What Is Ground Granulated Blast Furnace Slag?

Granulated blast furnace slag is a raw material for the production of cement. When the pig iron is smelted in the blast furnace, the obtained fused material mainly containing silicate and aluminosilicate is quenched and granulated to obtain granulated blast furnace slag.

Granulated blast furnace slag, formed by melting slag from blast furnace iron-smelting, is mostly formed without time to crystallize

Fine grained. The molten slag flows directly into the pool for cooling, also called water quenched slag, commonly known as water slag. After the slag is ground, it is an active mixed material of cement.

In addition to glassy substances in the slag, there are also a small amount of minerals such as dicalcium silicate, calcareous feldspar, and monocalcium silicate, so they have very weak hydraulic properties. Under the action of alkali or sulfate activator, it can show higher hydraulicity and produce strength similar to cement. Commonly used activators are lime, gypsum, portland cement and so on. Most of the silica in the slag is acidic slag, and most of the alumina and calcium oxide are alkaline slag. Alkaline slag is more active than acid slag.

Granulated blast furnace slag is a molten material containing calcium aluminosilicate as the main component obtained during iron smelting by pig iron in a blast furnace. Most of the industrial solid slag obtained after water quenching into granules is mostly glassy and has potential hydraulic properties. Gelability. Fly ash is an industrial solid waste discharged from a pulverized coal-fired boiler in a thermal power plant. It is mainly glassy and has volcanic ash characteristics. It is one of the main raw materials for cement production, concrete preparation and wall material production ^[2]

The comprehensive utilization of slag in the cement industry has mainly passed through three stages:

The first stage (before 1995) granulated blast furnace slag was mainly used as a cement mixture. Mainly mixed grinding. The slag is difficult to grind, so the amount of cement in the cement is limited, generally not more than 30%.

In the second stage (1995 ~ 2000), foreign technology was learned. Slag powder, as a high admixture for high-performance concrete, was widely used in construction projects. However, the specific surface area of slag powder is required to be above 600m ² / kg, and there are only a few grinding stations in China. The main reasons are: imported equipment is expensive and production line investment is quite large.

In the third stage (after 2000), the most economical grinding fineness of slag powder should be controlled at about 400m ² / kg. Such slag powder can not only be directly supplied to the concrete mixing station as an admixture, but also can be used to synthesize high content slag cement with clinker and gypsum powder. As the cycle has approached 100 million tons / economy, the output of slag powder has doubled every year, and a new industry producing building materials is being formed in China.

The full name of "slag" is "granulated blast furnace slag". It is a waste slag produced by iron and steel plants when smelting pig iron. In addition to iron ore and fuel (coke) in the blast furnace ironmaking process, in order to reduce the smelting temperature, appropriate amounts of limestone and dolomite are added as fluxes. The calcium oxide, magnesium oxide, waste ore in iron ore, and the ash phase in coke are melted in the blast furnace to produce a molten material containing silicate and aluminosilicate as main components. On the surface of the molten iron, it is regularly discharged from the slag discharge port, and is rapidly cooled by air or water to form granular particles. This is slag. Contains more than 95% of glass and dicalcium silicate, perovskite, wollastonite and other minerals, which are close to the cement composition ^[3] .