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This study evaluates the laboratory and field performance of stone mastic asphalt (SMA) mixtures with nominal maximum aggregate sizes (NMAS) of 9.5, 8.0, and 5.6 mm. Aggregates and fine aggregates of these sizes were produced using an impact crusher and a polyurethane screen. Mix designs for SMA overlays on aged concrete pavement were developed. Laboratory tests assessed rutting performance using full-scale accelerated pavement testing (APT) equipment and reflective cracking resistance using an asphalt mixture performance tester (AMPT). Field evaluations included noise reduction using CPX equipment, skid resistance using SN equipment, and bond strength using field cores. Results showed that for 8.0 mm SMA mixtures to achieve the same rutting performance as 9.5 mm SMA, PG76-22 grade binder was required, whereas 5.6 mm SMA required PG82-22. The 8.0 and 5.6 mm SMA mixtures showed 22.2% and 25% reduced crack progression, respectively, compared with the 9.5 mm SMA mixtures. Field evaluations indicated that 8.0 mm and 5.6 mm SMA pavements reduced tire–pavement noise by 1.7 and 0.8 dB, increased skid resistance by 8.5% and 2.0%, and enhanced shear bond strength by 150%, compared with 9.5 mm SMA. Overall, the 8.0 mm SMA mixture on aged concrete pavement demonstrated superior durability and functionality toward sustainable pavement systems. [ABSTRACT FROM AUTHOR]

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC – asphalt concrete, AC AF – asphalt concrete “anti-fatigue”, SMA – stone mastic asphalt and SMA-MA – stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100–160C°) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture.

Due to advantages like abrasion resistance, increased operating and service life, high coarse aggregate content and high resistance to deformation, increased fatigue life, and others, stone mastic asphalt (SMA) mixtures have recently become a popular asphalt pavement type in road sections such as highways, tunnels, and bridges. There hasn't been much research on the topic, despite the fact that gradation significantly affects the performance of SMA combinations. In this study, the experimental findings of three distinct gradations of SMA mixtures with hybrid materials (basalt coarse aggregate, limestone fine aggregate) and carbon fiber were compared. As a result, it was concluded that the hybrid aggregate used with carbon fiber, maximum aggregate size, and coarse aggregate % had a positive impact SMA mixtures.

The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction–lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture in the gyratory compaction process was defined based on the multiphase granular volume method. Secondly, the gyratory compaction curves of asphalt mixtures were taken based on this calculation method of compaction degree. The dynamic change law of each compaction index (compaction, percentage of air voids, compaction energy index, etc.) during the compaction process was analysed. Finally, the effects of different initial compaction temperatures and different asphalt content on the friction–lubrication effect and compaction characteristics of asphalt mixtures were studied. Research shows that it is reasonable to define the compaction degree by the ratio of the apparent density of the asphalt mixture to the maximum theoretical density of the asphalt mixture during gyratory compaction. The dynamic prediction equations of the compaction degree K and the compaction energy index CEI with the amount of compaction were established, and could effectively predict the compaction degree, percentage of air voids and compaction energy index CEI. The compaction process of the asphalt mixture needed to go through three phases, including periods of rapid growth, slow growth, and stabilisation, and the compaction degree increased by about 10%, 5%, and 1%, in that order, finally tending towards a stable value. The effect of the initial compaction temperature on the forming compaction degree of the asphalt mixture is significant; therefore, it should be controlled strictly in the compaction construction of asphalt mixtures. When the initial compaction temperature of SMA-13 is about 170 °C, the compaction effect is optimal, and the effect of the increase in the amount of compaction at a later stage on the increase in the compaction degree of the asphalt mixture is very low. With the optimal asphalt content, the friction–lubrication effect between the asphalt and aggregate particles is optimal, because it can effectively form an asphalt film, reducing the frictional resistance of the particles moving each other during the compaction process, and the voids will be embedded and filled with each other, finally producing the best compaction result. [ABSTRACT FROM AUTHOR]

Due to advantages like abrasion resistance, increased operating and service life, high coarse aggregate content and high resistance to deformation, increased fatigue life, and others, stone mastic asphalt (SMA) mixtures have recently become a popular asphalt pavement type in road sections such as highways, tunnels, and bridges. There hasn't been much research on the topic, despite the fact that gradation significantly affects the performance of SMA combinations. In this study, the experimental findings of three distinct gradations of SMA mixtures with hybrid materials (basalt coarse aggregate, limestone fine aggregate) and carbon fiber were compared. As a result, it was concluded that the hybrid aggregate used with carbon fiber, maximum aggregate size, and coarse aggregate % had a positive impact SMA mixtures. [ABSTRACT FROM AUTHOR]

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC - asphalt concrete, AC AF - asphalt concrete "anti-fatigue", SMA - stone mastic asphalt and SMA-MA - stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100-160°C) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture. [ABSTRACT FROM AUTHOR]

Anti-icing asphalt pavements can delay surface icing by reducing the freezing point to a certain degree. This study conducted the laboratory and field investigation to compare the anti-icing effectiveness and mechanical performance of two anti-icing stone mastic asphalt (SMA). Two types of anti-icing modifiers (e.g. LX II and MFL) were used in SMA respectively. The electrical conductivity test, ice melting test, and outdoor snow melting test were conducted on fresh and aged LX II SMA and MFL SMA, respectively, to evaluate the anti-icing effectiveness. The effect of anti-icing additives on high-temperature stability, low-temperature cracking resistance, and water stability of SMA were also analyzed. Two in-situ pavements were constructed using LX II SMA and MFL SMA. The anti-icing effectiveness of LX II and MFL pavement were compared by the observation of ice formation and snow accumulation on pavement surface on snowy days. The results showed that after long-term aging of anti-icing SMA, the chloride in LX II and MFL was more easily released. Two anti-icing additives had no significant effect on the water stability of SMA, and only slightly reduced high-temperature stability and low-temperature cracking resistance. LX II presented better anti-icing performance than MFL in both laboratory and field conditions. [ABSTRACT FROM AUTHOR]

Stone mastic asphalt is a type of hot mix asphalt that requires much coarse aggregate, so substitution waste aggregate, such as steel slag, will be an economic reason. The problem is that there are still many things that have not been consistent in various studies related to the moisture resistance of steel slag. The study aimed to compare the effect of CA(OH)2 on the moisture resistance of the steel-slag stone mastic asphalt mixture and to determine the optimal CA(OH)2 dosage for improving the mixture resistance. This study employs basalt aggregate, steel slag from Krakatau Steel Company, 60/70 penetration asphalt, a stabilizing substance made of bamboo fiber, and CA(OH)2. The Texas boiling and the static immersed methods are used to test the adhesion on a loose mixture. The retained Marshall stability and indirect tensile strength are used to test the adhesion on the compacted mix. Testing result of Krakatau steel slag shows that steel slag has a much higher Fe2O3 content than steel slag in general and has low water absorption; a poor affinity for asphalt results from this. The result of the Texas boiling method showed a decrease in the percentage adhesion value between steel slag and asphalt compared to natural basalt aggregates and asphalt. Marshall Stability Ratio and Tensile Strength Ratio increased after mixing the asphalt with CA(OH)2. Marshall test results show decreased stability in mixtures with steel slag substitution. Adding CA(OH)2 increased stability and resistance to moisture significantly. This indicated that CA(OH)2 enhances moisture resistance on stone mastic asphalt with modified steel slag. Stability, Marshall stability ratio, indirect tensile strength ratio, particle loss, and Texas boiling test significantly improved with adding CA(OH)2. [ABSTRACT FROM AUTHOR]

The evaluation of asphalt mixture fatigue performance holds increasing significance in the context of asphalt concrete pavement and various polymer modifiers. This study focuses on assessing the fatigue and reflection crack performance of two asphalt types: a conventional 10 mm SMA mixture with a fixed PG grade (PG 76–22) and a modified asphalt employing SBS, available in multiple grades (ranging from PG 76–22 to PG 82–22). Additionally, this study incorporates crumb rubber powder (CRP-6%) and epoxy resin (ER-4%) into the conventional SBS-modified SMA binder, reducing conventional asphalt binder consumption and promoting the utilization of recycled waste materials. To achieve this goal, comprehensive evaluations of fatigue cracking performance were conducted on SMA mixtures through multiple stressed creep and recovery tests, Texas overlay tests, and direct tensile cyclic fatigue tests. The results reveal that the modified binder exhibited superior strain recovery and a reduced strain rate in comparison to the reference binder under creep loads at MSCR levels of 0.1 and 3.2 KPa. The findings also indicate a 19.5% load reduction in the modified asphalt mixture with PG 72–22 binders, epoxy, and CRP after 1000 cycles, compared to 39.8% for the conventional mixture with a PG 76–22 binder. Moreover, the modified mixture demonstrated significant improvements, with 3.7 times more repetitions and 3.9 times more interactions to failure at strain levels of 330 and 360, respectively. Importantly, the research highlights the superior fatigue crack resistance performance of the PG 76–28 grade mixture compared to PG 76–22, positioning it as an optimal choice for aged concrete overlay applications. In conclusion, this study contributes to the development of more durable and reliable polymer-modified SMA mixtures enhanced with epoxy and crumb rubber, facilitating the advancement of sustainable road infrastructure.

The binder content of rubberised asphalt mixtures is usually increased compared to that used in conventional asphalt. This increase is deemed important to compensate for the reduction in the actual bitumen due to the existence of rubber particles. This study presents the results of performance evaluation conducted on different rubberised Stone Mastic Asphalt (SMA) mixtures produced using different types and contents of rubberised bitumen. The energy ratio (ER) computed from Superpave Indirect Tensile (IDT) tests was used to evaluate the cracking resistance of asphalt mixtures while the rutting behaviour was evaluated using the Repeated Load Axial Test (RLAT). The indirect tensile stiffness and strength were used to evaluate the moisture susceptibility. Using the same binder content for rubberised SMA mixtures as used in the conventional mixtures can still give superior performance properties. Adding crumb rubber to softer base bitumen can produce asphalt mixtures with superior cracking and rutting resistance. [ABSTRACT FROM AUTHOR]

The usability of waste seashell aggregates instead of basalt aggregate in stone mastic asphalt (SMA) mixtures was investigated. Maximum size of the seashell aggregates were choosen as 0.425 mm, 0.180 mm, and 0.075 mm. The rate of seashell aggregate was applied as 5%. In addition, the effects of the methods of adding seashell fillers to basalt aggregate by dry aggregate method, moist aggregate method, and slurry method were investigated. The use of seashell aggregates has been found to increase the stability, low temperature cracking resistance, water damage resistance, and deformation resistance of SMA mixtures. It was found that with the reduction of the seashell aggregate size, the improvement in the mechanical properties of the mixture increased, and the best properties were obtained with the use of seashell in filler size. When evaluated in terms of filler addition methods, the moist aggregate method gives better results than the slurry method and dry aggregate method. [ABSTRACT FROM AUTHOR]

The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction–lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture in the gyratory compaction process was defined based on the multiphase granular volume method. Secondly, the gyratory compaction curves of asphalt mixtures were taken based on this calculation method of compaction degree. The dynamic change law of each compaction index (compaction, percentage of air voids, compaction energy index, etc.) during the compaction process was analysed. Finally, the effects of different initial compaction temperatures and different asphalt content on the friction–lubrication effect and compaction characteristics of asphalt mixtures were studied. Research shows that it is reasonable to define the compaction degree by the ratio of the apparent density of the asphalt mixture to the maximum theoretical density of the asphalt mixture during gyratory compaction. The dynamic prediction equations of the compaction degree K and the compaction energy index CEI with the amount of compaction were established, and could effectively predict the compaction degree, percentage of air voids and compaction energy index CEI. The compaction process of the asphalt mixture needed to go through three phases, including periods of rapid growth, slow growth, and stabilisation, and the compaction degree increased by about 10%, 5%, and 1%, in that order, finally tending towards a stable value. The effect of the initial compaction temperature on the forming compaction degree of the asphalt mixture is significant; therefore, it should be controlled strictly in the compaction construction of asphalt mixtures. When the initial compaction temperature of SMA-13 is about 170 °C, the compaction effect is optimal, and the effect of the increase in the amount of compaction at a later stage on the increase in the compaction degree of the asphalt mixture is very low. With the optimal asphalt content, the friction–lubrication effect between the asphalt and aggregate particles is optimal, because it can effectively form an asphalt film, reducing the frictional resistance of the particles moving each other during the compaction process, and the voids will be embedded and filled with each other, finally producing the best compaction result.

All over the world, highway traffic is increasing rapidly, as is the population and the road network. The country's maximum and minimum temperatures also vary greatly. Moreover, the pavements are subjected to various types of damage. Pavement binders and mixtures are a constant area of research and development for scientists and engineers. Adding fibers to bituminous mixes may improve the properties of fatigue and strength of the material. Natural fibers may be used to improve asphalt mixtures performance due to their inherent compatibility with asphalt cement and excellent mechanical properties. Also, the high stone content and relatively high asphalt content in SMA mixture led to the occurrence of drain-down of the asphalt mastic from the mixture, and this problem requires the use of stabilizing additives such as cellulose fibers, mineral fibers, or polymers to mitigate this problem and ensure long-term performance. The most public sort of stabilizing additives is cellulose fiber. Overall, natural fibers in stone mastic asphalt mixes are discussed in this paper. An additional focus is on how asphalt concrete will be affected by natural fibers, mixing techniques, and managerial decisions. According to the review, the stabilizing and strengthening impact of natural fibers on the performance of asphalt mixes have been extensively researched. Natural fibers can significantly increase the rut and flow resistance of asphalt mixtures. Adding natural fibers to pavement can increase structural resistance to pavement distress. [ABSTRACT FROM AUTHOR]

The usage of polymer-modified asphalt binders has increased as a result of the significant increase in the number of conventional cars operating on Iraqi roads in recent years. This has resulted in increased strains being placed on pavement structures and materials. Global exploration has focused on the development of stabilizing Stone Mastic Asphalt mixtures for improved pavement behavior. Numerous effective efforts were made to stabilize stone mastic asphalt mixes with polymers and fibers. Iraq produces a considerable amount of waste polymer materials each year. Usually, they are sent to landfills for disposal. These wastes are dumped, occupying a sizable portion of landfill space and creating various serious environmental issues. The study focuses on how waste polymer additions, such as recycled plastic bottles, shopping boxes, and tire crumb rubber, affect the mechanical performance and durability of stone mastic asphalt mixtures. The mechanical performance attributes were assessed. It is evident from the findings that the drain-down amounts were within the permissible requirement range. The findings also showed that the indirect tensile strength, Marshall Stability, moisture damage resistance, and resistance for permanent deformation of stone mastic asphalt mixtures have all increased as a result of the use of waste polymer components. The recycled polymer-modified mixes are the combinations that are most resistant to rutting, according to the results of the repeated load axial creep tests. Iraq may have new options to employ the significant volumes of recycled polymers that are becoming accessible as a result of recycling waste polymers. [ABSTRACT FROM AUTHOR]

Nowadays, the most common ways to dispose of acid tars and paper production waste are burial or incineration, but it is ecologically and economically expedient to use such waste in building materials. A new variant of filler aggregate—wastepaper sludge ash (paper production waste) and a chemical activator for filler aggregates—acid tar (oil-refining industry waste) is proposed. Elemental and mineralogical compositions of wastepaper sludge ash for comparison with commodity limestone mineral powder are established. Chemical activation of wastepaper sludge ash and limestone mineral powder was carried out and the wetting properties of the obtained materials were investigated by means of primary and neutralized acid tar. The physical and mechanical properties of stone mastic asphalt samples with different filler aggregate variants were studied. The possible chemical transformations in stone mastic asphalt using limestone mineral powder and wastepaper sludge ash activated by acid tar are shown. The possibility of replacing traditional limestone mineral powder with industrial wastepaper sludge ash has been proven, and the effectiveness of activating filler aggregates by acid tar has been confirmed. It was established that acid tar as an activator for filler aggregates does not require neutralization because stone mastic asphalt, in this case, demonstrates better properties compared to acid tar neutralization. As a result of our research, the application of wastepaper sludge ash is possible as a filler aggregate for stone mastic asphalt. And to obtain improved stone mastic asphalt characteristics, wastepaper sludge ash is required to activate 5 wt.% acid tar. [ABSTRACT FROM AUTHOR]

Stone Mastic Asphalt (SMA) pavements have advantages such as increasing durability and resistance to cracks. Gap-graded SMA pavements are more preferred because they reduce rutting and delay fatigue cracks. In SMA pavements, the filler and bitumen ratio is higher than conventional asphalt pavements. In addition to the positive aspects of SMA pavements, there are also some negative aspects that need to be taken care of. The bitumen draindown during the time it takes from the production in the plant to the application on the road. The draindown of the bitumen causes disruption of the homogeneity in the pavement. In addition, as a result of laying the SMA mixture on the road with a paver and compacting it with a roller, the bituminous binder rises from the pavement to the surface and desorption. In this study, the effect of using different aggregates and bitumen for fiber and non-fiber SMA mixtures with constant gradation on the percentage of draindown was investigated. As a result of the Schellenberger bitumen draindown tests, it was observed that the increase in the specific gravity and softening point of the bitumen decreased the drain down percentage. In mixtures prepared from the same refinery bitumen with different aggregates, it was found that a decrease in bitumen absorption of aggregates increases the draindown percentage, but an increase in the peeling strength of aggregates and the use of aggregates from the Sedimentary Rock class in the fine aggregate part of the mixture reduces the draindown percentage. [ABSTRACT FROM AUTHOR]

Thermal cracking has long been a major concern for airport bituminous pavements in cold regions since it is in close connection with the safe operation of aircraft. This study aims to develop a design method for low-temperature performance-oriented airport bituminous mixtures. The research work mainly includes selecting design parameter, establishing design procedure, and verifying design method. The test and analysis results showed that the destructive tensile strain (DTS) of low-temperature splitting test was sensitive to the change of bitumen content, and can accurately characterize the thermal cracking resistance of the bituminous mixtures. Therefore, DTS was suitable as the design parameter, and its critical values were proposed for different climatic conditions. Furthermore, a new design procedure was established by incorporating DTS into the designs of gradation and optimum bitumen content. Through tests under different low temperature environments, it was verified that the design method can significantly improve the anti-cracking ability of designed bituminous mixtures. This study provides a new idea for enhancing the thermal cracking resistance of airport bituminous pavements in cold regions in terms of bituminous mixture design. [ABSTRACT FROM AUTHOR]

The road-transport sector has a significant impact on energy consumption. A relevant component of this energy usage is associated with rolling resistance (RR) between tires and pavement. In Denmark, CO2 emissions from road transport alone have been quantified as 4.6 Mt/yr. Replacing standard stone asphalt with durable low-RR pavements is expected to reduce CO2 emissions up to 1%. The Danish Road Directorate started, back in 2012, optimising a surface layer for reducing RR. The low-RR mixture was designed to provide a durable texture capable to meet all safety requirements. In 2016, two low-RR mixtures and reference asphalt concrete were paved on a test section. To evaluate the texture durability these mixtures were sampled at the construction site and tested with a circular road tester. The results show that the durability of low-RR pavements can be enhanced by using premodified binder, which reduces changes in texture properties and increases rutting resistance. [ABSTRACT FROM AUTHOR]

Gap-graded mixtures are one of the areas of improving the permanent deformation strength of hot-mixed asphalt mixtures. Additional filler materials can be needed due to the high bitumen amount and the less fine aggregate amount in the mixture. In this study, the effects of filler additives on moisture susceptibility of the gap-graded hot-mixed asphalt mixtures and mixing methods are investigated. Filler additives such as class C and class F fly ashes and hydrated lime are used 0.5 %, 1.0 %, 2.0 %, and 4 % of the total weight of mixture instead of mineral filler. Design mixtures are prepared according to the Turkish Highway Technical Specifications (THTS). To determine the effect of mixing methods, dry and wet (slurry) methods are used to mix the filler materials. Modified Lottman method (AASHTO T283) are used to determine the moisture susceptibility. An indirect tensile strength test is the measurement of bitumen film thickness which is also conducted. Test results showed that class C fly ash is significantly improved the moisture susceptibility of mixtures. While the slurry method does not give the expected improvement on class C fly ash added mixtures, it shows a positive effect on class F fly ash and hydrated lime added mixtures.

The utilization of synthetic, natural, and waste fibers in asphalt mixtures is constantly increasing due to the capability of fibers to improve the mechanical performance of asphalt mixes. The combination of fibers in asphalt mixes contributes to ecological sustainability and cost benefits. The objective of this paper is to introduce a citation-based review on the incorporation of synthetic, natural, and waste fibers in bitumen, dense-graded asphalt mix, stone mastic asphalt, and porous asphalt mix. Additionally, this article aims to identify research gaps and provide recommendations for further work. The outputs of this article demonstrated that there has recently been a growing interest in the use of natural and waste fibers in asphalt mixtures. However, more future studies are needed to investigate the performance of fiber-modified stone mastic asphalt and porous asphalt mix in terms of resistance to aging and low-temperature cracking. Furthermore, the period of natural fibers' biodegradability in asphalt mixtures should be investigated. [ABSTRACT FROM AUTHOR]

A good asphalt mixture is very important to maintain the triangle of sustainability. Many accidents occur due to pavement damage such as permanent deformation caused by the external loads induced by heavy traffic. Stone Mastic Asphalt (SMA) has a low resistance to moisture and other performances. Many researchers have conducted on SMA using various types of fiber. However, not much research has been done using steel fiber in the SMA mixture and has analyzed the result obtained using a statistical approach. The objective of this research was to identify the optimum amount of steel fiber in a modified asphalt mixture and characterize the performance of steel fiber in the SMA mixture using the statistical approach of Response Surface Methodology (RSM) in Design Expert Software. In this study, various steel fiber proportions of 0 percent, 0.3 percent, 0.5 percent, and 0.7 percent by the total weight of the SMA mixture were used. The Marshall stability and flow test, dynamic creep and moisture susceptibility test, and ultimately, RSM analysis were used to evaluate the properties and performance of the steel fiber-modified SMA, which contained 6.2 percent of PEN 60/70 asphalt binder content. The testing findings unmistakably demonstrated that the addition of steel fiber greatly improves the SMA mixture's resistance to moisture and permanent deformation. An amount of 0.3 percent was found to be the most optimum steel fiber content from the optimization by using Response Surface Methodology, thus proven with additional steel fiber in the SMA mixture enhancing the performance of the mixture. As a result, it can be determined that the addition of steel fiber to SMA asphalt mixtures has improved the properties and performance in the construction of asphalt pavements, and the RSM method is an efficient statistical method for producing an appropriate empirical model for relating parameters and predicting the best performance of an asphaltic mixture. [ABSTRACT FROM AUTHOR]

The usage of polymer-modified asphalt binders has increased as a result of the significant increase in the number of conventional cars operating on Iraqi roads in recent years. This has resulted in increased strains being placed on pavement structures and materials. Global exploration has focused on the development of stabilizing Stone Mastic Asphalt mixtures for improved pavement behavior. Numerous effective efforts were made to stabilize stone mastic asphalt mixes with polymers and fibers. Iraq produces a considerable amount of waste polymer materials each year. Usually, they are sent to landfills for disposal. These wastes are dumped, occupying a sizable portion of landfill space and creating various serious environmental issues. The study focuses on how waste polymer additions, such as recycled plastic bottles, shopping boxes, and tire crumb rubber, affect the mechanical performance and durability of stone mastic asphalt mixtures. The mechanical performance attributes were assessed. It is evident from the findings that the drain-down amounts were within the permissible requirement range. The findings also showed that the indirect tensile strength, Marshall Stability, moisture damage resistance, and resistance for permanent deformation of stone mastic asphalt mixtures have all increased as a result of the use of waste polymer components. The recycled polymer-modified mixes are the combinations that are most resistant to rutting, according to the results of the repeated load axial creep tests. Iraq may have new options to employ the significant volumes of recycled polymers that are becoming accessible as a result of recycling waste polymers.

The paper presents the results of studies of the physicomechanical properties of stone mastic asphalt (SMA) with the use of stabilizing additives of multifunctional action aimed at increasing the strength characteristics of SMA, resistance to plastic deformations, increase in shear stability of asphalt concrete, as well as reduction of the negative impact of technological temperatures on oil bitumen contributing to its oxidation and premature aging in the production of asphalt mixes. The structure of bitumen modified with composite thermoplastic elastomer was studied by nuclear magnetic resonance. For experimental verification of the effectiveness of additives in the composition of SMA, standard methods used for all types of asphalt concrete were applied and the following indicators of physical and mechanical properties were studied: compressive strength, water saturation, shear resistance, abrasion, resistance to plastic deformation. The results of studies of physical and mechanical properties of SMA grades 10 and 15 containing additives of the Viatop Plus CT40 and Viatop Plus FEP series showed that the values of compressive strength at 20 and 50 °C exceed similar indicators of properties of SMAs with the use of a stabilizing additive Viatop 66 considered as control compositions.

This paper aims to assess the influence of encapsulated rejuvenators on plant-produced asphalt's performance. The polymeric capsules are evaluated as cellular materials that deform and absorb energy while they experience a progressive collapse of their porous structure, rather than a simply means to release the rejuvenator. Additionally, variables during asphalt manufacturing that may affect their plastic deformation under loading are assessed too. Firstly, plant-produced asphalt's mechanical and morphological properties were evaluated, including the capsules' distribution and integrity after mixing. Then, results were contrasted with lab-produced asphalt under controlled conditions. Lastly, the capsules' deformation was qualitatively evaluated using a FE model to verify findings from the testing campaign. It was concluded that (i) cellular capsules can resist mixing at an asphalt plant without compromising their performance; (ii) the deformation of the capsules affected asphalt's stability by up to 13%, reduced the particle loss by up to 25% and increased asphalt's macrotexture by 10%; (iii) to maximize their energy absorption, the cellular capsules must be part of the aggregate skeleton. [ABSTRACT FROM AUTHOR]

The use of fibers and polymers in asphalt mixtures leads to improved quality, higher lifespan, and lower maintenance costs by making mechanical, physical, and chemical changes. This results in eliminating or reducing the weaknesses of mixtures in the production, implementation, and service phases. In this study, the Stone mastic asphalt mixtures with the same gradation curve, but different additives are evaluated. In the first, second, and third groups of experiments, SEBS elasto-plastomer polymer (SEBS), SEBS elasto-plastomer polymer with cellulosic fibers (SEBS-CF), and SBS elasto-plastomer polymer with cellulosic fibers (SBS-CF) were added to the mixture in various weight percentages, respectively. Also, Stone mastic asphalt mixtures without any additives (SMA-S) and SBS-modified mixtures (SBS) as the most common modifiers were considered as the control mixtures. To evaluate the designated mixtures related to moisture sensitivity, several tests including saturated marshal, indirect tensile strength, resilient modulus, and drain down tests were applied. The results showed that the designated asphalt mixtures meet the requirements for the moisture sensitivity and resilient modulus tests successfully, and it is concluded that among these samples of mixtures, 4% SEBS has the best performance compared to other mixtures; it had even better performance than the SBS mixtures, which are the most common modifiers. Therefore, this issue can be a great help considering the advantages of this polymer over other modifiers to select and use it to modify asphalt mixtures among the mixtures although SEBS-CF had a higher percentage of optimum bitumen achieved less drain down, which shows that the bitumen of these mixtures has become more behaviorally stable due to modification with polymer and fiber at the same time. [ABSTRACT FROM AUTHOR]

Stone mastic asphalt is a gap-graded mix and is usually related to its high bitumen content and its skeleton-like constitution. Although famous for its durability, high resistance to fatigue and rutting, issues such as bleeding and premature aging do occur in the mix since it has a high bitumen content and voids due to its gap-graded structure. In order to encounter these problems from affecting the mix, some instances such as adding additives, rejuvenators and stabilizers into the mixture has been implemented. Nowadays, nano materials are being used in the asphalt mixtures and nano titanium is being introduced as a modifier to the asphalt binder in order to improve the mechanical properties of the stone mastic asphalt mix. The related tests done in order to access the improvement are resilient modulus, dynamic creep, moisture susceptibility and binder drain down. The content of nano titanium used in this research are 1%, 2%, 3%, 4% and 5%. This study is done to assess the mechanical performance of stone mastic asphalt with nano titanium modified binder.

The deterioration of Malaysia's flexible road pavements due to rutting and moisture damage presents a critical problem. Meanwhile, disposing of glass fiber wastes from manufacturing process further worsens environmental concerns. This research explores the feasibility of using glass fiber wastes as bitumen modifiers and stabilizers in stone mastic asphalt (SMA). The performance of SMA14 incorporating glass fiber waste using wet method and dry method were compared in this study. Bitumen 60/70 PEN was modified with varying percentages of glass fiber waste namely, 0.5%, 1.0%, 1.5%, and 2.0% by weight of bitumen. The SMA14 mixture was modified with glass fiber waste at 0.3% by the weight of total mixture. The physical and rheological characteristic of modified bitumen binder were assessed using penetration, softening point, storage stability, viscosity, and dynamic shear rheometer (DSR) tests. The Marshall properties and performance of the SMA14 mixture incorporating glass fiber waste were evaluated. The findings demonstrate that glass fiber waste-modified bitumen exhibits enhanced penetration, softening point, viscosity, and rutting resistance compared to the unmodified sample. Adding glass fiber waste using dry method shows significant resistance to abrasion and rutting and demonstrates higher indirect tensile strength and TSR value., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Gap-graded mixtures are one of the areas of improving the permanent deformation strength of hot-mixed asphalt mixtures. Additional filler materials can be needed due to the high bitumen amount and the less fine aggregate amount in the mixture. In this study, the effects of filler additives on moisture susceptibility of the gap-graded hot-mixed asphalt mixtures and mixing methods are investigated. Filler additives such as class C and class F fly ashes and hydrated lime are used 0.5%, 1.0 %, 2.0 %, and 4 % of the total weight of mixture instead of mineral filler. Design mixtures are prepared according to the Turkish Highway Technical Specifications (THTS). To determine the effect of mixing methods, dry and wet (slurry) methods are used to mix the filler materials. Modified Lottman method (AASHTO T283) are used to determine the moisture susceptibility. An indirect tensile strength test is the measurement of bitumen film thickness which is also conducted. Test results showed that class C fly ash is significantly improved the moisture susceptibility of mixtures. While the slurry method does not give the expected improvement on class C fly ash added mixtures, it shows a positive effect on class F fly ash and hydrated lime added mixtures. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the impact of pavement thickness and modified asphalt mix on pavement performance. Experimental, numerical, and parametric studies were performed. In the experimental stage, the mechanical properties and performance of the road pavements subjected to traffic loads were examined for different exposure times and analyzed based on current standards. In the numerical stage, a total of twelve finite element models corresponding to unmodified hot mix asphalt (HMA) and modified stone mastic asphalt (SMA) road pavements with different thicknesses were designed. The relationship between stress and strain values was examined using numerical analyses. Vertical-lateral stresses and strains between the pavement, base, and sub-base layers were obtained from finite element models. In the final stage, the stress and pavement thickness relationships were determined by regression analysis using twelve numerical models. The results revealed that SMA pavements have high strength, impermeability, and homogenous structure with higher resistance against wear and plastic deformation compared to HMAs.

The utilization of synthetic, natural, and waste fibers in asphalt mixtures is constantly increasing due to the capability of fibers to improve the mechanical performance of asphalt mixes. The combination of fibers in asphalt mixes contributes to ecological sustainability and cost benefits. The objective of this paper is to introduce a citation-based review on the incorporation of synthetic, natural, and waste fibers in bitumen, dense-graded asphalt mix, stone mastic asphalt, and porous asphalt mix. Additionally, this article aims to identify research gaps and provide recommendations for further work. The outputs of this article demonstrated that there has recently been a growing interest in the use of natural and waste fibers in asphalt mixtures. However, more future studies are needed to investigate the performance of fiber-modified stone mastic asphalt and porous asphalt mix in terms of resistance to aging and low-temperature cracking. Furthermore, the period of natural fibers’ biodegradability in asphalt mixtures should be investigated.

Globally, a huge quantity of alum sludge waste is produced as a by-product material from drinking water treatment plants that utilize aluminum salts as an essential coagulate and is the most generally produced water treatment remaining sludge around the world, which causes a serious environmental problem. Direct discarding of this substance has ecological effects. Hence, it is important to reuse this alum sludge waste material in such a manner to diminish its detrimental impacts on the environment. This research investigates the possibility of reusing alum sludge waste as a partial replacement of cement filler in stone mastic asphalt (SMA) paving mixtures. For this investigation, the alum sludge was used as a filler material in SMA mixtures in two modes; dried alum sludge at 110°C and burned alum sludge at 700°C. Different percentages of alum sludge were used as a replacement by the total weight of mineral filler at 0, 20, 40, 60, 80, and 100%. The results showed that using alum sludge as a substitution of filler in SMA mixtures reduces the performance of the mixtures in terms of Marshall properties and tensile strength for both dried and burned alum sludge compared with a standard mix. However, the performance of the mixtures containing burned alum sludge gave a better performance than the mixtures containing dried alum sludge. [ABSTRACT FROM AUTHOR]

In this study, results from long-term monitoring of the tyre/road noises of the exposed aggregate cement concrete (EACC) with the highest grain size of 8 mm and stone mastic asphalt (SMA) surface with the highest grain size of 11 mm performed by close-proximity (CPX) method are presented. There are certain concerns that the EACC surface will have inferior noise properties than SMA. These concerns are based on previous experience with the cement concrete surface with transverse tining texture which is very noisy. The main aim of this article is to demonstrate that these concerns are unfounded. A section of the motorway was chosen for the measuring and the testing speed for all measurements was 80 km·h−1. Provisional results (based on six years of monitoring) show that the noise levels measured on both these surface types are similar over their lifetime and exhibit logarithmic acoustic behaviour. [ABSTRACT FROM AUTHOR]

Hydrotalcite, a type of layered double hydroxide (LDH), reveals an interesting potential for the modification of bitumen. The LDH can induce a barrier effect that prevents the loss of volatiles, retards oxidation, and protects against ultraviolet radiation. Such properties can enhance the aging resistance of the bitumen. However, there is a gap in knowledge regarding the effects of the modification with hydrotalcite in the properties of the asphalt mixture. To contribute to fill such a gap, the current study presents a characterization of the effects of the modification with nano hydrotalcite in the surface characteristics, mechanical performance, and aging resistance of an asphalt mixture. To better explore the effects of the modification, the selected asphalt mixture was a high binder content (7.5%) Stone Mastic Asphalt (SMA). The experimental study indicates that the binder-rich SMA presented adequate performance for application in surface courses. If compared to conventional mixtures, the binder-rich SMA presented better initial mechanical performance (unaged conditions). Furthermore, it presented smaller variation in the parameters between unaged and aged conditions, indicating enhanced aging resistance. The modification with nano hydrotalcite induced smaller evolution in the fatigue resistance parameters, indicating enhanced aging resistance; however, in the remaining tests, the trends were not clear. [ABSTRACT FROM AUTHOR]

Stone Mastic Asphalt (SMA) is based on the concept of designing a coarse aggregate skeleton in order to attain stone -on -stone contact is obtained, which provides a highly rut resistant bituminous course for heavy traffic loads. It is a homogeneous mixture of selected gap graded aggregate, filler and bitumen in such proportion as to yield a plastic and void less mix. The main objective of this study is to evaluate the effect of different fillers (stone dust, bagasse ash and palm oil fuel ash) on the SMA mixes in terms of Marshall Stability values. A comprehensive laboratory tests were conducted on aggregates, Bitumen (VG-30) and fillers. The prepared SMA specimens with varying combination of filers such as 10% of stone dust, 5% of stone dust and 5% of Bagasse ash, 5% of stone dust and 5% of palm oil fuel as along with 0.3% of mineral additive (waste plastic) were subjected to marshall stability tests and results indicates that use of partial replacement of bagasse ash for stone dust as a filler material gives more stability values and less voids when compared to absolute stone dust (10%).

Globally, a huge quantity of alum sludge waste is produced as a by-product material from drinking water treatment plants that utilize aluminum salts as an essential coagulate and is the most generally produced water treatment remaining sludge around the world, which causes a serious environmental problem. Direct discarding of this substance has ecological effects. Hence, it is important to reuse this alum sludge waste material in such a manner to diminish its detrimental impacts on the environment. This research investigates the possibility of reusing alum sludge waste as a partial replacement of cement filler in stone mastic asphalt (SMA) paving mixtures. For this investigation, the alum sludge was used as a filler material in SMA mixtures in two modes; dried alum sludge at 110°C and burned alum sludge at 700°C. Different percentages of alum sludge were used as a replacement by the total weight of mineral filler at 0, 20, 40, 60, 80, and 100%. The results showed that using alum sludge as a substitution of filler in SMA mixtures reduces the performance of the mixtures in terms of Marshall properties and tensile strength for both dried and burned alum sludge compared with a standard mix. However, the performance of the mixtures containing burned alum sludge gave a better performance than the mixtures containing dried alum sludge.

Using stone mastic asphalt (SMA) has increased considerably, mostly due to the improvement in serviceability of pavements. This type of asphalt mix is made with more coarse aggregates than fine aggregates. Therefore, using proper bitumen with a better coating among the aggregates is important. On the other hand, since the population grows, the production of waste materials drastically increases. Therefore, the importance of using recycled materials in other industries has increased every day. One of the most prominent types of waste materials is high-density polyethene (HDPE). HDPE is polymer waste and can improve the performance of bitumen. HDPE can be found in many municipal wastes, such as plastic bottles. Therefore, constructing pavements containing HDPE can reduce waste materials and the cost of maintaining and rehabilitating roads from the improvements of mechanical properties and performances of mixtures. This study aimed to investigate the effectiveness of HDPE on the mechanical properties and performance of SMA. Hence, Marshall properties, maximum density, bulk density, and stability were measured for the mechanical properties. Wheel tracking and four-point bending test were carried out as the performance evaluation of rutting and fatigue resistance, respectively. The results showed SMA mixtures containing 4% HDPE had the best fatigue resistance, while rutting performance was 8% HDPE. The maximum fatigue life and minimum rutting depth were recorded as 157,090 cycles and 1.05 mm, respectively.

Moisture damage is one of the most common and main distresses in asphalt pavements. Using Nanomaterials due to their unique and outstanding properties in the asphalt pavement industry has received much attention in recent years. This paper investigated the effects of Nano Zinc Oxide (ZnO) and Nano Reduced Graphene Oxide (RGO) on moisture susceptibility resistance of Stone Mastic Asphalt (SMA) mixtures. SMA mixtures are a type of hot mix asphalt (HMA) containing two main parts of coarse aggregates and bitumen-filled mortar (bitumen, stabilizing additives, and filler aggregates). There is a wide range of test methods for evaluating the moisture resistance of asphalt mixtures; this study used the immersion Marshall test, indirect tensile strength test, boiling water test, static creep test, pull-off adhesion, and Semi-circular bending (SCB) fracture test for this aim. The pure bitumen was modified with three content of Nano ZnO and Nano RGO (0.2 %, 0.4 %, and 0.6 % by weight of asphalt binder). The experimental results obtained in this research indicated that the addition of Nano RGO in pure binder increases the softening point and viscosity and decreases the penetration and ductility properties of pure bitumen. Also, the addition of Nano ZnO in bitumen can increase the ductility, softening point, and viscosity, and decrease the penetration properties of pure bitumen. The mechanical test results showed that an increase in the percentage of Nano ZnO and RGO lead to a rise in Marshall Stability, indirect tensile strength, accumulated strain, pull-off adhesion strength, and fracture energy and improve the bitumen coating on aggregates in SMA mixtures. According to calculated moisture susceptibility indices of the mentioned tests above, the Nano ZnO and Nano RGO can significantly improve the resistance of stone mastic asphalt mixtures against moisture susceptibility. Examination of the test results showed that the ITS, pull-off, and Semi-circular bending (SCB) fracture test can give a good estimation of the moisture susceptibility of asphalt mixture. In addition, the results of the ANOVA test depicted that in ITS, Pull-off, and SCB fracture tests, Nano ZnO has a more significant effect on improving moisture susceptibility than Nano RGO.

This paper aims to assess the influence of encapsulated rejuvenators on plant-produced asphalt’s performance. The polymeric capsules are evaluated as cellular materials that deform and absorb energy while they experience a progressive collapse of their porous structure, rather than a simply means to release the rejuvenator. Additionally, variables during asphalt manufacturing that may affect their plastic deformation under loading are assessed too. Firstly, plant-produced asphalt’s mechanical and morphological properties were evaluated, including the capsules’ distribution and integrity after mixing. Then, results were contrasted with lab-produced asphalt under controlled conditions. Lastly, the capsules’ deformation was qualitatively evaluated using a FE model to verify findings from the testing campaign. It was concluded that (i) cellular capsules can resist mixing at an asphalt plant without compromising their performance; (ii) the deformation of the capsules affected asphalt’s stability by up to 13%, reduced the particle loss by up to 25% and increased asphalt’s macrotexture by 10%; (iii) to maximize their energy absorption, the cellular capsules must be part of the aggregate skeleton.

Various additives can be used to minimize basic deterioration problems and to provide performance improvements in asphalt mixtures. The addition of styrene-butadiene-styrene (SBS) is among the most preferred additives. It is known that SBS increases rutting, water damage and cracking resistance and improves fatigue behavior. However, due to its high cost and poor compatibility with bitumen, problems may arise in its use. When nanoclay is added to polymer modified bitumen, it can increase the storage stability of polymer modified bitumen and improve the mechanical properties of the final asphalt mixture. In this study, the effect of nanoclay addition (2% and 3%) with different SBS rates (5%, 4%, 3%, 2% and 1%) was investigated in terms of water damage, permanent deformation and cracking resistance, reducibility of SBS ratio was questioned. According to the test results on stone mastic asphalt mixtures, 2% nanoclay-3% SBS ratio was found to give higher water damage and low temperature cracking resistance than other modification options. [ABSTRACT FROM AUTHOR]