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PennDOT performed a literature review, survey of other states, and a cost benefit analysis of multiple thin surface treatments, and finds that the equivalent annual cost of micro surfacing is 44% lower than that of thin overlay and can provide 6-8 years of service life when applied at optimal times. PennDOT also recommends the consideration of expanded use of micro surfacing, from both a geographical and traffic level point of view.
This report summarizes the state-of-the-art and current state-of-the-practice of crack treatments and concludes with current best practices. This report is limited to crack sealing and crack filling of asphalt pavements, and does not consider joint filling on concrete pavements, reflective cracking retardation techniques, joint construction techniques, or other related issues.
The objective of this study is to determine if the scrub seal is more cost effective than microsurfacing, chip seals and the 1" hot mix overlay. Scrub seals were placed at 10 different locations and reviews of each section were made to determine the usefulness of the seal. Most of the scrub seals are very promising although it has been determined they should be limited to areas of less than 7500 ADT. Most of these scrub seals are about 1 year old and we are hoping to get a life span of 3 to 4 years from them.
A 1-year research project was sponsored by TxDOT and conducted by University of Texas at Austin researchers to evaluate the Cape seal process as a pavement rehabilitation technique. During the course of this research project, most of the Cape seal projects that have been constructed within the state were visited as part of the evaluation. Projects documented during the visits included both successes and failures.
The primary objective of this project was to develop a test for measuring the bond strength between pavement layers. The research was also to evaluate tack coat materials and application rates for the Alabama Department of Transportation (ALDOT).
This Technical Brief provides an overview of tack coats and their vital role bonding multiple asphalt layers into one monolithic system. Poor tack coat techniques result in compromised bonding of the asphalt layers. This leads to pavement distresses. Possible slippage cracking and delamination are associated with poor bonding. Additionally, poor bonding can lead to structural distresses, namely fatigue cracking and potholes. Often this lack of sufficient bonding is not recognized as the source of failures.
Find the full report here.
Asphalt tack coat is a light application of asphalt, usually asphalt diluted with water. It is used to ensure a bond between the surface being paved and the overlying course. Normally, hot asphalt cements, emulsified asphalts, or cutback asphalts are used as tack coats. The objective of this study was to evaluate the practice of using tack coats through controlled laboratory simple shear tests and determine the optimum application rate.
See Report Here.
In 2005, the Georgia Department of Transportation (GDOT) moved away from chip seal treatments due to vehicle damage caused by loose stone and friction loss due to bleeding. Recently, however, GDOT sought to bring the process back by changing both the construction methods and the materials used. The GDOT Maintenance Department determined that a pilot project, called a triple chip seal, would be the most appropriate way to test the new approach.
Louisiana’s US Route 84 was suffering from extensive pavement wheel path rutting and shoving. To correct the problem, the Louisiana Department of Transportation and Development (LADOTD) provided a budget of $2.25 million to execute repairs for the 17.5-mile length of road.
In order to keep residents satisfied and to attract industry, DeSoto County proactively treats their roads to maintain high quality trasportation infrastructure for a fraction of what it would cost to wait until more expensive repairs are needed. Safety of the network is improved as well.
No VOC Penetrating Emulsion Prime Coat, ePrime, contains no added solvents. The PEP penetrated the surface within 15 minutes and withstood a garbage truck that drove through the work zone.
Sometimes field changes are necessary. The importance of utilizing test strips prior to starting a project cannot be understated.
Using Optimized Solutions for Extreme Soil Conditions
Hot in-place recycling helps the combined City and County of Denver meet its Sustainability goals while lowering energy requirements and extending pavement life. The City of Denver is increasing its use of hot in-place recycling in order to meet their own sustaniability criteria, in terms of the amount of material recycled , and cumulative emissions as opposed to other conventional maintenance methods.
Contractor successfully repaired Lake Louise Marie Road in the Town of Thompson located in Sullivan County New York. Fiber reinforced interlayer with a Paver Placed Surface Treament overlay.
Mass cracking of roadways in Yuma County, AZ, had become so severe, they required immediate attention. After evaluating all of the options and taking budget constraints into consideration, a rejuvenating chip seal was chosen as the best solution to the challenge.
Sylvania, OH is using micro surfacing to save money when resurfacing streets. They expect 8 - 12 years of life extension with micro surfacing, costing 35 cents on the dollar compared to asphalt mill and repair.
Micro surfacing was successfully placed on one of the busiest and most congested roads in the Greater Columbus area. By working with the Ohio DOT, the contractor was able to minimize traffic disruption while placing a high quality material.
This synthesis report provides an overview of successful chip seal practices in the United States, Canada, and overseas. Although not meant to be an exhaustive study, it covers the spectrum of chip seal practice and presents, where possible, the state of the art, as reported in the literature and survey responses. The report presents ways to assist in the development and implementation of pavement preservation programs by identifying the benefits of using chip seal as part of a preventive maintenance program. Innovative and advanced chip seal programs from around the world were identified with respect to critical factors that can be incorporated by other transportation agencies. Approximately 40 best practices were identified in the areas of chip seal design methods, contract administration, equipment practices, construction practices, and performance measures. The increased use of chip seals for maintenance can be a successful, cost-effective way of using preventive maintenance to preserve both low-volume and higher-volume pavements.
- Significant cost savings can be achieved by organizing pavement preservation work so that the contractor will have several weeks of work in one geographic area.
- Delaying pavement preservation by applying a treatment on an existing pavement with a PCI of 60 instead of 80 will result in an increase in equivalent annual treatment costs between about 70 to 100%.
- Delaying the application of the treatment to an existing pavement condition of 40 will result in an increase in the equivalent annual treatment cost of about 300%.
This is an educational document containing instructions and examinations. It discusses basic procedures for prime coat application, distributor operations, inspection, and documentation. This is of particular value for construction inspectors.
TRB’s National Cooperative Highway Research Program (NCHRP) Report 712: Optimization of Tack Coat for HMA Placement presents proposed test methods for measuring the quality and performance characteristics of tack coat in the laboratory and the field, and includes a training manual presenting proposed construction and testing procedures for tack coat materials.
It is available for Purchase as a PDF from TRB here.
A comprehensive guideline for prime coat use. A prime coat and tack coat guide publication for project development and field personnel to provide decision-making guidance on how to use, when to require, and when to eliminate prime and tack coats.
Following damage that appeared on the surface layers (fatigue cracks, peeling, rapid structural fatigue), the IBEF International Bitumen Emulsion Federation launched a survey in 1998. The goal of the survey was to assess the current situation of this technique worldwide by studying the practices, proportions and specifications that exist.
Find full report here.
The constructability review of surface treatments on base courses. It contributes to the development of a surface treatment design and construction guide, updates to the TxDOT surface treatment training manual, and updated specifications.
The main objective of this research project was to evaluate the effectiveness of prime coats and determine which combinations of methods and materials provide the most benefit to TxDOT. The use of prime coats are described, and their construction requirements are discussed in Item 310 of the Texas Department of Transportation (TxDOT) Standard Specifications.
This study was centered on elucidating the chemical reactions that bring about soil stabilization and modification. It has been established that the chemical compounds found in soil; quartz, feldspar, dolomite, calcite, montmorillonite, kaolinite etc. react with the chemical constituents found in different identified chemical stabilizers. This research work will better place designers, constructors and researcher on the choice of soil chemical stabilizer and techniques and the extent of chemical reactions that take place during soil chemical stabilization.
Two alternative detailed guidelines for incorporating mixing-grade emulsified asphalt into the uppermost layer of base course.
"Stabilization projects are almost always site-specific, requiring the application of standard test methods, along with fundamental analysis and design procedures, to develop an acceptable solution. As with any such process, adherence to strict environmental constraints is vital to project success. The use of cementitious materials makes a positive contribution to economic and resource sustainability because it allows enhancement of both standard and substandard in situ soils to levels consistent with the requirements of a given application."
"This study concluded that the improvements to key properties of cold mix by the addition of Portland Cement can be explained by a range of mechanisms, including improved rate of emulsion coalescence after compaction, cement hydration and enhancement of binder viscosity."
Micro surfacing is an effective surface treatment to prolong the life span of paved roads by preserving or improving the condition of paved roads. Whether used as a preventative treatment, corrective treatment, or holding strategy, micro surfacing lowers pavement life-cycle costs.
The researchers found that, in most cases, the extra energy embodied in the cool material was far greater than the energy savings from increasing the albedo.
“Over the life cycle of the pavement, the pavement material matters substantially more than the pavement reflectance,” - Ronnen Levinson of Berkeley Lab.
“I was surprised to find that over 50 years, maintaining a reflective coating would require over six times as much energy as a slurry seal. The slurry seal is only rock and asphalt, which requires little energy to produce, while the reflective coating contains energy-intensive polymer.” - Ronnen Levinson of Berkeley Lab.
Read full source here.
"The Federal Aviation Administration requires the use of stabilized bases for all pavements that will be required to support aircraft weighing 45,350 kg (100,000 lbs) or more. literature review was performed to determine the current state of the art in terms of understanding stabilization mechanisms, design procedures, and considerations. were collected to provide a review of the performance of many pavements at high-volume airports that support heavy aircraft loads. Field data collected included structural data in the form of nondestructive testing (NDT) performed with a falling weight deflectometer, visual condition survey using the pavement condition index (PCI) procedure, and construction and maintenance history data. The NDT was evaluated to determine modulus values for the various pavement layers. he PCI data were compared to historic PCI data to determine trends in performance. he construction and maintenance history records were reviewed to determine rehabilitation efforts required to maintain the pavements at appropriate levels."
The purpose of this study was to explore the effectiveness of chemical stabilization practices on unpaved roads. A 550-ft-long segment of Hurley Lane, a gravel road in Loudoun County, was selected for testing. The construction technique known as full-depth reclamation (FDR) was used. The existing unpaved road section was pulverized to a depth of 12 in and subsequently blended with 5% cement by weight using road reclaiming equipment. The surface was then covered with a double chip seal. The main objective of this project was to provide stability while still maintaining the appearance and “feel” of a gravel road.
"Complete excavation of frost-susceptible material is not economically viable in all cases. Emulsion mixes have been used successfully to follow roadbed soil movement without cracking. Laboratory and field observations indicate that emulsion mixes have membrane-like mechanical properties rather than the slab-like properties of standard hot bituminous mixtures. Furthermore, emulsion mixes are not as susceptible to thermal cracking as regular standard hot bituminous mixtures."
Stabilized road gravel was tested to compare with that of unaltered raod gravel. " California bearing ratio (CBR), resilient modulus (Mr) , and unconfined compression (qu) tests were conducted on road surface gravel alone and the fly-ash stabilized road surface gravel samples prepared in the field to evaluate how addition of fly ash improved strength and stiffness. After 7 days of curing, the stabilized road surface gravel compacted in the field from a field-mix sample had CBR ranging between 48 and 90, Mr between 96 and 125 MPa, and qu between 197 and 812 kPa, whereas the road surface gravel alone had CBR of 24, and Mr of 51 Mpa."
The Strategic Highway Research Program (SHRP) H-106 maintenance experiment and the Federal Highway Administration (FHWA) Long-Term Monitoring (LTM) of Pavement Maintenance Materials Test Sites project studied the treatment (sealing and filling) of cracks in asphalt-surfaced pavements. Many different treatment materials and methods were investigated between 1991 and 1998 through test sites installed at five locations in the United States and Canada. The findings of these combined studies have been merged with standard highway agency procedures to provide the most useful and up-to-date information on the practice of asphalt crack treatment.
This Manual of Practice is an updated version of the 1993 SHRP Crack Sealing and Filling Manual. It contains the latest information pertaining to the performance of treatment materials and methods, the availability and relative costs of sealant/filler materials, and the proper ways of planning, designing, constructing, and monitoring the performance of crack treatment projects. It also provides an updated partial listing of material and equipment manufacturers.
This Manual is intended for field and office personnel within highway maintenance agencies and contracted maintenance firms. It contains valuable information for supervisors and foremen in charge of individual crack treatment operations, engineers in charge of planning and overseeing many crack treatment projects, and managers in charge of establishing crack treatment policies and standards.
On June 18 and 19, 2007, Caltrans District 9 (D9) placed six rejuvenator seal test sections to preserve a section in the eastbound number two lane ( right lane), often used by trucks, on Highway 58 between PM 123.3 and 125.1 east of Mojave, California in Kern County . This roadway is 4-lane divided freeway with a 65 MPH speed limit. The weather during the application was dry with light winds.
The California skid test (CT372) and ASTM E274 locked wheel skid trailer were used to evaluate friction before and after treatment application. Two of the 6 treatments (CRF and Reclamite) were sanded after application to blot excess emulsion. The skid numbers dropped about 30 % after the application of the treatments.
Cores were obtained before and after treatments to determine if the rejuvenators softened the upper millimeters of existing pavement. The bending beam rheometer (BBR) stiffness and m-value testing showed the CRF and PASS-QB products softened the existing pavement; however, this finding is unexpected based on previous experience by the monitoring team. The CQS-1h emulsion significantly increased the stiffness of the pavement. The dynamic shear rheometer (DSR) test method was too variable (coefficient of variation of about 50%) to determine if there was any statistical difference between the treatments and the control sections.
In the summer of 2011, a follow-up survey was completed and additional testing conducted. The results of the survey showed that the treatments have improved the performance compared to the control with some treatments softening the existing pavement more than others
This is the initial phase of further planned testing. Conclusions cannot be drawn until further work is done and the remaining test sections are completed.
The use of preservation seals on asphalt pavements is a crucial part of any effective pavement management program. It is important to optimize the use of available budgets to extend the life of our pavements as much as possible. The nation’s highway system is one of our most valuable assets.
Analysis of the performance of surface treatments on Utah pavements indicates that Open Graded Surface Courses (OGSC) have an average life, based on skid resistance of almost 9 years and that Chip Seal Courses (CSC) have a significantly longer life.
Out of all the factors analyzed, traffic has the most significant effect on the performance of the treatment. Factors such as aggregate source and asphalt supplier were also investigated but lack of data prevented from reaching any significant conclusion.
Based on the relative cost of both treatments and the performance observed through this study, it is recommended that Utah Department of Transportation expand the use of CSC to certain roads with AADTs up to 20,000 vehicles and continue the existing procedure of using CSC in highway sections with AADTs below 5,000. It is also recommended that UDOT modified the existing policies and limit the use of OGSC where the running speeds are 55 mph or greater and AADTs are in excess of 25,000 vehicles. Medium volume facilities (5,000 to 25,000 AADT) should be sealed with treatments new to UDOT but proven in other states.
An initial cost analysis showed that the implementation of the changes suggested as part of this report will results in savings of over $2 million per year in the maintenance budget. Thus allowing for better use of resources while still serving the traveling public.
This report presents the results of a research study funded by SOLARIS University Transportation Center. The research evaluated the long-term performance of cape seals with micro surfacing and slurry seal in the Truckee Meadows and Incline Village areas of Northern Nevada.
Recently, use of pavement preservation technologies, such as bituminous seal treatments, has increased. Seal treatments are often used to rejuvenate aged asphalt pavements and can decrease permeability and retard oxidation, cracking, and raveling. Many factors affect rejuvenation, and current specifications governing how rejuvenation is characterized could be enhanced. Viscosity testing of asphalt binder extracted and recovered from a pavement’s near surface is the predominant means of characterizing rejuvenation (e.g., a product must reduce viscosity by 40% to be classified as a rejuvenator). This paper presents data that suggest other rejuvenation approaches are worth considering because (a) extraction and recovery can adversely affect viscosity results, (b) viscosity testing cannot be conducted without forced and unrealistic blending of aged binder and rejuvenator, (c) high test temperatures may not be the most informative for distresses of interest (e.g., cracking), and (d) viscosity could not detect rejuvenation behaviors of some proprietary products.
This document provides detail on guidelines and best practices on Bonded Wearing Course from Caltrans
This report documents the current state of the practice and research efforts on the use of thin asphalt concrete overlays for pavement maintenance, rehabilitation, and preservation. This synthesis was performed by conducting a literature review, including both U.S. and international technologies, as well as a survey of state departments of transportation (DOTs) and selected local agencies. Information was also gathered from selected individuals and private industry representatives.
Micro surfacing can be expected to provide an average service life of 7 years if the underlying road is in good condition.
Micro surfacing provides good friction characteristics for up to nine years of service.
Micro surfacing is a pavement preservation and maintenance tool with very few technical or operational limitations.
Fog seal increases pavement life and postpones major rehabilitation. The reduction of permeability due to fog sealing will reduce moisture induced damage, but this benefit comes with a temporary loss of surface friction. However, quantifying the effectiveness of fog seal by measuring the permeability is a difficult task. While fog seal may be a good low-cost maintenance option for low volume roads, the rate of recovery of the friction may be very slow due to less rubbing action between fog sealed surface and tire. Four low volume parish roads in Caddo parish, LA have been selected for this study. Two emulsions, namely CSS-1H and E-fog, with three different application rates, were used to evaluate the reduction in hydraulic conductivity and to assess the characteristics of friction over time. Results show that fog seal is expected to be fully cured within 2.5 to 3.5 hours for 0.2-0.4 gal/yd2 application rate. The same field-cores were tested before and after fog sealing to exactly quantify the reduction in hydraulic conductivity. It was observed that fog seal has significant potential to reduce the hydraulic conductivity. Considering all four pavements and application rates of 0.1-0.22 gal/yd2, the average reduction in hydraulic conductivity was 38.5%. Reduction in hydraulic conductivity shows very slight sensitivity to the application rate. Irrespective of road type, emulsion and application rate, fog seal causes a sudden drop in the International Friction Index parameter F60 by 20 to 40%. Fog sealed surface does not return to the original level of friction after three months, however, the rate of recovery was the highest for the busiest of the observed Caddo parish roads.
The Town of Fairfield saves their network using micro surfacing as the primary backbone of a robust pavement preservation program.
Progressive agencies are constantly seeking the most cost effective methods to improve ride quality and decrease cracking as part of their overall pavement management strategy. More and more agencies like MnDOT are finding the use of micro-milling and high performance micro surfacing mixes to be worthwhile investments of their limited funding.
Base Stabilization was selected for its efficiency and cost savings over total removal and replacement. Problems with failing pavement layers, but not deep subgrade issues, made their parking lot a perfect candidate for Base Stabilization.
Arizona studies 17 CIR projects constructed from 1981 to 2001, finds improved IRI, better resistance to cracking, lower post-construction maintenance costs, and “significant improvements in performance.”
Study examines 24 CIR asphalt roads constructed in Iowa from 1986 to 2004. Research finds that sample roads with good subgrade support have 36% longer service lives than roads with poor subgrade support in addition to revelations in varying factors affecting performance in CIR between high and low traffic roads.
Illinois study examines CIR, FDR and Hot Mix asphalt projects. Research supports the recommendation that CIR and FDR with Asphalt Products be considered a “standard procedure”
FHWA report includes summary of performance seen by multiple agencies, confirms CIR has better results than mill & fill; And the same or longer pavement life, with equal or lower NPV than conventional HMA. Report recommends an AASHTO structural layer coefficient of 0.32-0.34 for CIR mixes.
For years, the Town of Lexington, Massachusetts had maintained its streets with a program that consisted of mill and overlay and reclamation, along with crack sealing as necessary. But Town Engineer John Livsey has never been a fan of letting roads go until they need major repair, and over the past five years, his team has introduced a number of pavement preservation techniques into its overall program, including micro surfacing and fog sealing. In August 2016, the Town initiated cape sealing, testing the technique on one street with 21,867 square yards of treatment.
When cities turn to implementing a pavement preservation plan, the life of the pavement can be significantly extended. To ensure a quality project, the contractor must prepare the streets and project properly, use proper application techniques, and manage traffic properly.
The Lewisville Fire Department needed to rehabilitate the asphalt paved areas and expand the parking lot of its fire house. By electing to use the Full Depth Reclamation (FDR) process, the department saved time, money and transformed the deteriorated parking area into one that will last for years to come!
Georgia DOT micromilled 500,000 square yards of interstate highway pavement in a single weekend. This innovative approach added 3-5 years of life and delayed complete removal/replacement, saving taxpayers millions of dollars and miles of inconvenience.