Rheological and Molecular Characterization of Rubberized Asphalt Emulsion

An experimental study was conducted to evaluate the rheological and molecular characterization of rubberized asphalt emulsion. One rubberized asphalt emulsion and an asphalt rubber (CRS-2TR and AC20-TR) and two conventional emulsions (CRS-2 and CRS-2P) were evaluated. The emulsions were characterized by conducting rheological and physical testing. The influence of adding crumb rubber on the binder chemical composition was investigated in the laboratory using Fourier Transform Infrared Analysis (FTIR) on the original, Rolling-Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV)-aged binder residues. Results showed that CRS-2TR and AC20-TR had lower carbonyl and sulfoxide indices indicating better resistance to aging compared to conventional asphalt emulsions. Results of High-Pressure Gel Permeation Chromatography (HP-GPC) on the original, RTFO and PAV-aged binder residues showed that CRS-2TR and AC20-TR had similar High-Molecular Weight (HMW) content compared to that of conventional asphalt emulsions indicating similar susceptibility to brittleness with age

Mitigation Strategies of Reflection Cracking in Pavements

LTRC project Number: 14-4PFReflection cracking is a serious challenge associated with pavement rehabilitation. Practical experience shows that reflection cracking propagates at a rate of 1 in. per year. The primary objective of this synthesis study is to conduct an in-depth literature review of research projects on reflection cracking and a survey of the practices of highway agencies with regard to the types of cracking mitigation strategy used. Based on the results of the literature review and the survey questionnaire, a summarized assessment is presented for each reviewed treatment method. Further, a number of treatment methods were identified for further evaluation. For existing hot mix asphalt (HMA) pavements, crack sealing and overlay, chip seal and open-graded interlayers, full-depth reclamation, and cold-in place recycling are the most promising treatment methods. For existing Portland cement concrete (PCC) pavements, saw and seal, chip seal and open-graded interlayer systems, and rubblization are the most promising treatment methods. Based on the results of this study, the research team recommends that a follow-up study be conducted in order to evaluate the cost-effectiveness of the most promising treatment methods and to develop guidelines for the control of reflection cracking. The developed crack control guidelines will present recommended treatment methods for different classes of rehabilitated pavements in order to achieve adequate control of reflection cracking in a cost effective manner

Evaluation of Hot-Mix Asphalt Sampling Techniques

Insuring the integrity and security of hot mix asphalt (HMA) samples is critical to assuring the quality of the installed product and complying with Federal requirements. Samples of HMA are often taken at the plant with limited state supervision. Further, samples are taken from a truck where obtaining a representative sample can be difficult. The concept of moving the sample location to the job site offers the potential to address the weaknesses cited above. However, there are a number of different approaches, each with advantages and disadvantages. The objective of the proposed research project was to produce a review of successful methods and practices currently used to sample HMA during production and installation. This included visiting other states and providing detailed documentation of the visits. While achieving this objective, sufficient data were collected to allow IDOT’s personnel to draw a final recommendation for the optimum technique to be adopted for HMA sampling in future projects. During the course of this project, sampling practices in six highway agencies were evaluated (Kansas, Iowa, Ohio, Michigan, Florida, and Ministry of Transportation of Ontario). Four of these agencies specify roadway sampling, while one agency is experimenting with a new generation of mechanical sampling device and another agency samples directly from a Material Transfer Device (MTD). During the course of this project, areas of improvement in the current Illinois QC/QA program were also identified. In general, sampling behind the paver is being conducted by many states without much difficulty. Based on the site visits conducted in this research, the TRP group determined that the roadway sampling procedure adopted by Michigan DOT is the most appropriate for possible implementation in Illinois. In addition to this sampling technique, sealed bags adopted by Iowa DOT may be used, if necessary, to safely transport samples from the field to lab. Results of this research project also indicated that all visited states have a much higher sampling/testing frequency than Illinois and have successfully implemented an incentive/disincentive specification system. In addition, all visited states comply with the FHWA Technical Advisory (TA) or are in the process of making changes to comply with the TA. Based on these findings, the TRP has determined that the current Illinois QC/QA program is in need of several modifications to ensure successful implementation of roadway sampling, to comply with the TA, and to encourage high-quality construction of HMA. While changing sample location would improve sample security, it would not address shortcomings of the existing QC/QA program. In conjunction with implementation of roadway sampling, it is recommended to base sampling on tons instead of time, that IDOT personnel determine random sampling locations, witness samples taken, and take immediate possession of samples; adopt incentive and disincentive pay; and accept density based on field cores. It is also recommended that the formed TRP group continue effort in revising the QC/QA program to gain compliance with the TA and to introduce changes deemed necessary from our field visits.Illinois Department of Transportationpublished or submitted for publicationnot peer reviewe

Guidelines for Identification of Top-down Cracks (TDC) in In-Service Flexible Pavements

The objective of this study was to establish guidelines to identify top-down cracking (TDC) in flexible pavements using digital image analysis and the characteristics of these cracks. Past studies indicated that the time after construction of the pavement and location of the cracks are key parameters to identify top-down cracking. The cracks were reported to appear on the wheel path or at the outer edge of the wheel path typically within 3 to 8 years of construction. In-service pavement sections were selected for analysis based on the parameters identified from the literature and computer-vision techniques were employed to investigate the geometric characteristics of these cracks. Based on the results of the analysis, the average crack width was observed to be 3 to 7 mm. With respect to the orientation of the crack, the cracks segments were mostly longitudinal with typical deviation of 20 degrees. The orientation and intensity characteristics of top-down cracks were found as useful features in crack identification

Determination of Usable Residual Asphalt Binder in RAP

For current recycled mix designs, the Illinois Department of Transportation (IDOT) assumes 100% contribution of working binder from Recycled Asphalt Pavement (RAP) materials when added to Hot Mix Asphalt (HMA). However, it is unclear if this assumption is correct and whether some binder may potentially be acting as ???black rock,??? and not participating in the blending process with the new binder. Furthermore, it is also unclear whether binder modifications should be considered in the mix design for recycled HMA. The goal of this research was to determine if the current IDOT mix design practice required modification with respect to the use of RAP. A set of mixtures was prepared using RAP in accordance with current practice. Additional sets were prepared using recovered binder and recovered aggregate to simulate the effect of RAP binder blending with virgin binder. Mixes containing 0, 20, and 40%RAP were prepared and the dynamic modulus testing results of these mixtures were compared to illustrate the effect of RAP on HMA. Tests on recovered, virgin, and blended binders were also conducted using the Dynamic Shear rheometer (DSR). This study found that up to 20% RAP in HMA does not require a change in binder grade. However, at 40% RAP in HMA, a binder grade bump at high temperature and possibly at low temperature is needed; more tests are required to verify the need for low temperature binder grade bumping. In addition, this study recommends RAP fractionation in the preparation of laboratory specimens.ICT-R27-11published or submitted for publicationis peer reviewe

Nighttime Construction: Evaluation Of Lighting Glare For Highway Construction In Illinois

This report presents the findings of a research project that studied the veiling luminance ratio (glare) experienced by driveby motorists in lanes adjacent to nighttime work zones. The objectives of the project are to (1) provide an in-depth comprehensive review of the latest literature on the causes of glare and the existing practices that can be used to quantify and control glare during nighttime highway construction; (2) identify practical factors that affect the measurement of veiling luminance ratio (glare) in and around nighttime work zones; (3) analyze and compare the levels of glare and lighting performance generated by typical lighting arrangements in nighttime highway construction; (4) evaluate the impact of lighting parameters on glare and provide practical recommendations to reduce and control lighting glare in and around nighttime work zones; (5) develop a practical model to measure and quantify levels of glare experienced by drive-by motorists; and (6) investigate and analyze existing studies and recommendations on the maximum allowable levels of veiling luminance ratio (glare) that can be tolerated by nighttime drivers. The research work was performed in four main tasks: literature review, site visits, field studies, and model development. In the first task, a comprehensive literature review was conducted to study the latest research on quantifying and controlling lighting glare. In the second task, several nighttime highway construction sites were visited to identify practical factors that affect the measurement of glare. In the third task, field experiments were conducted to measure the levels of glare generated by commonly used construction lighting equipment and to evaluate the impact of lighting parameters on glare levels. In the fourth task, practical models were developed to enable resident engineers and contractors to measure and control the levels of glare experienced by drive-by motorists in lanes adjacent to nighttime work zones.Illinois Center for Transportationpublished or submitted for publicationis peer reviewe

Mitigation strategies for reflection cracking in rehabilitated pavements – A synthesis

The placement of an asphalt overlay on top of an existing pavement is rarely a lasting solution. Due to continuous movement of the existing pavement, existing discontinuities such as cracks and joints propagate through the overlay causing reflection cracking. Reflection cracking is a serious challenge associated with pavement rehabilitation. Practical experience shows that reflection cracking propagates at a rate of 1 in. per year. As the need grows for new rehabilitation methodologies to improve the performance of overlays against reflection cracking, a number of state transportation agencies tasked the authors of this paper to conduct a comprehensive review of treatment methods available to delay or to prevent reflection cracking in rehabilitated pavements and to survey current state of practice in addressing this distress. Based on the results of the literature review and the survey questionnaire, a summarized assessment is presented for each treatment method. Further, a number of treatment methods were identified for further evaluation by the state transportation agencies. For existing HMA pavements, crack sealing and overlay, chip. Keywords: Reflection cracking, Mitigation strategies, Fractured slab approaches, Saw and seal, SAMI, Chip sea