Nickel particle-based self-sensing pavement for vehicle detection Baoguo Han a,b , Kun Zhang a , Xun Yu a,⇑ , Eil Kwon c , Jinping Ou b,d a Department of Mechanical and Industrial Engineering, University of Minnesota Duluth, Duluth, MN 55812, USA b School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China c Department of Civil Engineering, University of Minnesota Duluth, Duluth, MN 55812, USA d School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian 116024, China article info Article history: Received 21 February 2011 Received in revised form 19 May 2011 Accepted 21 June 2011 Available online 28 June 2011 Keywords: Self-sensing pavement Cement-based sensors Sensing capability Vehicle detection abstract In this paper, a new self-sensing pavement for vehicle detection is designed. Smart nickel particle filled cement-based sensors with high sensitivity are used as vehicle detector. The sensor array is embedded into a concrete pavement to form the self-sensing pavement. The vehicle detection capability of this pavement is investigated in outdoor road tests. Exper- imental results show that the proposed self-sensing pavement can accurately detect the passing vehicles. This finding indicates that the self-sensing pavement embedded with smart cement-based sensors has a great potential for traffic detection and monitoring. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Vehicle detection is one of the critical elements in traffic management and operations. Currently various detection systems are being used to collect and process traffic data. These traffic data include traffic flow rates, vehicular speed, vehicle length and headway, traffic density and occupancy ratios, which are obtained from vehicle sensors buried under the pavement or installed along the roadway. To date, many kinds of vehicle detection sensors, such as electrical, magnetic, optical, acoustic and video detectors have been used [1–4]. Among these sensors, the inductive loop detectors are the most common vehicle detection sensors, due to their mature technologies, insensitive responses to weather conditions, and relatively low costs. The inductive loop detectors can accurately measure traffic occupancy ratios, vehicle speed and headway. However, this kind of detectors has some negative effects on the pavement life due to their unfavorable compatibility with the pavement. Recent advances in sensor, computing and communication technologies promote the development of other detection technologies including microwave radars, infrared sensors and video image processors. However, these new developed sensors are facing with the limitations of high cost of sensors, high maintenance cost, poor performance in inclement weather conditions (rain, snow and fog), and so on. Further, most of these sensors require additional mounting structures and time- consuming calibration processes [2–4]. Smart cement-based composites provide a new way for developing vehicle detection sensors. They are fabricated by adding conductive fillers into cement-based materials to increase their ability to sense the strain or stress while maintaining good mechanical properties. As the compos- ites are deformed or stressed, the contact between the fillers and the matrix is affected, thereby affecting the elec- trical resistivity of the composites [5,6]. The vehicle detec- tion sensors fabricated with the smart cement-based composites have several advantages over the conventional detectors, such as easy installation, low cost, easy maintenance, long service life and good compatibility with pavement structures, since they are made of cement-based materials [5–10]. Shi and Chung [7] firstly used carbon fiber filled cement-based composites to develop sensors for traffic 0263-2241/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.measurement.2011.06.014 ⇑ Corresponding author. Tel.: +1 218 726 8415; fax: +1 218 726 8596. E-mail address: xunyu@d.umn.edu (X. Yu). Measurement 44 (2011) 1645–1650 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement