Production Of Asphalt Concrete Mixtures Research Articles

Life Cycle Assessment for the Use of Waste Plastics in Asphalt Concrete Mixes

Improper waste disposal poses the risk of contaminating natural water bodies and soil. The low recycling rate of plastics and their fate in landfills are significant global environmental concerns. Efforts to increase the use of recycled plastics worldwide aim to address the hazardous consequences of improper plastic treatment. One potential solution is incorporating plastics as binder or mixture modifiers in asphalt concrete (AC) mixtures, which repurposes waste plastics while reducing environmental impacts related to AC production. This study calculated the environmental impacts of repurposing waste plastics, specifically low-density polyethylene and polystyrene, into modifiers in AC mixes. Wet and dry processes were considered. The environmental impacts of plastic-modified AC mixes were compared with those of styrene-butadiene-styrene (SBS)-modified mixes. The life cycle assessment covered the following processes: (1) collection, sorting, and shredding of waste plastics; (2) transportation of waste plastics from landfill to recycling facility and then to the asphalt plant; (3) supply and transportation of virgin materials; (4) production of AC mixtures; (5) transport of material and equipment to site; and (6) onsite operations. The study concluded that waste plastic-modified mixes outperformed SBS-modified mixtures with regard to environmental performance, except for ozone depletion resulting from certain recycling process activities. The high-shear mixing in the wet process had a significant impact. Sensitivity analyses revealed the influence of binder content and material transportation on the overall environmental assessment.

ИССЛЕДОВАНИЕ ПРОЦЕССА ВСПЕНИВАНИЯ БИТУМА В СМЕСИТЕЛЕ

The article discusses the main ways to save material, labor and financial resources in the production of asphalt concrete mixtures. It has been shown that a promising way to save energy and reduce harmful effects on the environment is to reduce the temperature of the bitumen. A foam generator design has been proposed that allows efficient mixing of bitumen with the generated steam. To describe rheology, the article uses the Ostwald-de Waele power-law fluid model. An expression for the current function is obtained, which allows to find the characteristics of the flow of the carrier phase in the mixer, taking into account the geometric parameters of the mixer, such as the diameter and length of the pipe, the radius of the screw, and the flow parameters at the inlet to the mixer. It is shown that under the same flow conditions, in order to obtain the same flow rate in the case of a pseudoplastic fluid, it is necessary to apply a greater pressure gradient compared to a Newtonian fluid. Experimental studies are carried out on the developed laboratory installation, which make it possible to determine the rational design and technical parameters of the foamed bitumen installation, the parameters of which are changed during the experiment. A regression equation is obtained in coded form, expressing the dependence of the quality of adhesion of foamed bitumen to inert material depending on the design and technological parameters of the developed bitumen foaming device

Rheological Characterization of Reclaimed Asphalt Binder Blended with The Neat And Sbs-pma Binders

Reusing reclaimed asphalt pavement material guarantees a substantial optimization of non-renewable material resources, emissions reduction, and decreasing landfill space, along with the economic benefits associated with saving the costs of purchasing and transporting new aggregate and asphalt binder for asphalt concrete mixture production. This study aims to investigate the influence of aged asphalt binder from reclaimed asphalt pavement on the virgin asphalt binder’s rheological properties. Therefore, different dosages of RAP binder (20%, 30%, and 40% by weight of the total mix) were blended with neat asphalt binder (40-50), penetration grade (P40), and SBS polymer asphalt (SBS-PMA) binder. Using both traditional and Superpave performance testing methods, the effects of RAP on the blend's consistency, viscosity, softening, elastic recovery, rutting (permanent deformation), fatigue cracking, and low temperature cracking were evaluated. The results revealed that the RAP binder decreased the penetration value of both neat and SBS-PMA binders. The neat asphalt binder’s viscosity and softening point increased with the increase in RAP content, whereas they decreased for SBS-PMA. The RAP binder decreases the SBS-PMA elastic recovery. where the neat asphalt experienced a little improvement in elastic recovery when blended with the RAP binder. The Superpave test results revealed that the RAP binder deteriorates the performance of the SBS-PMA binder at high, intermediate, and low testing temperatures. With the addition of 20%, 30%, and 40% RAP, the high-temperature PG grade of SBS-PMA blends decreased by 0.64%, 0.95%, and 1.10%, respectively, while the low-temperature PG grade increased by 23%, 31%, and 32%, respectively. In contrast, the RAP improves the neat asphalt blend's high-temperature performance grade and deteriorates intermediate and low-temperature performance grades. The addition of 20%, 30%, and 40% RAP increased the neat asphalt blends' high-temperature properties by 1.5%, 3.3%, and 4.5%, respectively. whereas the neat asphalt low-temperature PG grade increased by 5%, 11%, and 15% with the addition of 20%, 30%, and 40% RAP, respectively. In summary, the performance of virgin and RAP binder blends depends on the individual characteristics of the blended asphalt binders

STUDY OF THE PROPERTIES OF ASH-REMOVAL OF DIFFERENT ORIGIN TO COMPLY WITH NATIONAL REQUIREMENTS

Introduction. In Ukraine, about 30% of all electricity is produced by burning solid fuels - coal, shale, and peat. In our country, there are about 15 operating thermal power plants, which generate about 5-6 million tons of ash and slag waste as a secondary product per year. Thus, the waste of the fuel and energy complex, which is formed in the furnaces of thermal power plants, is a huge accumulation of ash in the form of dust-like residues and lumpy sludge, as well as various ash-slag mixtures. These products of high-temperature processing (1200-1700 ºС) of the mineral part of the fuel are widely used in many countries of the world, and taking into account the global trend of increasing the share of the secondary market for the use of waste, it is necessary to predict an increase in the rate of their processing in Ukraine as well. Problems. In Ukraine, as a filler, the material obtained by crushing carbonate rocks is used as a filler, which is established in DSTU B B.2.7-121. At the same time, as a result of burning coal, millions of tons of dust-like waste - fly ash - are generated at power-generating enterprises of Ukraine. The grain composition of this material approaches the filler requirements according to DSTU B V.2.7-121 and can be used for the production of asphalt concrete mixtures. The purpose of the work is to establish the possibility of using fly ash of various origins for the production of asphalt concrete mixtures. Materials and methods. Fly ash of various origins was used during the research. The results. It has been established that these materials meet the requirements of DSTU B B.2.7-121 according to all the specified indicators in accordance with the non-activated mineral powder of the I brand. Conclusions. Conducted studies on determination of grain composition, porosity, swelling and structuring ability showed that the studied fly ash meets the requirements of table 5 of DSTU B B.2.7-121, and the indicators are close to limestone mineral powder.

ESTABLISHMENT OF TECHNICAL REQUIREMENTS REGARDING DRAINING ASPHALT CONCRETE

Introduction. It has been established that porous draining asphalt concrete (DAC) is an open-frame asphalt concrete that is specially designed with a high content of air voids, which are designed to remove water from the surface of the road surface. Pavement surfaces that include draining asphalts, permeable wear courses, and porous asphalt pavements are gaining more and more acceptance in the road industry worldwide. Drainable asphalt can be susceptible to freeze-thaw damage in cold climates and will require winter maintenance practices. The service life of such coatings varies greatly depending on climatic conditions, intensity of traffic and loads, design and construction methods. Drainage asphalt pavements were created to increase road safety, but in addition to high traction characteristics, they have high porosity, which provides water permeability, which reduces the amount of surface water and thus reduces the formation of splashes in rainy weather. This leads to a reduction in the risk of aquaplaning and an increase in road visibility, and ultimately to an increase in road safety.. Problem statement. The issue of timely removal of surface water from the road surface is mandatory and is solved by providing the road surface with a transverse slope. As practice shows, this does not sufficiently protect the road surface from the negative effects of water. High operational safety, improvement of the operational characteristics of the road surface is achieved due to the removal of the accumulation of water stains from its surface, which reduce the adhesion of the wheels to the road surface. These qualities can be improved by introducing draining asphalt concrete. However, the service life of draining asphalt concrete varies greatly depending on climatic conditions, traffic intensity and loads, design concepts and construction methods. In order to further improve the current state-of-the-art instructions for the production and application of DAC to solve regional, road and climate problems, a comprehensive analysis of the currently available applications of DAC mixtures for the construction and maintenance of road surfaces is necessary. Therefore, on the basis of this, today in Ukraine it is expedient to introduce normative documents that would regulate the design, manufacture, technical requirements and performance of works according to this technology, which would allow for practical use, optimization and development of the road industry of Ukraine in this direction. Purpose. Production of asphalt concrete mixtures and arrangement of road surface from draining asphalt concrete. Assessment of the regulatory framework of the world and establishment of recommendations and technical requirements for the production and installation of draining asphalt concrete. Materials and methods. Experimental and experimental-analytical. Results. An analysis of the existing experience of using draining asphalt concrete, conditions of its use, was carried out. Theoretical studies of the process of forming asphalt concrete with a structure of interconnected open pores. Experimental studies on the selection of grain composition and bitumen content in draining asphalt concrete have been conducted. Recommendations for the production of draining asphalt concrete mixtures and the arrangement of a covering from them have been developed. Conclusions. An important role in the operational reliability and durability of draining asphalt concrete is played by the properties of the components, as well as the ratio between mineral materials and bituminous binder. In European countries, the greatest attention is paid to the narrow grain composition of mixtures, especially the requirements for large aggregates and bituminous binders. For the production of drainable asphalt concrete, crushed stone of narrow fractions is used, since it has a special granulometric composition, unlike typical dense and crushed-mastic asphalt concrete, it has sufficiently large porosity and requires extremely high attention and strict requirements for crushed stone materials. Therefore, an important step for the implementation of a promising construction technology would be the development of recommendations for draining asphalt concrete in Ukraine, which will include technical requirements, recommendations for design and application, acceptance rules and control methods.

Thermodynamic Approaches in Assessing Quality, Efficiency and Environmental Friendliness of Asphalt Concrete

The experience of developed countries shows that the development of the road network and transport infrastructure determines the intensity of economic ties and is one of the most important conditions for the development of the state’s economy. Optimization of the composition and production technology of asphalt concrete mixture – the basis of paved roads, is of great importance, both from an economic and environmental point of view. The production of asphalt concrete mixture directly (during the production process at asphalt concrete plants) and indirectly (during delivery from the plant to the place of installation) determines the energy costs for the production of asphalt concrete. At asphalt-concrete plants the specific energy consumption per ton of hot asphalt concrete mixture varies from 0.3 to 0.7 GJ. The range in energy costs is large. This situation indicates the presence of a significant energy-saving potential of asphalt concrete mixture thermal technology. The exergy analysis of technical systems proposed in this paper, which are operated in the asphalt concrete mixture production processes, makes it possible to judge the efficiency of energy use in their thermal units. This approach is expedient not only in the primary production of asphalt concrete mixture, but also for more environmentally friendly, energy- and resource-saving production processes for the operation of equipment during the regeneration of road asphalt concrete.

МИНЕРАЛЬНЫЙ ПОРОШОК В СОВРЕМЕННОЙ СИСТЕМЕ ПРОЕКТИРОВАНИЯ АСФАЛЬТОБЕТОННЫХ СИСТЕМ

Within the framework of this article, the potential raw material base for obtaining mineral powders for the production of asphalt concrete mixtures is analyzed. The main stages of structure formation in asphalt concrete in the process of interaction of a bitumen binder with mineral materials are considered. Within the boundaries of modern approaches to the design of asphalt concrete mixtures, an assessment of the current regulatory framework is carried out in relation to the requirements for the indicators of the properties of mineral powders and the sampling methodology for assessing their quality. According to the research, despite the increased attention to the characteristics of mineral powders, the requirements for the methodological approach to sampling mineral powder and the quality assessment of the binary system "bituminous binder - mineral powder" or asphalt binder, which is the most significant component of asphalt concrete, is currently weak elaborated in the normative documentation. In the light of modern approaches to the design system of asphalt concrete mixtures, including the methodology of volumetric-functional design, it is of interest to develop a qualitative and quantitative assessment of the effect of mineral powders of different nature on the structuring of bituminous binders and, as a consequence, a change in their rheological properties.

Increasing pavement bitumen adhesion with DAD adhesion additives

An important factor that largely determines the water resistance and durability of asphalt pavements is the adhesion of bituminous binders to the surface of stone materials. The most common method of increasing the adhesion of binders is the use of adhesive additives. Given that the range of adhesives used in the road industry is con-stantly updated, and their effectiveness is determined by the characteristics of binders and stone materials, issues related to the assessment of the impact of additives on the properties and, in particular, the adhesion of bituminous binders, are relevant. Goal. The aim of the study was to evaluate the effects of adhesive additives of the DAD series on the proper-ties of bitumen used in the road industry of Ukraine. Methodology. For bitumen modified with DAD-1, DAD-K and DAD-KT 2 additives, standard quality indicators have been determined in accordance with the norms of national standards DSTU 4044 and SOU 45.2-00018112-067. Particular attention was paid to determining the adhesive properties of binders, which were evaluated by the method of adhesion to the glass surface and the method of rotation of the bottle, and the thermal stability of additives is evaluated by changes in adhesion after aging of binders by TFOT and RTFOT. Based on the obtained experimental data, it was found that the adhesion additives of DAD have practically no effect on the basic standard quality indicators of road viscous bitumen. When modifying bitumen with the maximum concentrations recommended by the manufacturer, the additives significantly increase the adhesion of bitumen to the glass surface. The surface of the grains of the ac-cepted stone materials treated with bitumen modified with the additive DAD-KT 2, after the test by the method of rotation of the bottle for 6 hours showed 40% of them remain covered with binder. Novelty. The thermal stability of DAD adhesive additives significantly depends on the accepted method of aging. The main factor that reduces the adhesive properties of the DAD-1 additive is the intense interaction with air. The adhesion properties of bitumen modified with the addition of DAD-CT 2 is significantly increased after aging. Practical value. The expediency and efficiency of the use of additives of the DAD series in the production of asphalt concrete mixtures should be established based on the characteristics of the bitumen and stone materials used.

Practical quality monitoring of bituminous binders used at federal highways construction

The work is devoted to the applied bitumen binders’ quality practical monitoring results at construction sites, repair and reconstruction of highways in the Russian Federation at all the production and technological stages, from their manufacture by the supplier, including transportation and storage, and ending with their use in the production of asphalt concrete mixtures. The quality control of bituminous binders was carried out according to the modern methods of Russia and abroad

АНАЛИЗ ВЛИЯНИЯ КАЧЕСТВЕННОГО СОСТАВА АСФАЛЬТОБЕТОННОЙ СМЕСИ НА ОСНОВНЫЕ ПОКАЗАТЕЛИ ХАРАКТЕРИСТИК АСФАЛЬТОБЕТОНА В ПОКРЫТИИ

the paper presents an analysis of information quality assurance of production of asphalt concrete mixtures, as well as the study of the relationship of the qualitative composition of asphalt concrete mixtures and physical and mechanical characteristics of asphalt concrete pavement. The study of the main characteristics was carried out on the example of asphalt concrete type B and grade I and crushed-mastic asphalt concrete – SchMA-20. It is established that the deviation of asphalt mixtures in composition from the required values leads to their under-compaction in the pavement. It is also established that increasing the number of inconsistencies in the asphalt concrete mixture leads to an increase of physical-mechanical characteristics that differ from the requirements of GOST 9128-2013 and GOST 31015-2002 respectively. As an information base for the assessment of the influence of granulometry of the mineral part of asphalt concrete, as well as the amount of bitumen on the main characteristics of asphalt concrete, the data of the current ACP of Belgorod region were used. Analysis of the particle size distribution was carried out using a laser analyzer of asphalt ABA7/35B. The obtained data became the basis for a further study of the influence of various parameters on the properties of asphalt mixes, as well as improving the efficiency of the asphalt mix production management system.

Opportunity applying response surface methodology (RSM) for optimization of performing butonic asphalt mixture using plastic waste modifier: a preliminary study

Non-biodegradable waste plastic made of polyethylene terephthalate (PET) based drinking bottles waste was used as additive in asphalt concrete mixture production. This paper used modified Buton asphalt (MBA) as base binder. The asphalt concrrete mixtures containing 0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5% of waste PET were prepared with one source of aggregates, filler and stone dust. The effect of waste PET and MBA to asphalt concrete mixture on volumetric properties namely specific gravity, void in mix (VIM), void mineral aggregate (VMA) and void filled bitumen (VFB) is studied. The results of volumetric evaluation indicated that waste PET and MBA could be incorporated in asphalt concrete mixture. After calculating specific gravity, VIM, VMA and VFB, a table was designed as a preliminary study based on Response Surface Methodology (RSM) that can be used as a basis of modelling for continuous improvement of asphalt concrete prepared with waste PET and MBA.

Equipment desing automation at asphalt-concrete production modernization

The relevant task in the field of road construction and maintenance is gradual transition to the production of asphalt-concrete mixtures on polymer-bitumen binders. Most asphalt-concrete plants of small and medium capacity consider this transition as challenging due to a relatively high cost of the specialized equipment for polymer-bitumen binders production. Most proposed techniques involve the utilization of colloid mills. The practice of such mills operation shows that production lines experience long downtime periods due to the necessity of preventive maintenance and repair. A promising direction in polymer-bitumen binders manufacture is to use polymer waste materials for the bitumen modification. This provides the reduction of the modified binder costs and the solution of environmental problems. The paper deals with the problem of asphalt-concrete plants modernization to obtain polymer-bitumen binders in its own production using agitated mixers common in the chemical industry. Optimization problem is formulated for design and operating parameters of such equipment to provide required quality indicators for the resulting polymer-bitumen binders. Algorithmic and software assistance is developed to solve the set problem. The proposed technical solutions were tested when solving the modernization problems regarding the process diagram of the asphalt-concrete plant to release products on polymer-bitumen binder of its own production.

Granulated asphalt mix based on industrial and domestic waste

The paper presents the results of experimental studies to identify the possibility of using large-tonnage industrial mineral waste in the production of asphalt concrete mixtures. As a raw material for the production of asphalt used phosphogypsum - waste production of phosphoric acid, resulting from the processing of apatite. The reserves of this product are measured in millions of tons and are constantly replenished, stored in open dumps, representing a serious threat to the environmental situation in the surrounding areas. Phosphogypsum is a mineral powder material, the dispersion characteristics of which correspond to the mineral powder in the production of asphalt concrete. The method of production of granulated as-falto-concrete mixture developed by the authors of the article by the method of rolling involves the use of a significantly higher content of expensive mineral powder in comparison with typical mixtures. Therefore, the use of cheap phosphogypsum for these purposes is very attractive. However, the first attempts to obtain a granulated product based on phosphogypsum were unsuccessful - the asphalt-concrete mixture did not withstand the effects of moisture. Further studies allowed us to solve the problem of material resistance by modifying bitumen with polyethylene terephthalate, one of the most common household plastic waste. The subject of the article is devoted to the development of prescription and regime parameters of the process of obtaining new material. Test methods for asphalt concrete are strictly standardized in connection with which standard techniques were used. As a result of the research, an asphalt-concrete mixture was obtained, surpassing typical materials in many performance characteristics and allowing to solve a global environmental problem.

Possibilities of using the dispersed waste of asphalt-concrete plants in the Republic of Buryatia

This article considers the possibility of using the dispersed waste of asphalt-concrete plants, namely the dust-entrainment, which is formed during the drying and heating of inert materials and accumulates in special dust-collecting facilities. The material under investigation corresponds to a finely dispersed filler used for the production of asphalt concrete mixtures for a number of features. It has been established that substitution of up to 50% of the mineral powder with its own dust-entrainment allows obtaining asphalt-concrete mixtures satisfying the requirements for the sharply continental climate.

The influence of the unloading mode of asphalt concrete mixing plant hot bin on the homogeneity of screened fractions

Abstract The analysis of hot asphalt concrete mixture production in asphalt concrete mixing plants of intermittent operation according to the traditional technology scheme is presented. The segregation degree of hot mineral materials fractions of 0–5 mm and 5–15 mm sieved in hot bins and the influence of their screening mode on the homogeneity of the flow running to the measuring hopper were identified during the experimental tests carried out in two asphalt concrete mixing plants. To evaluate the degree of segregation and kinetics according to three different methodologies 214 separate samples of hot fractions grouped into three series A, B, C were taken. Statistical characteristics of each series samples grading and coarseness modulus (fraction of 0–5 mm) as well as arbitrary coarseness modulus (fraction of 5–15 mm) were identified. The data analysis proved that the degree of segregation of hot materials sieved in the bin sections is high and the homogeneity of their flows decreases when the range and f...

THE INFLUENCE OF THE UNLOADING MODE OF ASPHALT CONCRETE MIXING PLANT HOT BIN ON THE HOMOGENEITY OF SCREENED FRACTIONS

The analysis of hot asphalt concrete mixture production in asphalt concrete mixing plants of intermittent operation according to the traditional technology scheme is presented. The segregation degree of hot mineral materials fractions of 0–5 mm and 5–15 mm sieved in hot bins and the influence of their screening mode on the homogeneity of the flow running to the measuring hopper were identified during the experimental tests carried out in two asphalt concrete mixing plants. To evaluate the degree of segregation and kinetics according to three different methodologies 214 separate samples of hot fractions grouped into three series A, B, C were taken. Statistical characteristics of each series samples grading and coarseness modulus (fraction of 0–5 mm) as well as arbitrary coarseness modulus (fraction of 5–15 mm) were identified. The data analysis proved that the degree of segregation of hot materials sieved in the bin sections is high and the homogeneity of their flows decreases when the range and frequency of quantity fluctuation increases.

CONDITIONAL OPTIMIZATION MATHEMATICAL MODEL OF THE ASPHALT CONCRETE MIXTURE GRADING

A new partial conditional optimization method which enables to select the best ratio of imported fillers not only while designing the composition of asphalt concrete mixture but also while adjusting the composition of the produced asphalt concrete mixture according to the actual quality of hot fractions is presented. The constructed mathematical model, algorithm and the solved task prove that irrespective of the number of fillers (from 2 to 7 and more) the ratio of their mass can be selected which enables to produce an asphalt concrete mixture which meets the requirements of the composition project best. The mass ratio λ of imported fillers A 1 and reclaimed dust A 2, which settled and accumulated in the dry purification equipment of an asphalt concrete plant presented in Regulations DAT.AD-96 was taken into account for the first time. Methodological scientific novelty and a possibility to apply it in practice can improve the control of asphalt concrete mixture production.

THEORETICAL PRINCIPLES AND EXPERIMENTAL DATA TO IDENTIFY STABILITY OF ASPHALT CONCRETE COMPONENTS IN FINALLY DOSED MINERAL MATERIALS

The duration of asphalt concrete functioning depends on the quality of the asphalt concrete mixture used to pave the road. Grading of hot fractions sieved through technological sieves of asphalt concrete mixture, their pollution with particles of different size as well as stability influence on the quality of an asphalt concrete mixture. Each j - (j = 1...., m) aggregate mineral material or mixture is made up of two (mineral powder, particle of size less than 0,09 or 0,071 mm, and sand, particle of size from 2 to 0,09 mm or 5-0,071 mm) or three (crushed stone, particle size is larger than 2 or 5 mm) mineral components (i = 1, ..., k) . When required technological operations of asphalt concrete mixture production are carried out, the quantity and stability of any i - component in mineral materials change when they move through an asphalt concrete mixer. The more stable the quantity of mineral components in mineral materials (especially in finally dosed) is, the more uniform the composition of asphalt concrete mixture is produced. The experiments showed that when asphalt concrete mixture is produced applying a traditional technology in an asphalt concrete mixer of model D-597, D-508-2A, D-645-3 andD-590, sieved hot fractions of 0–5 mm and 5–15 are polluted with particles of different size by more than 10 per cent; and this pollution is neither uniform nor stable. Following a well-known theory, an average quadratic deviation σ of arithmetic undersized particles sieved through laboratory sieves ~aggregate mineral materials is the greatest when their mean X makes up 50 per cent; therefore, hot fractions of 0–5 mm and 5–15 mm were produced on the experimental data obtained from production as well as regression equations σ = ƒ( X )of statistical indeces of cold mineral powder. The values of average quadratic deviations σ µij of mineral component quantities in those finally dosed mineral materials are obtained from curves drawn according to the regression equations. They can be used to estimate dispersion σ2 Gi of mineral component i in asphalt concrete mixture which depends on the accuracy and stability of technological factors of an asphalt concrete mixer.

CONDITIONAL OPTIMIZATION MATHEMATICAL MODEL OF THE ASPHALT CONCRETE MIXTURE GRADING

A new partial conditional optimization method which enables to select the best ratio of imported fillers not only while designing the composition of asphalt concrete mixture but also while adjusting the composition of the produced asphalt concrete mixture according to the actual quality of hot fractions is presented. The constructed mathematical model, algorithm and the solved task prove that irrespective of the number of fillers (from 2 to 7 and more) the ratio of their mass can be selected which enables to produce an asphalt concrete mixture which meets the requirements of the composition project best. The mass ratio λ of imported fillers A 1 and reclaimed dust A 2, which settled and accumulated in the dry purification equipment of an asphalt concrete plant presented in Regulations DAT.AD-96 was taken into account for the first time. Methodological scientific novelty and a possibility to apply it in practice can improve the control of asphalt concrete mixture production. Frist Published Online: 30 Jul 2012

MAIN PROBLEMS OF MANUFACTURING ASPHALT CONCRETE MIXTURES IN LITHUANIA/ASFALTBETONIO MIŠINIŲ GAMYBOS SVARBIAUSIOS PROBLEMOS LIETUVOJE

The article describes the main problems of manufacturing asphalt concrete mixtures at the factories under Ministry of Communication in the Republic of Lithuania. The Lithuanian Road Network is up to 21.122 km of state roads. 1.455 km of them are motorways, 3.415 km—national roads and 16.251 km—regional roads. Half of the state roads in Lithuania are paved with asphalt concrete. 98% of the motorways and 36% of the regional roads have asphalt pavement. Asphalt concrete pavement resistance to corrosion can be increased by improving asphalt concrete mixture production technology: ie by updating technological equipment, changing technological conditions and developing new methods of asphalt concrete mixture production. Therefore, the updating of asphalt concrete mixture production technologies is a very important factor for improving road operating properties and ensuring proper duration of asphalt concrete pavements. Here is the essence of the new separate successive technology: crushed stone and sand are mixed with bitumen in the main asphalt concrete mixer, the amount of bitumen being calculated according to the bitumen absorption in the materials. Then the asphalt cement material produced in a separate high-speed mixer is passed, and the whole mixture is remixed in the main mixer and supplied to the customer. Both separate consequent technologies differ from each other in the order of supplying asphalt cement material into the main mixing unit. Separate successive technology was theoretically grounded by the correlation between the technological thickness of bituminous film and the chemical-mineralogical composition and size of constituents, by the correlation between the particle size and their capability to compose aggregates, by the emergence of the oriented binding material coating on the technological bituminous film encoating mineral particles. Special attention is given to the manufacturing of asphalt cement material in a separate high-speed mixer (3 Table). It was theoretically grounded that mineral filler passing through the intensive shift zone between the paddle ends of the high-speed mixer and the walls of mixing chamber disintegrate and new active surfaces become visible. The molecular structure changes and free radicals appear. This intensive mixing guarantees high bitumen adsorption on the surface of mineral filler, which increases asphalt concrete resistance to corrosion and its durability, improves ecological environment in the asphalt concrete plant. In order to confirm the reliability of research results and explain correlative and regressive regularity, statistical data were processed applying statistical data processing programming system “STATGRAPHICS”. The linear regressive analysis for determining close relations of separate asphalt concrete quality indicators with speed gradient of asphalt cement material shift in a high-speed mixer was performed. Therefore, the possibility to change shift speed gradient from 3000 to 5000 1/s is provided in terms of reference for manufacturing asphalt concrete mixing plant. Correlation between separate asphalt concrete quality indicators and asphalt cement material shift speed gradient as well as bitumen amount in the asphalt cement material was determined by multi-dimensional regressive analysis of experimental data. The calculated correlation factor squared (R2) and F criteria indicate the adequacy and reliability of the multidimensional regression model.