Modeling of construction waste processing system development

Construction waste is the most important source for reducing raw material resources. In this regard, many countries conduct large-scale research in developing progressive construction waste utilization technologies and creating highly efficient production equipment. Current experience in this field views the construction waste processing system as a number of interconnected subsystems: organizational and technical preparatory measures; waste collection and sorting; waste containerization, packaging and transportation; waste processing and manufacturing of recyclable resources. Each sub-system consists of a set of measures which characterize the change in material quality and properties. Modeling of the construction waste processing system addresses the task of assessing the actual level of the system and subsystems and determining the condition of the same within certain forecasted time perspectives. For this purpose, the cost vs. revenue comparison tools are used. To develop the construction waste processing system and maintain it in working condition it is important that, early on in the project, a waste classification catalogue and a relevant glossary of terms be compiled with all waste processing contractors having to agree to it and observe it. Also, a data bank containing all the relevant engineering and process documentation shall be drafted and maintained


Introduction
Annually over 5 billion cubic meters of construction waste is processed into a valuable raw material internationally, which allows for construction and reconstruction costs for building and structures to be significantly reduced, raw material resource consumption to be cut down, landfill capacities to be spared and ecology to be improved [1,2].
The bulk of construction waste in Russia comes from construction operations due to rebuilding and repair projects of buildings and structures -65.8%, demolition and dismantling facilities -29.3% of the total volume of construction waste. While the share of construction waste in new construction accounts for 1.4%, construction companies report the figure not exceeding 3.5% accounted for by rejects and discarded items of reinforced concrete structures. The construction waste nomenclature includes 21 types of waste, among which concrete and reinforced concrete waste, scrap brick, scrap asphalt prevail (Table 1). Bituminous, tar, bitumen-tar, polymeric-bitumen, rubber-tar and bituminous unsupported materials (sealing membrane) and cardboard-based materials (bituminous waterproofing, asphalt roofing paper, tarpaper), glass-based materials (fiberglass roofing material), asbestos paper-based materials (asbestosbased asphalt felt) Plastic and polymer waste Linoleum, vinyl tiles waste Polymer roofing materials waste foam plastic, porous foam waste (polystyrene, polyurethane) Plastic and polymer waste Plastic water supply pipes, drainage and electrical conduit Hand railing and staircase railings Polymer-based molding waste For the EU zone average rate in weight percent accounts for 57% of scrap brick, 37% of concrete and reinforced concrete waste, 2% of wood waste.
In many parts of the world, for example, in Germany, Holland, Belgium, Japan, etc., landfills are never used for dumping construction waste. Under the existing laws of these countries, waste grinding and recycling should be carried out at the demolition site [3]. Diverse and large-scale research in developing progressive construction waste utilization technologies [4,5,6] and creating highly efficient production equipment [7,8] have a great impact on construction waste processing system development. As a result, developed rules regulate the use of recycled crushed stone and sand; recycled aggregate determination of the concrete mix compositions; parameter estimation of recycled materials [1,9].Particularly, experience and results of such companies as Parker Plant Ltd (England), 'Agrikon' (USA), 'Stincorol' (Holland) etc. are widely used. The first stationary disposal plant was built in Holland in 1970. Currently, there are over 50 stationary plants in operation in this country. Machine-building enterprises of the country designed equipment for work in urban settings with minimal environment impact. For example, 'City'-like equipment has a number of advantages like usage of environmental friendly hydraulic system fluids and oiling; it's low-noise; it's fitted out with highly-efficient dedusting system of working area [10,11]. First-class factories assembling crushing and screening plants can be found in Austria. For example, 'Maschinenfabrik Liezen und Gieberei Ges.m.b.H (MFL)' is the leading European equipment manufacturer for grinding and processing of minerals and recycled construction material scrap. Austrian companies have innovative production facilities, fitted out with high-performance equipment and technical instruments, which allow producing a vast range of crushing and screening plants on a turnkey basis [12,13,14].
In many countries, the primary importance to the issue of construction waste processing consists of sound policy of tax on land, occupied by dumps and landfills; and stimulation system, used by manufacturers, who process waste. In this vein in 1992 Canada passed the law on increasing tax on land, occupied by environmental friendly waste. Waste recycling is not just an alternative to mineral raw materials but it also can reduce environmental damage. This results in reduction in volume of mineral raw materials extraction, which is closely connected with decrease of land exploitation, conservation of all types of natural resources and landscape. The ecological situation of cities improves due to recycling waste production conducting demolition works. Therefore, this direction of waste processing has been developing successfully for many years [4,11].
A series of countries (Germany, Holland, etc.) elaborates and passes waste laws, where mandatory quota of residual materials is determined, in order to use obligatorily construction waste as raw material. However, quota rate grows higher with every passing every year. For example, in Germany processing and realization quota accounts for 60% of construction waste, 40% of construction facility waste, 90% of road construction waste.
In Russia until 1990, construction waste was almost never recycled. The bulk of it was buried in landfills. The situation has changed radically by now. The leader in this direction is Moscow building complex. Due to the rise of the construction industry, construction waste production began to increase rapidly since 1994 in Moscow. For example, about 2 million 51 thousand tons of construction and demolition waste were received on just commercial orders in 2003. Today construction waste volume is about 10 million tons. As practice shows, crushing and screening complexes in Moscow are constantly increasing processing construction waste capacity. Around 40% of scrap concrete was recycled in 2003, in comparison with about 85% in 2016. Scrap metal waste just as glass waste comes in great volumes, and a number of organizations ('Vtortsvetmet', 'Vtormet', etc.) receive them for recycling.
There are two technological schemes in forming construction waste processing facilities stationary and mobile plants. Stationary plants are based, as a rule, in industrial zones, and they are not linked to specific objects. These plants are fitted with stationary equipment; construction waste is delivered there by road, rail or water. Stationary plants are typical of large cities and are intended to process concrete and reinforced concrete waste, asphalt concrete, scrap brick, granite waste, etc.
Mobile plants include relocatable and transportable units, and it is recommended that these are installed in the areas of mass demolition of buildings and structures. Relocatable units consist of several modules, which should be installed on a foundation. The units have a loading bin, flight conveyer, sorting drum, magnetic separator, grinder, etc. Caterpillartracked and wheel-mounted mobile units are manufactured by machine-building industry. These units have power-plant, a charging bin, grinder, magnetic separator, conveyor system, sorting drum.
Domestic and foreign experience shows that it is possible to avoid negative implications of the formation and accumulation of construction waste only by controlling all the processes of collecting, sorting, transporting and processing wastes, combined by tasks and objectives and fit in with city (district) general sanitation plan. This system can be represented as a system for processing construction waste on the base of inter-related measures, tasks and objectives of organizational, technical, technological, economic and social principles, providing systematic and continuous collecting, sorting, transporting and processing of construction waste; and recycled raw material with preplanned technical-and-economic indexes.
The system is rooted in purposeful activities of customer service, construction, engineering, transport, supply organizations and processing companies; due to actions coordination, balanced labor and material-technical resources; guaranteed execution of planned volume of development and realization of recycled raw material.
Structurally the construction waste processing system should consist of the following subsystems: organizational and technical support; waste collecting and sorting; waste containerization, packaging and transportation; waste processing and output of recycled resources. When creating the construction waste processing system one should consider the following: wide range of construction waste based on materials and their combinations; wide range of collecting, sorting, delivering and processing waste forms and methods; territorial dispersion of the waste acceptance and processing enterprises; restrictions to temporary construction waste storage; bulk of construction waste accumulation onsite enterprises and landfills. According to its goals the construction waste processing system can be divided at least into three levels.
Level 1 has four main goals -environmental safety, assurance of recycled materials quality, labor costs minimization, profit-maximization.
At level 2 environmental safety can be achieved by constant monitoring of environment, effectiveness of laws and regulations, compliance with the requirements of waste burial. First, compliance with technology regulations and appropriate work of quality control unit are the basic key to succeed in recycled materials quality. Labor saving, personnel development, rational resources concentration, constant delivery organization of construction waste and stability of market conditions are of great importance with regard to labor costs minimization and profit-maximization.
Level 3 is different from the levels above as it has more sub-goals. Ecological appraisal, construction waste delivery in closed containers, assessment and punitive sanctions for environment pollution are very important at the stage of environmental safety. Product certifi-4 MATEC Web of Conferences 251, 02032 (2018) https://doi.org/10.1051/matecconf/201825102032 IPICSE-2018 cation, application of waste-free technology and effective equipment are of exceptional importance for recycled materials quality assurance. These criteria are also crucial for labor costs minimization and profit-maximization sub-levels, where such sub-goals as sorted waste and its constant delivery organization and relevancy of construction industry demand are needed.
Materials and methods of each subsystem are summarized in Table 2.

Main part
The program-and purpose-oriented development model of the processing construction waste system is determined by the system goals dominating over sub-system goals.
Bench-mark data include: 1. Nomenclature code of construction waste -L l , 1    17. Part by volume gain coefficient of l-nomenclature during processing (burial) of one ton (cubic meters) of construction waste {d l }.
The equation of connection between subsystems of collecting, sorting, transporting and processing of construction waste can be expressed through the costs: It is required to find the values of V τ and Wτ , characterizing the interconnections of subsystems development.
In order to simplify the model it is accepted It's appropriate to assume that the quantities Q (1) , Q (2) , G (1) and G (2) are constant values for the whole time period. It's appropriate to assume the equation (1) as the difference The principle of algorithm development assumes that the first summand interprets development of collecting, sorting, transporting of construction waste subsystems, and the second summand represents development of processing construction waste subsystem.
In such case capacities for processing construction waste should be sufficient at a given time. Therefore, the maximum production capacity is to be selected out of all possible options. As a rule V is a part of construction waste to be buried in specialized landfill sites.
As we see from studies and calculations, construction waste processing system development is assured for the whole time period, if for each time duration τ = 1, 2, 3, …, t the arrangement of the formula is going to be: The values of α, в, с, d are determined by the methods of differential calculus: Where: α is waste volume l-nomenclature in 1 ton (cubic meters) of construction waste; в is waste volume l-nomenclature, corresponding to their increase; c is waste volume l-nomenclature, expendable on obtaining 1 ton (cubic meters) of recycled resource; d is waste volume l-nomenclature, expendable per unit of capacity of processing enterprises. To develop the construction waste processing system and maintain it in working condition it is important that, early on in the project, a waste classification catalogue and a relevant glossary of terms be compiled with all waste processing contractors having to agree to it and observe it. Also, a data bank containing all the relevant engineering and process documentation shall be drafted and maintained. Engineering and introduction of data bank and its functions make possible to outline the main directions of data analysis and meteringintroduction of a unified register of construction waste, registration of technology regulations for management of construction and demolition waste, the analysis of the current state and growth of construction waste forecast , development of recommendations for effective usage of waste, creation of the system, operating with recycled resources, performance of monitoring functions.
The technical regulations on waste treatment process, as a basic working paper, should be of a standard form and represent the whole waste treatment process, from collection to processing or burial. This regulation is developed separately for each waste production facility.