Abdenour Nazef

Experimental Evaluation of a Pavement Imaging System: Florida Department of Transportation’s Multipurpose Survey Vehicle

The Florida Department of Transportation (FDOT) has acquired and validated a multifunctional survey vehicle for the collection of highway pavement-related data at normal operating speeds. With its ability to collect pavement, right-of-way, and side-view images together with position location, cross-slope, grade, curvature, rutting, and roughness data, this state-of-the-art vehicle enables the rapid and automated evaluation of roadway performance and identification of hazardous conditions. Manual surveys that involve a high degree of subjectivity, a low production rate, and exposure to hazardous conditions are still the most widely used means for evaluating pavement distress. The pavement evaluation subsystem of the FDOT survey vehicle represents an efficient, cost-effective, and safe alternative for the collection and evaluation of pavement distress data. In the research reported in this paper, the precision and accuracy of the pavement imaging subsystem was tested under different lighting conditions, spe...

INVESTIGATION OF RECYCLED CONCRETE MADE WITH LIMESTONE AGGREGATE FOR A BASE COURSE IN FLEXIBLE PAVEMENT

The research objectives were to investigate the feasibility of using recycled concrete aggregate (RCA) as a base course material in asphalt pavement, to evaluate the physical properties of RCA, and to develop practical and reliable guidelines and specifications. The tasks included literature review, sample collection, laboratory testing, accelerated performance testing and pavement distresses monitoring, falling weight deflectometer (FWD) test, theoretical analysis of pavement, and development of guidelines and specifications for the use of Florida RCA. Three test sections of asphalt pavement were constructed at the University of Central Florida’s circular accelerated test track. Two sections of different thicknesses were constructed with RCA base and one section with limerock (LR) base. A total of 362,198 load repetitions were applied to the test sections. This is equal to 811,324 repetitions of the 18-kip (80-kN) equivalent single-axle load. The pavement distresses of rutting, cracking, and settlement were monitored during the course of the performance testing. The FWD test was performed on the pavement test sections to backcalculate the in situ resilient moduli of RCA and LR for theoretical analysis of life expectancy. The findings support the hypothesis that RCA can be used effectively as a base course when appropriate quality control techniques are used. On the basis of the information obtained, a set of specifications for the use of RCA as a base course in flexible pavements was developed.

Semi-Automated Faulting Measurement for Rigid Pavements

Faulting measurements have traditionally been conducted manually by means of fault meters. However, operating any manual device such as a fault meter close to vehicular traffic is hazardous to both the operator and the traveling public. Automated methods, such as those associated with high-speed profilers, offer a safer, more efficient, and cost-effective alternative. Therefore, there is a need to develop an automated method for measuring joint faulting with longitudinal profiles from high-speed profilers. A study was initiated with the primary objective of determining an appropriate profiler sampling interval to accurately locate transverse joints. A secondary objective was to determine how well faulting estimated from profile elevation compares with faulting measured with a Georgia fault meter. An algorithm was developed: it can accurately detect on average 95% of transverse joints from profile data collected at highway speed with a 0.68-in. (17.3-mm) sampling interval. This algorithm was also adapted to estimate faulting measured with a Georgia fault meter (AASHTO R36-04). Although the algorithm results are repeatable, the algorithm overestimated the faulting at joints by 0.05 in. (1.3 mm) to 0.06 in. (1.5 mm) compared with faulting measured with the Georgia fault meter.

Optical Texture-Based Tools for Monitoring Pavement Surface Wear and Cracks Using Digital Images

Evaluation of traffic and environmental impact on pavements using digital images has become increasingly popular in recent years because of the improved efficiency it brings to pavement management. Meanwhile, significant leaps have been made in the sciences of computer vision and image processing. Although automated pavement distress evaluation using digital images has benefitted from the advances in image processing, innovative techniques used in computer vision, such as image characterization using quantification of optical texture properties of images, has not been exploited adequately in pavement evaluation. Several widely used optical texture techniques for characterization of digital images are introduced in this paper, and their useful applications in pavement evaluation are highlighted. Automated and accurate detection of correspondences in progressive images of the same pavement captured during different times is essential for close monitoring of cracks or wear at the project level. Two reliable methods for determining correspondences among pavement images irrespective of the illumination at capture are (a) texture masking and minimum texture distance method, applicable to locations with no significant distress, and (b) homogeneous coordinate geometrical matching and the maximum texture distance to detect the locations of distress. Scaled scattering index, which is a parameter ideal for estimating the size of texture primitives required for texture analysis and characterization of the pavement surface composition, is also introduced. Finally, texture characterization is applied to detection of exact locations of crack propagation and excessive pavement wear.

Alternative Validation Practice of an Automated Faulting Measurement Method

Several states have adopted profiler-based systems for automatic measurement of faulting in jointed concrete pavements. However, little published work exists that documents the validation process for these automated faulting systems. An alternative practice for making an initial assessment of a newly developed automated faulting method was documented. Findings from this experiment showed that a high-speed inertial profiler used in conjunction with a faulting reference device provides a practical validation method under controlled conditions. Furthermore, the algorithm that controls the automated faulting measurement method provides reliable and highly repeatable faulting results. The test equipment used in the experiment, as well as the data collection process, the analysis, the subsequent findings and recommendations, are documented.

Innovative Techniques with a Multipurpose Survey Vehicle for Automated Analysis of Cross-Slope Data

Manual surveying methods have long been used in the field of highway engineering to determine the cross slope and the longitudinal grade of an existing roadway. However, these methods are slow, tedious, and labor intensive. Moreover, manual survey methods almost always require partial or full lane closure, which results in traffic delays, increases in costs, and inconvenience to the traveling public. In 2003, the Florida Department of Transportation acquired a state-of-the-art multipurpose survey vehicle (MPSV) that combines the advantage of an inertial profiler with the additional ability of simultaneously collecting images, cross slope, longitudinal grade, curvature, rutting, and roughness at highway speed. To complement the MPSV system, an automated analysis tool has been developed to process pavement geometry data for identifying areas with deficiencies in cross slope and longitudinal grade in a fast, efficient manner. In addition, this analytical tool computes a drainage path along the pavement surface. The program also displays the analysis results in two- and three-dimensional graphical formats, allowing for an easier interpretation of the data. The MPSV technology coupled with the developed cross-slope analysis tool provides an effective, practical, and cost-effective method to identify quickly potential problem-prone areas along a highway. This paper presents an innovative technique for the analysis of data on cross slope and longitudinal profile that helps identify areas with deficiencies in cross slope and surface drainage. Highway agencies can successfully implement similar systems and analysis methodology to complement and enhance their existing safety and pavement management programs.

Precision of Florida Methods for Automated and Manual Faulting Measurements

Traditionally, the Florida Department of Transportation (DOT) has measured faulting with a manual fault meter. However, this method is slow and labor intensive, disrupts traffic, and presents safety hazards. Extracting the fault magnitude from a pavement profile collected with an automated high-speed inertial profiler is a more efficient and cost-effective alternative. Thus, the Florida DOT developed the Florida automated faulting method (FAFM), which detects joints and calculates faulting from longitudinal profile data. A study was conducted to establish the accuracy and precision of the FAFM. In addition, an improved manual fault meter was developed by the Florida DOT and used as a reference device for the FAFM in the field. Because accuracy and precision measures for the new fault meter were not readily available, the study assessed the accuracy of the fault meter under controlled laboratory conditions, as well as the precision in both laboratory and field conditions. The results of the study indicated that the manual fault meter demonstrated no bias and a repeatability of 0.06 mm (0.002 in.) in laboratory conditions. Under field conditions, the fault meter showed a repeatability of 0.42 mm (0.02 in.). Also under field conditions, the FAFM achieved accuracy in terms of bias ranging between 0.2 mm (0.01 in.) and 0.7 mm (0.03 in.). The repeatability and reproducibility of the FAFM were determined to be 0.6 mm and 0.9 mm (0.04 in.), respectively.

Application of Improved Crack Prediction Methodology in Florida's Highway Network

With the growing need to maintain roadway systems despite increasing competition for resources while ensuring safety and comfort for travelers, sound network-level decision making becomes more vital than ever. A stochastic process known as the Markov chain has been used extensively to capture the uncertainty associated with pavement performance over time and to support this critical decision-making process. By application of the Markov chain, this paper investigates the crack histories of flexible pavements to gain insight into the impacts of two primary factors that contribute to the rapid deterioration of surface cracks in flexible pavements: excessive traffic loading and delayed maintenance and rehabilitation. The empirical results of the investigation, obtained by using the data from the Florida Department of Transportations pavement condition survey database, are presented. The results show that the impacts of the two factors mentioned above are statistically different from one another in terms of the rate of deterioration of Floridas pavements because of cracks. These findings will assist highway authorities in making more timely and efficient network-level decisions.

Assessing the Precision of Falling Weight Deflectometer for Field Measurements

Deflection-based techniques are being widely used to evaluate the structural integrity and for estimating the elastic moduli of in-service pavements. These deflections can be non-destructively induced and measured using various commercially available devices. In recent years, the Falling Weight Deflectometer (FWD) has gained worldwide acceptance among most highway agencies due to its versatility and ease of use. However, as with any testing using subject-driven, instrumented devices, the major concerns of the end usefulness of the resulting data are accuracy and precision. Although a level of uncertainty is always inherent to any measurement process, it must also be appropriately quantified or assessed. Therefore, the Florida Department of Transportation initiated the present field study to assess the level of precision of FWD measurements on flexible pavements. Deflection data were acquired using three FWD units concurrently on four different asphalt pavement sections. The precision was then addressed in terms of testing repeatability and reproducibility. In addition, the effects of buffer designs on deflection measurements were also evaluated. This paper presents a description of the testing program, data collection efforts, and subsequent analyses and findings. Precision statements for repeatability and reproducibility of field measurements were developed and are summarized herein. A generally high level of repeatability and reproducibility of the deflection measurements is demonstrated.

Development of a Road Deficiency GIS Using Data from Automated Multi-sensor Systems

Traditional survey methods have long been used in the field of highway engineering to measure the cross-slope, longitudinal grade, rut depth, and ride quality of existing roadways. However, these methods are slow, tedious, labor intensive, and almost always require partial or full lane closure resulting in traffic delays, increase in costs, and inconvenience to the traveling public. Advances in inertial sensor and inertial navigation technologies have allowed their implementation as state-of-the-art mobile data collection systems. The Florida Department of Transportation (FDOT) operates two mobile data collection systems referred to as Multi-Purpose Survey Vehicles (MPSVs). They collect pavement data including but not limited to cross-slope, longitudinal grade, and wheel-paths’ rut depth at typical highway speeds. The MPSVs are equipped with a position and orientation system (POS) coupled with an inertial profiler unit. The core of the POS consists of a tightly-coupled Inertial Measurement Unit (IMU) and a Differential Global Positioning System (DGPS). This paper presents a methodology for the development of an Automated Roadway Deficiency Information System using Geographical Information System (GIS) software to map areas prone to hydroplaning. The functionality of the developed information system was tested on a pilot project using MPSV collected data. Highway agencies can successfully implement this methodology to complement and enhance their existing safety and pavement management programs.