Mineral powder is used as one of the components of organomineral mixtures, including asphalt concrete.
Substance characteristics
Under the mineral powder is understood the material that is obtained after grinding rocks or powdery industrial residues. As a normative document, SNIP and GOST are used. Mineral powder meets the requirements of state standard of the Russian Federation No. 52129-2003 “Mineral powder for asphalt concrete and organic-mineral mixtures”.
It is made by grinding the following hard rocks: dolomitic limestones, dolomites, limestones. Non-carbonate raw materials and industrial waste, in particular fly ash in various industries, are also used as raw materials.
Two types of powder are used: activated and non-activated. For the first variety of material, special activating substances are used. 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 bitumen-containing rocks.
- MP-2. This is a mass of powdery residues in industrial plants and non-carbonate rocks.
Powder activation
Asphalt mix will have better performance if the constituent powders are activated. This is easy enough to do. For these purposes, 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 crushing stage, the raw materials are processed by the activator. A strong bond is formed between the crushed material particles and the activator. Thus, the surface of the powders becomes hydrophobic, and individual particles interact better with bitumen. Of the total composition of the asphalt mix , it is mineral powder that is chosen for activation, since it has a large specific surface (in the region of 4 thousand cm 2 / g). This is the most homogeneous component of the mixture.
Asphalt mix, which includes activated mineral powder, has several advantages:
- Increased material density.
- Stronger consistency.
- Resistance to moisture and frost.
- Improved crack resistance.
- Bitumen consumption is reduced by 15%.
- Mixing is carried out at a lower temperature.
Production method
The production of mineral powder occurs in several stages. It all starts with the preparation of the necessary raw materials. The source material is dried in special drying drums. If limestone crushed stone has high strength, it undergoes preliminary crushing on roll or hammer installations. In some cases, this step is skipped.
At the same time, the preparation of activating substances occurs. Bitumen and surfactants are heated to operating temperature. A mixture is being prepared for activation. The dried raw materials and activating mixture are taken in the right quantities and mixed in paddle mixers. But other types of apparatus can be used. When the mixture is well mixed, it is sent to the grinding plant for grinding to the required fineness. After that, the finished mineral powder is sent to the storage hopper or to a warehouse for storage.
Storage and transportation
Mineral powder is stored in silos or silos. In these cases, it is necessary to periodically conduct special events that prevent the material from caking. It can be aeration, pumping and other processing methods. When packing in small containers (bags), the material is stored in warehouses. During production, the powder is transported via conveyors, conveyors, and screws, which are completely enclosed by protective covers. For transportation through the territory of the enterprise pneumatic transport is used.
It is necessary to transport the powder outside the enterprise in cement trucks, closed wagons (bunkers), and containers. Bags of small packaging should be multilayer paper or polyethylene. In this case, the mineral powder is transported in simple, closed freight wagons.