Polymer-modified Asphalt Mixtures Research Articles

Evaluation of warm mix effect in laboratory using a self-developed WMA additive Alube

In response to the problems of high mixing temperatures and energy consumption of polymer-modified asphalt mixtures in road construction, a surfactant-based warm mix additive ‘Alube’ was developed. The warm mix SBS-modified asphalt and its mixture were prepared. Their rheological performance and chemical structure were analysed by the rheological and microscopic tests. The active mixing power (P) of asphalt mixtures were examined by the variable speed mixing (VSM) test. The mixing flowability model was then established to evaluate the warm mix effect. The results indicated that the mixing flowability of asphalt mixtures obeyed the linear Bingham visco-plastic model, and the slope and intercept of the flow straight characterised the mixing viscosity and plastic limit. It is evaluated that 0.7% Alube1 and Evotherm reduced the mixing temperature of SBS-modified asphalt mixture by 14°C and 12°C, respectively. Moreover, Alube1 is suitable for a wide range of applications through warm mix asphalt technology.

Use of Recycled Polyethylene in Asphalt Mixture

Abstract Plastics and plastic products have become part of our lives extremely quickly. Although, they make our lives easier in many aspects, at the end of their useful life, especially thanks to the thoughtless actions of people, they are becoming a serious environmental problem. Even though the laws and legislation are still forcing limits of using the plastic products and thus prevent waste, the concept of plastic-free living is probably not going to be reached easily and quickly. Using the recycling technology, we can prepare the recycled material, which represents a new raw material resource. With the right choice of physical-chemical parameters of recycled materials and using a suitable reaction condition we can incorporate them into the asphalt mixtures. Since their introduction the polymer-modified asphalt mixtures have gained in importance during the second half of the twentieth century, and they now play a fundamental role in the field of road paving. Moreover, the use of recycled plastic in such a product will contribute to the technical and economic recovery of secondary raw materials. The use of various recycled material in paving industry is a common practice but needs further research work. Thus, this study aims to the incorporation of recycled plastics into asphalt mixture. The main objective of our work was to find a suitable recycled plastic, which with its physico-chemical and technical parameters is suitable for incorporation into the asphalt mixture. In our study the recycled low-density polyethylene granulate was used, taken from films and various packaging materials. Our preliminary laboratory experiments were based on the possibilities to prepare and characterized the asphalt mixtures containing recycled plastic at different percentage, i.e., 4 %, 6 %, 8 % and 10 % by weight of bitumen. The experimental tests performed in the study were bitumen content, intergranularity, maximum bulk density, water sensitivity and resistance to permanent deformations. The results showed that the mix containing 6 % by weight of recycled plastic has ideal properties and meets most of the criteria that have been set for asphalt mixes. A commercially available polymer of similar chemical composition to the recycled material was used as a reference sample.

Asphalt recycling in polymer modified pavement: A test section and recommendations

While recycling of Reclaimed Asphalt Pavement (RAP) is accelerating, road owners still often restrict the use of RAP in polymer-modified pavement. Here we used a balanced mixture design for preparing polymer-modified asphalt mixtures for wearing and binder courses having 30 % to 60 % RAP content. Findings from the paved test section show that it is possible to design polymer-modified mixtures with 30 % to 50 % RAP that have a good crack propagation resistance, high fatigue resistance, acceptable stiffness, and sufficient rutting resistance. Based on the findings, recommendations for RAP use in polymer-modified layers are provided.

Linear viscoelastic properties and fatigue S-VECD based evaluation of polymer-modified asphalt mixtures

Direct tensile fatigue tests associated with the simplified continuous damage viscoelastic model (S-VECD) have proven to be an effective tool for evaluating fatigue in asphalt materials. Thus, this study evaluated the fatigue damage of asphalt mixtures modified by the addition of polymer based on the results of the direct tensile fatigue test using the S-VECD model. Three asphalt mixtures were produced: a control asphalt binder with 50/70 penetration, a polymer-modified styrene-butadiene-styrene (SBS) asphalt binder, and a mixture produced with a modified asphalt binder (composed of 98.38% control + 1.26% Ethylene Methyl Acrylate and Glycidyl Methacrylate (EMA-GMA) + 0.21% High-Density Polyethylene (HDPE) + 0.15% Polyphosphoric Acid (PPA116%)). The binders were evaluated for physical and rheological properties, and fatigue using the Linear Amplitude Sweep (LAS) test, applying the S-VECD model. Asphalt mixtures were evaluated for stiffness using tensile strength, resilient modulus and flow number tests. The viscoelastic linear behaviour (LVE) was characterized based on the dynamic modulus test and the fatigue performance was evaluated from the uniaxial direct traction test with the application of the S-VECD viscoelastic damage model. The results of the LAS test indicated that the modified binder presented the best fatigue performance, being classified according to the binder fatigue factor (FFB) as excellent. Mixtures with binders modified by polymers showed the highest values in mechanical performance tests. As for the LVE behaviour, the mixture with the modified binder showed the expected behaviour, with higher dynamic modulus values at high temperatures (low reduced frequencies), and the lowest modulus values at lower temperatures (high reduced frequencies). In addition, for the entire spectrum of frequencies and temperatures, the modified mixture presented the lowest values of phase angle, indicating more elastic and less viscous behaviour. From the direct tensile test, based on the GR failure criterion, the modified mixture showed better fatigue performance, with a higher value of the Fatigue Factor of the Mixture (FFM). Based on the DR failure criterion, from the Sapp damage capacity, mixtures with polymers were classified with the best performances concerning fatigue. Therefore, the use of polymer-modified binders promoted asphalt mixtures with better fatigue damage performance.

Unraveling the influence of fibers on aging susceptibility and performance of high content polymer modified asphalt mixtures

High-Content SBS Polymer Modified Asphalt Mixtures (HCPMA) combined with fibers have gained popularity in porous pavement construction due to their superior performance. Although the aging behavior of HCPMA has been extensively studied, the impact of fibers on performance and aging susceptibility remains unclear. This research investigates the influence of two representative fibers (lignin and polyester) on the raveling, cracking, fatigue, and rutting resistance of HCPMA before and after aging using Cantabro loss tests, SCB strength tests, SCB fatigue tests, and Hamburg Wheel-Tracking tests. The results indicate that in the original state, polyester fiber slightly enhances HCPMA performance, while lignin fiber shows limited or even adverse effects on cracking, raveling, fatigue, and rutting resistance. However, both fibers exhibit a more pronounced enhancement effect after short- and long-term aging. FTIR analysis reveals that fiber addition does not significantly impact bitumen oxidation and polymer degradation. The excellent properties of High-Content SBS Polymer Modified Bitumen (HCPMB) in the original state create a "masking" effect that conceals the enhancement effect of fibers, which becomes more evident after long-term aging. Consequently, it is recommended that the performance evaluation and design of open-graded asphalt mixtures containing HCPMB be based on post-aging performance.

Durability of Polymer-Modified Asphalt Mixture with Wasted Tire Powder and Epoxy Resin under Tropical Climate Curing Conditions.

The quality of pavements in tropical climates is negatively affected by the frequent wet and dry cycles during the rainy season, as well as by issues related to overloading from heavy trucks and traffic congestion. Contributing to this deterioration are factors such as acid rainwater, heavy traffic oils, and municipal debris. In light of these challenges, this study aims to assess the viability of a polymer-modified asphalt concrete mixture. This study investigates the feasibility of a polymer-modified asphalt concrete mixture with the addition of 6% crumb rubber powder from waste car tires and 3% epoxy resin to counter the harsh conditions of tropical climate weather. The study involved subjecting test specimens to five to 10 cycles of contaminated water (100% rainwater + 10% used oil from trucks), curing for 12 h, and air drying in a chamber of 50 °C for 12 h to simulate critical curing conditions. The specimens underwent fundamental laboratory performance tests such as the indirect tensile strength test, dynamic modulus test, four points bending test, and Cantabro test, as well as the double load condition in the Hamburg wheel tracking test to determine the effectiveness of the proposed polymer-modified material in actual conditions. The test results confirmed that the simulated curing cycles had a critical impact on the durability of the specimens, with the greater curing cycles leading to a significant drop in the strength of the material. For example, the TSR ratio of the control mixture dropped from 90% to 83% and 76% after five and 10 curing cycles, respectively. Meanwhile, the modified mixture showed a decrease from 93% to 88% and 85% under the same conditions. The test results revealed that the effectiveness of the modified mixture outperformed the conventional condition in all tests, with a more prominent impact observed under overload conditions. Under double conditions in the Hamburg wheel tracking test and a curing condition of 10 cycles, the maximum deformation of the control mixture sharply increased from 6.91 to 22.7 mm, whereas the modified mixture increased from 5.21 to 12.4 mm. Overall, the test results confirm the durability of the polymer-modified asphalt concrete mixture under harsh tropical climate conditions, promoting its application for sustainable pavements, especially in Southeast Asian countries.

Effects of Bitumen Thickness on the Aging Behavior of High-Content Polymer-Modified Asphalt Mixture.

The film thickness of asphalt mixtures is critical for determining their performance and aging durability. However, understanding of the appropriate film thickness and its influence on performance and aging behavior for high-content polymer-modified asphalt (HCPMA) mixtures is still limited. This research aims to examine the relationship between film thickness, performance, and aging behavior of HCPMA mixtures in order to establish an optimal film thickness that ensures satisfactory performance and aging durability. HCPMA specimens with film thicknesses ranging from 6.9 μm to 17 μm were prepared using a 7.5% SBS-content-modified bitumen. Various tests, including Cantabro, SCB, SCB fatigue, and Hamburg wheel-tracking tests, were conducted to evaluate raveling, cracking, fatigue, and rutting resistance before and after aging. The key findings indicate that insufficient film thickness negatively affects aggregate bonding and performance, while excessive thickness reduces mixture stiffness and resistance to cracking and fatigue. A parabolic relationship between the aging index and film thickness was observed, suggesting that increasing film thickness improves aging durability up to a point, beyond which excessive thickness adversely impacts aging durability. The optimal film thickness for HCPMA mixtures, considering performance before and after aging and aging durability, falls within the 12.9 to 14.9 µm range. This range ensures the best balance between performance and aging durability, offering valuable insights for the pavement industry in designing and utilizing HCPMA mixtures.

Short-Term Performance Characterization and Fatigue Damage Prediction of Asphalt Mixtures Containing Polymer-Modified Binders and Recycled Plastics

This study evaluated the short-term performance properties and predicted cracking performance of asphalt mixtures containing polymer-modified asphalt (PMA) binders and recycled polyethylene (RPE). To that end, binder rheological testing, mixture performance testing, and FlexPAVE simulations were conducted. Furthermore, three PMA mixtures were selected for field evaluation on the National Center for Asphalt Technology Test Track and rapid performance testing during production. The PMA binders modified with styrene-butadiene-styrene (SBS), reactive elastomeric terpolymer (RET), and RET-compatibilized RPE had significantly improved elasticity and rutting resistance compared with the unmodified binder. The PMA binders also exhibited good storage stability with minimal separation tendency. Both polymer modification of the asphalt binder and adding RPE via the dry process improved the rutting resistance of the mixture. Although the unmodified and PMA mixtures exhibited notably different load-versus-displacement curves from the Indirect Tensile Asphalt Cracking Test (IDEAL-CT), they had similar cracking tolerance index ( CTindex) results. The Gf-versus- l75 /m75 interaction diagram allowed a more robust understanding of the IDEAL-CT results by considering mixture toughness and brittleness, and their interactions with CTindex. In all cases, polymer modification increased the stiffness and fatigue damage resistance of asphalt mixtures, while adding RPE via the dry process embrittled the mixtures, making them more susceptible to fatigue damage. The PMA mixtures had significantly better predicted cracking performance in FlexPAVE simulations than the unmodified mixture. This improvement was mainly caused by polymer modification of the asphalt binder. Finally, adding dry RPE pellets improved the rutting resistance but reduced the intermediate-temperature cracking resistance of the plant-produced PMA mixture containing an SBS-modified binder.

A case study of the comparison between rubberized and polymer modified asphalt on heavy traffic pavement in wet and freeze environment

Ground tire rubber (GTR) usage in asphalt pavement with the dry process has gained more prominence in recent times. The objective of this work is to investigate the pavement performance of GTR-modified asphalt pavement and polymer-modified asphalt pavement on heavy volume of traffic conditions in Michigan's wet and freeze environment. A suite of laboratory tests was done to evaluate the pavement performance of GTR-modified and polymer-modified asphalt mixtures. To reveal the strain and stress relationship under different frequencies and temperatures, the dynamic modulus test was applied. The Hamburg wheel tracking device (HWTD) was used to assess the high-temperature deformation resistance. The disc-shaped compact tension (DCT) test was used to evaluate the low-temperature cracking characteristics. The characteristics of the asphalt binder were assessed by the dynamic shear rheometer (DSR) for high-temperature properties and the asphalt binder cracking device (ABCD) for low-temperature properties. After the construction, a field noise test was conducted. The experimental results stated that the polymer-modified asphalt mixture and GTR-modified asphalt mixture showed higher dynamic modulus and better ability to prevent cracking than the conventional asphalt mixture at low temperatures, as well as better permanent deformation and stripping resistance than the conventional asphalt mixture. The fracture energy of the GTR-modified hot mix asphalt (HMA) is 13–16 % larger than the polymer-modified HMA. The number of passes to the stripping point of GTR-modified was 510–518 % higher than the conventional HMA. When compared to the field core, the lab-compacted HMA offers superior pavement performance. The extracted asphalt binder test results show the GTR-modified asphalt has better rutting resistance and cracking resistance than polymer-modified asphalt, and the results in the noise test demonstrated that the rubber-modified asphalt pavement mitigated the noise level by 2–3 dB on the road at different vehicle speeds. Moreover, the pavement condition was noticeably enhanced after the reconstruction of the surface course. The total number of passenger tires to be used in this project is about 2270. To summarize, better rutting and cracking properties in asphalt pavement are shown by the project's utilization of rubber technology. And the GTR-modified HMA is comparable to polymer-modified HMA. Therefore, it may be appropriate to utilize rubber technology on high-traffic volume asphalt pavement in Michigan's wet and freeze climate.

Comprehensive Performance Evaluation of Asphalt Mortar Based on Multi-Index Weighted Decision Model

Abstract Aggregate is the key factor to ensure the performance of asphalt mixture. In order to analyze the impact of limestone, basalt, diabase, and steel slag on the road performance of asphalt mortar, with the ratio of mineral powder to asphalt in asphalt mortar being the same as the asphalt concrete (AC)-13 Styrene Butadiene Styrene (SBS) polymer–modified asphalt mixture, the four types of asphalt mortar specimens with different aggregates were designed and molded. The high-temperature performance, low-temperature performance, water stability, and fatigue performance tests were carried out to obtain the performance parameters of asphalt mortar. The multi-index weighted decision model was used to quantitatively evaluate the influence of the four types of aggregate on the comprehensive pavement performance of asphalt mortar. Results indicated that basalt asphalt mortar had the best high-temperature performance, steel slag asphalt mortar had the best low-temperature crack resistance and fatigue performance, and limestone asphalt mortar had the best water stability. Moreover, basalt asphalt mortar had the best comprehensive pavement performance. Finally, the optimized basalt asphalt mortar and steel slag asphalt mortar were applied to the engineering field, and both met the requirement.

Influence of ageing and moisture damage on the Illinois flexibility index value of polymer modified asphalt mixture

Asphalt pavements undergo ageing and moisture damage over the service life. The ageing and moisture process resulted in more cracking susceptibility and lowered pavement serviceability. Recently, the semi-circular bending (SCB) test has been widely utilised to characterise the fracture resistance of asphalt mixtures. In this study, the Illinois Flexibility Index Test (I-FIT) were utilised to investigate the impact of long-term ageing and moisture damage on the cracking resistance of asphalt mixtures modified by crumb rubber and plastic waste. This test is currently being adopted as a routine test in Illinois and has shown good correlations with the field cracking performance of asphalt mixture. For the Semi-Circular Bending (SCB) test, a sample width of 50 mm and a notch length of 15 mm was used for conducting the fracture test using a constant loading rate of 50 mm/min and a test temperature of 25 °C. The fracture energy-based crack mouth opening displacement of the control and modified mixtures was also evaluated using Digital Image Correlation (DIC). The results showed that the flexibility index (FI) values from the I-FIT are sensitive to the modifier type (elastomers or plastomers) and long-term ageing while underestimating the impact of moisture conditioning on the fracture performance of asphalt. Fracture energy results were higher for the rubberised mixture compared to the control and plastic waste modified asphalt mixture. Ageing condition has noticeably decreased the flexibility index (FI) of the rubberised mixture and consequently reduced the fracture performance.

Comparison of Rubber Asphalt with Polymer Asphalt under Long-Term Aging Conditions in Michigan

The objective of this study is to compare the long-term aging performance of dry-processed rubber-modified asphalt mixture with styrene–butadiene–styrene polymer-modified asphalt mixture on heavy traffic volume roads in the wet-freeze environment of Michigan. The rutting performance was evaluated using the Hamburg wheel track device. The disc-shaped compact tension test was used to assess the fracture energy. The dynamic modulus experiment was used to estimate the load and displacement relationship. The asphalt binder properties were evaluated using multiple stress creep recovery and the linear amplitude sweep test. The pavement distresses were evaluated using the pavement mechanistic–empirical design. All three types of asphalt mixture show excellent rutting resistance after long-term aging conditions, while the fracture energy of the rubber mix is 17.1% to 30.5% higher than that of the control mix and 6.8% to 9.1% higher than that of the polymer mix. The rubber and polymer incorporated with the asphalt binder improved the resistance to permanent deformation and improved the fatigue life of the asphalt binder. In summary, the rubberized asphalt technology using the dry process shows better cracking resistance and fatigue life. Therefore, rubberized asphalt using the dry process will exhibit adequate performance when used for high-volume roads in the wet-freeze environment of Michigan.

Production of polymer-modified-asphalt mixture as an alternative method to the conventional polymer-modified-bitumen mixtures

The transfer of new materials and technologies that are necessary for the development of new practices will lead to the development of innovation. These options are considered as (1) innovation, which means a significant improvement in the currently required parameters, mostly in parallel with the price increase, (2) innovation will meet the current parameters, but at a lower product / technology price, (3) innovation will achieve compliance with the applicable parameters, but at a higher price of the product / technology. In most cases, this is the second option, i. e. help the customer to enter the market at a lower price while maintaining the required product quality. This case also concerns the application of mixtures of the polymer-modified asphalt mixture type. The main goal of this work was the production and real laying on the verification section of the polymer-modified asphalt mixture. Based on the results obtained from this work, we can conclude that the values of the observed properties prescribed for a given class of asphalt mixtures in the catalogue sheets of asphalt mixtures were achieved without serious problems. Due to the trouble-free production of such mixtures in the plant, spreading and compaction of mixtures, we can express a clear conclusion that such mixtures are an ideal alternative to conventionally used polymer-modified-bitumen mixtures.

Performance Optimization Approach of Polymer Modified Asphalt Mixtures with PET and PE Wastes: A Safety Study for Utilizing Eco-Friendly Circular Economy-Based SDGs Concepts.

Eco-friendly waste utilization helps in the development of sustainable infrastructures. Recently, researchers have focused on the production of road infrastructures using the circular economy concept of human safety. The objective of this study is to investigate and explore the utilization of optimum polymer waste content for the development of polymer-modified asphalt mixtures using response surface methodology (RSM). RSM based on Box–Behnken design (BBD) was employed to optimize experimental design and included three factors: X1, polymer type; X2, polymer contents; and X3, testing day. The optimized responses determined by the RSM were as follows: MS of 42.98 kN, MF of 5.08 mm, and MQ of 8.66 kN/mm, indicating a favorable and consistent precision in comparison with experimental values. Moreover, the Marshall characteristics of samples prepared with PE were quite improved compared to PET. In conclusion, the incorporation of such polymer wastes in road construction is a sustainable and cost-effective way of improving their engineering properties. This study will help in the development of sustainable road infrastructures supporting human safety and environmentally friendly practices.

Field calibration and validation of a pavement aging model

ABSTRACT A pavement aging model (PAM) is established by calibrating and validating the NCHRP 09–54 kinetics model's predictions against field core measurements. Field cores, laboratory-mixed loose mixtures, and binders from a wide range of pavement sections are used, including both conventional hot mix asphalt (HMA) mixtures and modern materials (i.e. reclaimed asphalt pavement (RAP), warm mix asphalt (WMA), and polymer modified asphalt (PMA)). Field aging levels are measured at different depths from binder extracted and recovered from in-service field cores. The original component materials of these pavement sections are aged in the laboratory and used to calibrate the kinetics model. The measured field aging levels are compared against those predicted from the kinetics model to inform a depth and time dependent field calibration function for the PAM. The validation of PAM using an independent set of field sections shows that, within the limited data used in this study, the calibrated PAM may be able to predict the aging of the conventional HMA, RAP, WMA, and PMA mixtures. The PAM predictions are lastly found to outmatch the predictions by the Global Aging System (GAS) model.

Multi-Level Laboratory Performance Evaluation of Conventional and High Polymer-Modified Asphalt Mixtures

Asphalt concrete (AC) overlays have been one of the most common treatments used by the Virginia Department of Transportation (VDOT) for maintaining/rehabilitating pavements. However, when the overlay is placed on existing composite pavements or cracked AC pavements, differential movements across any cracks or joints can result in physical tearing of the AC overlay. Thus, the long-term performance of many AC overlays will highly depend on their ability to resist cracking. The purpose of this study was to assess the viability of using high polymer-modified (HP) AC mixtures in Virginia as a crack mitigation technique or when deemed appropriate as a tool for increased resistance to rutting and cracking on higher volume facilities. Another objective was to assess the ability of various testing protocols to discern the performance of pavements through a comprehensive evaluation of three conventional polymer-modified (PMA) and five HP field-produced mixtures placed in Virginia. This included laboratory testing at multiple levels of complexity (basic, intermediate, and advanced) on collected asphalt binders, plant-produced asphalt mixtures, and field cores. The performance characteristics of PMA and HP mixes were evaluated in the laboratory in relation to durability and resistance to rutting and cracking. Based on the mixes tested, stone matrix asphalt (SMA) mixes showed better performance than dense-graded surface mixes (SM) regardless of the asphalt binder type. Moreover, HP mixes showed better performance than PMA mixes regardless of the mixture type. Overall, SMA-HP mixes showed the most promising performance among all evaluated mixes.

Performance-based characterization of recycled polymer modified asphalt mixture

Due to the introduction of secondary materials, the asphalt mixtures to be designed and tested in our laboratories are constantly becoming much more complex than traditional asphalt mixtures making difficult to use conventional laboratory procedure and/or predict expected results. This study proposes a comprehensive characterization of asphalt mixture modified with recycled polymer compound by using both wet and dry process proposing adjustments to laboratory mixing and sample compaction procedure. Accordingly, three AC20 Hot Asphalt Mixture (HMA) were designed and their conventional and performance related properties were assessed by looking at a) Indirect Tensile test (ITS) a) moisture damage by Indirect Tensile strength Ratio (ITSR) test; b) cracking by fatigue and Semi-Circular Bending tests and c) rutting both considering Stiffness Modulus (ITSM) and susceptibility to deform by Wheel Tracker. The results demonstrate that the addition of recycled polymer compounds using dry process might lead to the need to adaptation of the laboratory mixing procedure and the proposed mixing and compaction procedures allowed to engineer a superior recycled polymer modified asphalt mixture manufactured through the dry process, since an increment of mechanical related properties, than traditional asphalt solutions, was exhibited by these modified asphalt mixtures in terms of ITS (+32%), ITSM (11% at 10 °C, +18% at 20 °C, and +34% at 40 °C), rutting resistance (rut depth of 1.86 mm vs 1.92 mm) and fatigue life.

Additional procedures for characterizing the performance of recycled polymer modified asphalt mixtures

Great efforts have been made in recent years to improve the mechanical properties of asphalt mixtures by replacing conventional mix components with innovative ones or by adding materials such as polymers. Hence, the innovative-sustainable road materials to be investigated through laboratory tests require articulated procedures, the research here presented aims to provide an experimental-methodological approach to analyse the mechanical performance of untraditional hot asphalt mixtures made up using a polymer compound of recycled plastics. Three Asphalt Concrete 20 (AC20) Hot Asphalt Mixtures (HMA) were analysed by measuring base properties (i.e., indirect tensile strength and moisture damage) and advanced features (i.e., stiffness, fatigue, cracking and rutting resistance). As a result, the addition of polymer compound using dry process might lead firstly to change the laboratory mixing procedure than the traditional hot limestone asphalt solutions. The main benefits derived from the adoption of this innovative technology compared to the conventional ones are as follows: a) an improvement of resistance to moisture damage (at 15 °C); b) a suitable stiffness at 10, 20 and 40 °C; c) an increment of the cracking resistance (at 10 °C) and d) a good rutting resistance in terms of rut depth (at 60 °C)..

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.