In pavements, MEMS have the capability of supplementing, if not replacing, nondestructive testing of pavement condition, they suggest. “Recently, vigorous efforts have been devoted into developing sensing technologies and nano-technology in infrastructure condition monitoring,” write Wang and Li. For crack monitoring purposes, a MEMS transducer has been developed for an ultrasonic flaw detection system, which can be used to detect the initiation of a crack.

Geometrically smaller size of nanoparticles increases the relative surface area available to react with cement in concrete.

Also, networks of nanosensors embedded in roadways could provide real-time information to better manage congestion and incidents, or to detect and warn drivers about fast-changing environmental conditions such as fog and ice. “In recent years, more and more attention has been paid to MEMS-based moisture sensors,” they write. It’s clear that MEMS will play a big role in the intelligent highway systems of the future.

Nanotechnology is leading to self-cleansing signs. The so-called “lotus effect” – which describes the self-cleansing surface of the lotus leaf, which takes place at the molecular level – is being replicated in lotus effect-based self-cleansing nano materials into traffic and work zone signage, and in particular traffic-control devices, which require labor-intensive periodic washing to remove road grime and enhance visibility.

Cleaner air from pavements: Titanium dioxide nanoparticles in both concrete and asphalt pavement surfaces have the ability to remove – via photocatalytic reaction – nitrogen oxides and sulfur dioxide from the atmosphere.

“On a hydrophobic, easy-clean surface, particles of dirt are just moved around by moving water, but on a lotus-effect surface, dirt and grime are collected by water drops and rinse off,” Wang and Li write. “Coatings that mimic the properties of the lotus leaf may well lead to signs that shed dirt and never need washing.”

Thin Film Technologies

Nanoscale research could lead to an increased use of recycled materials in pavements through a better understanding of bonding of different materials, and the design of very thin coatings to optimize use of reclaimed materials.

In their 2010 Transportation Research Board paper, New Possibilities and Future Pathways of Nanoporous Thin Film Technology to Improve Concrete Performance, Jose F. Muñoz of the Department of Material Science and Engineering, University of Wisconsin–Madison, and Richard C. Meininger and Jack Youtcheff of the Pavement Materials and Construction Team at FHWA’s Turner-Fairbank Highway Research Center, find that nanoporous thin films (NPTFs) may improve the interfaces between aggregate and cement paste.

“Aggregates are often considered as inexpensive inert filler material in concrete,” the authors write. “However, the mixture of the aggregate with the cement paste creates one of the most vulnerable areas of concrete, the interface of aggregate and cement paste. The judicious application of nanoporous thin films on the aggregate’s surface is an effective way to improve those interfaces.”

The most recent work on concrete shows that the use of different types of NPTF can induce changes in different properties of concrete or in an aggregate’s mineralogy, the researchers say. The observed improvements in mechanical properties such as compressive, flexural and tensile strengths, modulus of elasticity and drying shrinkage can ameliorate longitudinal and transverse cracking, corner breaks, punchouts and D-cracking, they write.

Improving Traffic Safety

Nanotechnology also has a role in improving transportation safety, according to Satish V. Ukkusuri, Ph.D., assistant professor, and Gitakrishnan Ramadurai, graduate student, Rensselaer Polytechnic Institute, in their 2009 TRB paper, A Comprehensive Review of Emerging Technologies for Congestion Reduction and Safety.

Looking ahead 20 years, the researchers identified future technologies, and focused on nanotechnology, as well as other emerging fields. “Nanosensors have potential to track bioterror agents, stress in materials and detect polluting agents in the atmosphere and tailpipes,” they say. “Nanosensors could be used in transportation to monitor pavement conditions, bridge conditions, pollution deduction, bioterror agent detection and air-quality monitoring.”