Polymer-modified Asphalt Emulsion Research Articles

Effect of Simultaneous Application of Glass Fiber Reinforcement and Polymer-Modified Asphalt Emulsion on DBST’s Resistance to Aggregate Loss Using Laboratory Investigation

Double bituminous surface treatment (DBST) has been a widely utilized pavement maintenance material due to its capability to restore the surface roughness of existing pavement and provide a layer of protection against weathering, aging, and moisture. However, DBST is highly prone to aggregate loss at an early stage, which is a very common problem experienced by surface treatment. Therefore, to lessen the aggregate loss and prolong the service life of DBST, fiber additive can be incorporated to strengthen the adhesion between the asphalt emulsion and aggregates. This study investigated the performance of glass fiber-reinforced polymer-modified DBST against aggregate loss by conducting laboratory tests using typical DBST as the benchmark of the test results. Four laboratory tests were chosen to represent different loading applications on the surface of the pavement: the bitumen bond strength (BBS) test, the sweep test, the Hamburg wheel-track test (HWT test), and a one-third-scale model mobile load simulator (MMLS3) model. Furthermore, the curing time of the asphalt emulsion was considered in the BBS test and sweep test. Based on all results from the conducted laboratory tests, polymer-modified DBST with glass fiber reinforcement presented an increased resistance to aggregate loss compared with typical DBST. Moreover, it was found that a longer curing time of the asphalt emulsion, whether it was typical or modified, strengthened the surface treatment’s resistance to aggregate loss.

Characteristic of asphalt emulsion modified with natural rubber latex

Polymer modified asphalt emulsions offer superior performance and lifespan as compared to conventional asphalt emulsions or hot mix asphalt surface treatments, as well as reduced life cycle costs. This study’s objective was to examine the characteristics of latex-modified asphalt emulsions using a range of tests, including those for softening point, penetration, ductility, viscosity and solubility. In order to determine the optimal latex modified asphalt emulsion, latex was added into emulsion type CSS-1hP at various ratios ranging from 1 to 9 percent, with 2 percent interval while 0 percent serving as the control. From the experiments described, the best latex modified asphalt emulsion measurement was selected using a decision matrix analysis. Decision Matrix Analysis was performed to determine that asphalt emulsion with 5 percent latex is the best choice since it offers the highest quality polymer modified asphalt emulsion.

Investigating the Laboratory Performance of Crumb-Rubber-Modified and High-Float Polymer-Modified Asphalt Emulsions in Chip Sealing

Chip sealing is a widely popular pavement maintenance treatment because of its low initial cost and convenient construction process. Bleeding, loss of aggregate, reduced skid resistance, and aging have been identified as the most common type of distress that lead to the failure of chip sealing. The objective of this study was to evaluate the laboratory performance of a crumb-rubber-modified asphalt emulsion and a high-float polymer-modified asphalt emulsion in chip sealing and to evaluate the effects of crumb rubber as a modifier as well as its utilization as part of the aggregate stone. To achieve this objective, four types of emulsion were evaluated, namely a crumb-rubber-modified asphalt emulsion (CRS-2TR), a high-float polymer-modified emulsion (CHFRS-2P), a polymer-modified emulsion (CRS-2P), and a conventional unmodified emulsion (CRS-2). Based on the results of the experimental program, it was concluded that the aggregate retention properties of polymer-modified and crumb-rubber emulsions were superior to the unmodified emulsion. In addition, the granite aggregate performed better than the granite–crumb-rubber blends regardless of the type of emulsion used. However, a small percentage of crumb rubber may be used in chip sealing without significantly affecting its performance. According to the rheological and physical test results, CHFRS-2P showed the highest useful temperature interval (92.7), followed by CRS-2P (87.8), CRS-2TR (82.6), and CRS-2 (76.7). Based on Fourier transform infrared spectroscopy and saturate, aromatic, resin, and asphaltene test results, both CRS-2TR and CHFRS-2P showed lower carbonyl indices growth as compared to the other emulsions, indicating superior resistance to aging.

Preparation and Performance Assessment of Asphalt Emulsion Modified by the Fabricated SBS Latex

Polymer modified asphalt emulsion (PMAE) has recently been proven to be one of the most effective methods to overcome the common distress of asphalt surface treatments, such as abrasion, rutting, ravelling, and poor durability. Because of the limited research studies about the preparation of PMAE using SBS latex, a new method to prepare SBS latex was developed and the feasibility of using it in preparing SBS latex modified asphalt emulsion (SBS‐LMAE) was verified in this study. The optimized swelling parameters for linear SBS solutions were swelling 24 h at the temperature of 50°C with the toluene/SBS (T/S) mass ratios of 2.5 : 1 to 2.0 : 1 which was determined according to the analysis of viscosity and Tyndall effect. After that, the SBS latex with favorable dispersivity and stability was successfully fabricated with the T/S ratio of 2.0 : 1. At last, the well‐specified SBS‐LMAE was prepared using the fabricated latex and tested for its conventional performances and microstructure. The results show that the SBS‐LMAE samples all meet the main requirements of PMAE for microsurfacing and possess appropriate uniformity and stability.

Improving the high-temperature performance of cold recycled mixtures by polymer-modified asphalt emulsion

With the development of modified emulsified asphalt, cold recycling technique has the potential to be used in pavement layers closer to surface. Three modified emulsified asphalt binders were carefully prepared by adding Styrene–butadiene rubber (SBR) latex, styrene-ethylene–butylene-styrene (SEBS) copolymer and chloroprene rubber (CR) latex, respectively. In order to characterise how the properties of asphalt binder related to the rutting of cold recycling mix. The high temperature Dynamic Shear Rheometer (DSR) and Multiple Stress Creep Recovery (MSCR) tests were conducted under varying test temperatures ranging from 46 to 76 °C. An advanced cyclic creep test was conducted to study the rutting resistance of the full-depth pavement structures with cold recycling mix. According to the test results, the high-temperature performance were improved significantly by adding the polymer modifiers, and adding CR latex seems to be a more effective way to improve the rutting resistance of emulsified asphalt. Results from MSCR test under temperatures no less than 64 °C shows a better correlation with test results from the advanced cyclic creep test than the G*/sin δ from high temperature DSR test. Thus, by carefully choosing the test temperature and stress, the MSCR test shows promise to be a surrogate to the existing DSR test.

Assessing The Durability of Polymer Modified Asphalt Emulsions Slurry Seal

Slurry Seal is an application of road preservation in the form of impermeable nonstructural thin layer with maximum thickness of 10 mm, which consisting of a cold laid mixture of asphalt emulsion with continuous graded fine aggregate, mineral filler, water and other added ingredients. Road preservation use slurry seal only functioning as a surface layer on the existing pavement structure. This preliminary research was conducted to determine the value of consistency, setting time, and indirect tensile strength of polymer modified slurry seal. The laboratory tests were conducted to determine the optimum residual asphalt content. The results show that the value of the optimum water content by pre-wetting 5% is getting smaller with increasing levels of residual asphalt emulsion. The addition of water 0 – 2.5% with 5% water for pre-wetting, the mixture provides a sufficient consistency in accordance with the specifications. The increasing levels of residual asphalt emulsion obtained the longer setting time at all slurry seal mixtures, but all of the mixtures still meet the specifications. The use of polymer modified asphalt emulsion on slurry seal was improved durability significantly, based on the value of indirect tensile strength.

긴급보수용 개질 유화아스팔트 고비율 순환골재를 사용한 상온 아스팔트 혼합물의 성능 평가

PURPOSES : The purpose of this study was to evaluate the performance of rapid-setting polymer-modified asphalt mixtures with a high reclaimed asphalt pavement (RAP) content. METHODS: A literature review revealed that emulsified asphalt is actively used for cold-recycled pavement. First, two types of rapid-setting polymer-modified asphalt emulsion were prepared for application to high-RAP material with no virgin material content. The quick-setting polymer-modified asphalt mixtures using two types of rapid-setting polymer-modified asphalt emulsion were subjected to the following tests: 1) Marshall stability test, 2) water immersion stability test and 3) indirect tensile strength ratio test. RESULTS AND CONCLUSIONS : Additional re-calibration of the RAP was needed for laboratory verification because the results of analyzing RAP aggregates, which were collected from different job sites, did not deviate from the normal range. The Marshall stability of each type of binder under dry conditions was good. However, the Type B mixtures with bio-additives performed better in the water immersion stability test. Moreover, the overall results of the indirect tensile strength test of RAP mixtures with Type B emulsions exceeded 0.7. Further research, consisting of lab testing and on-site application, will be performed to verify the possibility of using RAP for minimizing the closing of roadways.

Advanced Characterization of Clear Chip Seals

Abstract Chip seals are widely used throughout the world for the construction and preventive maintenance of asphalt pavements because they are recognized as cost-effective solutions able to improve skid resistance while creating a waterproof surface. On the other hand, chip seals are often affected by early stone loss because of several, not always easily manageable, material-related and traffic-related factors. It is, therefore, in the interest of researchers to develop scientific methods able to predict the aggregate retention performance of chip seals. Given this background, in the present paper, a performance-based evaluation of chip seals with regard to aggregate retention properties is carried out through a laboratory test based on the Ancona shear testing research and analysis equipment. In this study, a chip seal prepared with a clear emulsion derived by emulsifying a synthetic clear binder was analyzed and compared with two traditional chip seals manufactured with a plain cationic bituminous emulsion and a styrene butadiene styrene polymer-modified asphalt emulsion, respectively. Specifically, six chip seals obtained by combining the three selected emulsions with two types of aggregates (crushed limestone and basalt) were tested at three different temperatures. Moreover, a rheological characterization of emulsion residues was also carried out through the dynamic shear rheometer and the binder bond strength adhesion tester. Results mainly showed that the investigated clear synthetic emulsion can be successfully used for the construction of clear chip seals in combination with aggregates of different mineralogy.

Cracking resistance of thin-bonded overlays using fracture test, numerical simulations and early field performance

Thin-bonded bituminous overlays are becoming an increasingly popular pavement maintenance treatment, which can be used to restore smoothness, seal and renew the pavement surface and increase skid resistance. Thin-bonded overlays (TBOs) are constructed using a specialised type of paving equipment called a ‘spray paver’. A spray paver combines the operation of applying a tack coat and laying down asphalt concrete in a single pass. This allows for the application of a high rate of polymer-modified asphalt emulsion tack coat. Due to reduced thickness, cracking distress is more of a concern in this type of system. This paper describes a new approach for the evaluation of the cracking performance of TBO systems through fracture mechanics-based testing of laboratory and field specimens. Computer simulations and early field performance data are also used in the evaluation. This study is conducted in the context of three field projects which encompass seven different pavement test sections. The test sections allowed a number of variables to be studied, including type and application rate of tack coat emulsion and type of hot-mix asphalt gradation structure (gap graded vs. dense graded). Comparisons are also made between overlays constructed using spray paver and conventional paving process. All seven sections were computationally simulated to evaluate their performance in the context of thermal and reflective cracking potential. Fairly good agreement is observed between laboratory tests, computer simulations and field performance data. The results indicate that good thermal and reflective cracking resistance are expected from TBOs. Furthermore, it was observed that the cracking performance of TBOs depends on the type of gradation for the overlay mixture and the tack coat emulsion type and its application rate.

Physical properties of asphalt emulsion modified with natural rubber latex

Asphalt is an important material that has been used widely in road paving industry as a binder for aggregate. There are a lot of studies that have been conducted to modify asphalt for the preparation of hot mix asphalt (HMA). From the study, it is proven that polymer modified asphalt can improve asphalt performance. However, there are very few studies that focus on modification of asphalt emulsion that were used for cold mix asphalt (CMA). In this study, natural rubber latex was selected as a modifier to modify asphalt emulsion. Post blending method was used to prepare polymer modified asphalt emulsion. The addition of natural rubber latex (NRL) into the asphalt emulsion was made in a cylindrical flask that is equipped with a propeller with three variables: the amount of polymer, mixing time and blending velocity. From the result, it can be concluded that natural rubber latex can be used to improve the rheological properties of modified asphalt emulsion residue. The maximum useful amount of polymer that could be added to the prepared asphalt emulsion is discovered by the study to be at 7 percent whereas the blending time of 20 minutes was selected as the useful blending time to blend NRL in prepared asphalt emulsion.

Development of a Composite Specimen Interface Cracking (CSIC) Test for Top-Down Cracking

Abstract Pavement top-down cracking performance not only depends on pavement layer material characteristics, but also on layer interface conditions. Interface conditions involve both the shear resistance along the interface and the cracking resistance across the interface provided by the interface bonding agents. Regarding hot-mix asphalt (HMA), currently available tests are mainly focused on pavement layer material properties. When thick polymer modified asphalt emulsion (PMAE) was applied at the interface between an open-graded friction course (OGFC) and a dense graded structural layer, a bonded interface was formed by the migration of PMAE up into the OGFC air voids. Shear strength tests, which can well characterize the adhesive film effect of interface bonding agents, cannot fully capture the effect of bonded interface on pavement cracking performance. To simulate the crack initiation and propagation process and evaluate the effect of bonded interface conditions on top-down cracking performance, a composite specimen interface cracking (CSIC) test was developed. The developed system involves repeated tensile loading and monitoring of the rate of damage development (reduction in stiffness) on composite specimens specifically designed for this purpose. Number of loading cycles to failure and damage rate results from the proposed test on three different interface conditions clearly indicate that this test method can be used to optimize bonding agents and application rates for enhanced cracking performance. This method may also provide a suitable specification test for evaluation of interface conditions on reflective cracking performance.

A mechanistic test to evaluate effects of interface condition characteristics on hot-mix asphalt overlay reflective cracking performance

Reflective cracking is a distress mode that is of particular concern for pavements with thin hot-mix asphalt (HMA) overlay as a maintenance and/or rehabilitation method. Traditionally, efforts have been made to mitigate reflective cracking by increasing overlay thickness, using anti-reflective cracking interlayer systems and special treatments on existing pavements and cracks. A new way to improve HMA overlay reflective cracking resistance is to use highly polymer-modified asphalt emulsion (PMAE) interface. Tests currently available are not appropriate to evaluate the effects of interface conditions on reflective cracking. This paper presents the second phase of a study devoted to develop a mechanistic test to study effects of interface conditions on pavement cracking performance. A new approach to represent reflective cracking (a teflon spacer introduced in an existing pavement layer) instead of the traditional notch method was introduced to the composite specimen interface cracking test developed for top-down cracking. In this study, effects of two types of interface conditions, conventional tack coat and PMAE, on reflective cracking were evaluated. HMA fracture mechanics was employed to identify the reflective cracking mechanism when the teflon spacer was installed in the composite specimen. Test results clearly indicated that the proposed test method with the teflon spacer was able to simulate reflective cracking mechanism and evaluate effects of interface conditions on reflective cracking.

Test Method to Evaluate the Effect of Interface Bond Conditions on Top-Down and Reflective Cracking

A composite specimen interface-cracking (CSIC) test was developed to evaluate the effect of the characteristics of the interface between asphalt layers on resistance to top-down and reflective cracking. The system involves repeated tensile loading and monitoring of the rate of damage development (reduction in stiffness) on composite specimens specifically designed for this purpose. Top-down cracking tests were performed on open-graded friction course (OGFC) mixtures placed on dense-graded mixtures using both a conventional tack coat and a polymer-modified asphalt emulsion (PMAE) at a higher application rate. Reflective cracking tests were performed on dense-graded mixtures. Results clearly indicated that use of polymer-modified bonding material significantly reduced the rate of damage development for both top-down and reflective cracking. The testing and interpretation methods developed can be used to optimize bonding materials and application rates for enhanced cracking performance. The methods may also provide a suitable specification test for bonded systems.

Effects of interface condition characteristics on open-graded friction course top-down cracking performance

Top-down cracking is a distress mode that is of particular concern for pavements with Open-Graded Friction Course (OGFC) because open-graded mixture has considerably lower resistance to fracture (lower fracture energy limit and lower resistance to damage) than dense-graded mixture. This particular cracking phenomenon initiates on the pavement surface and propagates downward; so because the OGFC layer is thin, cracking performance relies on the properties and characteristics of three components near the pavement surface: OGFC, underlying structural layer, and the interface between. For this reason, to increase the durability of pavements surfaced with OGFC, it is significant to ensure a quality fracture resistant bond between OGFC and the structural layer. This research investigated top-down cracking performance of OGFC with different tack coats using a newly developed composite specimen interface cracking (CSIC) test. In addition, X-ray computed tomography (CT) was employed to analyze the interface characteristics between OGFC and dense-graded HMA. HMA fracture mechanics was employed to quantify the effect of polymer modified asphalt emulsion (PMAE) on pavement top-down cracking resistance enhancement. Results clearly indicated that PMAE-created bonded interface conditions greatly increased pavement top-down cracking resistance as compared with conventional tack coat.

Chip Seal with Lightweight Aggregates for Low-Volume Roads

Chip seal is widely used for preventive maintenance of low-volume roads in many states, including Kansas. Although there are no distinct design guidelines for using lightweight aggregates in chip seals, these aggregates are extensively used in Kansas to limit windshield damage caused by flying chips. Lightweight aggregates were used with polymer-modified asphalt emulsion to determine proper aggregate and emulsion application rates to minimize chip loss in longer-lasting chip seals on low-volume roads. A statistical analysis was conducted to evaluate chip seal performance characteristics that include aggregate retention, aggregate embedment depth, and rutting. Results show that aggregate retention and embedment depth depend on aggregate–emulsion interaction, whereas rutting depends on the type of aggregates used.

Experimental Investigation on Fracture and Tensile Characteristics of Micro-Surfacing Containing Crumb Rubber

The major objective of this research was to evaluate the tensile and fracture properties of micro-surfacing, which as a preventive maintenance surface treatment on asphalt pavement, that formed the basis for the ISSA recommendation of an optimum micro-surfacing design incorporating crumb rubber. The research involved a full-factorial experiment with different rubber contents (0, 2 and 5%) and different polymer modified asphalt emulsion contents ranged from 10 to 13% by total weight of crushed aggregate in micro-surfacing. Fracture and indirect tension tests were performed on micro-surfacing beams and Marshall test samples, respectively, at two different test temperatures of 25 and -10°C. The variables studied were indirect tensile strength, peak center-point load carried, and load-point displacement. The results show that higher mean values of indirect tensile strength were obtained corresponding to the highest modified asphalt emulsion content (13%), irrespective of rubber contents, particularly at lower temperatures. A statistical analysis of the test results reveals that there are no significant differences among the means of most of the variables studied corresponding to different rubber contents. However, the differences are significant for different asphalt emulsion contents.

Georgia Department of Transportation’s Experience with Microsurfacing

Microsurface mix, or microsurfacing, can be used for sealing and providing a friction surface for cracked and deteriorated surface mixes. This mix, essentially consisting of 9.5-mm (0.37-in.) screenings bonded by a polymer-modified asphalt emulsion, is economical and can be placed very swiftly. Microsurfacing is also aesthetically pleasing because of its resemblance to hot-mix asphalt. In 1990–1991, the Georgia Department of Transportation (GDOT) successfully used microsurfacing in a test section on I-75 in Henry County, which had high traffic volumes and a heavy truck concentration. Two varieties of the mix were used, and both showed little deterioration after 2 years. In 1996, GDOT opted to use microsurfacing for a 9.2-km (5.7-mi) section of I-285 in Atlanta between Conley Road and Old National Highway. This 92 lane-km (57-lane-mi) project was initiated to address the raveling and cracking in the section and improve its appearance before the 1996 summer Olympics. The I-285 project began in late May 1996 and was completed in 1 month. The microsurfacing used on I-285 has performed quite well since the project was completed. No additional problems with raveling or load cracking have been encountered. The mix has provided excellent smoothness and good friction, with a minimal increase in pavement noise levels. Microsurfacing may be suitable for use on cracked pavements in lieu of more conventional rehabilitation methods such as crack sealing, leveling, and double surface treatments.