Technology for the production of modifying additives for concrete and asphalt concrete

The article presents the results of the development of modifying additives for concretes and asphalt concrete, consisting of spherical SiO2 and fulleron, extracted from silicon production waste. The use of these additives can reduce the destruction of asphalt concrete pavements, increase water and frost resistance. The proposed technology is energy- and resource-saving, converting metallurgical production wastes into the class of “associated mineral raw materials” and improving the environmental situation in regions with the presence of metallurgical industries. The paper presents studies of the feedstock and characteristics of waste gases of silicon production, the characteristics of the main technological equipment for the production of modifiers, the instrumental-technological scheme of the production process, the chemical composition and quality indicators of the resulting spherical silicon dioxide. The order and relationship of the processes that make up the technology of the associated additives based on production of silicon have been determined. The economic effect of the use of these modifiers in asphalt concrete pavements is achieved by increasing the durability and increasing the turnaround time.


Introduction
One of the most common types of road surfaces is asphalt concrete. In recent years, the speed and traffic density of vehicles has increased. This leads to the destruction of asphalt concrete pavements and, as a result, to the need to make repairs earlier than the standard terms. One of the main reasons for the destruction of road surfaces is the insufficient water and frost resistance of asphalt concrete. However, one of the most effective ways is the use of modifying additives. In modified asphalt concrete, special compositions are used as a binder, including petroleum bitumen and a modifier. Modifiers are additives that change the physical and mechanical properties and structure of asphalt concrete in the right direction.
One of the variants of such modifiers is silicon dioxide [1][2][3][4][5], the other is carbon nanotubes and fullerene-like carbon [6][7]. Both of these components are contained in the dust of the gas purification plant of silicon production [8][9][10][11]. There are solutions for the automation of the technological process for the production of such modifiers. It is also worth noting the high importance of creating modifying additives specifically from production waste in order to improve the environmental situation [12].

Characteristics of raw materials, basic technological materials and equipment
The raw material for the associated production of modifying additives for concrete and asphalt concrete is dust from the gas cleaning system, waste gases from the ore-thermal furnace. The characteristics of waste gases from the production of silicon in an ore-thermal furnace are shown in Table 1.

Characteristics of the main equipment
The equipment used in the associated production of modifying additives for concrete and asphalt concrete based on the dust of the gas cleaning system is shown in Table 2.  Table 2. The equipment used in the associated production of modifying additives for concrete and asphalt concrete based on the dust of the gas cleaning system in the production of silicon.  The technological process must comply with the requirement: • POT RM 016-2001 "Interindustry rules on labor protection (safety rules) when working in electrical installations." Measures to ensure industrial fire safety and working conditions must comply with the legislative norms and requirements of the Russian Federation.
The equipment used must ensure the safety of work during operation and repair, comply with the requirements.

Conclusion
Developed technology: • describes the technology for the production of modifying additives for concrete and asphalt concrete based on dust from waste gases in the production of silicon; • establishes requirements for the quality of raw materials and materials used for the production of modifying additives from the waste gases of the ore-thermal furnace for silicon production; • determines the order and interrelation of the processes that make up the technology of the associated production of modifying additives based on carbon in the production of silicon. The developed technology contains provisions, the implementation of which is mandatory for all technological personnel of the workshop for the production of modifying additives for concrete and asphalt concrete. Additives produced using this technology can act as modifiers for concrete and asphalt concrete of highways.