Polymer-modified Asphalt Mixtures Research Articles

Evaluation and Comparison of Mechanical Properties of Polymer-Modified Asphalt Mixtures.

Polymer modification is extensively used in the Kingdom of Saudi Arabia (KSA) because the available asphalt cement does not satisfy the high-temperature requirements. It was widely used in KSA for more than two decades, and there is little information regarding the differences in the performance of different polymers approved for binder modification. Pavement engineers require performance comparisons among various polymers to select the best polymer for modification rather than make their selection based on satisfying binder specifications. Furthermore, the mechanical properties can help select polymer type, producing mixes of better resistance to specific pavement distresses. The study objective was to compare the mechanical properties of the various polymer-modified asphalt (PMA) mixtures that are widely used in the Riyadh region. Control mix and five other mixes with different polymers (Lucolast 7010, Anglomak 2144, Pavflex140, SBS KTR 401, and EE-2) were prepared. PMA mixtures were evaluated through different mechanical tests, including dynamic modulus, flow number, Hamburg wheel tracking, and indirect tensile strength. The results show an improvement in mechanical properties for all PMA mixtures relative to the control mixture. Based on the overall comparison, the asphalt mixture with polymer Anglomk2144 was ranked the best performing mixture, followed by Paveflex140 and EE-2.

Effect of Different Polymer Modifiers on the Long-Term Rutting and Cracking Resistance of Asphalt Mixtures.

To evaluate the long-term performances of different polymer-modified asphalt mixtures, three modifiers were chosen to modify AC-13 (defined as the asphalt concrete with the aggregate nominal maximum particle size of 13.2 mm); namely, high viscosity modifier (HVM), high modulus modifier (HMM), and anti-rutting agent (ARA). The deformation and cracking resistance of different polymer-modified mixtures were checked at different aging conditions (unaged, short-term aged, and long-term aged for 5, 10, and 15 days respectively). The results of the Hamburg wheel-track test and uniaxial penetration test (UPT) showed that the rutting resistance of all asphalt mixtures changed in a V-shape as the aging progressed. From the unaged stage to the long-term aging stage (5 days), the rutting resistance decreases gradually. While after the long-term aging stage (5 days), the rutting resistance increases gradually. Results from the semicircular bending test (SCB) and the indirect tensile asphalt cracking test (IDEAL-CT) indicated that the cracking resistance of all the mixtures gradually decline with the deepening of the aging degree, indicating that aging weakens the crack resistance of asphalt mixtures. Additionally, test results showed that the rutting resistance of ARA AC-13 (defined as AC-13 containing ARA) is the best, the cracking resistances of ARA AC-13, HMM AC-13 (defined as AC-13 containing HMM) and HVM AC-13 (defined as AC-13 containing HVM) have no significant difference, and different polymer modifiers had different sensitivities to aging due to the polymer content and the type of modifier. The conclusions of this study help to further understand the long-term performance of polymer-modified asphalt mixtures during service life and to help guide the selection of modifiers for mixtures.

Performance improvement of asphalt concretes using fiber reinforcement

This study reports on the laboratory performance, field performance and cost analysis of fiber-reinforced asphalt concrete (FR-AC) pavement using AC60/70 and polymer modified asphalt (PMA) as binders. The performance testing included indirect tensile resilient modulus, indirect tensile strength modulus, indirect tensile fatigue life, dynamic creep and wheel-tracker tests. Field trials of AC60/70 and PMA mixtures, were undertaken with and without fibers and the International Roughness Index, texture depth, and rutting of the mixtures were measured over time. The PMA + Fiber mixture exhibited the best performance among the materials tested. The performance of AC60/70 + Fiber mixture were comparable to PMA mixture. The improvement of both fatigue cracking and rutting were similar for AC60/70 + Fiber mixtures while the improvement of fatigue cracking was higher than rutting for the PMA mixtures. Since the performance of FR-AC was similar for both laboratory and plant mixed specimens, the laboratory mix design results can be used to interpret the field performance. The fiber reinforced AC60/70 mixture was found to be the most economical. The outcome of this research can be used as a guide, for establishing the specification of FR-AC pavement in Thailand and other countries using similar mix design.

Effects of Combined Environmental Factors on Stiffness and Rutting Properties of Warm Mix Asphalt

Abstract Warm mix asphalt (WMA) is a sustainable clean product that can be fabricated at lower temperatures. This is an environmentally friendly mixture due to its lower emission and energy consumption in asphalt production plants. Moisture conditioning and aging process are two environmental factors that can adversely affect the stiffness properties of this product. In the field, WMAs are subjected to both moisture damage and aging. In this paper, a new laboratory method was used for evaluating the combined effects of aging and moisture conditioning of WMA samples. WMA specimens were fabricated at various compaction temperatures with different amounts of a surfactant-wax warm additive. Stiffness properties of asphalt mixtures were quantified from the resilient modulus and dynamic creep test. The results showed that moisture conditioning and aging are competing to affect the stiffness properties of mixtures. Polymer modified asphalt mixtures were found to be less susceptible to moisture damage when compared to mixtures fabricated with unmodified binder. Compaction temperature was the most significant factor that affected the resilient modulus of WMA. In the dynamic creep test, the combined effects of aging and moisture conditioning reduced the cumulative micro strain of samples regardless of binder type, additive content and compaction temperature.

State of the Practice for High Polymer-Modified Asphalt Binders and Mixtures

The objective of this paper was to provide information on the state of the practice for using high polymer-modified (HP) asphalt concrete (AC) mixtures in the United States (U.S.) and Canada. This information was collected through a survey of U.S. and Canadian provincial agencies combined with a search of HP-related specifications, special provisions, and field trials or pilot projects previously constructed. Moreover, the Virginia Department of Transportation’s (VDOT) current state of the practice with regard to using HP paving material was determined. This was achieved through a navigation of VDOT databases to report tonnage and types of produced HP AC mixtures, and experience, lessons learned, and best practices on behalf of multiple asphalt contractors in the area. The majority of the agencies that currently use or have constructed field trials and pilot projects using HP AC mixtures are located in the eastern part of the U.S. In general, HP AC mixtures have been used in a wide range of applications ranging from full-depth AC to thin AC overlays under heavy traffic on interstates and slow-braking loads at intersections. No major field-related construction issues in relation to mixing temperatures and in-place compaction of HP AC mixtures were reported, and standard construction practices and equipment were used. Finally, good communication between the polymer/binder supplier and the contractor, and solid planning before conducting the work were important lessons learned with regard to paving with HP AC mixtures.

Effect of ultraviolet aging on dynamic mechanical properties of SBS modified asphalt mortar

Many in-door ultraviolet (UV) aging tests have been conducted on the performance of asphalt mixture, however, there is still lack of guidance for the determination of UV intensity and radiation time for proper simulation of field long-term aging. In order to evaluate the UV aging time and intensity equivalent conversion effect on the performance of asphalt mixture, the asphalt mortar of Styrene Butadiene Styrene (SBS) polymer-modified AC-13 asphalt mixture was prepared and molded. The bending modulus, dynamic modulus, and scanning electron microscope (SEM) tests were carried out to evaluate the dynamic mechanical properties and micro-structure morphology characteristics of asphalt mortar after UV aging. Based on the dynamic mechanical analysis (DMA), the equivalent conversion equation were developed for the impact evaluation of the UV intensity and aging time. Results also found that the bending modulus of SBS modified asphalt mortar increased with the increase of UV intensity and aging time. The storage modulus and complex modulus gradually increased with the intense of aging, but the aging impact of loss modulus and loss factor were not obvious. The SEM result clearly showed that the damage such as wrinkles, cracks and pits were developed from the surface layer to the bottom of the asphalt mortar, and which can be characterized by four different stages.

Development of characteristic-based guidelines to determine maximum allowable reclaimed asphalt pavement content in polymer-modified asphalt mixture

ABSTRACT Current Florida Department of Transportation specifications limit reclaimed asphalt pavement (RAP) usage to 20% in polymer-modified asphalt (PMA) mixtures, because aged and brittle RAP binder may reduce benefits of polymer modification. Previous studies indicated RAP binder stiffness and RAP gradation were important characteristics related to RAP mixture cracking performance. This study focused on developing guidelines to determine maximum RAP content in PMA mixtures based on these RAP characteristics. Eight RAP sources covering a broad range of RAP binder stiffness and RAP gradation were used to assess the effect of these RAP characteristics on cracking performance. The interstitial component fracture energy (FEIC) which is correlated well with mixture fracture energy (FEmix) was employed as a surrogate for FEmix to assess all RAP mixture combinations, and FEIC was determined by the IC direct tension test. FEmix obtained from Superpave indirect tensile tests was used to evaluate findings from FEIC results. Finer RAP and stiffer RAP was more detrimental to cracking resistance, indicating characterising RAP binder stiffness and RAP gradation was necessary to increase the current maximum RAP content in PMA mixture. Developed guidelines allowed up to 40% RAP depending on RAP characteristics and were validated by the way of full mixture testing.

Evaluation of Polymer Modified Asphalt Mixtures in Pavement Construction. (Dept. C)

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Mechanistic-based verification of a structural layer coefficient for high polymer-modified asphalt mixtures

Extensive laboratory performance testing and advanced statistical analyses led to the determination of a fatigue-based structural layer coefficient of 0.54 for high polymer-modified (HP) asphalt concrete (AC) mixtures in new pavements. The objective of this paper was to verify, using mechanistic-empirical (ME) analyses, the structural capacity of HP AC pavement sections designed using the 0.54 layer coefficient. The ME analysis for rutting, shoving, and top-down cracking in the AC layer resulted in most of the cases in a better performance for the HP AC mixes when compared with their respective PMA AC mixes. Moreover, the rut depths determined in the unbound layers were observed to be lower than the maximum allowable rut depth indicating an acceptable performance for the HP pavement sections which had a thinner AC layer thickness. In summary, the verification efforts supported the use of a structural coefficient of 0.54 for HP AC mixes in new pavements.

The cracking characteristics of the polymer-modified asphalt mixture before and after aging based on the digital image correlation technology

To study the effect of thermo-oxidative aging on the cracking characteristics of the crumb rubber asphalt mixture (CR-MA) and the styrene–butadienestyrene asphalt mixture (SBS-MA), the image acquisition of loading processes of the semi-circular bending (SCB) test of two polymer-modified asphalt mixtures was carried out by the digital image correlation (DIC) technology. The horizontal strain of test specimens during loading processes was calculated by the VIC-3D software. The new indexes for evaluating the meso-cracking characteristic of asphalt mixtures were proposed. Through the bending beam rheological (BBR) test of asphalt and the contact angle measurement test of asphalt-aggregates, the cracking characteristics of CR-MA and SBS-MA were analyzed from two aspects of cohesion and adhesion failure before and after aging. The results indicated that the new indexes (the horizontal strain density DE and the horizontal strain toughness JE) for evaluating the meso-cracking characteristic of asphalt mixtures had a good correlation with the results of BBR and the contact angle measurement test. The cracking resistance and adhesion of two polymer-modified asphalt were reduced after aging, which led to the decline in the cracking resistance of CR-MA and SBS-MA. The cracking resistance and adhesion of CR-modified asphalt were better than that of SBS-modified asphalt under the same conditions, which meant the cracking resistance of CR-MA was better than that of SBS-MA before and after aging. Compared with SBS-MA, CR-MA had more excellent anti-aging properties.

Approach for Determination of Maximum Reclaimed Asphalt Pavement Content in Polymer-Modified Asphalt Mixture

Reclaimed asphalt pavement (RAP), commonly generated from the millings of damaged roads, contains recyclable asphalt and aggregate. Polymer-modified asphalt (PMA) binders have had proven success in mitigating rutting and cracking in asphalt pavements. However, benefits associated with PMA binder may be reduced by aged and more brittle RAP binder. Currently, the maximum usage of RAP in PMA mixture is limited to 10–20% by several Departments of Transportation in the United States. Other than maximum RAP content, no criterion related to RAP characteristics is used to limit RAP usage in PMA mixture. Recent studies showed RAP binder stiffness and RAP aggregate gradation appeared to be important characteristics related to cracking performance of PMA mixture containing RAP. Therefore, this research focused on determining maximum allowable RAP content in PMA mixture for individual RAP sources based on key RAP characteristics identified, that is, RAP stiffness and RAP fineness. Interstitial component direct tension (ICDT) test was conducted to determine fracture energy for interstitial component (i.e., the fine portion of PMA mixture containing RAP), which is known to be correlated well with the fracture energy of the corresponding mixture. Results showed introduction of coarser and less stiff RAP generally resulted in greater fracture energy, which allowed up to 40% RAP usage in PMA mixture. Integration of key RAP characteristics identified and the results of ICDT test provide a systematic approach for determination of maximum RAP content in PMA mixtures. Further research is recommended to evaluate additional RAP sources to verify the proposed approach.

Influence of Natural Zeolite and Paraffin Wax on Adhesion Strength Between Bitumen and Aggregate

Asphalt mixture that is used for the construction of flexible pavements is mainly composed of two constituents i.e. bitumen and aggregate. Sturdy adhesion among bitumen and aggregate is the sign of durability of asphalt pavements. Adhesion is considered as one of the most important factors for sustainable asphalt pavement. This is the motive why its miles utmost important to deeply understand the phenomenon of adhesion considering the effect of alternate in temperature, moisture conditions. In this study softer binder 80/100 was selected that has less adhesion compared to hard pen grades. Limestone aggregates which is commonly used for the construction of asphalt pavements has also been selected. Two types of modifiers (Zeolite and Paraffin Wax) were selected because of the extensive use in asphalt foaming and the polymer modified asphalt mixtures as temperature reducing agent. To investigate the strength of adhesive bond, Bitumen Bond Strength (BBS) was performed at different temperatures, in dry, and wet conditions. To quantify the effect of modifiers on penetration grade and softening point conventional testing is performed. For performance grading, the PG test was performed using Dynamic Shear Rheometer. The comparisons were developed among pull of tensile strength at dry and after 72hrs water conditioning while preserving the temperature at 25 .To check the effect of temperature BBS is performed at 15 . The results illustrate that 2% zeolite shows best results in terms of adhesion and performance grade while Paraffin wax has less adhesion and poor performance grade.

Influence of ageing on high content polymer modified asphalt mixture stripping, cracking and rutting performances

The outstanding properties of High Content Polymer Modified Asphalt (HCPMA) have been widely recognised, but there are only scattered studies have investigated the influence of ageing on HCPMA properties, and even fewer researches have discussed this at the mixture level. This study seeks to evaluate the HCPMA mixture performance with the influence of ageing taken into consideration. Mixture stripping, cracking and rutting resistances were evaluated by the means of Cantabro loss test, Semi-Circular Bend (SCB) test and Hamburg Wheel-Tracking (HWT) test, respectively. Both laboratory short-term ageing and long-term ageing were conducted and different ageing durations/temperatures were investigated. Results indicated that an unaged HCPMA mixture (7.5% SBS) has much improved overall performance over conventional modified mixture (4.5% SBS). However, it is also more ageing susceptible. All three types of performances evaluated in this study were negatively influenced by ageing. Stripping and rutting resistance were more sensitive to higher ageing temperatures while cracking resistance was sensitive to both higher ageing temperatures and longer ageing duration. Mixture rutting performance after ageing is seldom considered as a critical performance. However, in the case of HCPMA mixture, it may need extra attention and related specification should be developed. Moreover, binders extracted from the aged mixtures were examined and the results well agreed with the mixture ageing behavior except for the inconsistency between the 210°C_2 h aged mixture’s deepest rutting depth and its smallest Jnr3.2 value, which pointed out the possibility that Jnr3.2 parameter from MSCR may overestimate the contribution of binder elasticity on mixture rutting resistance.

High-Temperature Performance of Polymer-Modified Asphalt Mixes: Preliminary Evaluation of the Usefulness of Standard Technical Index in Polymer-Modified Asphalt.

The objectives of this study are to evaluate the high-temperature performance of polymer-modified asphalt and asphalt mixtures, and to investigate if the standard technical indexes are useful in the performance evaluation of the polymer-modified asphalt. There are four typically used polymer-modified asphalt types employed in the study. The standard high-temperature rheological test, such as the temperature sweep test, was used to express the high-temperature performance of the polymer-modified asphalt. Also, considering the non-Newtonian fluid properties of the polymer-modified asphalt, the multiple stress creep recovery (MSCR) and zero-shear viscosity (ZSV) tests were employed for the characterizations. Besides, based on the mixture design of SMA-13, the high temperature of the polymer-modified asphalt mixture was evaluated via Marshall stability and rutting tests. The test results concluded that the ranking of the four kinds of polymer-modified asphalt was different in various laboratory tests. The TB-APAO has the best technical indexes in MSCR and ZSV tests, while the WTR-APAO performed best in the temperature sweep test. In addition, the correlation between the polymer-modified asphalt and the asphalt mixture was very poor. Thus, the present standard technical indexes for the profoundly polymer-modified asphalt mixtures are no longer suitable.

Performance evaluation and field application of hard asphalt concrete under heavy traffic conditions

In order to improve the service performance of asphalt pavement under high temperature and rain during summer under heavy traffic conditions, this research compared the pavement performance of hard, heavy-duty AH-70, and Styrene Butadiene Styrene (SBS) polymer-modified asphalt mixtures through high temperature performance, low temperature crack resistance, fatigue resistance, and water stability tests. Results indicate that 30# hard asphalt mixture remarkably improves high temperature performance compared with 70# and 70# SBS asphalt mixtures. Moreover, the water stability of these asphalt mixtures is comparable. The fatigue performance of 30# hard asphalt mixture is comparable with that of 70# asphalt mixture. Finally, after 10 years of pavement performance, the hard asphalt concrete pavement structure achieved the best road conditions.

Microcapsule and polymer reinforcement techniques developed asphalt for use of pothole repairs in winter and rainy seasons

This paper proposes a new Polymer Modified Asphalt (PMA) for cold mixtures used to patch potholes in the adverse weather conditions of low temperature and rain. The new PMA is based on the microcapsules and polymer reinforcement techniques. Test results of the PMA binder found that the PMA improved the performance of the asphalt in low temperature and improved the adhesion of the cold mixtures by importing corresponding foundational groups. For example, the conjugated olefinic bond was used in the microcapsule formation and polybutadiene was used to improve the performance in low temperature as compared with the matrix asphalt and terpene resin cutback asphalt (TRCA). The modifier and adhesive stored in the microcapsules were distributed evenly in the asphalt. Test results of the cold mixtures verified that the PMA mixtures had a better performance than the TRCA mixtures, involving cohesion, stability and freeze-thaw resistance. Field surveys taken over 12 months indicated that the pothole patches filled with the PMA patching materials met the requirement for ride-ability and traffic safety standards. Therefore, it is concluded that the PMA is an adequate asphalt binder for pothole repairs in cold temperature and wet conditions.

Fatigue cracking performance evaluation of laboratory-produced polymer modified asphalt mixture containing reclaimed asphalt pavement material

This study investigated the effect of reclaimed asphalt pavement (RAP) on the rheological properties of a polymer modified binder and the fatigue cracking performance of polymer modified asphalt mixture. Performance grading, master stiffness curve and black space analysis were conducted on the asphalt binders at different laboratory ageing conditions. The repeated loading semi-circular (R-SCB) test was conducted on the mixtures. Test results of the asphalt binder showed that the addition of RAP increased the stiffness and the Glove-Rowe (G-R) Parameter value of asphalt binder. Higher RAP binder could be susceptible to non-load-associated cracking after long-term ageing or in a cold climate as binders with more than 30% RAP after the PAV 40 h ageing condition had a G-R value greater than 180 kPa. The fatigue damage in R-SCB test were analyzed by energy consumption approach and can be divided into three stages including the steady and cumulative damage stage and jump damage. The cumulative energy increased linearly with the loading cycles and the cumulative energy evolution meets Linear Miner’s Law in R-SCB test, then the average consumption per cycle (ECPCAVE) was selected as the index to evaluate the fatigue cracking performance of asphalt mixtures. It is found that higher ECPCAVE, faster cumulative rate of fatigue damage causing a lower fatigue life and poor fatigue cracking performance of asphalt mixtures. The addition of RAP contributed to the increase of ECPCAVE and the cumulative rate of fatigue damage. The higher RAP contents, the faster the cumulative rate of fatigue damage was, which caused smaller fatigue life. This paper suggests that ECPCAVE is a useful indicator to evaluate the fatigue cracking performance of asphalt mixture with and without RAP.

Field performance of asphalt pavement maintenance using Cup Lump Rubber Modified Asphalt (CMA)

It was typical in Malaysia that pavement failures at high stressed area were due to the bituminous layer aging subjected to extreme long loading times by the slow moving of heavy commercial vehicles. This scenario causes major structural deteriorations and permanent deformation of the bituminous road surfacing. In order to fix this problem, the used of Polymer Modified Asphalt (PMA) in asphalt mixture to form PMA mixtures was selected as an alternative method to increase the durability and lifespan of the pavement. PMA had been observed for a long time in improving the performance of asphalt pavement and increase the pavement lifespan. Although, it significantly improves the quality of the asphaltic layer and prolongs the life of the pavement, the construction cost was very high. Cup lump rubber was referred to the natural rubber in frozen form and it had been used as an additive in the conventional asphalt to produce cup lump modified binder (CMB). The mixture of cup lump modified binder with aggregates will produce the cup lump modified asphalt (CMA). Recently, Public Work Department of Malaysia and Malaysian Rubber Board recently had been conducted a field study at several locations to identify the benefits and CMA levels of performance as well as the constructability of the CMA pavement in actual field site. The monitoring and testing elements in this research were including mix design, construction methods and performances monitoring. The results have been showed that the performance of CMA was not shown significant improvement as compared to conventional asphalt section after six-month construction. From the result, it was noted that the longer observation period was needed to identify the actual field performance of cup lump asphalt pavement compared to the conventional asphalt pavement.

Effect of MSCR Percent Recovery on Performance of Polymer Modified Asphalt Mixtures

The AASHTO M332 specification includes a relationship between the non-recoverable creep compliance at 3.2 kPa ( Jnr3.2) and the percent of elastic recovery ( R3.2) from the multiple stress creep and recovery (MSCR) test. Justification for the exact position of this curve based on binder performance is largely undocumented in the technical literature as is the singular effect of higher or lower R3.2 values on mixture performance. In this study, nine binders were tested to evaluate the effect of R3.2 on the performance of asphalt mixtures. Binders with similar Jnr3.2 and varying MSCR R3.2 were divided into four groups based on their Jnr3.2 value. Comparisons were made based on results obtained from the dynamic modulus test, Hamburg wheel tracking test, and axial fatigue test. Based on these tests, it was shown that R3.2 had a strong relationship to the dynamic modulus of asphalt mixtures especially at intermediate and high temperatures. Binders with lower R3.2 had a higher dynamic modulus but showed no correlation to phase angle. Both modulus and phase angle of the mixture correlated to the binder shear modulus and phase angle. Binders with high R3.2 had a greater fatigue resistance and the effect is quite noticeable. However, R3.2 was shown to have little to no effect on the rutting resistance of the asphalt mixtures for the temperatures tested in this study. Finally, an alternative Jnr3.2 versus R3.2 relationship based on the results of this study is also presented.

Laboratory Testing of Self-Healing Polymer Modified Asphalt Mixtures Containing Recycled Asphalt Materials (RAP/RAS)

The objective of this study was to evaluate the efficiency of an innovative light-induced self-healing polymers in enhancing the durability of asphalt mixtures and improving its self-healing properties. Mixtures were prepared using two different binders, with and without recycled materials, and self-healing polymer. Results showed that the addition of recycled asphalt material to mixtures prepared with an unmodified binder negatively affected the healing recovery at room temperature. Furthermore, Self-healing properties of the mixtures were improved by increasing the healing temperature. The addition of 5% self-healing polymer to the control mixture, followed by UV light exposure resulted in an increase in self-healing properties of the mixtures prepared with PG 67-22 binder. Semi-Circular Bending (SCB) test results showed that the incorporation of self-healing polymer and 48 h of UV light exposure improved the cracking resistance. Loaded-Wheel Test (LWT) results showed that the self-healing polymer caused an increase in the rut depth of the samples prepared with an unmodified binder. However, the final rut depth was less than the acceptable rutting performance. Thermal-Stress Restrained Specimen Test (TSRST) test results showed that self-healing polymer improved the low temperature cracking performance of the mixtures.