1. What Are The Types Of Slag
What are the types of slag? Slag is a general term for our daily life, and the professional name in the industry is called iron and steel metallurgical slag. It is a solid waste produced by the iron and steel metallurgical industry. Iron and steel metallurgical slag is mainly divided into several categories such as blast furnace slag, steel slag, ferroalloy slag, dust and mud. The slag we often refer to more often refers to blast furnace slag.
(1) Water slag: It is formed by the rapid cooling of cold water, the texture is looser, and the water content is generally larger
Water slag accounts for 80% of blast furnace slag and has potential hydraulic cementing properties. It can show hydraulic cementing properties under the action of activators such as cement clinker, lime and gypsum. It is an excellent raw material for cement. Therefore, it is mostly used as a raw material for cement mixing materials, non-clinker cement and concrete admixtures, and a small part is used to produce slag bricks and tiles.
(2) Heavy slag: natural cooling or slow cooling with a small amount of water, which can be used in various construction projects instead of crushed stone
(3) Expanded slag beads: semi-quenching effect, divided into
1) Hole——Lightweight aggregate and fireproof and heat insulation materials for construction
2) Glass body-raw material for cement production
2. Application Scope Of Ground Slag Powder
Finely ground slag powder is the powder made by drying, grinding and grading water slag. It is commonly referred to as slag powder. The full name is granulated blast furnace slag powder, also called slag powder. The main raw material for production is water slag. Part of gypsum can also be added, based on SO3%, generally 2%.
The ground slag powder is divided into three levels: S105, S95, S75. The higher the level, the higher the specific surface area and the better the activity.
S105 slag powder activity index is ≥105% in 28 days, ≥95% in 7 days, fineness ≥500m2/kg;
S95 slag powder activity index is ≥95% in 28 days, ≥70% in 7 days, fineness ≥400m2/kg;
The activity index of S75 slag powder is ≥75% in 28 days, ≥55% in 7 days, and fineness ≥300m2/kg.
The scope of application of ground slag powder is mainly concentrated in the cement production industry and concrete admixtures.
Due to the differences in production technology, industrial development, and standard formulation, the application of mineral powder varies from country to country. Some are mainly used to produce cement, such as Japan and Brazil; some are mostly used as concrete admixtures, such as the United States; some are both, such as China and the European Union.
1. Making slag cement, saving the amount of cement raw materials
When the specific surface area reaches 450 m2/kg～550 m2/kg and the 7d activity index reaches about 100%, a small amount of clinker (about 25% clinker) can be used to produce 32.5～42.5 grade slag cement, which not only reduces production costs, but also It saves a lot of energy, reduces environmental pollution, and has significant economic and social benefits. At present, the mixing amount of Portland slag cement produced by most domestic companies is about 55%.
The grindability of slag is poor. The slag grinding technology determines its quality and output. The use of slag powder in cement production is directly related to the grinding technology and the activity of the slag powder. The proportion of slag mixed in cement It is related to the activity of slag powder. The higher the activity, the higher the blending ratio, and the cement strength produced can reach the standard.
Tip: The production process of a cement plant is generally
Mining-crushing-pre-homogenization-storage-measurement, batching-raw meal grinding-storage, homogenization-waste heat decomposition, kiln calcination-clinker cooling, storage-measurement, mixing ratio-cement grinding-cement storage , Storage-bulk, bag delivery
2. As a concrete admixture, instead of cement
The slag powder after strict processing procedures can be close to or greater than 100% due to its 28-day activity index. The slag powder can replace part of the cement in an equal or excessive amount to prepare concrete, thereby reducing the amount of cement in concrete, reducing concrete production costs, and saving resources. Reduce energy consumption. In Japan, there has even been a low-carbon concrete that uses slag powder as the main body of cementing material and does not use any cement. At present, our country’s technology can mix 10-40% of slag powder to produce concrete.
In addition, slag powder can effectively enhance the strength of concrete and configure high-strength concrete. The state also clearly advocates the development of concrete mixing plants, the promotion of ultra-fine grinding of slag and fly ash, and the preparation of cement and high-performance concrete according to market demand.