Development of an Improved System for Oregon to Accurately Quantify Dense-graded Hot Mix Asphalt Pavement Density

Development of an Improved System for Oregon to Accurately Quantify Dense-graded Hot Mix Asphalt Pavement Density
Author: Suraj Darra
Publisher:
Total Pages: 484
Release: 2010
Genre: Pavements, Asphalt
ISBN:

The Oregon Department of Transportation (ODOT) standard specifications require a minimum density for the construction of dense-graded hot mix asphalt (HMA) pavements. Currently, the standard specifications call for density measurements for quality control (QC) and quality assurance (QA) testing to be made using nuclear density gauges that are calibrated using reference blocks and correlated (adjusted) to densities from pavement cores. QC measurements (performed by the contractor) are verified by QA measurements (performed by ODOT); then ODOT utilizes the contractor's QC results for determining acceptance of the pavement (in conjunction with other specification criteria). Hence, appropriately accepting an HMA pavement, based on the in-place density criterion, relies on the accuracy of the density measurements. However, density measurement results using nuclear gauges have been observed by ODOT to be questionable on a number of projects, and repeatability and reproducibility with the same gauge and between gauges has been unattainable. The overall objective of the project described herein was to develop a system that accurately quantifies density of dense-graded HMA pavements. More specifically, the objectives were to: 1) investigate the efficacy of the various methods used by ODOT and other agencies for determining in-place HMA density; 2) assess current practices used by ODOT and other agencies for determining in-place HMA density using nuclear gauges; 3) conduct field and laboratory testing and analyses to determine the most accurate and reliable state-of-the-practice means for determining in-place HMA density; 4) provide recommendations for changes to current practices to improve accuracy and reproducibility of in-place HMA density measurements using nuclear gauges; and 5) provide recommendations for alternate means for determining in-place HMA density. To satisfy the first objective, a literature review was conducted and summarized herein. For the second objective, practices employed by ODOT were observed and assessed. For the third objective, state-of-the-practice methods used to measure HMA density (i.e., tests on core samples using the saturated surface-dry and automatic vacuum sealing methods, nuclear density gauge measurements and electromagnetic density gauge measurements) were investigated. Numerous statistical comparisons of the results were made to determine the best combination of measurement methods to ensure accurate assessment of HMA density for a variety of construction scenarios. Finally, the findings from the first three objectives were used to formulate the recommendations identified in the fourth and fifth objectives. Some of the significant findings that are based on the supporting evidence from the research are as follows: 1) Nuclear gauge densities should be adjusted to core densities for future in-place density testing of HMA pavements; 2) Cores should be tested in accordance with CoreLok testing procedure and not by using the SSD methods; 3) Cores should be extracted from the overlapping portion of the footprints of the nuclear gauge measurements; 4) It is sufficient to take two nuclear gauge readings (perpendicular and parallel to the direction of paving) rather than four readings; 5) Under certain conditions, the core adjustment factors obtained from the bottom lift can be used to adjust the nuclear gauge densities on at least the next two overlying lifts of the same pavement; and 6) The electromagnetic gauge adjustment factors could be used on more lifts than nuclear gauge adjustment factors to adjust measurements; and, electromagnetic gauge densities were not significantly different from core densities.

Density Measurement Verification for Hot Mixed Asphalt Concrete Pavement Construction

Density Measurement Verification for Hot Mixed Asphalt Concrete Pavement Construction
Author: Todd V. Scholz
Publisher:
Total Pages: 350
Release: 2010
Genre: Asphalt concrete
ISBN:

Oregon Department of Transportation (ODOT) requires a minimum density for the construction of dense-graded hot mix asphalt concrete (HMAC) pavements to ensure the likelihood that the pavement will not experience distresses that reduce the expected service life of the pavement. Currently, the ODOT Standard Specifications call for density measurements for both quality control and quality assurance testing to be made using nuclear density gauges that are calibrated using reference blocks. Hence, acceptance (i.e., purchase) of the HMAC pavement (or portions thereof) relies on the accuracy of the measurements. However, it has been observed that density measurement results using nuclear gauges have been questionable on a number of projects and that repeatability and reproducibility with the same gauge and between gauges have also been unattainable. Further, these observations have called into question the confidence placed in the use of nuclear gauges for determining HMAC pavement density. The overall objective of the project was to recommend a system that accurately quantifies density of dense-graded HMAC pavements. This involved critically evaluating how ODOT currently measures HMAC density, investigating and evaluating what other agencies do to measure HMAC density, and conducting testing and analysis of alternate ways of measuring HMAC density (e.g., by measuring the density of cores). Statistical analyses comparing nuclear gauge measurements to core densities provided convincing evidence that correlation of nuclear gauge measurements to core densities is necessary to ensure accurate results from nuclear gauges. Analyses comparing correlation factors across lifts of pavements constructed under three differing construction scenarios provided strong evidence to suggest correlation factors established for one lift can be used on other lifts under certain constraints. Correlations are recommended for all gauges on each lift and whenever a new mix design is introduced. ODOT should implement use of the CoreLok device for measuring densities of pavement cores and laboratory-prepared specimens as well as further investigate the use of electromagnetic gauges for in-place HMAC density measurement.

Density Measurement Verification for Hot Mix Asphalt Concrete Pavement Construction

Density Measurement Verification for Hot Mix Asphalt Concrete Pavement Construction
Author: Todd V. Scholz
Publisher:
Total Pages:
Release: 2010
Genre: Asphalt concrete
ISBN:

Oregon Department of Transportation (ODOT) requires a minimum density for the construction of dense-graded hot mix asphalt concrete (HMAC) pavements to ensure the likelihood that the pavement will not experience distresses that reduce the expected service life of the pavement. Currently, the ODOT Standard Specifications call for density measurements for both quality control and quality assurance testing to be made using nuclear density gauges that are calibrated using reference blocks. Hence, acceptance (i.e., purchase) of the HMAC pavement (or portions thereof) relies on the accuracy of the measurements. However, it has been observed that density measurement results using nuclear gauges have been questionable on a number of projects and that repeatability and reproducibility with the same gauge and between gauges have also been unattainable. Further, these observations have called into question the confidence placed in the use of nuclear gauges for determining HMAC pavement density. The overall objective of the project was to recommend a system that accurately quantifies density of dense-graded HMAC pavements. This involved critically evaluating how ODOT currently measures HMAC density, investigating and evaluating what other agencies do to measure HMAC density, and conducting testing and analysis of alternate ways of measuring HMAC density (e.g., by measuring the density of cores). Statistical analyses comparing nuclear gauge measurements to core densities provided convincing evidence that correlation of nuclear gauge measurements to core densities is necessary to ensure accurate results from nuclear gauges. Analyses comparing correlation factors across lifts of pavements constructed under three differing construction scenarios provided strong evidence to suggest correlation factors established for one lift can be used on other lifts under certain constraints. Correlations are recommended for all gauges on each lift and whenever a new mix design is introduced. ODOT should implement use of the CoreLok device for measuring densities of pavement cores and laboratory-prepared specimens as well as further investigate the use of electromagnetic gauges for in-place HMAC density measurement.

AASHTO Guide for Design of Pavement Structures, 1993

AASHTO Guide for Design of Pavement Structures, 1993
Author: American Association of State Highway and Transportation Officials
Publisher: AASHTO
Total Pages: 622
Release: 1993
Genre: Pavements
ISBN: 1560510552

Design related project level pavement management - Economic evaluation of alternative pavement design strategies - Reliability / - Pavement design procedures for new construction or reconstruction : Design requirements - Highway pavement structural design - Low-volume road design / - Pavement design procedures for rehabilitation of existing pavements : Rehabilitation concepts - Guides for field data collection - Rehabilitation methods other than overlay - Rehabilitation methods with overlays / - Mechanistic-empirical design procedures.

Density Measurement of Compacted Asphalt Mixtures Using Non-destructive Ground Penetrating Radar

Density Measurement of Compacted Asphalt Mixtures Using Non-destructive Ground Penetrating Radar
Author: Mardeni Roslee
Publisher:
Total Pages: 468
Release: 2009
Genre:
ISBN:

This thesis describes the development of Ground Penetrating Radar (GPR) system based on the electromagnetic wave reflection to determine the density of road pavement. The proposed method is simple, fast, non-destructive and within an acceptable accuracy of road pavement density. The theoretical analysis based on the three existing GPR Mixture Model (GMM) methods has been improved to produce the most optimized function to be incorporated within the proposed GPR system. The study involves three main procedures which are theoretical analysis, laboratory scale experimentation and reliability analysis. From these studies, the Lichtenecker Mixture Model is found to be the most accurate function compared to the other models like Nelson and Landau due to the smallest mean error between the prediction and the experimental result. During the laboratory experimentation, an engineering GPR prototype has been developed and used to measure the road pavement density of the road pavement slab sample. The GPR to measure the road pavement density of the road pavement slab sample. The GPR system consists of the transmitter which is signal generator as a microwave source, horn antenna for transmitting and receiving the signal, directional couple with an adapter and spectrum analyzer to analyze the received signal. Nine road pavement slabs of middle boundary and ten slabs of upper and lower boundary of Hot Mix Asphalt (HMA) gradation were developed and tested at four different frequencies within the range of 1.7-2.6GHz. The predicted signal attenuation from the theoretical analysis is compared to the signal attenuation measured from the laboratory experimentation. The comparison produces the relative error between these two results and it is used in the optimization process. The finding from the optimization process suggested that three additional constant parameters which are Volume factor, Permittivity factor and Attenuation factor need to be included to improve the existing GMM model. A field test had been conducted as an outdoor reliability analysis to validate the optimized GMM model. From the field test, it shows that the proposed GPR system works well with an error range from 3.37 % to 4.72 % for nine locations. Finally, a complete GPR system has been developed based on the optimized GMM attenuation curve to predict the density of a real road pavement.

Initial Performance Assessment for Implementation of Hot Mix Asphalt Containing Recycled Asphalt Shingles in Oregon

Initial Performance Assessment for Implementation of Hot Mix Asphalt Containing Recycled Asphalt Shingles in Oregon
Author: Faisal Ahmed Samoo
Publisher:
Total Pages: 181
Release: 2011
Genre:
ISBN:

This thesis documents the evaluation of the initial performance of pavement containing recycled asphalt shingles (RAS) in Oregon. The research was funded by the Oregon Department of Transportation (ODOT) and the Federal Highway Administration and was conducted at Oregon State University. The key objectives of this thesis are to document the state-of-the-practice for implementation of recycled asphalt shingles in hot mix asphalt (HMA) mixtures, and to evaluate the initial field and laboratory performance of mixtures containing RAS. Recent oil price increases, coupled with environmental impacts has encouraged industry to use materials containing asphalt binder, such as asphalt shingles as a partial replacement of virgin materials in the construction of bituminous pavement. Residential home reroofing projects generate RAS as does the asphalt shingle manufacturing industry as a waste product at a rate of approximately 11 million tons per year nationwide. Disposal of these materials ordinarily involves discarding the materials in landfills. However, since these shingles contain asphalt binder, many states and asphalt pavement contractors have made efforts to incorporate these materials into asphalt pavements. Asphalt shingles are produced with asphalt binders that have substantially higher stiffness than paving grade asphalt binders. With increased stiffness comes increased brittleness. Consequently, incorporating RAS into hot mix asphalt may expose the pavement to an increased likelihood of low temperature cracking and fatigue cracking unless modifications are made to the mixtures to compensate for increased stiffness due to the RAS binder. House Bill 2733, proposed before the Oregon Legislative Assembly in 2009, would have required ODOT to use up to 5% RAS in HMA. However, inclusion of RAS in HMA raised concerns within the agency with regard to the potential for reduction in pavement performance ultimately leading to increased costs due to early failures. Consequently, considering these concerns the legislation on this bill was postponed pending completion of research to investigate the performance of pavement containing RAS in Oregon pavements. As a result, ODOT sponsored preliminary research on use of RAS in HMA in 2009 and subsequently through the research project described herein. The research work described herein was separated into three distinct but interconnected tasks. The first involved conducting a detailed literature review to gain an understanding of the state-of-the-practice for successful implementation of RAS in pavements. Emphasis during this effort was placed on selection of the virgin binder grade to offset the effects of increased stiffness due to incorporation of RAS binder, batching and mixing procedures for inclusion of RAS in HMA mixtures, ignition oven calibration factors for mixtures containing RAS, and quality control/quality assurance procedures for pavements built with RAS mixtures. There exists a substantial body of literature covering use of recycled asphalt pavement (RAP) as a partial replacement of virgin materials in HMA pavements. Due to many similarities of RAP and RAS, many of the documents reviewed covered only RAP, but with the aim of extending the technologies used for RAP mixtures to those containing RAS or RAS and RAP. The second task involved conducting laboratory investigations to verify the practicality and effectiveness of procedures found in the literature for batching and mixing materials containing RAS and/or RAP and RAS. Finally, the third task involved investigations of performance of two pavements containing RAP and RAS constructed as pilot projects. The investigations involved an assessment of field performance and laboratory tests on samples obtained from the two pavements. For comparison purposes, the same investigations were performed on pavements and samples from pavements that contained RAP but no RAS. These were constructed adjacent to, and at the same time as, the pavements with RAP and RAS. Based on the findings from the literature review, this thesis contains recommendations for: 1) selection of a virgin binder grade when RAP and/or RAS is used in an HMA mixture; 2) a procedure for effectively and efficiently extracting and recovering asphalt binder from RAS; 3) batching and mixing procedures for manufacturing laboratory test specimens containing RAS; 4) a method for determining ignition over calibration factors for mixtures containing RAS; and 5) quality control/quality assurance procedures for pavements built with RAS mixtures. The recommended batching and mixing procedure was verified through laboratory investigations while ongoing research is in the process of verifying the remaining procedures. Laboratory investigations involving dynamic modulus testing and comparative analyses of RAP-only mixtures (control mixtures) versus RAP and RAS mixtures indicated a trend of reduced dynamic modulus due to the addition of RAS in the mixture on both pilot projects. However, when the mixtures were compared at a 95 percent confidence level, a significant difference was found for only one of the two projects. This reduction in dynamic modulus was likely due to the softening of blended binder and the increased air voids in the mixtures containing RAS. In addition, fatigue testing and comparative analyses using phenomenological and dissipated energy approaches indicated that there was no significant difference in fatigue resistance of the RAP-only mixture versus the RAP and RAS mixture at a 95 percent confidence level. Assessment of field performance through visual inspections of the pavements built with mixtures containing RAS revealed no low temperature cracking following the first winter season in service. Nor did the inspections reveal any fatigue cracking. Although these inspections occurred within 8 months of construction of the pavements, the findings provide encouraging early-life performance of the mixtures.