the characteristics of fuel, energy sources, and life cycle. In a remarkably novel approach to sustainable transportation, Krystyn Van Vliet discusses how other things matter too" namely the materials we build our bridges from, the infrastructure of the road, and of course, the tires we drive on. They are all parts of the sustainable equation. For the U.S. to achieve the reductions in C02 consistent with the 2050 Kyoto protocols, a substantial portion of that must be made by reducing the CO2 from the construction of highways and bridges.
Vliet tell us that traditionally, materials used to build transportation infrastructures are high volume ones that are critical for their performance, but also for human life" they are grossly overdesigned in case of failure. Once the materials are proven and accepted" there is a long road to changing them" not unlike the road of the FDA approving a new drug. Van Vliet adds: " Since the materials are used in such large volumes why has there been relatively so little innovation in them? The main reason is that the materials are inexpensive. Because of their low cost, cost is not a strong driving factor." But, she says, "New approaches over the past few years allow us to innovate at the level of the nanoscale and provide high impact change".
Beginning with rubber" which is used not only in tires" but also in seals, train bearings, and many other transportation components" Van Vliet demonstrates how the tools of nanoscience can be applied to discover rubber's macroscopic properties and map its polymer" particle matrix . Visual Information based on mechanical imaging of rubber at the nanoscale level reveals entirely new understanding. This understanding, in turn, can be used to fine tune the mechanical properties of rubber; for example, to produce it with different fillers, change the thickness of the materials, and its glass transition temperature points. Patents harnessing these innovations are underway.
The case of cement is even more compelling, and like the rubber in tires, there has not been, until recently a lot of innovation around this material. Van Vliet describes it as the "utility of modeling such an old, dirty and not very interesting materials with a lot of atomistic power to make an interesting difference."
The "DNA" of this material, reveled through nanotechnology, is suggesting entirely new ways of thinking about it. Cement is made up of three simple materials" calcium oxide, silica, and water. They mix to create what scientists call a gel. The pre"production process of calcination, and producing calcium oxide is the source of C02 emissions some sources estimate that as much as one ton of cement produces one ton of C02 emissions. Global emissions the from calcium oxide accelerate as India and China rapidly expand their infrastructure with concrete buildings and roadways.
In both lab tests and simulations, Van Vliet and her colleagues have shown that it is possible to use less cement-- by achieving higher efficiency, and to mix the cement composition with other compounds. And, a "pie in sky" concept which could happen, is to infuse the cement with titanium dioxide, which would break down and scrub the air of gasoline emissions, and return a healthier, cleaner air.
Host(s): School of Engineering, Transportation@MIT
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