Mineral powder for the production of asphalt mixtures

Mineral powder is used as one of the constituent organomineral mixtures, including asphalt concrete.

Characteristics of the substance

A mineral powder is a material that is obtained after grinding up rocks or powdered remnants of industry. As a normative document, SNIP and GOST are used. Mineral powder meets the requirements of the state standard of the Russian Federation No. 52129-2003 "Mineral powder for asphalt-concrete and organomineral mixtures".

It is made by grinding the following hard rocks: dolomitized limestone, dolomite, limestone. As raw materials, non-carbonate raw materials and industrial wastes are used, in particular fly ash in various types of production.

Two types of powder are used: activated and non-activated. Special types of activating substances are used for the first version of the material. They are a mixture of surfactants with bitumen. Depending on the properties and raw materials used, the material is divided into two grades:

• MP-1. These are powders from carbonate rocks and bituminous rocks.
• MP-2. This is a mass of powdered residues in industrial plants and non-carbonate rocks.

Activation of powder

The asphalt-concrete mixture will have the best performance if the powders included in its composition are activated. It is quite easy to do this. For this purpose, the so-called activation of the powders is carried out with a mixture of surfactants and bitumen.

The essence of the process is as follows. At the stage of crushing, the raw material is treated with an activator. Between the crushed particles of the material and the activator, a strong bond is formed. Thus, the surface of the powders becomes hydrophobic, and the individual particles interact better with bitumen. Of the total composition of the asphalt-concrete mixture , mineral powder is chosen for activation, since it has a large specific surface area (in the region of 4,000 cm ² / g). This is the most homogeneous component of the mixture.

Asphalt-concrete mixture, which includes an activated mineral powder, has several advantages:

• Increased density of the material.
• More durable consistency.
• Resistance to moisture and frost.
• Improved resistance to cracking.
• The consumption of bitumen is reduced by 15%.
• The mixture is laid at a lower temperature.

Method of obtaining

The production of mineral powder occurs in several stages. Everything begins with the preparation of the necessary raw materials. The starting material is dried in special drying drums. If limestone crushed stone has high strength, it passes preliminary crushing on roller or hammer installations. In some cases, this step is skipped.

Simultaneously, the preparation of activating substances takes place. Bitumen and surfactants are heated to operating temperature. Preparing the mixture for activation. The dried raw material and the activating mixture are taken in the correct quantities and mixed in lobed stirrers. But other types of apparatus can be used. When the mixture is well mixed, it is sent to the grinding unit for grinding to the required fineness. After that, the ready-made mineral powder is sent to a storage bin or storage facility.

Storage and transport

Mineral powder is stored in bins or storage silos. In these cases, it is necessary to periodically carry out special measures that do not allow the material to cake up. This can be aeration, pumping and other processing methods. When packing in small containers (bags), the material is stored in warehouses. During the manufacturing process, the powder is transported through conveyors, conveyors and screw conveyors completely enclosed by protective covers. For transportation on the territory of the enterprise, pneumotransport is used.

Transportation of powder outside the enterprise is necessary in cement carriers, closed wagons (bunkers), containers. Sacks of small packing should be multi-layered paper or polyethylene. In this case, the mineral powder is transported in simple closed freight cars.