Chip Seal Research Articles

Evaluation of Reclaimed Asphalt Pavement Materials from Ultra-Thin Bonded Bituminous Surface

Abstract Ultra-thin bonded bituminous surface (UBBS) is a surface treatment that consists of a thin, gap-graded hot-mix asphalt (HMA) layer applied over a thick polymer-modified emulsion membrane. The aggregates and asphalt used in UBBS are of very high quality. The objective of this study is to evaluate whether reclaimed asphalt pavement (RAP) materials from existing UBBS layers can be used in chip seal and Superpave mixtures. UBBS RAP were studied with two different polymer-modified emulsions to assess their performance as precoated aggregates in chip seal using ASTM D7000-04 sweep test. Three different Superpave mix designs were developed for both 12.5-mm and 9.5-mm nominal maximum aggregate sizes (NMAS) using three different percentages (0 %, 10 %, and 20 %) of UBBS RAP materials. The designed Superpave mixes were then tested using the Hamburg wheel tracking device (HWTD) and the modified Lottman tests. Sweep test results showed that UBBS millings did not improve chip retention. Superpave mix design data indicated volumetric properties of Superpave mixes with UBBS millings met all requirements. HWTD and modified Lottman test results indicated all designed mixes performed better with the addition of UBBS RAP materials.

Quantifying the Effects of Chip Seal Volumetrics on the Occurrence of Pavement Flushing

AbstractThe reported study was undertaken to investigate the micromechanical interactions that occur between sprayed seal (chip seal) layer materials in order to examine their relationship to the initiation of flushing. In particular, the deformation patterns of chip seal pavement samples with respect to lateral cyclic loading as well as the changes that occur to the distribution of air voids within a chip seal layer during loading were investigated. The effect of binder volume and air void volume on the development of flushing of the chip seal samples was also investigated. The reported study was based on laboratory testing of chip seal pavement samples (cores) that were obtained from in-service, flushed pavements in New Zealand. The cores, of 200-mm diameter and thicknesses ranging from 32.4 to 55.5 mm, were subjected to varying levels of lateral cyclic loading using a wheel tracking machine and the deformation that had occurred on the surface of the cores was measured. The cores were then scanned using...

Verification of effectiveness of chip seal as a pavement preventive maintenance treatment using LTPP data

It is hypothesised that maintenance treatments should be applied in the preventive mode before pavements display significant amounts of distress in order to be more cost-effective. The objective of this study was to verify the concept of preventive maintenance by examining the long-term effectiveness of chip seal treatment in four climatic zones in the USA using the long-term pavement performance database. Pavement sections were categorised into smooth, medium and rough pavements, based upon initial condition (IC) as indicated by the international roughness index. Pavement performance of treated and untreated sections was collectively modelled using exponential regression analysis. Effectiveness was evaluated in terms of life extension, relative benefit and benefit–cost ratio. The results showed that preventive maintenance is cost-effective. The life extension, relative benefit and benefit cost ratio were highest for sections whose IC was smooth at the time of treatment. Chip seal treatment effectiveness showed no correlation to climatic conditions or to traffic levels.

Reduction of Pavement High Temperature with the Use of Thermal Insulation Layer and High Reflectivity Surface

This paper presents a study that was conducted to evaluate the concept of using an insulation layer along with a relatively high reflectivity surface for insulating pavements from extremes of temperature. Both finite element modeling (FEM) and experiments were carried out. FEM models were used to evaluate the effectiveness of higher reflectivity and lower conductivity on the temperature of the HMA pavement. Combinations of geosynthetic (as insulation) with and without chip seals (with partially exposed light colored aggregates as high reflectivity surface) were studied with experiments that were conducted with actual solar radiation. Temperature data were collected at the surface and at various depths. The temperature at different depths of the samples with the geosynthetic reinforced chip seal (GRCS) were found to be lower than that of the conventional hot mix asphalt (HMA) sample. The reduction in temperature is greater at higher solar radiations and warmer temperatures. It can be concluded that a GRCS can be used effectively to reduce the temperature of asphalt pavements and help in reducing their rutting potential.

Caltrans use of scrap tires in asphalt rubber products: a comprehensive review

The California Department of Transportation (Caltrans) has been using scrap tire rubber in asphalt pavements since the 1970s in chip seals and the 1980s in rubberized hot mix asphalt(RHMA). Both the wet (field blend) and dry processes were used in early trials. Caltrans has also used rubber modified binders containing both crumb rubber modifier and polymer modifier that could be manufactured at a refinery facility, a terminal blend wet process. Since the beginning of this century, Caltrans increased the use of scrap tire rubber in paving projects and invested considerable resources in developing technically sound, cost effective, and environmentally friendly strategies for using scrap tire rubber in roadway applications. By the end of year 2010, approximately 31 % of all hot mix asphalt (HMA) placed by Caltrans was rubberized HMA, roughly 1.2 million tons. Caltrans efforts in using asphalt rubber products were also demonstrated in its research and technology development. These included the construction of two full-scale field experiments, five warranty projects, and an accelerated pavement study using a heavy vehicle simulator. Additionally, terminal blend asphalt rubber and rubberized warm mix asphalts began to be experimented on trial basis. This paper provides a comprehensive review of Caltrans experience over four decades with asphalt rubber products. Current practices and future outlook are also discussed.

Using Multiple Investigative Techniques to Assess Flushing of Chip Seal Surfaces

Flushing is a defect that has a damaging effect on the functional performance of chip seal pavements. The reported study was conducted to develop techniques to identify and assess flushed pavements effectively. The main aims of the study were first to investigate the effects of chip seal volumetrics on development of flushing and second to develop a model to forecast flushing of chip seal pavements. The study methodology consisted of mechanical testing of chip seal pavement samples and analysis of pavement performance data. Laboratory testing was conducted on samples obtained from flushed chip seal pavements from four regions in New Zealand. Samples were loaded by using a wheel-tracking device, and imaging techniques were used to assess the effects of micromechanical changes on development of flushing. Data analysis was performed on pavement condition data to identify factors providing the best prediction of flushing, and regression analysis was performed to develop a model to predict the initiation and progression of flushing. Study results revealed a direct relationship between flushing and reduction in air void volume that occurred as a result of loading. Data analysis revealed that the combination of factors providing the best indication of flushing was surface thickness, surface age, rut depth, and grade of aggregates. The flushing initiation model had an accuracy of 76%, and the flushing progression model was robust at predicting the quantity of flushing. By using the study outcomes, a pavement condition assessment guideline was developed to aid with assessing and managing flushed chip seal pavements.

Mean profile depth analysis of field and laboratory traffic-loaded chip seal surface treatments

This paper presents a laboratory and field study to evaluate the mean profile depth (MPD) parameter that represents the surface texture of chip seal pavements. A three-dimensional laser profiler is used to determine the MPD values from both field pavement sections and field samples that have been tested in the laboratory using the third-scale model mobile loading simulator (MMLS3). Data obtained from five different field-constructed chip seal sections are used to evaluate the effects of different factors on the MPD of chip seal pavements. These factors include aggregate type, emulsion application rate, field versus MMLS3 traffic loading and traffic volume. The results presented in this paper suggest that: (1) chip seal pavements constructed using lightweight aggregate have larger initial MPD values and faster reduction in MPD as a function of the number of wheel passes than those constructed using granite 78M aggregate; (2) MPD values obtained from a drier section (with drier indicating a lower emulsion-to-aggregate ratio than that of the sections it is being compared against) initially drop quickly and significantly, resulting in a much smaller ultimate MPD value; (3) in general, the MPD values obtained under MMLS3 loading are similar to those obtained from field traffic loading, thus allowing the translation of the laboratory MMLS3 data to the field response data; (4) a short rest period in a high-traffic volume road retards the recovery of the binder and, therefore, leads to more permanent changes in the MPD and (5) the initial measured MPD value can help predict aggregate loss performance.

The Status Quo and Development Tendency of Domestic Synchronous Chip Seal Truck

As road construction machinery, Synchronous chip seal truck achieves the synchronization of asphalt and aggregate spilling to improve and enhance the quality of the road surface sealing layer, and wide application in road construction and maintenance. Synchronous chip seal technology, construction technology and synchronous chip seal truck were discussion introduced. Technology status quo of domestic synchronous chip seal truck was analyzed and the development tendency was discussed.

Evaluation of pavement surface friction subject to various pavement preservation treatments

This study compared the effectiveness of preservation treatments on pavement surface friction and investigated the long-term variation of friction using the data collected in the Specific Pavement Studies-3 (SPS-3) of the Long Term Pavement Performance (LTPP) program. The SPS-3 focuses on the effect of four preservation treatments (thin overlay, chip seal, crack seal, and slurry seal) on pavement performance under five design factors (traffic, precipitation, temperature, existing pavement condition, and subgrade type). Both the simple ranking method and statistical methods (boxplot and Fisher’s Least Significance Difference test) were used to compare the effectiveness of preservation treatments on friction improvement. The statistical analysis results indicate that slurry seal causes significantly greater friction number compared to the control section; and the ranking from high to low based on the average friction number among four preservation treatments is: slurry seal, chip seal, thin overlay and crack seal. Among the five design factors, subgrade type and existing pavement condition show less influence on pavement friction compared to climate and traffic factors. Stepwise regression analysis was conducted to quantify the influence of various factors (material, traffic, temperature, precipitation, and freezing index) on the long-term variation of pavement friction within the monitoring period. It was found that the application rate of slurry seal and chip seal affected the friction variation and temperature showed negative correlation with friction. In addition, pavement roughness was found having certain correlation with friction for the control sections and the sections with crack seal.

Performance of Preventive Maintenance Treatments of Flexible Pavements

Actual pavement performances of various rehabilitation strategies for flexible pavements were evaluated using Long-Term Pavement Performance (LTPP) distress data. Forty-eight flexible pavement sections were selected from the southern region of the United States. The Specific Pavement Studies (SPS-3) section of the LTPP database was utilized to study the effectiveness of various preventive maintenance strategies based on performance. In order to assess the rank and effectiveness of preventive maintenance treatments, three primary performance factors; average rate of distress acceleration; average duration of fix; and average distress measure were lumped together to get an overall performance factor of pavement section. The ranking based on overall performance showed that the chip seal had the highest and the crack seal had the lowest performance factors. Although, there was no direct relationship between the pavement condition index and the overall performance factor the ranking of the treatments was consistent using both the indices. The ranking results were confirmed by the pavement condition index, commonly used by the Department of Transportation. This study indicates the significance of the effective use of the LTPP distress data and provides a robust technique to evaluate the performance of various rehabilitation actions. Thus, allowing the state highway agencies to choose rehabilitation alternatives that best suit their needs based on the actual pavement performance.

Effect of aggregate surface properties on chip seal retention performance

A common distress type of chip seals is scabbing (loss of aggregate) which is caused by insufficient adhesion between aggregate and binder. Both the physical and chemical properties of the aggregate and binder play important roles on aggregate binder adhesion. This study focuses on evaluating the effects of aggregate surface properties on adhesion performance of chip seals using Accelerated Chip Seal Simulation Device (HSKSC) test procedure. 100/150 penetration neat and modified bitumen were used in experiments as binder. Also, clean, dusty and precoated forms of three different type aggregates were used in HSKSC tests. The results showed that performance of precoated aggregate considerably better in compare to dusty and clean aggregate. In addition modified binder demonstrated better chip retention than the neat binder.

유화아스팔트 바인더와 골재 특성이 칩씰 포장의 공용성에 미치는 영향 연구

PURPOSES : The objective of this study is to evaluate the effect of physical characteristics of emulsion asphalt and aggregate on performance of chip seal pavements. METHODS : In order to evaluate the performance of chip seal materials, the sweep tests and Vialit Plate Shock tests were conducted on the mixtures with five emulsion asphalt binders and three aggregate types. The sweep tests was intended to investigate the change of bonding properties between emulsion asphalt and aggregate with curing time. The Vialit Plate Shock test was used to evaluate the bonding properties of chip seal materials at low temperatures. RESULTS : Results from sweep tests showed that polymer modified emulsion asphalt can reduce the curing time by 1.5 hour comparing with typical emulsion asphalt. It is also found that the Flakiness Index of aggregates and absorption rate of binder are the major factors affecting the bonding properties of chip seal materials. The Vialit Plate Shock test results showed that the average aggregate loss of CRS-2 is ten times higher than CRS-2P No.2 indicating that the use of polymer additives in emulsion asphalt can improve the performance of chip seal materials in low temperature region. CONCLUSIONS : The use of polymer in emulsion asphalt can decrease the curing time of chip seal materials and increase the bonding properties between aggregates and asphalt binder. It is also concluded that the lower Flakiness Index and absorption rate of aggregates can improve the performance of chip seal pavement.

Developing a macrotexture prediction model for chip seals

Chip seals are known as one of the most efficient and cost-effective rehabilitation and maintenance application for flexible pavements. The performance prediction and service life determination of chip seals are very important for decision makers within pavement management system. Macrotexture is one of the most important performance indicators in chip seals. In this study, a regression based macrotexture prediction model was developed using the construction parameters, traffic volume, daily temperature conditions as well as the laboratory and in situ test results.

Effects of Curing and Oxidative Aging on Raveling in Emulsion Chip Seals

Although chip seals have a proven history of performance, several distresses are commonly encountered in the field. The most common distresses in chip seals are flushing or bleeding and aggregate loss from the top layer (i.e., raveling). Raveling is not restricted to the early life of the chip seal, but continue throughout the service life. The current state of knowledge and testing of the mechanisms governing raveling in chip seals does not sufficiently account for the effects of in-service emulsion–aggregate bond maturation and oxidative aging on chip loss over the expected service life of the chip seal. Emulsion–aggregate adhesion was thought to control the early raveling process, while the residual asphalt binder rheological properties and aggregate embedment in the emulsion might contribute to later raveling in chip seals. Raveling of chip seals subjected to varying degrees of time–temperature conditioning was evaluated to account for different chemical and physical interactions at the aggregate–asphalt interface. Testing results showed that the rate of in-service raveling depended on the curing process and subsequent in-service oxidative aging as the adhesive and cohesive forces at the emulsion–aggregate interface changed. The initial bond maturation resulted in a decreased rate of chip loss, and the in-service oxidative aging of the asphalt emulsion led to a higher aggregate loss as a result of the emulsion's strain intolerance and inability to relax stresses induced by traffic.

Use of Sweep Test for Emulsion and Hot Asphalt Chip Seals: Laboratory and Field Evaluation

Abstract Currently, the scope of the standard test method for sweep test of bituminous emulsion surface treatment samples (ASTM D7000) is limited to emulsion-based chip seals only. To this end, the objective of this study is to evaluate the sensitivity of the sweep test for both emulsions and hot asphalts, with respect to aggregate mineralogical types, aggregate precoating, aggregate moisture content, asphaltic materials type, and application rates of asphaltic materials. For the field evaluation, fifteen chip seal test sections were prepared with three asphaltic materials and five aggregates in a 9-acre parking lot. Two years after construction, each of the 15 sections were visually inspected for aggregate loss and bleeding. Each section was given a distress rating. The % aggregate loss from the sweep test was then compared with the field distress rating. Both laboratory and field tests indicate that overall, expanded shale lightweight aggregate is better than any crushed stone, whereas clay lightweight performed the worst among the six aggregates tested in this study. Precoated expanded shale lightweight aggregates performed better than uncoated shale lightweight aggregates, with respect to % aggregate loss. Between the two hot asphalts, PAC-15 performed better than AC20-5TR. In the case of hot asphalt, the % aggregate loss increases as moisture content increases in oven dry, air dry, and saturated surface dry aggregates. However, for emulsion, air dry aggregates performed the best. For both emulsion and hot asphalt, an increase in asphaltic materials application rate reduces the % aggregate loss significantly. Distress rankings in all 15 sections, except for one PAC-15 section, matched sweep test rankings. Overall, the results indicate that the sweep test using both emulsion and hot asphalt can be an effective tool for evaluation of performance of chip seals.

Chip Seal Adhesion Performance with Modified Binder in Cold Climates

The purpose of this study was to evaluate chip seal performance with neat and polymer-modified asphalt cement. These chip seals were fabricated with various aggregate combinations to emphasize aggregate retention in cold climates with the accelerated chip seal simulation device. Three aggregate types at low temperatures were used to compare the aggregate retention performances of neat versus modified asphalt cement. A major finding of this research was that polymer modification of neat asphalt cement improved aggregate retention performance. In addition, results showed that a decrease in temperature causes increasing aggregate loss.

Exploration of a Performance Test for Emulsion Treated Asphalt Surfaces

Abstract Asphalt emulsions are a key material used for pavement preservation. Over time, asphalt concrete pavements become oxidized, which can lead to cracking and other surface deterioration. The addition of pavement maintenance treatments, such as scrub seals, chip seals, or fog seals, can rejuvenate the pavement surface as the asphalt emulsion penetrates the oxidized layer of pavement. However, most existing test methods for asphalt emulsions are empirical in nature and do not directly address field performance. With the aim of improving material characterization and testing so as to better capture field properties, this research explored using a bending beam rheometer (BBR) to measure the stiffness and rate of change of the stiffness (or m-value) of asphalt concrete mixture beams treated with asphalt emulsions. There were three components of this study. First, procedures for fabricating BBR beams from field asphalt concrete samples were developed, as the top portion of pavement is often brittle after field aging and oxidation. It was determined that beams could be successfully fabricated with reasonable geometric variability. Second, asphalt concrete BBR specimens compacted and fabricated in the laboratory were sawn and tested, with and without asphalt emulsion, to determine whether the addition of emulsion could be detected. Third, the same emulsion applied to the laboratory fabricated specimens was applied to field mixes to determine the influence of asphalt emulsion on candidate materials for pavement preservation. Overall, beam fabrication was repeatable, and coefficient of variation values for test results were lower for the laboratory compacted plant mix (10 % to 25 %) than for the field mixtures (9 % to 57 %). Emulsion addition increased the m-value and decreased the stiffness of all pavements, which indicates rejuvenation of the asphalt concrete. BBR mixture beams appear to be able to capture the effect of adding emulsion to both lab produced and field specimens, but more types of emulsions, a more comprehensive conditioning regime, and more asphalt concrete mixtures should be examined in order to determine the effectiveness of the measured performance properties of asphalt concrete with the addition of asphalt emulsion.

Otta Seal Surfacing

Natural gravel materials have traditionally been used for upgrading roads from earth to gravel or for regraveling existing gravel roads. However, serious concerns have arisen regarding the continuous use of vast amounts of gravel—a nonrenewable, finite resource—which not only is being rapidly depleted in many countries but also is unsustainable in the medium to long term. This problem has prompted road engineers to consider the use of low-cost bituminous surface treatments on these gravel roads as an alternative to regravelling. One type of surfacing that can provide an economic and practical alternative to traditional surfacings, such as the chip seal, is the Otta seal. Unfortunately, lack of information regarding this relatively new type of bituminous surfacing has suppressed its more widespread use despite its excellent performance in a number of countries. In view of this problem, state-of-the-art information on the provision of the Otta seal surfacing as an economic and practical alternative to the more traditional bituminous surface treatments is presented. The origin, properties, and design and construction of the Otta seal are outlined, and its implementation impacts and the various factors that contribute to its sustainability are discussed. Brief information is presented on the global use of the Otta seal.

Asphalt Emulsion Sprayability and Drain-Out Characteristics in Chip Seals

Streaking and drain-out are two common early chip seal failures related to the viscosity of the asphalt emulsion used. An emulsion with a high viscosity at spraying could result in streaking, while another with a low viscosity after spraying could drain off the road surface under gravity. Some emulsions also tend to show reduction in viscosity during handling; this reduction aggravates the potential for drain-out. The Saybolt Furol viscometer [SFV (ASTM D7496-09)] is currently used to characterize the viscosity of asphalt emulsions. However, the SFV cannot be operated under varying shear rate conditions as experienced by emulsions at different stages. A new test procedure is presented for evaluating sprayability, drain-out, and recovery kinetics of emulsions with a rotational viscometer. The test procedure allows for emulsions to be tested at a higher shear rate to evaluate sprayability and at a low shear rate to evaluate drain-out. Twelve emulsions of different grades and chemistries were tested. Results showed that the proposed test procedure was sensitive to emulsion chemistry, grade, and testing temperature. Sprayability, drain-out, and recovery kinetics were found to be significantly affected by emulsion chemistry and testing temperature. This protocol with variable shear-rate viscosity is recommended for use as a basis for replacing the SFV test as a better performance-related test method. Specification criteria can be easily developed and implemented because rotational viscometers are widely available in the industry, and there is a wealth of experience with various emulsions in the field.

Revision and Further Validation of Surface Performance-Graded Specification for Chip Seal Binders

The design and selection of chip seal binders for adequate performance in service are currently based on specifications that include tests of emulsion residues or hot-applied asphalt cements at standard temperatures that do not cover the entire range of in-service temperatures, measure properties that are not performance related, and do not consider representative aging conditions for the critical first year. A surface performance-graded (SPG) specification for the evaluation and selection of chip seal binders that addressed these shortcomings was developed as part of previous Texas Department of Transportation (DOT) and NCHRP research projects. In the current study sponsored by the Texas DOT, the SPG specification was revised and further validated. This was accomplished through use of a single emulsion residue recovery method, determination of performance-related properties and exploration of additional criteria, and further validation of the SPG specification thresholds for these properties based on field performance monitoring and a comparison with laboratory results. This study was limited to producing a revised SPG specification for performance-related properties that addressed aggregate retention and bleeding in service. Specifically, the threshold for minimum shear strain at 0.8 G*i was reduced from 25% to 17.5%, and the m-value was removed. The effects of construction and quality control processes were beyond the scope of this study, and additional specifications are needed for use in conjunction with the SPG specification to address these issues and ensure adequate performance.