NJTxtr—A Computer Program Based on LASER to Monitor Asphalt Segregation Geoffrey M. Rowe 1 ; Jay N. Meegoda 2 ; Andris Jumikis 3 ; Mark J. Sharrock 4 ; Nishantha Bandara 5 ; and Chamil H. Hettiarachchi 6 Abstract: Abstract: This paper describes the research funded by the New Jersey Department of Transportation to develop an automated technology to monitor segregation during construction of hot-mix asphalt concrete pavements. A Laser-based system was used to measure surface texture and to detect segregation. Two segregated test sections and a control test section were tested to evaluate the applicability of Laser texture method to detect and quantify segregation. Laser texture data were gathered from all three sections. Ratios of texture in segregated areas to that in nonsegregated areas were set as the basis for detection of different levels of segregation. By combining the level of segregation and extent of segregation, an AREA index was developed to determine the acceptability of a pavement section. Based on AREA index, pay adjustment factors were proposed to reduce the payment to account for loss of pavement life due to segregation. Further remedial actions were proposed to correct segregated pavement sections with acceptable AREA index. Based on the above concepts, Windows-based computer program NJTxtr was developed to detect and quantify segregation. This computer program uses the Laser- equipment-collected pavement texture data and determines whether the pavement section is acceptable or unacceptable based on the level of segregation within a pavement section, and provides bonus or penalties to the contractor. The paper describes a novel technology using laser and associated software for construction quality control of asphalt concrete pavements. The proposed methodology was applied to detect segregation in an interstate highway section in New Jersey, and this section was repaved based on visual observation and recommendation from this study. DOI: 10.1061/(ASCE)0733-9364(2004)130:6(924) CE Database subject headings: Construction management; Asphalt pavements; Concrete pavements; Computer programs; Asphalt mixtures; New Jersey; State government. Introduction Segregation may be defined as a lack of homogeneity of constitu- ents in hot-mix asphalt (HMA) concrete pavements that acceler- ates pavement distress. Asphalt cement, aggregates, additives, and air voids are the constituents of HMA. Segregation produces re- petitive patterns of nonuniformity; therefore, standard quality- control/quality-assurance (QC/QA) procedures that randomly de- fine sampling locations would have a low probability of adequately identifying this problem. Ideally, some type of longi- tudinal pavement profile, using one or more nondestructive mea- surements at selected transverse locations, can be identified. An alternative methodology is needed to address random but local- ized areas of nonuniformity. There are several traditional and emerging methods of detecting and quantifying texture so that a QC/QA program can be built into the design and construction of HMA pavements. Among all these techniques, laser technology seems to be quite capable of quantifying the surface texture and hence the segregation of HMA pavements (Meegoda et al. 2002, 2003). Surface Texture Measurements Using Laser Segregation in asphalt materials can occur for a variety of rea- sons. The manifestation on-site is an uneven distribution of ag- gregate surface texture associated with uneven distribution of ag- gregate, asphalt binder, and/or air voids. Over the past 20 years the use of laser technology to define surface texture has been gaining wide popularity. The basic concept of the measurement system is illustrated in Fig. 1. The technology uses a rapidly puls- ing semiconductor laser to produce an infrared light that is pro- jected onto the pavement surface. The light is scattered off of the surface and a receiving lens focuses this scattered light onto a linear array of photodiodes. The diode receiving the most light corresponds to the distance to the surface. Using mathematical algorithms, the distance to the surface at a discrete point is ob- tained. The measurements are conducted very rapidly as the laser- 1 President, Abatech, Inc., 1274 Rt. 113, P.O. Box 356, Blooming Glen, PA 18911. 2 Professor, Dept. of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102. 3 Supervising Engineer, Pavement Management Unit, Pavement Management Division, New Jersey Dept. of Transportation, P.O. Box 600, 1035 Parkway Ave., Trenton, NJ 08625. 4 Software Specialist, Abatech International Limited, Abatech House, Bull Close Ln., Lenton, Nottingham NG7 2UL, UK. 5 Research Engineer, Abatech Inc., 1274 Rt. 113, P.O. Box 356, Blooming Glen, PA 18911. 6 PhD Candidate, Dept. of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102. Note. Discussion open until May 1, 2005. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on March 10, 2003; approved on January 12, 2004. This paper is part of the Journal of Construction Engineering and Manage- ment, Vol. 130, No. 6, December 1, 2004. ©ASCE, ISSN 0733-9364/ 2004/6-924–934/$18.00. 924 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / NOVEMBER/DECEMBER 2004