Production Of Asphalt Mixtures Research Articles

Regulating asphalt pavement temperature using microencapsulated phase change materials (PCMs)

The use of phase change materials (PCMs) to regulate pavement temperatures has been previously studied, with the most successful studies using porous aggregates to stabilize the PCMs. However, this technique can lead to issues with PCM leakage and low PCM content. A less studied method is the use of PCM microcapsules, which also presents challenges since most microcapsules are not strong nor stable enough to survive the high temperatures and compressive forces experienced during asphalt mixture production and placement. This work presents a study of the properties of a new commercial microcapsule type with robust walls and high thermal stability, that are expected to overcome the aforementioned issues. Results from differential scanning calorimetry and thermogravimetric analysis confirmed the microcapsules exhibited high latent heats (200 J/g) and are thermally stable below 400 °C. Additionally, approximately 90% of the capsules remained unbroken after being milled at 140 °C for 20 min, suggesting they are capable of withstanding the mixing and compaction stages of asphalt pavement construction. When PCM microcapsules were added to HMA, thermal cycling experiments showed that specimens containing 10 and 20 vol% PCM exhibited temperature lags of 5 to 10 °C from the control mixture, as they approached the PCM melting/freezing temperature. These results confirm the ability of microencapsulated PCMs to regulate asphalt pavement temperature. However, results from measurements conducted at 40 °C and 1 Hz showed a 75% reduction of the dynamic modulus in specimens containing PCM microcapsules, which could indicate that the addition of these materials also affect asphalt mixture stiffness.

Investigating the effect of preheating conditions and size effect on asphalt blending in recycled asphalt mixture: New approach based on artificial aggregate and laser scanning confocal microscopy

• The influence of preheating conditions and size effect on the blending phenomena were evaluated through 3D-FIT method. • The difference of asphalt blending between virgin and RAP aggregate were also investigated. • The longer curing time does not mean better blending, which exists a limited value and an optimal storage time. • Smaller sizes of virgin aggregate can mobilize more active reclaimed asphalt from RAP aggregate. The blending phenomena between virgin and reclaimed asphalt is a significant concern in asphalt paving, which play a crucial role in the final performance of the recycled asphalt mixture. Although past studies broadly discussed the asphalt blending by various test methods, the blending process holds 3D features due to the different aging degrees of reclaimed asphalt and different dispersity of virgin asphalt. The three-dimensional observation in the asphalt blending is still limited. Simultaneously, many factors (e.g., preheating temperature and time, transportation temperature, storage time, and aggregate gradation) will affect the blending process. The relationships between those factors and the blending phenomena are still unknown. To overcome this problem, this paper proposed a 3D fluorescence image method by laser scanning confocal microscopy and artificial aggregate. The artificial aggregate in the wooden cube form was used to analyze the blending process of virgin and RAP aggregate in three-dimension, respectively. Meanwhile, preheating conditions and size effect on the blending phenomena were also evaluated. The results indicate that temperature presents a more significant influence on the blending than the curing time. A longer curing time does not mean better blending, which exists a limited value and an optimal storage time. Compared to RAP aggregate, more homogeneous blending occurred on virgin aggregate after 2 h curing time at 180 °C, so the blending process on virgin aggregate should also be considered by researchers. This study may help to explain the production of recycled asphalt mixture and understand the blending phenomena in asphalt paving.

Migration behavior of reclaimed asphalt pavement mastic during hot mixing

The production of hot central plant recycling asphalt mixture (RHMA) is more complex and uncertain than conventional hot mix asphalt. An adequate blend of virgin and aged asphalt is essential to recovering the performance of aged asphalt in reclaimed asphalt pavement (RAP). Therefore, the amount of aged asphalt migrating from the RAP into the recycled material system determines the level of blending and the durability of RHMA. To reveal the influencing factors of migration rate, we used fine aggregates in RAP as tracers to measure the RAP mastic concentration in the blended mastic. The considered factors included mixing time, asphalt-aggregate ratio, rejuvenator content, mixing sequence, RAP pseudo ratio, and RAP agglomeration rate. Then, the migration behavior of aged mastic was investigated from the viewpoints of the temperature field and microscopic features using the infrared thermogram and CT scan techniques, respectively. In addition, FTIR, GPC, and AFM were used to study the influence of migration of RAP mastic on the composition of blended asphalt. Finally, the effect of RAP mastic migration on moisture stability of RHMA was investigated using moisture induced sensitivity test, freeze-thaw indirect tensile test, and water immersion rutting test. The results show that the migration rate of RAP mastic during hot mix can be improved by reducing RAP content, raising the preheating temperature of RAP, extending the mixing time, increasing the asphalt content, and using dry mixing method, whereas the amount of regenerator has no significant effect. The temperature is the essential factor affecting the migration level. The RAP mastic migration is highly synchronized with RAP aggregate movement under forced mixing. Furthermore, increasing the migration level of RAP mastic can significantly increase the proportion of aged asphalt in blended asphalt. At last, the higher RAP mastic migration can prevent void development in RHMA under freezing-thawing and hydrothermal washing, thereby improving the moisture stability of RHMA and alleviate peeling aggregates and mastic. This study contributes to current knowledge by explaining the essence of RAP mastic migration during hot mixing, the results should be interested by road contractors, producer of RHMA, and academic society.

Study of the mechanical behavior of asphalt mixtures in terms of creep and Superpave compaction parameters

This was a study on the mechanical behavior of hot asphalt mixtures with regard to permanent deformation, considering static creep tests and the parameters derived from the Superpave compaction curve. For the asphalt mixture production, mineral aggregates and two types of asphalt binder (CAP 50/70 and AMP 60/85) were used. These mixtures were designed using the Superpave methodology and compacted in the content and number of gyrations according to the design. For the design condition, asphalt mixtures using the conventional CAP 50/70 asphalt binder showed better workability and lower deformation than asphalt mixtures with the AMP 60/85 polymer binder. Furthermore, the influence of asphalt binder content on the behavior of asphalt mixtures in relation to permanent deformation and compaction indices was studied, considering the maximum number of gyrations in the design. Regarding this investigation, asphalt mixtures with higher asphalt binder content tend to show higher permanent deformation and better workability. Complementarily, the compaction curve indices (Construction Densification Index, CDI; modified Traffic Densification Index, TDIm and Locking Point, LP) were correlated with parameters obtained from static creep tests (total deformation after the recovery period, Dt; creep modulus, CM and curve inclination, Icurve) through curves obtained by the correlation between these indices. Based on this analysis, a good correlation was found between the results of static creep tests and compaction indices, showing the potential of these indices for predicting the mechanical behavior of the analyzed mixtures in relation to the development of permanent deformations.

Analysis of the Behavior of Low-Noise Asphalt Mixtures with Modified Binders under Sinusoidal Loading.

The paper presents the results of tests of the stiffness modulus according to the 4PB-PR method of low-noise asphalt mixtures with the addition of rubber granulate (RG). Mixtures of this type are characterized by an increased air void content (about 10–25%). This causes a rapid bitumen oxidation, which results in oxidative hardening, contributing to a faster deterioration of the properties of the mixtures. This means that binders of appropriate quality should be used in the process of producing asphalt mixtures, which will provide the mixtures with sufficiently high technical properties. The tested asphalt mixtures are differentiated according to the type of bitumen modifiers: styrene–butadiene–styrene copolymer (SBS) and crumb rubber (CR). The article presents the tests results of the stiffness modulus using the 4PB-PR method. This test has a high correlation with regard to “in situ” tests. The research proved that each of the modifiers used increased the stiffness modulus of low-noise asphalt mixtures. Replacing the mineral aggregate with 30% RG leads to a tenfold decrease in the stiffness modulus. In the entire range of analyzed temperatures, mixtures with the use of modifiers show higher values of the elastic component of the stiffness modulus, as evidenced by lower values of the phase angle.

Reclaimed Asphalt Pavement Binder Extraction and Recovery Evaluation and Their Effects on the Recycling Agent Assessment

The use of reclaimed asphalt pavement (RAP) has proved to be an advantageous alternative for the restoration and construction of new roads, with regard to the economical and environmental performance of the recycled material. However, one of the concerns about the use of RAP in the production of new asphalt mixtures is related to its inherent variability, manifested mainly in the asphalt binder. Some procedures to recover the aged binder are commonly used, such as extraction with solvents and recovery applying distillation techniques. These methods might change the intrinsic properties of the asphalt binder (e.g., rheological and chemical characteristics), which may lead to flaws in the dose of the recycling agent. The present study evaluated the variability of the techniques of asphalt binder extraction-recovery from a RAP source, and its effects on the final assessment of binder blend between RAP binder and a softer binder for recycled hot mix asphalt. The results show that automated extraction provided statistically satisfactory values for determination of the RAP binder content. The recovery method conditions, however, were not efficient with regard to solvent removal for 40% of the analyzed RAP samples. Pearson’s coefficients indicated a weak correlation between RAP binder aging indices and its rheological behavior, probably because of the presence of solvent. Tetrachlorethylene (TCE) spectrum band at wavelengths of 903 to 915 cm−1 tends to affect binder stiffness more than wavelengths of 771 to 783 cm−1, underestimating high temperature continuous performance grade ([Formula: see text]) and consequently the binder blend results.

Prelimitary study about use of secondary lead smelting slag in the production of asphalt mixtures

En las últimas décadas se ha presentado un rápido incremento en la producción de residuos industriales. Para la mayoría de los residuos no se encuentra un uso efectivo y causan una crisis de disposición, contribuyendo así a los problemas ambientales. Este trabajo se basa en la valoración de una escoria secundaria de plomo, como agregado en mezclas asfálticas. La escoria proviene de una industria colombiana que se dedica a la producción y comercialización de baterías de plomo-ácido. Se caracteriza por tener una forma amorfa, está compuesta por óxidos de hierro, azufre, sodio, entre otros. El objetivo del trabajo fue realizar un estudio preliminar sobre la viabilidad técnica y ambiental de la aplicación de una escoria de fundición de plomo secundario en mezclas asfálticas, con el propósito de aprovechar y darle un valor agregado a dicho residuo. Se realizó una caracterización del residuo, en cuanto, al tamaño de partícula, composición química y mineralógica; además se midieron parámetros de calidad para agregados en mezclas asfálticas, así como también se realizó el ensayo de Procedimiento de Lixiviación Característico de Toxicidad (TCLP por sus siglas en inglés) para determinar las características tóxicas de la escoria. Se observó que la escoria secundaria de plomo tiene potencial para ser utilizada en mezclas asfálticas, cumpliendo con los estándares límites de toxicidad.

Influence of thermal aging and long term-aging on Ni and V content in asphalt fractions and their determination in air particulate matter from asphalt mixing plants

Ni and V can contribute to the deterioration of asphalt pavement by catalyzing the oxidation of some organic molecules present in the binder structure. In this work, the influence of the aging process on Ni and V compounds was studied by comparing the concentration of these two metals in the maltenic and asphaltenic fractions of virgin and aged asphalts. Long-term aging process was simulated by the combination of the rolling thin film oven test (RTFOT) and the SUNTEST method. The results showed that up to 56% of Ni and 53% of V were lost after aging. The greatest changes were observed for the acidic subfraction of both maltenes and asphaltenes. RTFOT/SUNTEST process was also compared to thermal aging using an extraction and collection device (DEC). All V losses were due to the emission of its volatile compounds during thermal aging. Ni losses were attributed to both UV–VIS radiation and sample heating. The presented results help to understand the behavior of both metals during asphalt aging, which has important economic value and can be useful to find solutions that delay the aging process. Ni and V were also determined in the organic fraction of air particulate matter from two asphalt mixing plants. Concentrations of Ni and V ranged from 0.42 to 0.84 ng m−3 h−1 and from 0.08 to 1.79 ng m−3 h−1, respectively, showing that the production of asphalt mixtures can contribute to the air pollution through the emission of Ni and V compounds.

Effects of retrieving powder on mechanical and shrinkage properties of vertical vibration compacted cement-stabilized macadam

Retrieving powder (RP) is the main by-product of asphalt mixture production, and its application in cement-stabilized macadam (CSM) helps control environmental pollution by reducing the need for waste dumps. To investigate the mechanical and shrinkage properties of CSM that contains RP, CSMs with six RP contents were produced via the vertical-vibration compaction method (VVCM). The unconfined compressive strength (UCS), splitting strength (SPS), drying shrinkage, and temperature shrinkage were evaluated and the mechanical strength prediction model of CSM was established. Then, the factors influencing the mechanical behavior were analyzed. Results show that the compressive strength of VVCM-compacted CSMs had a correlation of 90% with the field-core samples. The mechanical strength growth law of the CSMs can be accurately predicted using the proposed strength prediction model. Moreover, the unconfined compressive strength of CSM demonstrated a parabolic trend with increasing RP content, and an optimum amount of RP existed; however, the splitting strength linearly increased. The drying shrinkage and temperature shrinkage resistance of the CSMs both decreased depending on the increase of RP content but within reasonable limits. This study provides a novel alternative for the design and application of a new pavement structure.

Uso de Grano de Caucho Reciclado para mejorar la resistencia y durabilidad en pavimentos: una revisión literaria

For several years now, globally, large quantities of tire rubber have been discarded, which exacerbates the problem of environmental pollution. A good alternative to mitigate this problem and at the same time take advantage of it in an efficient way is to obtain granulated rubber from recycled rubber to use it in pavements since it improves its resistance and durability. The objective of this document was to carry out a systematic review of the literature on the main processes to produce asphalt mixtures and the way in which the use of recycled rubber grain (CBR) affects the design and improvement of the physical and mechanical properties in the asphalt. 50 articles indexed in the Scopus database between 2015 and 2021 on recycled rubber, incorporation of granulated rubber in asphalt mixtures and the physical and mechanical properties of granulated rubber mixed with granular soils in asphalt were reviewed. After investigating in different articles, it was determined that the most important processes to include CR in asphalt mixtures are the dry, wet and semi-humid process. It is concluded that the use of CBR in its mixture improves the mechanical properties of asphalt, such as the increase in the modulus of rigidity, the increase in resistance to humidity, the lengthening of its useful life, and even has applications in the damping of vibrations in construction sites. civil construction.

The Impact of the RAP Cluster Dissociation on Gradation and Shape Properties of Aggregates from Recycled Asphalt Mixtures

Abstract The presence of clusters in reclaimed asphalt pavement (RAP) is a critical point that affects the RAP homogeneity. In this phenomenon, different RAP particles are working together as a single aggregate. The cluster dissociation occurs during hot asphalt mixture production and compaction in the field. This research is concerned with the impact of the cluster disintegration on the recycled asphalt mixture aggregate properties. Stages of binder extraction were performed in six RAP materials to partially activate the RAP binder and create different levels of cluster dissociation from 0 to 100 %. Then, the gradation curve and the aggregate shape properties were obtained for each level. Using a gradation curve (without RAP) as a reference, a hypothetical recycled asphalt mixture was created with different RAP percentages to investigate the impact of cluster dissociation on the aggregate properties of the recycled mixture. The results indicate that the RAP aggregate properties are significantly affected by the cluster dissociation. Besides, there was a significant impact on the partial cluster dissociation, because of RAP-binder activation, on the gradation curve and aggregate shape of the recycled mixture, mainly when the level of RAP-binder activated is between 40 and 70 %.

Preventing emissions of hazardous organic compounds from bituminous composites

This study introduces a novel method to sequester hazardous organic compounds that are continuously emitted from bituminous composites during the service life of roadways, airports, bridge decks, roofs, and other exposed bitumen-covered surfaces. It has been recently reported that such emissions are not limited to high temperatures during the production of asphalt mixtures or paving operation; there are continuous emissions at ambient temperatures, and the emissions significantly worsen when surfaces are exposed to solar radiation or high temperatures. The loss of these compounds from bituminous composites negatively impacts both air quality and the durability of bituminous composites. This study creates an inherent scavenging system to reduce hazardous emissions from bituminous composites by using two abundant urban wastes: waste cooking oil, and end-of-life plastics containing polyethylene terephthalate (PET). We hypothesize that the superior durability of PET can be exploited to extend the durability and service life of the built environment that is associated with increased retention of bitumen's volatile organic compounds. Oil treatment of PET enhances the compatibility of PET with bitumen and improves bitumen capacity to retain volatile compounds. Our laboratory experiment shows that bitumen containing oil-treated PET is more resistant than neat bitumen to solar radiation; after 200 h of accelerated laboratory aging, the chemistry-based aging index and rheology-based aging index were significantly lower for bitumen containing oil-treated PET compared to neat bitumen. Our modeling based on density functional theory (DFT) verifies the effective coating of the PET surface via oil treatment and the capability of oil-treated PET to retain some organic compounds in bitumen. DFT modeling performed on six small organic compounds of bitumen showed a better interaction energy between these organic molecules and PET-oil chains compared to PET-PET chains. This study's outcomes highlight the significant role of oil-treated PET in improving the durability of bitumen and in reducing the hazardous emissions of bitumen, thereby promoting better air quality, resource conservation, and sustainability in the built environment.

The Performance Evaluation of Asphalt Mortar and Asphalt Mixture Containing Municipal Solid Waste Incineration Fly Ash.

The aim of the research is to quantify the property of asphalt mortar and asphalt mixture containing municipal solid waste incineration (MSWI) fly ash. The potential of partially replacing mineral fillers with MSWI fly ash in asphalt mixture production was investigated. Five different MSWI fly ash replacement ratios, which include 0%, 25%, 50%, 75%, and 100%, were adopted to assess the influence of fly ash dosage, and the optimum fly ash replacement ratio was proposed. The rheological characteristics of asphalt mortar with MSWI fly ash were assessed with the dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The high temperature properties of the mixture with MSWI fly ash were assessed with the Marshall stability test and the rutting test. The low temperature cracking property was determined with the indirect tensile strength test at low temperatures. The moisture stability property was identified with the immersed Marshall test and the freeze-thaw cycles conditioned indirect tensile strength test. Based on the test results, the addition of fly ash and mineral filler remarkably increased the ǀG*ǀ of the asphalt mortar. The δ of asphalt decreased as the dosage of fly ash and mineral filler increased. The addition of fly ash and mineral filler degraded the low temperature characteristics of the mortar. Fly ash improved the high temperature characteristics of the asphalt mixture. The asphalt mixture with MSWI fly ash was more susceptible to thermal cracking than the control sample. The addition of fly ash weakened the moisture stability of the asphalt mixture. In order to guarantee the low temperature characteristics and the moisture susceptibility of the asphalt mixture, the fly ash replacement ratio was recommended to be set around 25%. With proper mixture design and fly ash dosage, the asphalt mixture would have adequate performance, as well as reduced environmental impact.

Application of a novel EWMA-ϕ chart on quality control in asphalt mixtures production

Traditional Shewhart control charts have insufficient detection capabilities for the volatility of means in asphalt mixture production. This paper proposes an exponentially weighted moving average (EWMA) control chart to achieve quality control (QC) in asphalt mixture production based on the statistical process control (SPC) theory. We established a mathematical model of multiple-source variation and considered the effect of three sources of variation including internal variations in materials, variations between materials and variations between material batches in asphalt mixtures production. We analysed the differences between the Shewhart, Cumulative Sum (CUSUM) and EWMA control charts in practical engineering. The results show that the detection efficiency of the EWMA control chart is higher when the offset is larger, while the sensitivity is not sufficient, particularly when the offset is smaller. Therefore, in the proposed EWMA-ϕ control chart, parameters were constantly optimized by an exhaustive search optimization procedure to obtain the minimum extra quadratic loss (EQL) and performance comparison index (PCI) values to optimize the average production length (APL) that could enhance the detection ability over the entire shift range. Finally, a case of key indicator control for asphalt mixtures was introduced, and results showed that the APLs of CUSUM, EWMA and EWMA-ϕ control charts were 13, 9.14, and 7.88 days (taking temperature indicator as an example), respectively, which demonstrates that the EWMA-ϕ has timeliness superior to that of the EWMA control chart and the EWMA-ϕ control chart is more sensitive to the offset (particularly when small) for quality detection data. In addition, it showed significant superiority under any indicator monitoring, which illustrates that the proposed control chart is potentially generalizable to the QC of asphalt mixtures production.

Transformation of the chemical properties of soils in the zone of influence of the asphalt concrete plant

The article presents the results of studies of technogenically contaminated soils in the territory of an asphalt concrete plant. Toxic dust generated by the operation of the enterprise pollutes the air and settles on the surface of the soil. This anthropogenic impact is visually manifested in a decrease in the projective cover of the vegetation cover in the Baiterek region of the West Kazakhstan region. The studies represent the study of such parameters as wind direction, soil composition for readily soluble salts, heavy metals and oil products. In the analysis of soils for heavy metals and oil products, spectral and fluorescent methods were used. Easily soluble salts in an aqueous extract were determined by electrochemical, gravimetric, and direct titration methods. The dynamics of the accumulation of pollutants in the soil corresponded to the winds operating in the zone of the plant. In the northern and western directions from the plant, the analysis of soils for lead and cobalt showed that the permissible norms were exceeded by 5.8 and 6.1 times. The dynamics of petroleum products in the plant's soils also revealed that the approximate permissible norms were exceeded. Analysis of the salt content in the technogenic sediment showed an average salinity within the entire production site. As a result of the research carried out, we found out that the functionality of the plant, represented by the welding, boiler, asphalt mixture production units and the vehicle fleet, really exerts a technogenic load on the soil and vegetation cover. The authors recommend excluding the construction of residential buildings and livestock grazing in the northern and western directions from the design.

Comparative life cycle assessment of reprocessed plastics and commercial polymer modified asphalts

The use of waste plastics in asphalt mixtures as binder modifiers is an alternative to commercial polymers, which can contribute to solving problems related to waste management. It is anticipated that using reprocessed plastics in pavement construction decreases environmental impacts associated with the production of asphalt mixtures. The present study compares the environmental benefits and burdens of the application of reprocessed plastics (RPs) in asphalt mixtures in the dry process compared with those of commercial polymers. All processes for the production of plastic pellets from waste plastics, including the collection, sorting and reprocessing of waste materials, are considered, and the contribution of each stage to total impacts is identified. The results of cradle-to-gate life cycle assessment of a declared unit of one tonne of asphalt manufactured with RPs are compared with commercial polymers and conventional asphalt mixtures. The results show that, although the utilization of RPs increases the environmental burden of the manufacture of asphalt mixtures, it offers an environmentally friendly alternative to commercial polymers. Moreover, the high contribution of the collection stage to the resource damage category of RP pellet production highlights the importance of waste collection management in order to minimize the consumption of resources and associated impacts. Although the environmental benefits of RP modified asphalts decrease with increasing mixing temperature, these mixtures are environmentally superior to competing alternatives at lower temperatures and the optimum bitumen content of 5.3%. However, the emission of toxic fumes when temperature increases are subject to further assessment.

Assessing creep properties of asphalt binder, asphalt mastic and asphalt mixture

In this article, creep properties of asphalt binders and asphalt mastics (binder filler composite) are tested in the Dynamic Shear Rheometer using a single shear creep test and considering steady-state flow conditions. These tests are performed for a set of 10 different asphalt binders and 18 corresponding asphalt mastics. The same material combinations are used to produce asphalt mixtures in the laboratory, which are then subjected to cyclic compression tests to assess the creep properties of the asphalt mixture. Finally, the creep properties resulting from asphalt binder tests, asphalt mastic tests and asphalt mixture tests are comparatively analysed in terms of the material-specific creep rates. The results show reasonable and sound correlations across the different material scales. The authors concluded that the asphalt binder has a significant impact on the creep behaviour of the corresponding asphalt mixture.

Viability of Using High Amounts of Steel Slag Aggregates to Improve the Circularity and Performance of Asphalt Mixtures

Steel slag is a byproduct generated as waste during the steelmaking process and can be considered a cost-effective and environmentally acceptable alternative to replace natural aggregates. Using steel slag aggregates (SSA) to produce asphalt mixtures promotes sustainability and circular economy principles by using an industrial byproduct as a raw material. Thus, this work mainly aims to design more sustainable asphalt mixtures with high amounts of SSA that fit the circular economy expectations. This work developed two asphalt mixtures with SSA for surface (AC 14 surf) and binder/base (AC 20 bin/base) courses. Initially, the excellent wearing and polishing resistance of SSA and their good affinity with bitumen demonstrated the potential of this byproduct to be used in asphalt mixtures. Then, when analyzing the influence of using two different SSA incorporation rates (50% and a percentage close to 100%) in both asphalt mixtures, it was concluded that the use of SSA should be limited to 75% to avoid excessive air void contents and durability problems. The importance of considering the different particle densities of SSA and natural aggregates was highlighted during the mix design by defining a relationship between an effective and equivalent binder content. Finally, the mechanical performance of AC 14 and AC 20 with 75% SSA incorporation was compared to identical conventional mixtures produced with natural granite aggregates. The results obtained showed that the asphalt mixtures with 75% SSA have some workability problems due to the rough and porous surface of SSA. However, they present an excellent water sensitivity and permanent deformation resistance, surpassing the performance of the conventional asphalt mixtures.

Using Waste Plastics as Asphalt Modifier: A Review.

The use of waste products in the production of asphalt binders and asphalt mixtures has become widespread due to economic and environmental benefits. In particular, the use of recycled waste plastic in asphalt binders and mixtures is gaining more attention. This review presents analyses and comparisons of various forms of waste plastic used in asphalt modification, and approaches to incorporating waste plastic into asphalt mixtures, both for single and composite modifications. It focuses on the properties of waste plastics, asphalt binders, and asphalt mixtures. Overall, the incorporation of plastic waste into asphalt mixtures can significantly improve high-temperature performance and has potential economic and environmental benefits. The performance of modified asphalt is highly dependent on multiple factors, such as waste sources, waste plastic dosages, blending conditions, and the pretreatment methods for waste plastic. There are different ways to apply waste plastics to blend into a mixture. In addition, this paper discusses the current challenges for waste plastic-modified asphalt, including the stability, low-temperature performance, modification mechanism, and laboratory problems of the blends. The use of chemical methods, such as additives and functionalization, is considered an effective way to achieve better interactions between waste plastics and the binder, as well as achieving a higher sufficiency utilization rate of waste plastics. Although both methods provide alternative options to produce waste plastic-modified asphalt with stability and high performance, the optimal proportion of materials used in the blends and the microcosmic mechanism of composite modified asphalt are not clear, and should be explored further.

EXPLORING THE EFFECT OF ORGANIC ADDITIVES ON PHYSICAL PROPERTIES OF BITUMEN

Warm additives had wide popularity in recent years due to saving in energy and lowering emissions dealt with asphalt mixture production. Warm Mix Asphalt (WMA) is produced by using foaming technology or reducing -viscosity additives of binder to enhance the rheological properties. In this study, organic-based additives (Asphaltan A and Asphaltan B) are used to investigate their effect to minimize the viscosity and lower the temperature of asphalt mixture production. Bitumen is mixed with three doses of each additive: 1, 2, and 3% of its weight. The binder viscosity was measured by rotational viscometer with and without the additives at three different temperatures. The study showed that the organic additives have a positive impact on the behavior of the binder in terms of viscosity reduction and made enhancements in terms of bitumen properties. This result could be useful in the reduction of production temperature and quantity of odour emissions.