In this paper, a self-sensing carbon nanotube (CNT) concrete pavement system for traffic detection is proposed and tested in a roadway. Pre-cast and cast-in-place self-sensing CNT concrete sensors were simultaneously integrated into a controlled pavement test section at the Minnesota Road Research Facility (MnROAD), USA. Road tests of the system were conducted by using an MnROAD five-axle semi-trailer tractor truck and a van, respectively, both in the winter and summer. Test results show that the proposed self-sensing pavement system can accurately detect the passing of different vehicles under different vehicular speeds and test environments. These findings indicate that the developed self-sensing CNT concrete pavement system can achieve real-time vehicle flow detection with a high detection rate and a low false-alarm rate.

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In 1993, two hot-mix asphalt and four whitetopping overlay test sections were constructed on low-volume road TH 30 in southern Minnesota. A study was undertaken to examine the performance and costs associated with the test sections after 9 years of service. The field testing and evaluation are described, and the costs incurred through 2001 are tabulated. The hot-mix asphalt overlay test sections are performing up to their design expectations. Routine preventive maintenance has been applied to both hot-mix asphalt test sections, adding to their long-term cost of operation and ownership. The whitetopping test sections are performing very well at the midpoint of their design lives of 20 years. Most distresses to date are related to poor construction and materials rather than inherent design features. Some random longitudinal cracking has occurred in areas of the whitetopping control section. The doweled test section has numerous distressed transverse joints caused by dowels near the surface of the slabs. There is virtually no faulting of the transverse joints, and the ride quality has stabilized. No maintenance has been performed on the whitetopping sections through 2001. As of 2002, the most economical overlay design in this study is a 6-in.-thick bonded whitetopping. On the basis of recent observations, it appears that whitetopping performs well and is an economical option for rehabilitation of low-volume roads in Minnesota.