Superpave Method Research Articles

Development of an Energy-Efficient Method of Obtaining Polymer-Modified Bitumen with High Operational Characteristics via Polymer–Bitumen Concentrate Application

New requirements for the operational reliability of roads make the utilization of polymer-modified bitumen (PMB) more common in road construction. The application of polymer-modified bitumen based on traditional technology for the production of asphalt mixtures is associated with technological and economic difficulties and does not provide proper adhesion to the mixture’s mineral components. In addition, the method of producing a binder over a long time at high process temperatures leads to increased aging, which significantly reduces the service life of the material in the pavement. This paper presents the results of studies on the effect of polymer–bitumen concentrate (PBC) consisting of styrene–butadiene–styrene, plasticizer, and surfactant on the bitumen characteristics. It has been established that the use of PBC in the bitumen binder leads to an increase in the temperature range of plasticity, softening temperature, elasticity, and cohesive strength with a decrease in the viscosity of the modified bitumen. With a complex modifier rational content of 8% by weight of bitumen, the temperature range of plasticity is 79 °C, and elasticity is 82%, which exceeds the parameters of the factory PMB-60 based on SBS polymer. Tests of binders using the Superpave method allow classifying the modified binder to the PG 64-28, which shows an increase in the temperature range of viscoelastic properties by 6 °C compared with the binder produced by traditional methods. Thus, the expediency of using a complex additive containing a polymer and surface-active substances (surfactants) that can be distributed in bitumen without the use of a colloid agitator and plasticizer has been proven to improve the quality of an organic binder.

Investigating the Dynamic Creep and the Tensile Performance of Zeolitic Tuff-modified Warm Asphalt Mixtures

Aims This research investigates the effect of adding natural Jordanian Zeolitic tuffs to the SUPERPAVE asphalt mixture at the dynamic creep and the indirect tensile performance. Background Rutting and fatigue are considered the most common types of distress that affect pavements all over the world. Many factors can affect these properties, such as different aggregate properties, asphalt grades, and properties, as well as the type and amount of the mineral filler. Mineral fillers play an important role in enhancing the asphalt mixtures' performance by filling the voids in the mixture besides improving the cohesion of the binder as it has a small weight in addition to a very large surface area. Generally, the powder of limestone is the most used type of filler. However, studies showed that many materials could also be used as mineral fillers successfully. The focus of this study is using natural Jordanian Zeolitic tuff as a mineral filler. Jordanian zeolitic tuff mainly consists of Phillipsite, chabazite, and faujasite, which are considered the most abundant Zeolitic tuff minerals. The pyroclastic material is widely distributed in the Badia region of northeast Jordan. Zeolitic tuffs are located in Jabal Aritayn (30km northeast of Azraq), Tlul AlShahba (20 km east of Al Safawi), Tal Al-Rimah (35 km northeast of Al Mafraq), and other small deposits in central and south Jordan. Objectives The aim of this research was to study the impact of Zeolitic tuffs on overall Superpave asphalt mixture performance. Methods The specimens were prepared using the optimum asphalt content obtained by the SUPERPAVE method. Dynamic Testing System DTS-16 was used to apply both dynamic creep and indirect tensile tests that give a good idea about the rutting and fatigue behavior of asphalt mixtures. Both tests were conducted at 25 °C. Results The Zeolitic tuffs modified asphalt mixtures have lower accumulated strains and higher creep stiffness compared to the control mixture. Subsequently, the indirect tensile test results showed that the modified asphalt mixtures have a higher resilient modulus than the control asphalt mix. Generally, using Zeolitic tuffs as a modifier of asphalt mixtures enhanced the rutting and fatigue resistance. The results showed that asphalt mixtures fortified with 25% Zeolitic tuffs emerged as the best contenders for rutting resistance. Also, mixtures enriched with 50% Zeolitic tuffs stood out in fatigue resistance performance. Conclusion The best dynamic creep performance was by adding 25% Zeolitic tuffs by the mineral filler mass, while the best resilient modulus was by adding 50% Zeolitic tuffs by the mineral filler mass. Other The overarching goals encompass understanding the dynamic creep behavior of Zeolitic tuff-infused asphalt blends, deciphering its indirect tensile performance, pinpointing the ideal replacement ratio for mineral fillers, and drawing a performance comparison between WMA and conventional Hot Mix Asphalt (HMA) compositions.

Performance Evaluation of Asphalt Concrete Incorporating Steel Slag Powder as Filler under the Combined Damage of Temperature and Moisture

Recycling steel slag into asphalt concrete is an important way to save natural resources and protect the environment. The high asphalt absorption and adsorption and the sensitivity of steel slag aggregate (SSA) to the combined damage of temperature and moisture (volume expansion and poor durability under freeze-thaw cycle damage) still pose risks for the use of SSA in asphalt concrete. It is urgent to develop new utilization methods of steel slag. With this in mind, the material properties of steel slag powder (SSP) and performance characteristics of asphalt concrete incorporating SSP filler were evaluated in this research. The SSP was prepared in the laboratory by grinding steel slag with a particle size of 2.36–4.75 mm. Firstly, the material properties of SSP including the specific surface area, particle gradation, apparent density, chemical compositions, and thermal stability were analyzed. Steel slag (2.36–4.75 mm) and common limestone powder (LP) filler were used as control groups. The grindability of steel slag and the advantages of using SSP as a filler in asphalt concrete were preliminarily analyzed based on the test results of material properties. Then, the Superpave method was used to design asphalt concrete incorporating SSP and LP. Considering that steel slag is sensitive to the combined damage of temperature and moisture, the main engineering performance of asphalt concrete after the combined damage of temperature and moisture was evaluated to further reveal the feasibility of using SSP as a filler. Two combined damage modes, namely hot water damage and freeze-thaw cycle damage, were applied. Results suggest that although the steel slag is more difficult to grind compared to limestone particles, grinding steel slag into SSP has improved the uniformity of its material properties. Good uniformity of material properties, high alkalinity, and excellent thermal stability of SSP give it some advantages in its application in asphalt concrete. Although the freeze-thaw cycle damage has a slightly more significant effect on the engineering performance of asphalt concrete than hot water damage, compared to the asphalt concrete with LP filler, even after freeze-thaw cycle damage for three cycles asphalt concrete incorporating SSP still possesses comparable or better volume stability, mechanical performance, high-temperature deformation resistance, low-temperature crack resistance, fatigue crack resistance, and fatigue durability.

Features of dimentional design system for asphalt concrete mix on superpave technology and bituminous binder of pg grade determination

Introduction. This article discusses the technology of designing asphalt concrete pavements, using the Superpave method. The Superpave (SUperior PERforming Asphalt PAVEments) system was developed by the Strategic Highway Research Program (SHRP) in the USA. The aim of the program was to find new ways of designing asphalt concrete pavements that will work better at extreme temperatures and heavy traffic loads.Currently, the system of volumetric design of asphalt concrete mixtures is being actively implemented in Russian road construction industry. This is an adaptation of the American Superpave method and is being implemented in our country in the form of a series of new standards. The Superpave volumetric and functional design system in particular addresses several pavement-related problems: permanent deformation, which results from poor asphalt mix shear strength at high temperatures, and low temperature damage, which occurs when the asphalt pavement is subjected to stress exceeding the compressive and tensile strength. The elimination of the above problems is carried out due to the most reasonable selection of the components of the asphalt concrete mixture.Materials and methods. Studies of bitumen binders were carried out according to the methods laid down in the technical requirements: GOST R 58400.1-2019 Public roads. Materials binding petroleum bitumen. Technical requirements taking into account the temperature ranges of operation.The selection of the PG brand of bitumen binder using Superpave technology was carried out using the example of a polymer-bitumen binder that meets the requirements of GOST 52056-2003 PBB 90 (sample 4) and a bitumen binder obtained from tar with the addition of thermoplastic elastomer (hereinafter referred to as TEP) of the SBS type that meets the requirements of GOST 52056-2003 PBB 90 (sample 3).Results. The article provides a review of technical documentation in order to familiarize with the methodology for selecting the brand of bituminous binder for asphalt mix. In the course of the research, the technological features of the system of volumetric functional design of the asphalt concrete mixture according to the Superpave method, as well as the determination of the brand of bituminous binder, were considered. The introduction of foreign experience in road construction can contribute to the improvement and improvement of the quality of Russian roads.Discussion and conclusions. Based on the experimental data carried out in the work, it can be concluded that the goal has been achieved, namely, the brands of bitumen binder have been selected using Superpave technology that meet the requirements of GOST R 58400.1–2019 and GOST R 58400.2-2019, namely for polymer-bitumen binder (PBB 90 according to GOST 52056-2003) – PG 58-28, and on the basis of tar with the addition of SBS – PG 64-28 grade TEP, respectively.Having studied the physical and chemical characteristics of the initial reagents, as well as the results of numerous chemical experiments, brands of PG bitumen binders were selected using Superpave technology and depending on climatic conditions and transport loads GOST R 58400.1-2019 Public roads. Materials binding petroleum bitumen. Technical requirements taking into account the temperature ranges of operation and GOST R 58400.22019 Public roads. Materials binding petroleum bitumen. Technical requirements taking into account the levels of operational transport loads.

ОГЛЯД МЕТОДІВ ПІДБИРАННЯ СКЛАДУ АСФАЛЬТОБЕТОННИХ СУМІШЕЙ

Introduction. Asphalt mixtures are the most widely used road construction material for the arrangement of the top layers of road pavement. Asphalt mixtures are also used to arrange airfield runways, bridges deck surfacing, streets, pedestrian and cycle paths, etc. There is a large number of asphalt mixtures types that differ by grading, the largest nominal aggregate size, crushed stone content, crushed and uncrushed sand content, quality of components, and viscosity of the bitumen binder. Problem statement. The national method for asphalt mixture design is very similar to the Marshall method and the Superpave method in terms of determining the optimal bitumen binder content by the bulk properties of asphalt concrete. The only difference is that, according to the Marshall and Superpave methods, the optimal bitumen content is the one with an air pore content of 4.0 %. However, in accordance with the national method, the design air pore content varies depending on the type of asphalt mixture. A significant innovation of the Superpave method is the determination of asphalt performance indicators, such as rutting resistance, crack resistance, and resistance of the material to fatigue cracking. Apparently, these methods should also be implemented in Ukraine over time. Purpose. Analysis of the methods for asphalt mixtures design. Materials and methods. Analysis of literature sources on various methods of asphalt mixtures design. Results. The analysis of literary sources on different methods of asphalt mixtures design was carried out. Conclusions. The use of different methods of asphalt mixtures compaction can lead to the production of asphalt concrete with different volumetric properties, which will affect both the optimal bitumen content and the performance of asphalt concrete, thus further research should be aimed at defining the effect of the compaction method on the volumetric properties of asphalt concrete and their relationship with the production compaction of asphalt mixtures.

Laboratory Performance Evaluation of Alternative Approaches to Incorporate Recycled Binder Availability into Mixture Design Procedures

There is currently uncertainty in how to properly account for partial recycled binder availability within asphalt mixture design procedures so that content of recycled asphalt materials (RAM) can be maximized while still achieving good performance. This study evaluates and compares two alternative approaches to consider partial availability in mixture design: availability adjusted mix design (AAMD) and corrected optimum asphalt content (COAC). The AAMD method revises the calculation of volumetric properties by considering unavailable binder as part of the bulk aggregate volume and uses the RAM gradation to design the aggregate structure. In the COAC method, a mixture is first designed following the conventional Superpave procedures and then a specified increase to the virgin asphalt content is made. Two “control” mixtures containing RAM are evaluated that were originally designed according to the standard Superpave method. Alternative designs were prepared according to the COAC and AAMD methods while maintaining the RAM content in the respective control mixture. Baseline virgin mixtures and one mixture designed following the AAMD method with higher reclaimed asphalt pavement (RAP) content were also prepared. The cracking and rutting performance of the resultant mixtures was evaluated. The results show that the AAMD and COAC approaches lead to an improved cracking performance compared with the control mixtures even for the mixture designed with AAMD at a higher RAP content. However, the mixture designs prepared according to the COAC method presented increased rutting whereas the AAMD mixtures remained at the same level as their respective control mixture.

Utilization of Construction Waste Recycled Powder as Filler in Asphalt Concrete.

Processing construction waste into aggregate and reusing it in asphalt pavement is beneficial in terms of environmental protection and resource utilization. However, recycled aggregate (RA) possesses some property defects. Therefore, RA usually needs to be strengthened by modification technologies prior to use. In order to promote the convenient and low-cost utilization of construction waste, a new method of preparing construction waste into powder and using recycled powder (RP) as asphalt filler is proposed in this research. The property defects of RA and the applicability of RP used as filler were first analyzed based on their material characteristics. Then, asphalt concrete with RP was designed according to the Superpave method, and the engineering performance of the asphalt mixture was further investigated. According to the results, we recommend the use of acidic RP in combination with other highly alkaline fillers, such as Portland cement (PC), with a suitable blending ratio of RP to PC of 1:1. Preparing asphalt concrete with filler composed of RP and PC can achieve satisfactory engineering performance.

Optimizing asphalt mix design through predicting effective asphalt content and absorbed asphalt content using machine learning

Superpave mix design procedure is still empirical. Random and lengthy trials in a laboratory during the design procedure can consume immense manpower and materials resources. To simplify and accelerate the Superpave mixture design procedure, this study explored the use of machine learning models to achieve an automated and timesaving mix design method through predicting effective asphalt content (Pbe) and absorbed asphalt content (Pba). Five different machine learning (ML) algorithms including Support vector regression (SVR), bagging with ridge regression, Random Forest, Adaptive boosting (AdaBoost), and Gradient boosting were trained. The inputs related to mixture design include aggregates gradation, the bulk specific gravity of aggregates, blend absorption, air void, PG grade of the asphalt binder, and the number of gyrations (Ndes). The kernel density estimation was used to detect outliers of the datasets. The effect of different methods used to encode PG grade, which is categorical variables, on the performance of ML models was analyzed. The performances of ML models were evaluated by calculating different performance scoring metrics, such as coefficient of determination (R2), root means square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE). The improved mix design procedure based on an ML model was proposed. The result showed that compared to other encoding methods, the ordinal encoding method used to encode the variables of PG grade can achieve the best performance of ML models. The Gradient boosting algorithm (R2 = 0.9479, 0.9459) was found as the best estimator to predict the Pbe, and Pba, respectively, compared with those obtained by other machine learning models. Furthermore, determining Pb through predicting Pbe and Pba indirectly with ML models was more accurate than predicting Pb directly with ML models. Therefore, the Gradient boosting model was used in the improved mix design procedure. A case study was implemented to verify the feasibility of the proposed mix design method. The gradation and the optimal asphalt content obtained from the proposed method with the Gradient boosting model was consistent with that obtained by the traditional Superpave method with laboratory tests.

Structural sensitivity of an asphalt pavement to asphalt binder content and mix design method

The goal of this study was to analyze the structural sensitivity of a flexible pavement, whose asphalt layers underwent variations in its mechanical properties due to the asphalt binder content and the mix design method Marshall and Superpave. A variation of ±0.5% within the optimum asphalt binder contents was used (service tolerance) considering possible permissible variations in the asphalt binder content during the asphalt mixture manufacturing process. The values of resilient modulus and indirect tensile strength (Brazilian test) of the resulting asphalt mixtures were applied to the reference pavement structure analyzed by the me-PADS software. The results show that the variations in the asphalt binder content and the asphalt mixtures design method influence the mechanical properties and corresponding structural responses of the pavement investigated: the asphalt layers designed by the Marshall method presented greater sensitivity to the variation in asphalt binder content, which may constitute a technical differential of asphalt mixtures designed by the Superpave method.

Design and performance evaluation of Bi-block precast rubberized epoxy asphalt trackbed for railway

With the objective of improving the construction efficiency and provide excellent performance of railway trackbed, the dry-mixed rubberized epoxy asphalt mixture (DREAM) was proposed to prepare the bi-block precast epoxy asphalt trackbed structure. Based on the coarse aggregate voids filling method combining the similitude method for gradation design of coarse aggregate and Superpave method for gradation design of fine aggregate, the gradation of mixture was determined. To analyze the feasibility of proposed asphalt trackbed material for railway structure, the fatigue test under 3 million repeated loadings and semi-circular bending test under the effect of aging and freeze–thaw cycles were conducted. After comprehensively understanding the test results, it was concluded that the DREAM with 11 wt% crumb rubber (CR) exhibited a better fatigue and fracture resistance compared with another type of DREAM with a lower content of CR, i.e., 9 wt%. Owing to a larger amount of CR, the DREAM with11 wt.% CR owned an outstanding ability of deformation recovery and ductile failure. Therefore, it was determined to be an effective asphalt trackbed material. Once the designed DREAM was selected, the corresponding bi-block precast epoxy asphalt trackbed finite element model was generated by using the ABAQUS software for the life-time deformation analysis through the time–temperature superposition principle. The numerical study and calculation of time–temperature conversion indicated that the train loading was mainlyresponsibleforthe permanent deformation. The value of permanent deformation caused by the train loadings was two times higher than that caused by static loading (e.g., steel and fastening).

Effect of the incorporation of sugarcane bagasse fibers in asphalt mixture dosed by the Superpave method

Sugar industry waste bagasse contains many natural fiber materials, and the application of natural fibers in asphalt mixes such as SMA (Stone Matrix Asphalt) has become an attractive alternative for the construction of flexible pavements. This study aims to evaluate the mechanical performance of an asphalt mixture modified by incorporating 0.3% sugarcane bagasse fiber and with a size of 20 mm. The asphalt binder was submitted to penetration, softening point, and rotational viscosity tests to carry out this research, and the aggregates were characterized by specific mass, particle size, and absorption tests. Furthermore, the Superpave dosage was performed to produce the specimens to be evaluated in the splitting tensile strength test, resilient modulus, Marshall stability, and draindown sensitivity. As a result, the modified asphalt mixture presented a better performance in all evaluated strength tests and the leakage content within the standard specifications. Therefore, according to this, re-search, sugarcane bagasse fibers proved to be a viable alternative for SMA-type mixtures. Thus, the application of this material in asphalt paving and improving some essential characteristics can significantly reduce the environmental impacts generated by the inadequate disposal of these residues by sugar mills.

Comparative Study of Hot Asphalt Mixtures Properties Designed by Marshall and Superpave Methods. (Dept. C)

Comparative Study of Hot Asphalt Mixtures Properties Designed by Marshall and Superpave Methods. (Dept. C)

Investigations on the Effects of Styrene Butadiene Styrene in Asphalt Mixture Design

This study aims to determine the effect of using a styrene butadiene styrene modifier with basalt aggregate as coarse particles and using limestone as mineral filler. In general, several modified hot mix asphalt specimens at 4% air voids have been prepared to study the influence of different percentages of SBS (0%, 3%, 4%, 5%, 6%) with various portions of asphalt content (4.5%, 5%, 5.5%, 6%, 6.5%) using Marshall Method and Super-Pave Method. The investigations have shown that using limestone as mineral filler improves the bond strength between the basalt aggregate and the asphalt cement. Moreover, the optimum asphalt content using the Marshall method has been 5% at different percentages of Styrene Butadiene Styrene. On the other hand, super-Pave tests have showed that the best ratio of SBS in the MR test has been 3%, while, in the creep test, it has been 4% and 6% in the loss of indirect tensile strength and fatigue tests. In general, the best asphalt mixture performance is referred to as binder asphalt with 6% SBS.

Evaluación de la efectividad del uso del índice TDI (Traffic Densification Index) para la predicción del comportamiento de las mezclas asfálticas nanomodificadas frente a la deformación permanente

This article shows the results of a study on the evaluation of the use of the TDI (Traffic Densification Index) for the prediction of the behavior of a conventional asphalt mixture and two nano-modified asphalt mixtures (one with 2% of carbon nanotubes, CNTs, and another with 3% of organophilic nanoclay, NA) against permanent deformation. The mixtures were designed with equivalent granulometries and different asphalt binders (a conventional and two nano-modified binders). The design of the mixtures was made according to the Superpave method, and the TDI of the mixture was determined from the curves obtained in the compaction test (%Gmm vs number of cycles). For each mixture under study, two slabs measuring 50 x 18 x 5 cm were compacted on the BBPAC slabs compactor of IFSTTAR (Institut Francais des Sciences et Technologies des Transports, de L'Amenagement et des Reseaux). These slabs were subsequently subjected to the permanent deformation test in the French traffic simulator, Orniereur. The TDI obtained was compared with the performance of the mixtures in the permanent deformation test. The results obtained show that the TDI was not effective in predicting the behavior, in terms of permanent deformation, of asphalt mixtures with asphalt binders different from the conventional binder (nano-modified).

Evaluation of Superpave Moisture Susceptibility Considering Uncertainty

Abstract The existing Superpave method of evaluating moisture susceptibility is deterministic, relying only on the mean values. This technical note presents a new method for evaluating moisture susceptibility considering uncertainty. The method considers the uncertainties of the four measured properties (thickness and maximum load) of conditioned and unconditioned specimens in formulating the uncertainty of the tensile strength ratio (TSR). The probability distribution of TSR is established based on a normality assumption that is verified using Monte Carlo simulation. A simple formula is developed for checking whether the TSR criterion is satisfied, given a specified confidence level. Another formula that incorporates the uncertainty of the TSR criterion is also presented. The proposed method directly considers the uncertainties of the actual test variables and as such takes the current indirect National Cooperative Highway Research Program method of interlaboratory precision estimates one step further.

Investigation of the effect of Crumb Rubber Additive on the Fracture of characteristics of asphalt mixtures in control and asphalt rubber mixtures

The failure of cracking is one of the main concerns regarding the performance of hot mix asphalt (HMA). Since the characteristic of the materials of the mixtures has impact on their cracking potential, the main conception of this research is to evaluate the effect of the type of size and additive percentage of crumb rubber modified (CRM) on the resistance of mixtures to crack at mid and low temperatures. For this purpose, rubber bitumen containing 10% and 15% crumb rubber with fine and coarse sizes with wet process was prepared. Asphalt mixtures with dense and gap grading were designed by using rubber bitumen produced by superpave method. The three-points bending test of semicircle bending sample (SCB) was used to evaluate the fracture characteristics of asphalt mixtures at low and middle temperatures (25°C and -12°C). Accordingly, the failure characteristics of asphalt mixtures were evaluated in two modes with short-term and long-term aging. The failure test results indicated that the produced mixtures with crumb rubbers additive have high resourcing resistance compared to control mixtures (without crumb rubber additive), were also revealed. Mixtures with dense grading and fine crumb rubber have high fracture resistance compared to mix with gap grading and coarse crumb rubber. Also, the increasing of the percentage of crumb rubber improved the resistance of the mixed failure. In general, it can be stated that the addition of crumb rubber increases the fracture resistance of asphalt mixtures which can improve its performance before cracking at mid and low temperatures.

ระยะเวลาที่เหมาะสมของการบ่มตัวอย่างแอสฟัลต์คอนกรีตในห้องปฏิบัติจากการออกแบบโดยวิธีซูเปอร์เพฟ

ระยะเวลาที่เหมาะสมของการบ่มตัวอย่างแอสฟัลต์คอนกรีตในห้องปฏิบัติจากการออกแบบโดยวิธีซูเปอร์เพฟ

Influence of Compaction Method on Rutting Resistance of Hot Mix Asphalt

The main goal of the present investigation is the comparison between conventional Marshall and Superpave design methods for resistance to rutting if applied in the mix design of the wearing course layers in flexible pavements. Detailed work is completed to accomplish the goals of the study by implementing Marshall and Superpave specimens through utilizing aggregate from AL-Taji Quarry and asphalt cement with (40-50) grade from Dourah refinery plant and one sort of mineral filler. Specimens were fabricated by Marshall and Superpave methods and tested by creep tests to evaluate the strain for these mixes. The effect of compaction method and additives were investigated on the performance of these mixes. From the analysis results, it appears that; the Superpave blends are increasingly practical as compared to those with conventional Marshall blends. In addition, adding carbon fibers and lime to the blends decreases the strain mixture. It is additionally seen that the Superpave Gyratory compactor is equipped for accomplishing lower air void contents than the Marshall hammer. Furthermore, the Superpave mix reflects better resistance against permanent deformation. Finally, the present study recognizes the importance of using the Superpave system for design asphalt mix instead of the Marshall method in Iraq.

Rutting performance of asphalt mixtures with gradations designed using Bailey and conventional Superpave methods

This research was conducted to study the possibility of using Bailey method of aggregate gradation in designing Superpave HMA mixtures, and study its effect on rutting performance of these mixtures, and comparing it with rutting performance for asphalt mixtures produced using Superpave gradations.Four aggregate gradations were used in this research including coarse and fine gradations for Superpave and Bailey methods of gradation. Rutting performance was evaluated using the Simple Performance Tester (SPT). Results showed that rutting performance is strongly affected by aggregate gradation; finer mixtures give higher flow number, which means less rutting susceptibility and higher rutting resistant pavement.

ПРОЕКТИРОВАНИЕ И РАСЧЕТ ДОРОЖНОЙ ОДЕЖДЫ МЕТОДОМ СТРУКТУРНЫХ ЧИСЕЛ

Road surface is one of the main components of highways, its condition ensures the safety and speed of traffic. Modern road surface is a complex engineering structure: it consists of layers of road construction materials laid in stages, which have various physical and mechanical properties. These properties are taken into account to ensure the safe movement of vehicles at any time of the year at the estimated speed, while preventing accidents and reducing traffic convenience. The method of structural numbers is one of the methods for calculating roadways. The possibility of its application for the design and calculation of road surface is analyzed. The article shows the possibility of using this rather simple method used in many countries, using a specific example. Since Russia is actively switching to the design of asphalt-concrete mixtures using the Superpave method, which improves the performance of road surfaces, this method has advantages in the design and calculation of road coverings, consisting in ease of use.