Robert L Schmitt

AutoPave: towards an automated paving system for asphalt pavement compaction operations

Abstract Asphalt pavement density from roller compaction is a crucial factor in ensuring satisfactory pavement performance. Proper and uniform compaction of the pavement mat is essential in achieving the desired final compacted density. There is a necessity to investigate existing pavement construction practices, and provide more cost-effective modifications to the current scenario. Automation of the paving operation can increase the efficiency and quality of the operation, lead to reductions in overall project costs and time, and enhance pavement life. A system can be developed through algorithmic planning and real-time guidance strategies, and the development of a semi-automated path-planning and real-time guidance system that aims towards automating the paving operation. This system accepts relevant paving project inputs, generates appropriate path plans for the compactor, performs a graphical visualization of the generated path plan, and offers real-time guidance capabilities using Global Positioning Systems (GPS) technology. This system, named AUTOPAVE (v1.0), was developed in Microsoft Visual Basic™ programming language and offers a user-friendly and interactive graphical interface. The proposed new system will incorporate state-of-the-art GPS technology to standardize paving operations that are more amenable to rigorous quality control, and can result in considerable reductions in cost and time involved in asphalt pavement construction projects. This system was tested on several actual paving projects, and many operational issues related to the functioning of the system were successfully overcome.

Summary of Current Quality Control/ Quality Assurance Practices for Hot-Mix Asphalt Construction

State highway agencies and contractors have been implementing quality control/quality assurance (QC/QA) specifications in recent years to advance the quality of hot-mix asphalt (HMA) construction. During their continued development, attributes of these QC/QA specifications have varied among states. The objective of this paper is to provide a compilation of state-of-the-practice in QC/QA for HMA construction and provide recommendations for state highway agencies and contractors when modifying or developing a QC/QA specification. Survey data from 42 state highway agencies and 61 contractors working within 14 states found that a majority of states are using contractor data for acceptance. A review of QC/QA specifications from 40 states found that most states are using plant-produced mix properties, density, and smoothness tests to determine overall quality and acceptance of HMA construction work. A larger number of states are using quality level analysis for specification compliance by estimating percent within limits or percent defective for mix properties and density. Consideration is given to key attributes of a QC/QA specification, including (a) whether to use contractor or agency data for acceptance, (b) use of quantity or time for lots, and (c) testing frequency. State highway agencies and contractors may find this report useful for understanding the components of different QC/QA specifications and furnishing essential information as both parties collaborate during specification development.

An Operations Planning System for Asphalt Pavement Compaction

Asphalt density after compaction by the breakdown roller is a key factor influencing asphalt pavement performance. Among the several factors influencing asphalt pavement density, the number of passes required for a rolling operation is a critical factor and difficult to determine and measure appropriately. Furthermore, it is difficult to ensure that the roller will uniformly cover the entire length and width of the pavement mat. Without an efficient path planning system, errors in human judgment may cause variation in overlap areas and reduce compaction efficiency. The significance of achieving optimal asphalt density coupled with the problems associated with the present system of operation, motivates the search for a system that can more accurately decide coverage location, number of passes, and control the overlap area for the pavement compaction operation. Such a system could increase the operational efficiency, uniform compaction, and pavement performance. This research aims at establishing the framework for an affordable path planning system for the compaction operation using an on-board guidance facility. This facility would integrate an Asphalt Knowledge-Based System with an economical sensing system , such as

Innovative Approach for Asphalt Pavement Compaction Monitoring with Ground-Penetrating Radar

This paper demonstrates that ground-penetrating radar (GPR) is an effective tool for quality assurance and quality control during flexible pavement compaction and after construction. Density is one of the most important properties of asphalt concrete layers in flexible pavement. It is critical to monitor the change in asphalt concrete density during compaction; GPR can be used to measure asphalt mixture density nondestructively and rapidly. However, it is challenging to apply the GPR method during compaction because of the unknown effect of roller-sprayed water on the GPR signal. This paper presents the results of a study on the effect of surface water on the GPR signal when a 2-GHz antenna is used. It was found that the higher-frequency components of the ultrawide band signal were affected by water; however, the lower-frequency components were not significantly influenced. The process consisted of a band-pass filter with a passing band from 200 to 800 MHz and extracting the surface reflection amplitude after filtering. The extracted feature was found to be insensitive to the presence of surface water. Therefore, this technology could be used effectively during the compaction process. Field data collected from two construction projects were used for validating this approach. The proposed approach was found to be feasible for monitoring compaction status. Pavement thickness and density profiles were also obtained by GPR after construction. The density values obtained by GPR were similar to those obtained by nuclear density gauge.

Improving asphalt paving productivity

The asphalt paving industry has an opportunity to improve the productivity of labor, equipment, and material resources with existing technologies. A systems approach is provided for measuring and improving the use of asphalt paving resources with established productivity methods. Production data from an asphalt paving project are evaluated using crew balance charts and computer simulation to understand equipment interaction and minimize paving production costs. Implementation of productivity evaluation methods and construction process planning can reduce costs and increase profits on asphalt paving projects through more efficient use of resources. Owner agencies must be aware of contractor cost elements so that cost-effective project contract documents can be prepared. A review of current practices in asphalt paving productivity, analyses of traditional productivity measurement methods, and an application of improving productivity using collected data are provided. A productivity management system is proposed that uses existing global positioning system technology to process asphalt paving productivity data through real-time data acquisition, productivity analysis, and information feedback.

Understanding Statistics in Maintenance Quality Assurance Programs

From the 1990s to now, transportation maintenance quality assurance (MQA) programs have been developed to ensure that maintenance quality is being achieved. MQA programs must be capable of detecting insufficient maintenance efforts, poor material performance, and incorrect procedures when evaluating end-product performance. At the Maintenance Quality Assurance Peer Exchange held at Madison, Wisconsin, in October 2004, participants expressed interest in exploring how statistical tools might be more effectively applied in MQA programs. The purpose of this paper is to provide maintenance practitioners with knowledge of how to understand and use statistics in MQA programs. Literature pertaining to recent efforts in this area was reviewed and synthesized. In addition, hazardous debris data from Wisconsin and level of service data from North Carolina were analyzed to demonstrate how an agency could apply traditional statistical methods such as analysis of variance, confidence limits, means comparison, data stratification, and sample size determination to an MQA program.

Computer-integrated methodologies for real-time control of asphalt paving operations

A real-time control system is needed for measuring and improving productivity and quality in asphalt pavement operations . This paper presents four computerintegrated methodologies necessary to develop a real-time control system for asphalt paving operation. These methodologies include: ( 1) simulation modeling for optimal allocation of resources, (2) automatic truck dispatching system to maximize truck productivity. (3) Global Positioning System (GPS) for realtime positional data acquisition , and (4) semi-automated path-planning and real-time guidance system for rolling operations. Interrelating these independent methodologies using a systems approach will allow for the development of a real-time control system for asphalt paving operations. Developing a real-time control system by standardizing construction practices will create a system that is amenable to strict quality and cost control.

Predicting Field Permeability from Testing Hot-Mix Asphalt Specimens Produced by Superpave Gyratory Compactor

This study was conducted to develop laboratory and field permeability testing procedures for design and quality control of Superpave® mixtures in Wisconsin. Sixteen mixes including fine-graded and coarse-graded mixes were evaluated. The in-place field permeability was measured by using the National Center for Asphalt Technology (NCAT) device, field cores were taken for measuring permeability in the laboratory by using the ASTM D5084 method, and laboratory compaction was used to prepare and test samples from loose mixtures recovered from the field. Two compaction procedures called Method A and Method B were used in this study to produce Superpave gyratory compacted (SGC) specimens that have thickness, air voids, and aggregate orientation similar to the field cores. Result indicates that Method B, based on the use of Ndesign gyrations for different sample sizes, can be used to produce samples that give permeability values similar to values measured for field cores. Results of this study also indicate a good relationship between field permeability (using the NCAT device) and lab permeability measured on field cores of fine-graded mixes with the amount passing No. 8 sieve (P8) higher than 45%. However, the relationship between field permeability and lab permeability measured on field cores of coarse-graded mix (P8 lower than 40%) is poor. It is concluded that the NCAT permeability device could possibly be used in the field for fine-graded mix (with P8 higher than 45%). However, to measure the field permeability of coarse-graded mix (P8 lower than 40%), there appears to be no current alternative better than taking field cores and testing them in the laboratory. For estimating permeability during mixture design, a simple method for preparing and testing permeability of SGC specimens and interpolating based on expected field density is introduced.

Calibration of Nonnuclear Density Gauge Data for Accurate In-Place Density Prediction

Hot-mix asphalt (HMA) density is an important acceptance quality characteristic, which involves in situ tests for quality control and assurance (QC/QA). Highway agencies have conventionally used nuclear density gauges or core samples for mat density. More recently, alternate nondestructive testing methods have been considered to replace current test methods. Nonnuclear density gauges offer rapid testing while eliminating safety risks and costs associated with radioactive license. Although agencies have evaluated them, they are not implemented in acceptance testing so far. Results are presented from a field evaluation of three nonnuclear density gauges—PaveTracker, PQI 300, and PQI 301—conducted on Wisconsin Department of Transportation (WisDOT) paving projects. The main goal was to evaluate the performance and effectiveness of non-nuclear gauges for use in QC/QA activities by WisDOT. The study involved field tests at 16 project sites and included 21 mix designs and a variety of mix design and pavement design parameters, such as aggregate type, nominal maximum aggregate size, layer thickness, design traffic, and base type. Density measurements were recorded at 30 test points at each site with one nuclear gauge and three nonnuclear gauges. Although the mean standard deviation values of the nonnuclear gauge data were less than those of the nuclear gauge measurements, a consistent bias was observed between the two data sets. This bias was adjusted by using a calibration factor to yield density predictions statistically the same as the nuclear gauge measurements. It is recommended that a calibration factor determined from 10 points by using a slope function be implemented for agency use. Further, daily calibration for each mix design is recommended when the project involves multiple paving days.

Ranking Procedure Based on Statistical Hypothesis Testing

A key element in a highway maintenance management system is a means to establish an ordered list of those sections most in need of repair. Developing such a list requires a method of measuring and analyzing existing conditions to judge which system components are in greatest need of treatment. For highway pavement, for example, the challenge is first to survey the system to determine the range of condition, usually according to level of service or other suitable measure, and then to create an ordered ranking of individual segments of the system by need for repair. Toward this end, basic tools of statistical analysis have been used to develop a procedure that produces a logically ordered sequence of highway segments. The procedure can also be used to provide a graphical display of statistical results, which serves as a visual snapshot of the condition of the highway system. The procedure performs the equivalent of multiple hypothesis tests to establish the rankings, but it stops short of providing an optimal sequence of repair strategies based on economic considerations.