Initially, blast furnace slag was just a waste of steelmaking and nothing more. At the end of the 15th century, the melted slag was first used in Germany, at the time of his cast cannonballs. In the 17th century slag were used in the form of crushed stone for road fill and rubble as filler when pouring concrete foundations and supporting structures.
In the mid-19th century, when the metallurgical industry of the developed countries was in full swing, and mountain ash continued to litter the surrounding area businesses, the product of the melt domain has become a problem over which many scientists thinking and practice of the time. In order to save energy and natural resources through efficient use of waste product, it was necessary to expand the range of application of the slag.
In 1865, the year the first time the technology has been applied granulating slag with water, and scientists have identified cementing and hydraulic characteristics of this valuable material. It was from that moment it became widely used in construction, including the production of cinder block wall, concrete products, as well as in the construction of monolithic structures. Mainly slag used as an active additive capable of partially replace mineral additive in cement mark M 400. This saves on the production of cement clinker and cement markets of the country appeared at more affordable prices.
- "Magnitogorsk cement-refractory plant"
The first factory for the production of slag cement was launched in Dnepropetrovsk in 1914. A little later, at Kosogorsky metallurgical plant in Tula, was put into operation a plant for the production of cement from its own blast furnace slag. Since then, tens of cement plants in major steel plants. At present, the proportion of blast furnace slag cement production is about 30% of the total volume of cement produced in Russia. One of the largest is located in the city of Magnitogorsk, Chelyabinsk Region —
Slag by co-grinding Portland cement clinker two-step with the dried granulated slag. It also adds a small part of gypsum, which speeds up the process of initial seizure. As a result of experimental studies have shown that the content of the slag in the cement should not be less than 25 and not more than 60%, only in this case will have a waterproof cement properties without loss of quality.
In comparison with Portland cement, slag cement hardens more slowly during the initial period. This would seem to disadvantage an advantage, because a slow and uniform drying, the product of slag cement not show a tendency to decrease in strength and cracking, resulting in stress and tension. After 28-days shlakoportlandtsementny stone gaining high strength and characteristics are not only not inferior to conventional cement PTs 400 D20, and even surpass that the physicochemical properties cinder prevent exposure of fresh water and a corrosive effect on steel rebar, and as a result, products of slag cement not crack and significantly longer retain strength and resistance to bending and twisting.
- Indications electron microscope
Water resistant cinder products is very easy to explain) But just in name only, and is not using the term quite understandable, because in fact, during curing, a slag cement slurry flows complex chemical reaction: In the clinker part of the cement hydration occurs, resulting in hardening of the system form a saturated solution of calcium lime. Built environment is alkaline and sulphate slag grains excitement, the surface layers which are involved in the process of hydrolysis and are directly involved in the formation of a more dense structure of cement stone. Contact with the surface layers of slag glass in microcracks, lime mass transfer contributes to the solution of cations due to rupture of silicon-oxygen bonds. As a result, when entering into reaction with the lime, formed hydroaluminates calcium silicate and are similar in composition to the clinker minerals and having binding capacity.
To achieve maximum hydraulic and strength characteristics, breeze articles are subjected to mandatory moisture-heat "stewed" in special steam chamber at a temperature of 90-100 ° C, for 14-15 hours. In other cases, for example, by pouring ties, as well as during masonry or painting and decorating, slag concrete needs no further treatment.
In the modern world of blast furnace slag are popular in many areas of the construction industry. The main focus is the production of cement with conventional marking SPC. Cements of this brand are the foundation of hydraulic structures and massive concrete structures that require practicality and durability in contact with the water, as well as being under the influence of aggressive industrial and natural environments. Also, the slag is widely used in the production of asphalt concrete cinder blocks, foundation blocks, various kinds of water-and heat-insulating fillers and other building materials.