Steel slag is the waste residue discharged after steelmaking, which mainly means that the steel slag of open-hearth furnace and converter is stored for more than one year to replace crushed stone as the base material. Steel slag is grayish brown, honeycomb or dense, and its texture is hard. ?
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The use of steel slag:
1, application in steel field
Steel slag contains a considerable amount of iron, with an average content of about 25%, of which metallic iron accounts for about 10%. Many domestic steel mills have established production lines to treat steel slag, which are responsible for processing and applying the steel slag produced at present and recovering metallic iron from it. The content of scrap steel in steel slag recovered by medium-free autogenous grinding and magnetic separation is 8%.
No matter domestic or foreign large steel mills, the first thing to do with the produced steel slag is to recover a large amount of metallic iron and scrap steel contained in the steel slag by crushing magnetic separation technology for re-smelting.
2. Application of steel slag in infrastructure construction.
The chemical composition of steel slag shows that high alkalinity steel slag contains a lot of active substances such as C3S (tricalcium silicate) and C2S (dicalcium silicate), which has good hydraulic properties and can produce certain strength after hydration. Steel slag cement can be produced by mixing it with a certain amount of blast furnace slag, calcined gypsum, cement clinker and a small amount of activator.
A kind of hydraulic cementing material made of steel slag as the main component, adding a certain amount of other additives and appropriate amount of gypsum, is called steel slag cement.
The admixture for producing steel slag cement can be slag, zeolite fly ash, etc. In order to improve the strength of cement, silicate cement clinker with a weight not exceeding 20% is sometimes added. According to the types of additives, steel slag cement can be divided into steel slag cement, steel slag pumice cement and steel slag fly ash cement.
The production process of steel slag cement is simple, which consists of raw material crushing, magnetic separation, drying, proportioning, grinding and packaging. At present, there are several brands of steel slag cement produced in China, such as 275, 325 and 425, which can be used for plastering mortar and concrete in general buildings.
Steel slag cement can be used to prepare C 10~C40 ~ C40 grade concrete, and can be used for beams, slabs, stairs and blocks of civil buildings, as well as equipment foundations and crane beams of industrial buildings. When steel slag is used as raw material for cement production, it contains more f-CaO, which causes great expansion during hydration and cannot completely replace cement.
3. Application of steel slag in asphalt pavement engineering
With the continuous development of China's economy, expressway construction has also developed rapidly. Especially, 90% of expressway pavement structure adopts asphalt pavement structure. A large number of natural aggregates are used to meet the demand, so people consider steel slag as an alternative aggregate for asphalt concrete.
Judging from the usage of pavement, the pavement is basically flat, with rough surface and uniform particle distribution. There is no bulging and bulging on the pavement, there are some tiny cracks on the pavement surface caused by construction, and there are no pavement diseases such as cracking and looseness, which shows good anti-sliding characteristics and excellent road performance.
The paving of steel slag asphalt concrete pavement has achieved ideal results. In addition, it is of great economic and social significance for steel slag to replace ordinary natural aggregate in asphalt pavement.
Reference: Baidu Encyclopedia-Steel Slag