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The transport infrastructure’s pavement is made of asphalt layers, placed and compacted. The asphalt mixture is produced in an asphalt mixing plant (AMP) using expensive technological equipment which, when it becomes obsolete and worn out, is replaced with new equipment. One of the main problems related to the replacement process is that when it comes to purchasing new AMPs, the decision making involved is, in most cases, highly intuitive due to a lack of clearly defined criteria. In order to remedy this situation, this work presents an analysis of the correlation between the number of AMPs and the production of asphalt mixtures. Firstly, a correlation analysis was performed based on the European Asphalt Pavement Association (EAPA) data. Secondly, the current situation with the AMPs in European countries was analysed. Furthermore, a case study was performed and a system of nine criteria was created to identify why/when road construction companies operating in the Baltic States buy new AMPs. The weights of the criteria have been established by applying the Analytic Hierarchy Process (AHP) method. It was found that the most important criterion during the decision-making process for road construction companies is increased requirements for improving the quality of the asphalt mixture produced (criteria weight 25.0%). With a weight of 20.6%, the second vital criterion is the possibility of receiving support from European funds. The third criterion is the expectation of having a sizeable asphalt-paving site (weight 20.4%). The other six criteria are also significant, their weights varying between 1.6% and 13.5%. The industrial companies can use the obtained results for designing, producing and selling AMPs and adjusting strategic business plans.

Recycled hot-mix asphalt (RHMA) mixture is produced from reclaimed asphalt pavement (RAP) by adding an appropriate amount of new mineral materials improving the gradation of RHMA, a lower viscosity bituminous binder and a rejuvenator. The manufactured RHMA mixture must meet the same technical requirements as those for the hot-mix asphalt (HMA) mixture made of new materials only. It is also aimed at reducing its cost to the minimum in order to comply with technical requirements for the RHMA mixture in the asphalt mixing plant (AMP). These goals are ensured in the process of determining the composition of the RHMA mixture applying numerical and experimental methods for selecting an optimal content of old and new materials in the mixture. The article presents a method for determining the composition of the RHMA mixture, which allows calculating the maximum allowable percentage of RAP depending on its homogeneity. Setting the established maximum RAP amount as a constant size, the required content of new mineral materials is estimated thus taking into account bitumen capacities. The price of a single ton of the materials making the RHMA mixture and information on technical requirements for the composition of the RHMA mixture assist in applying certain technological restrictions, which makes it possible to calculate an optimal content of the components. The research findings obtained from the representative sample demonstrated that ready-for-use RAP was not homogeneous, and its five properties used for calculating its maximum allowable amount had different variations. The paper presents the algorithms that are actualized using mathematical programming methods upon the application of which the following objectives were solved: the assessment of technological requirements helped to obtain the RHMA mixtures of the cheapest or densest mineral part, and the mixture having the lowest content of bitumen was received. The article discusses mathematical analogues that can be used for determining whether the RHMA of the right gradation can be produced from the available mineral materials and allows analysing the mixtures that do not meet the established requirements thus identifying the causes of inappropriateness. The introduced algorithms can be applied at the initial stage of designing the RHMA mixture thus reducing the duration and cost of the design process. In order to determine whether the calculated content of old and new materials is appropriate, the standard specimens produced and examined in the laboratory need to be confirmed.

Asphalt mixture gradation homogeneity is one of the key factors for proper laying and compaction during road pavement and its long-term maintenance afterwards. To achieve the good quality asphalt mixture homogeneity of aggregates used in road pavement must be kept in mind. Regarding to this, gradation variation of five different granite aggregates fractions (0/2, 2/5, 5/8, 8/11 and 11/16) from one of the largest manufacturing plants in Lithuania were determined in this paper. Total of 244 samples were taken from conveyer belt at the manufacturing place and all the data was evaluated by statistical methods providing histograms with theoretical curves of normal distribution. After that, the results were compared to each other and the requirements issued by Lithuanian road administration authority. Regression analysis was used to determine the dependence of standard deviation of percent passing and the mean percent passing through the sieves. The obtained research findings revealed that the maximum value of standard deviation of this dependence was equal to mean of 50% percent passing. Further investigations should include other aggregates quality parameters variation and its homogeneity throughout different stages of technological and transportation processes. DOI: https://doi.org/10.3846/enviro.2020.601

European Union members seek to establish the principles of a circular economy, which is based on the efficient use of raw materials and resources. This requirement will have an impact on business and in particular on the road construction sector. Hence the need to improve the asphalt mixing plant (AMP) mixing technology utilizing as much as possible reclaimed asphalt pavement (RAP) to produce asphalt mixtures (AM) for road construction. The resources used to produce new AM in the world are endless and becoming more expensive in a time scale. The multi-cycle reuse of RAP producing AM is a priority, when thinking about of economical recycling materials usage and the saving of resources. The design and development of RAP hot recycling in-plant technologies has been in progress for approximately half a century. In high-level-economy countries, AM production currently processes on average approx. 80% of the amount of RAP using innovative techniques on AMPs. Design of various AMP, their assessment on the flexible application of innovative techniques depending on the RAP processing method, are described in this paper. In this paper different recycling technologies in AMP and their advantages and disadvantages are reviewed. The research result indicates technical possibilities hot recycling in-plant in Baltic countries. Local authorities, research institutes, road construction and road design companies could use these results in the future. DOI: https://doi.org/10.3846/enviro.2020.632

The last important production step in hot-mix asphalt aggregates production is a final screening (classifying) of secondary or tertiary crushed materials, which has to ensure high quality screening curves of end-products in accordance with standards and this process should run in most valuable economic way. The data of the screening machines from different 5 top manufacturers in same machine class were analysed in accordance with output, screening efficiency and owning and operation costs. This paper demonstrates to quarry managers possible correct choose of mobile screens, which ensure high production outputs and quality requirements and saves operation costs.

In determination of flexible pavement layers moduli using Falling Weight Deflectometer (FWD), the pavement depth temperature should be determined and then the moduli should be corrected into a reference temperature. As direct measurement of pavement temperature is time consuming and is difficult to be determined in trafficked roads, some models are developed to predict temperature of asphalt layers through pavement depth, including BELLS model. The objective of this research is to determine correlation between actual measurement and prediction of temperature variations through asphalt layers with applying BELLS model. Ten new and rehabilitated pavement sites were selected in hot climate regions in Khuzestan and Kerman provinces in southern part of Iran. In typical hot summer days, pavement temperatures were measured at half and at one-third of the depth of asphalt layers and FWD testing were performed. Results indicated that a linear regression analysis of BELLS predicted temperatures versus measured values, provides very good correlation with actual field measurements of temperatures through the asphalt layers. Furthermore, predictions were more precise in rehabilitated pavements rather than in newly constructed pavements. Finally, using multi parametric linear fitting analysis, a new model was developed to accurately predict the temperature of asphalt layers in new pavements.

Oxygen diffusion and oxidative reaction are two main factors in asphalt oxidative aging discovered by experiment, but the dynamic balance between them could not be easily studied by experimental methods due to its comprehensiveness. A pavement oxidation model was utilized to simulate this process in asphalt: oxygen molecules penetrate into the asphalt film and then react with the asphalt molecules. In some special cases, diffusion or reaction can become the determination step of asphalt oxidative aging. Another factor, asphalt hardening, which is a result of oxidative reaction, slows the oxygen diffusion seriously and consequently. With the help of the model simulation, the efforts of binder reaction kinetics, hardening properties and temperature on this balance have been studied and discussed in detail. A new standard for asphalt binder, solely from oxidation aspect, includes high activation energy, low hardening susceptibility and high hardening intercept. A new idea of anti-oxidant development was proposed. By decreasing oxygen diffusion, asphalt oxidation can be slowed down, but only works for oxygen diffusion determined cases.

The asphalt pavement made of high quality materials and having the optimal composition best resists destructive effects of environmental factors and vehicles. The optimal content of the mineral materials of the asphalt mixture and a bituminous binder is selected employing calculation and experimental methods. The properties of the designed asphalt mixture must meet the requirements of technical specifications thus reducing its cost. The paper presents algorithms for simulating the composition of the asphalt mixture applying mathematical programming techniques. The algorithms allow designing the asphalt mixture with minimal bitumen content, a low cost of the mineral part and the densest gradation assessing technological requirements for producing the mixture. Optimal bitumen content is calculated considering bitumen capacities specified for different types of rock and determined employing the most recent standard sieves screening for narrow fractions. For verifying the new proposed algorithms, a numerical experiment on the materials most commonly used in asphalt mixing plants was done. The analysis of findings indicates that the application of the algorithms assist in comparing real results. First published online:03 Apr 2017

This paper presents a simple method to determine dynamic modulus master curve of asphalt layers by con­ducting Falling Weight Deflectometer (FWD) for use in mechanistic-empirical rehabilitation. Ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in Khuzestan and Kerman provinces in south of Iran. FWD testing was conducted on these pavements and core samples were taken. Witczak prediction model was used to predict dynamic modulus master curves from mix volumetric properties as well as the bitumen viscosity characteristics. Adjustments were made using FWD results and the in-situ dynamic modulus master curves were ob­tained. In order to evaluate the efficiency of the proposed method, the results were compared with those obtained by us­ing the developed procedure of the state-of-the-practice, Mechanistic-Empirical Pavement Design Guide (MEPDG). Re­sults showed the proposed method has several advantages over MEPDG including: (1) simplicity in directly constructing in-situ dynamic modulus master curve; (2) developing in-situ master curve in the same trend with the main predicted one; (3) covering the large differences between in-situ and predicted master curve in high frequencies; and (4) the value obtained for the in-situ dynamic modulus is the same as the value measured by the FWD for a corresponding frequency.

This paper addresses simulation of asphalt on the macroscopic scale, using the Discrete Element Model (DEM). Asphalt mixture is considered as a particulate solid composed of relatively stiff deformable layered spherical particles embedded into a homogenised matrix. The discrete model presents a 3D network of one-dimensional elements connecting particle's centres and comprising mutual interaction of particles. The contribution of the film layer and the interface thickness for normal stiffness is described analytically and illustrated by simulation results. Development of the normal interaction model of layered particles contacting via interface on the meso scale is the key point of the current development. The model applied aiming to simulate deformation of asphalt mixture is able to capture properties of the weaker matrix interface while layered particle comprises of bitumen film in meso scale. The developed technique is applied for simulation of Marshall test, i.e. diametric compression of cylindrical specimen, widely used for characterisation of asphalt mixtures. Finally, suitability of the model is illustrated by comparison with the available experimental results.

Bitumen holds the aggregate in hot mix asphalt (HMA). Without asphalt binder, HMA would simply be crushed stone or gravel. A bitumen batching system (BBS) is comprised of bitumen storage, transportation, weighing and discharge equipment in an asphalt mixing plant (AMP). The function of the equipment is to batch the binder heated up to working temperature and to discharge it into a mixer in batches. In the entire system, the binder is exposed to high temperature and oxygen. Bitumen is slowly oxidized when it is in contact with oxygen. The degree of oxidation is highly dependent on temperature, time and thickness of a bitumen film. This article models the key factors influencing on the dynamics of bitumen oxidation in BBS equipment. Stone mastic asphalt (SMA) mixture was produced from the same materials according to the same job-mix formula (JMF) in neighbouring batch type AMP by changing the mixing time of materials from 20 to 60 s. Bitumen binder was separated from the taken SMA samples and its gradation was identified. Thus, Marshall specimens were produced and tested. PenetrationPen25of bitumen binder recovered in rotary evaporator, softening pointTspwas determined and penetration indexIpwas calculated. The presented findings of experimental investigation show that the properties of bitumen binder in BBS working at two different technologies changed inconsistently. Due to gravitation, the bitumen intensively flowing into a mixer (BBS1) is impacted by oxidation more than the bitumen batched by a high-pressure pump (BBS2).

Due to destructive factors (traffic loads, climatic and weather conditions, improper exploitation materials), bitumen properties irreversibly change in unserviceable asphalt concrete. Due to irreversible processes of oxidation the aged bitumen stiffens, its physiochemical properties, ductility, adhesion and cohesion as well as sectional composition (relative amounts of asphaltenes, oils and resins) change. Bitumen in the reclaimed asphalt pavement (RAP) may be restored to properties approximate to those of the virgin bitumen by adding the following rejuvenators: softening or rejuvenating agents as well as soft bitumen. The article presents the experimental data on RAP obtained from laboratory tests conducted with Marshall specimens without additives when RAP was supplemented by different types of virgin road bitumen, the paving grade of which was 50/70, 70/100, 100/150, 160/220, respectively. The content of newly added binder of all types to RAP was 0.5%, 1.0%, 1.5%, 2.0%, and 50/70 in addition and 4.0% and 6.0% of RAP mass. The total bitumen content increased by the same percentage amount in the reclaimed asphalt, which was not always optimal. Marshall specimens were formed with these bitumen contents, the tests of which enabled to identify stability (S), flow (F), Marshall quotient (S/F), air voids content (Vm), bulk density (SDD – ρb SD) of asphalt concrete samples and the maximum density of asphalt. Having extracted all RAP and reclaimed asphalt samples according to the differential method, the factual content of soluble binder in them and its penetration, softening point, Fraass breaking point, ductility and penetration index Ip were calculated. The dependences of the reclaimed asphalt physical and mechanical parameters on the virgin rejuvenating bitumen grade and its added percentage amount were obtained. Data analysis and their generalization was conducted.

Road asphalt concrete pavement is usually laid of hot-mix asphalt (HMA) mixture. HMA mixture is produced in an asphalt mixing plant (AMP) according to the technology applied in its structure. AMP shall meet certain requirements set in the norms not only to the quality of HMA mix produced in it, but to environmental protection as well. A possibility to produce an HMA mixture of all required types and marks in it shall be available through the use of various materials and additives, including reclaimed asphalt pavement (RAP). HMA mixture production costs shall be as low as possible. AMP shall be of appropriate technical condition and with proper equipment, which mostly influence on the technological, ecological and economic parameters. Its actual productivity shall meet the required scope (HMA mixture amount) of road construction works carried out in the serviced region. The article presents 9 criteria of operating AMP quality, mathematical models of determining their significance through the application of an expert research method as well as expert opinion correlation values. Ranks of AMP quality criteria have been replaced by their weight indices through the application of two different methodologies. Quality criteria weight indices may be used according to an additive model through the calculation of operating AMP quality multi-criteria index. A numerical sample is presented at the end of the article.

The paper describes the essential differences in determining optimal gradation of hot mix asphalt (HMA) mixture used in road building at the stages of its selection, initial design and production, and presents the respective algorithms. The models of constrained and unconstrained non-linear optimization are developed, allowing us to choose the best HMA mixture gradation based on mineral materials, whose gradation is known, when the total percent passing of HMA mixture aggregates is considered to be equally important for all sieves, or when preference is given to some of the sieves. A new linear optimization problem best suited for practical use due to its simplicity is offered. By introducing weight coefficients for the dimensions of the objective function of the model, zero deviations of the percent passing of HMA mixture aggregates from their standard values may be easily obtained, based on the preferences set. All mineral materials (aggregates) obtained at batch-type asphalt mixing plants should be used for HMA production. Their total mass is equal to unity, while the mass of each material is a positive quantity, and a predetermined relationship between the masses of imported filler and the reclaimed dust is used. In the experimental part of the work, the problems were solved using the SAS system.

The weighted mass of a binder in the bucket of the bitumen batcher of a batch-type asphalt plant should be such that its percentage of hot mix asphalt (HMA) mixture lot would comply with the design amount of the job-mix formula in all mix batches. A bitumen batcher does not always weigh bitumen portions precisely. Their mass deviations from the amount determined by the project and its variation impair HMA composition and performance. The paper provides data on a statistical evaluation of bitumen batcher modernization performed at Lithuanian enterprise „LL“. The article analyzes differences in the structures of reconstructed and not reconstructed bitumen batching systems and presents methods for determining modernization effectiveness. The paper also focuses on the effectiveness of the batching system, determining deviations from bitumen content in subsamples taken and extracted everyday during two seasons (before and after batcher‘s modernization) of producing HMA from the value of job-mix formula and comparing them to the values of tolerances. Article in Lithuanian Modernizuotos bitumo dozavimo sistemos įtakos karštojo maišymo asfalto mišinio sudėčiai tyrimas Santrauka Asfaltbetonio maišytuvo (ABMA) bitumo dozavimo sistema (BDS) priskiriama sudėtingam vamzdynų transportui. Ji privalo ne tik laikyti reikiamos temperatūros bitumą, jį tiekti iš talpyklų į maišyklę, bet ir tiksliai dozuoti rišiklį leidžiant minimaliai pakisti jo savybėms. Periodinio veikimo asfaltbetonio maišytuve bitumo dozatoriaus bakelyje atsverto rišiklio masė turi būti tokia, kad jo procentinis kiekis karštojo maišymo asfalto (KMA) mišinio partijos visuose maišiniuose atitiktų projektinį kiekį, nustatytą darbinėje mišinio formulėje (DMF). Ne visada bitumo dozatorius tiksliai ir glaudžiai atsveria bitumo dozes, o tai blogina KMA mišinio sudėtį ir savybes. Pateikti Lietuvos „LL“ įmonės (pavadinimas pakeistas) BDS patobulinti statistinio vertinimo duomenys. Išanalizuoti nepatobulintos ir patobulintos BDS konstrukcijų skirtumai ir pateikta modernizavimo efektyvumo nustatymo metodika. BDS kokybė tirta per du KMA mišinio gamybos sezonus (prieš ir po modernizavimo). Kiekvieną dieną imtų ir ekstrahuotų tūrinių ėminių bitumo kiekių nuokrypių nuo DMF vertės lygintos su tolerancijų vertėmis. Reikšminiai žodžiai: karštojo maišymo asfalto (KMA) mišinys, asfaltbetonio maišytuvas (ABMA), bitumas, bitumo siurblys, svėrimo bakas, vamzdis, vamzdynų transporto sistema, bitumo dozavimo sistema (BDS), tikslumas, glaudumas, nuokrypiai, darbinė mišinio formulė (DMF).

The aim of this work is to gather information about the national flexible pavement roads ruts depth, to determine its statistical dispersijon index and to determine their validity for needed requirements. Analysis of scientific works of ruts apearance in the asphalt and their influence for driving is presented in this work. Dynamical models of ruts in asphalt are presented in the work as well. Experimental outcome data of rut depth dispersijon in the national highway of Lithuania Vilnius – Kaunas is prepared. Conclusions are formulated and presented. Article in Lithuanian

With a view to saving bitumen and mineral substances and also for the purpose of preventing environmental pollution, the old asphalt pavement (AP) may be milled without increasing the thickness of pavement structure and subjected to hot recycling for reuse in the same or any other location. However, the suitability of reclaimed asphalt pavement (RAP) for reuse depends on its composition (the content and gradation of bitumen) and the properties of its components. Hence, the present study aims at providing a systematic analysis of factors that determine the inhomogeneity of RAP. To this end, RAP samples, taken from RAP being loaded from the milling machine onto the transport means and from RAP stored in the territorial storage facilities of asphalt concrete (AC) plants, were examined in an accredited laboratory to determine, for each sample unit, the composition (the content and gradation of aged soluble bitumen), the content of moisture and the gradation of non-extracted granules. The statistical characteristics showing the actual homogeneity of RAP sampled from different sources were also estimated and analysed. Further, there was elaborated a model for comparing the homogeneity of RAP from different sample sets by the max values of standard deviations in the percentage mass passing the sieves and, based on the experimental data, derived the respective regression equation. The results of the performed comparison showed the absence of any statistically significant difference in terms of homogeneity between the three different RAP sample sets, i.e. RAP-1 sampled from the road, RAP-2 taken from the stockpiles being formed in different locations and RAP-3 obtained from RAP kept stockpiled in an open storage facility. The study was finalized by determining, in line with the Specification of Technical Requirements TRA ASFALTAS 08, the max content of RAP allowed for inclusion in a hot mix asphalt (HMA) mixture depending on the actual homogeneity of RAP determined.

The aim of the study is to evaluate the influence of random errors of the stochastic technological process occurring in a batch type plant on the homogeneity of the hot-mix asphalt (HMA). The article presents the algorithm of prognosing mineral part composition of HMA, which takes into consideration a variation of mineral material cumulative percent passing through control sieves as well as errors of mineral material dose weight in the finite dosing. It is considered that percent passing and dose weight errors are independent random quantities, distributing according to the normal law. The original algorithm for the simulation of values of these two quantities is used. The mineral material grading and dose weight of the batches of HMA are selected through the use of the random number generator. To evaluate the homogeneity of the simulated lot of HMA batches, reference was made to Lithuanian Construction Recommendations R35-01, limiting the admissible deviations of components quantities of HMA in comparison with the job-mix formula. The example of simulation discussed above is presented, and the results are analysed.

It was determined that poor quality of asphalt concrete is the main cause (65 %) of early fatigue cracking of asphalt concrete pavement of roads in Lithuania and neighbouring countries with similar climatic conditions. The poor quality of asphalt concrete is mainly predetermined by production errors of hot mix asphalt (HMA) and designed suboptimal mass ratio of constituents. The development of theoretical principles for producing the best componential composition of asphalt concrete is highlighted. Optimal values of the portions of coarse aggregate, fine aggregate, filler and bitumen recommended by different authors are given. The main causes of deviations from the optimal composition of HMA produced by asphalt asphalt mix plants of different generations are systematised. The dynamics of rapid cracking of asphalt concrete paving of Lithuanian roads is shown emphasising the inadequacy of HMA structure and properties to increased traffic intensity and axial workloads. The permissible values of asphalt concrete components, optimal under the actual climate and traffic conditions, ensuring highest asphalt concrete resistance to fatigue and rational (8–9 years) service life, during which the cracked pavement area does not exceed 8 %, are proposed. A quality assurance method has been developed based on mathematical statistical methods. It helps avoid deviations of component proportions, occurring in the process of production, from the project proportion and to increase the homogeneity of the product.

More and more recycled asphalt mixtures with high reclaimed asphalt pavement (RAP) content are used in road pavement. Having determined and evaluated RAP composition (aged bitumen content and aggregate gradation) and properties, a suitable recycling agent and virgin materials are selected in the design process. The gradation of hot mix asphalt (HMA) mixture that is recycled in an asphalt mixing plant (AMP) shall correspond to its optimal gradation set out in its job-mix formula (JMF). When RAP is recycled in an AMP, inevitable systematic and random errors of performed technological operations and inhomogeneity of virgin materials and RAP have a significant influence. These factors influence the variation of components quantities of recycled hot mix asphalt (RHMA) mixture and deviations from JMF. In this study, the principles of asphalt pavement hot recycling are systematized, which allows analysis of the factors of components’ interaction influencing the results of the recycling process. The paper also presents and analyses asphalt recycling technologies in AMP and their comparative analysis. During the season of asphalt mixture production in 2014, statistical parameters were calculated according to the data obtained from one of the companies, which collected and systematized RAP batch masses, when before batching it was pre-dried and pre-heated in an additional dryer. These parameters of batch mass and RAP content in RHMA position and variation were used when evaluating the accuracy and precision of the recycling process in AMP. The obtained data showed that when RHMA mixtures are produced in a modern batch-type AMP, RAP is batched accurately, but not precisely enough.

Bitumen should always be stored and handled at the lowest temperature possible, consistent with efficient use. At higher temperatures and lower viscosities pumping is optimized; whereas at lower temperatures and higher viscosities pumping efficiency decreases rapidly. Thus viscosity and its control by temperature is an important consideration in respect to all handling operations. The minimization of bituminous hardening during storing, transportation and mixing depends on careful control of binder temperature. TRA ASFALTAS 08 regulates maximum permitted storage temperatures of various bitumens. Heating equipment of periodical asphalt mixing plant (AMP) bitumen batching system (BBS) shall be designed to maintain the same temperature of the binder in the whole BBS. This article presents the study of heat transfer in bitumen storage tanks and identifies the most important factors influencing on energy loss. The test showed that energy loss in currently operated AMP is too high and may be reduced by changing technological parameters of bitumen heating, updating and upgrading separate heating equipment and improving temperature control and handling of heating equipment. The method of convection and radiation heat flow calculation in bitumen storage tank is presented. The findings obtained through the use of the described method of heat flow calculation correspond to the actual data of the consumed electrical power displayed on AMP computer.

The article presents reclaimed asphalt pavement (RAP) processing technologies and equipment models used in the asphalt mixing plant (AMP). The schematic model indicating all possible ways to process RAP in AMP is shown. The model calculating the needed temperature of mineral materials used for heating RAP is given and an example of such calculation is provided. Article in Lithuanian Asfalto dangos regeneravimo asfaltbetonio maišytuvuose technologijų modeliavimas Santrauka Pateikiamas asfaltbetonio maišytuve regeneruojamo senos kelio dangos asfalto technologinių operacijų sekos ir įrenginių komponuotės modelis. Sudarytas scheminis modelis, kuriame susisteminti visi galimi regeneruoto karšto maišymo asfalto (KMA) mišinio gamybos asfaltbetonio gamykloje būdai. Pateiktas mineralinių medžiagų, perduodančių šilumą naudoto asfalto granulėms (NAG), reikiamos temperatūros skaičiavimo modelis ir jo skaitinis pavyzdys. Reikšminiai žodžiai: naudoto asfalto granulės (NAG), karšto maišymo asfalto (KMA) mišinys, mineralinės medžiagos, asfaltbetonio maišytuvas, džiovinimo būgnas, regeneruota asfaltbetonio danga (RAD), šilumos pernaša.

Some particular aspects such as the improvement methods of technological parameters for hot bitu‐ men storage in a pipeline transport system, transportation and dosed supply to batch asphalt mixing plant (AMP) are evaluated in this paper. Bitumen in asphalt concrete binds together the material of mineral particles into a strong conglomerate of a complicated structure, capable of withstanding the destructive effect of vehicles and the factors on the road pavements. The optimal amount of bitumen determined by calculation and laboratory testing should be maintained in mix batches of hot‐mix asphalt (HMA) obtained from AMP mixer. In the periodic type of the asphalt concrete blender mass of the weighted matrix in the all merging batcher's tanks should correspond in percents equally in the HMA to the designed amount of the job‐mix formula (JMF). The bitumen batcher does not always weigh bitumen portions precisely. Their mass deviations from the amount determined by JMF and its variation impair HMA composition and performance. In addition,, an additive model for calculating the effect of factors causing the variance of bitumen content in the produced HMA mixture is presented in this current paper as well. The data on statistical evaluation of bitumen batcher's modernization performed at certain Lithuanian Enterprise are discussed. The differences in structures of reconstructed and not reconstructed bitumen batching systems (BBS) are analysed and methods of determining modernization effectiveness are presented. The effectiveness of BBS is analysed too, defining the deviations of bitumen content in subsamples, taken and extracted everyday for two seasons (before and after the batcher's modernization) of HMA mixture production from the value of JMF and comparing them to the values of tolerances. The analysis of column charts and histograms shows that the made modernization helped to increase the precision of supplying the required amount of bitumen to HMA mixture insignificantly. However, the control of BBS has been considerably increased. First published online: 10 Feb 2011

In most countries, the pavement of motor roads, airfields and other trafficked areas is made of hot‐mix asphalt (HMA) mixture prepared by asphalt mixing plants (AMP) of various designs. The total output of HMA mixtures shows the dynamics of national road transport infrastructure's development, corresponding to the increasing number of vehicles, traffic intensity and axle loading. HMA mixtures are made by using various technologies, which have some advantages and disadvantages. The paper presents technological schemes of making HMA mixtures used in Lithuania and other countries. The development of AMP and technical and technological characteristics of new computer‐aided AMP models used at various asphalt production companies (APC) were analysed. Based on the data provided by the European Asphalt Pavement Association (EAPA), the correlational‐regression relation between the country's area and the amount of the produced HMA mixtures was established. The data on the total output of HMA mixtures in Lithuania cannot be found in the information provided by EAPA. For the first time, the dynamics of the production of HMA mixtures by particular APC in Lithuania over the last 10 years (1998–2007) has been determined based on the data directly obtained from their manufacturers. The data were analysed and compared to the output of HMA mixtures in other countries and the dynamics of the development of AMP models used in Lithuania and changes in their numbers were determined. Santrauka Daugelyje šalių automobilių kelių, skridimo aikštelių ir kitų eismo zonų danga įrengiama iš karšto maišymo asfalto (KMA) mišinio, pagaminto skirtingos konstrukcijos asfaltbetonio maišytuvuose (ABM). KMA mišinio gamybos apimtys rodo šalies kelių transporto infrastruktūros plėtros dinamiką ir atitiktį didėjantį automobilių skaičių, jų eismo intensyvumą ir ašies apkrovas. KMA mišinys gaminamas taikant skirtingas technologijas, turinčias privalumų ir trūkumų. Darbe pateiktos Lietuvos Respublikos ir kitų šalių KMA mišinių gamybos technologijos schemos. Išanalizuota ABM tobulinimo raida ir įmonėse veikiančių naujų modelių kompiuteriais valdomų ABM techninės ir technologinės charakteristikos. Naudojant European Asphalt Pavement Association (EAPA) duomenis, gauta koreliacinė-regresinė šalies ploto ir pagaminto KMA mišinio kiekio sietis. EAPA skelbiamoje informacijoje nėra duomenų, rodančių suminius Lietuvoje pagaminto KMA mišinių kiekius. Pirmą kartą iš asfalto mišinių gamintojų surinkus ir susisteminus duomenis, tiesiogiai gauta 10 metų (1998–2007) Lietuvos Respublikos asfaltbetonio gamyklose (ABG) pagaminto KMA mišinių kiekio dinamika ir ji palyginta su kitose šalyse pagaminto KMA mišinio kiekiais. Atlikta Lietuvoje veikiančių ABM modelių ir skaičiaus kaitos dinamika. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: karštai maišytas asfaltas, asfaltbetonio maišytuvas, asfaltbetonio gamykla, periodinio veikimo maišytuvas, produkcijos dinamika, technologiniai procesai.

Multi-attribute methods in road construction can be used on the national, organization and project levels. However, most assessment methods are seeking to find how to make the most economic construction decisions, and most of all these decisions are intended only for economic objectives. Computerised Asphalt Mixing Plants (AMP) are one of the most expensive and complicated equipments for construction of road pavements. Modern AMP is controlling by computer program, but there are still some problems. Properties of the AMP not always satisfy demands and requirements of road constructors. Quality of the asphalt hot mixtures, environmental contamination, pollution, firm economic well-being and possibility to satisfy demands of hot asphalt mixture users depend on the AMP quality. This paper proposes a multi-attribute model for efficient quality assessment of the AMP. For this problem were selected 9 main quality attributes and weighted by expert ranking method. The problem is solved by applying additive assessment. Also, a case study is presented.

A new classification of asphalt concerete pavement defects is presented in the article and the causes of their development are systematised. The dynamics of asphalt concrete pavement defect development in the road and the dependence of pavement deterioration on the type of defects are presented in the theoretical graphic model. The change of road pavement structural strength (stiffness modulus) depending on the pavement service life is also described. The dependence of the level of asphalt concrete pavement on the most important roads of the Republic of Lithuania (road Vilnius-Kaunas [Al] and motorway Vilnius Panevėžys [A2]) measured with one-wheel dynamometric trailer PKRS-2U (Russia) on the level of pavement deterioration has been identified through experiments. The analysis of the dependence of transport costs and driving speed on road pavement level has been carried out. Regression equations of such dependence and correlation coefficients as well as relations are presented too. Frist Published Online: 30 Jul 2012

Multi-attribute methods in road construction can be used on the national, organization and project levels. However, most of assessment methods are seeking to find how to make the most economic construction decisions, and most of all these decisions are intended only for economic objectives. Computerised Asphalt Mixing Plants (AMP) are one of the most expensive and complicated equipments for construction of road pavements. Modern AMP is controlling by computer program, but there still are some problems. Properties of the AMP not always satisfy demands and requirements of road constructors. Quality of the asphalt hot mixtures, environmental contamination, pollution, firm economic wellbeing and possibility to satisfy demands of the hot asphalt mixture users depends on the AMP quality. This paper proposes a multi-attribute model for efficient quality assessment of the AMP. For this problem were selected 9 main quality attributes and weighted by expert ranking method. The problem is solved by applying additive assessment. The case study is presented also.