1 Level (6 points)
History of the need for building materials
Requirements to construction materials
The basic requirements for materials include:
1. Sufficient compressive strength, tensile, bending and so on. D.
2. Deformation (elasticity, plasticity, creep, etc.) - To ensure minimum deformability of structures.
3. Resistance to dynamic effects.
4. Resistance to high and low temperatures.
5. The hardness and friability
6. Resistance to chemically active media
7. Resistance to climatic factors (temperature, environment, solar radiation, and so on. D.
8. Resistance to radioactive and other emissions.
9. Ability to surface hardening and bonding with other materials
10. The ability to create composites
11. Other properties (permeability, specific heat, thermal conductivity)
12. processability during manufacture, and as a structural material
13. Maintainability and interchangeability of structures and their elements
14. Reuse and recycling
15. Ecological safety for humans and animals.
The most widespread applications are silicate materials, their amount is 80% of the total volume of materials used in construction.
Cement production in the Republic of Kazakhstan
Most cement plants begin to feed the quarry where mined limestone (calcium oxide) and clay (oxides of silicon, iron and aluminum). D Depth can reach 100 meters, and the area - several dozen football fields. The raw material is crushed and mixed in a ratio of about 75% lime and 25% clay. The process of mixing the raw material mixture used to occur through mixing with water (slurry preparation - the so-called "wet" mode of production "). Now mainly used in the "dry method" of production, wherein the raw material mixture was prepared without mixing with water. This method can save up to 40 percent of the fuel (which was previously passed on subsequent drying of water), which significantly reduces the manufacturing cost of cement. There is also a combined method, or "semi-dry" method of production.
The obtained mixture was fed into a rotary searing oven where it is baked at 1450 ° C followed by quenching in air cooler. The output is a semi-finished product - the granules of up to 15 mm - so called cement clinker. The dimensions of the kiln at the wet process may be as high as 7 meters in diameter and 200 meters in length. In the dry method, the length of the furnace, typically less than 80 meters. The fuel for the clinker burning is usually natural gas. It is gaining popularity topic of alternative fuels such as used tires and rubber waste. Next is the step of preparing a proper cement from cement clinker - grinding in a grinding mill with the addition of gypsum (up to 5%, for adjusting the timing of cement) and mineral supplements (up to 30% depending on the brand of the resulting cement, slag, tripoli - to reduce costs) . Incidentally, the grinding step is sometimes transferred to a separate independent production when purchased cement clinker and transported over long distances.
As a rule, cement factories, there are several production lines. For example, the plant capacity of 1.5 - 2.5 million tons can be up to 4 rotary kilns and cement mills to 6.
Ready cement is supplied to the warehouse - cement silos, and then sent to consumers, either in bulk hopper cars and cement trucks, or packaging - bags of 1 - 1.5 tons (big bags) and bags of 50 kg.