Slag cement, often called “ground granulated blast-furnace slag” (GGBFS), is one of the most consistent cementitious materials used in concrete. It is actually a byproduct of iron production. When the iron is processed using a blast furnace, slag and iron both collect at the bottom of the furnace.
The molten slag is separated from the molten iron. The slag can be used to make slag cement by being finely ground.
Because it is a byproduct, there is a large supply of it and it is very low cost. It is not unusual for GGBFS to be cheaper than portland cement, even after transportation costs are considered. At the same time, GGBFS has very high quality control standards and in many respects it performs better than portland cement in concrete mixes.
A lot of research has gone into studying how slag cement influences concrete mixes over the years and we know that it has definite performance benefits including increased strength at all ages, increased durability and resistance to chemical attack and staining, improved workability and finishability and reduced permeability leading to better resistance to chloride penetration, alkali-silica reaction (ASR) expansion, sulfate attack and freeze-thaw deterioration
Slag cement, or ground granulated blast-furnace slag (GGBFS), has been incorporated into concrete projects in the U.S. for over a century. Earlier usage of slag cement in Europe and elsewhere demonstrates that long-term performance is enhanced in many ways.
Slag cement is a recovered byproduct of the iron manufacturing process and can be used to replace a portion of portland cement in concrete mix design. The use of slag cement has demonstrated long-term performance enhancements allowing designers to reduce the environmental footprint of concrete while ensuring improved performance and increased durability.
Slag cement requires nearly 90% less energy to produce than portland cement. According to the Slag Cement Association, substituting 50% slag cement for portland cement reduces greenhouse gas emissions by more than 40% and lowers the embodied energy of concrete by more than 30%.
Slag cement (also called ground granulated blast furnace slag) is a hydraulic cement formed when granulated blast furnace slag (GGBFS) is ground to suitable fineness and is used to replace a portion of portland cement. It is a recovered industrial by-product of an iron blast furnace. Molten slag diverted from the iron blast furnace is rapidly chilled, producing glassy granules that yield desired reactive cementitious characteristics when ground.
Historically, some slag has been used in cement production in the United States since before 1900. While not as popular for general use today as it was 20 years ago, slag cement continues to be recognized by engineers, architects, contractors and owners for its performance advantages along with its sustainability initiatives.
Today, slag cement (often called ground granulated blast-furnace slag) is used in concrete projects throughout the U.S., offering enhanced performance properties while reducing life cycle costs and supporting sustainable development initiatives.
Blast Furnace Slag: A Sustainable Material
Slag cement reduces permeability, thus increasing water resistance and durability; protects against chemical attack; provides a more uniform distribution of crystals within the hardened paste, thus increasing resistance to cracking; improves impact resistance and abrasion resistance
Slag cement is a recovered byproduct of the iron manufacturing process and can be used to replace a portion of portland cement in concrete mix design. The use of slag cement has demonstrated long-term performance enhancements allowing designers to reduce the environmental footprint of concrete while ensuring improved performance and increased durability.
Slag cement, originally known as granulated blast-furnace slag, begins with the production of iron. The heart of the process is the blast furnace that refines iron ore into iron. The ingredients are heated to nearly 1500 degrees centigrade to form two components: molten iron and molten slag. Molten slag floats on top of the iron and is drawn off as a co-product in liquid form, called “slag” or “iron silicate” (the proper chemical compound). This material can then be ground into a fine powder that exhibits hydraulic properties when mixed with water (hydraulic cement).
The term “slag” has a negative connotation to most and is not typically used in construction during the sales process. However, slag is one of the most sustainable construction materials with many advantages.
Slag cement is a hydraulic cement formed when granulated blast furnace slag (GGBFS) is ground to suitable fineness and is used to replace a portion of portland cement. It is a recovered industrial by-product of an iron blast furnace. Molten slag diverted from the iron blast furnace is rapidly chilled, producing glassy granules that yield desired reactive cementitious properties when ground into cement fineness.
The use of slag cement has demonstrated long-term performance enhancements allowing designers to reduce the environmental footprint of concrete while ensuring improved performance and increased durability. Slag cement can contribute to achieving LEED points to help your project attain this globally-recognized sustainability certification.
Slag cement is sometimes confused with fly ash, which is another supplementary – or replacement – cementitious material that has many similar characteristics, but does not give the same level of performance enhancements as slag cement.
Portland cement is an excellent material for the construction of civil engineering works, capable of hardening under water and resistant to chemical attack. However, the raw materials used in its manufacture are very energy intensive to process and release a high amount of carbon dioxide.
Blast Furnace Slag (BFS) is by-product from iron production. It is a non-metallic product composed primarily of silicates and alumino-silicates of lime. When used in concrete, ground granulated blast furnace slag (GGBFS) acts as a cementitious material with additional properties as pozzolanic.
This blog will cover some basic information on slag cement and its many benefits, especially regarding sustainability.
Slag cement is a hydraulic cement formed when granulated blast furnace slag (GGBFS) is ground to suitable fineness and is used to replace a portion of portland cement. It is a recovered industrial by-product of an iron blast furnace. Molten slag diverted from the iron blast furnace is rapidly chilled, producing glassy granules that yield desired reactive cementitious properties when ground into powder.
Slag cement can contribute to achieving LEED points to help your project attain this globally-recognized sustainability certification. GGBFS can be substituted for Portland cement at the concrete plant on a one-to-one basis or in combination with fly ash and silica fume as a blended cement. Slag cement use can contribute to meeting the following LEED credits:
* Credit 500 – Regional Materials: At least 10% of building materials are extracted, processed and manufactured regionally (within 500 miles of project site).
* Credit 620 – Rapidly Renewable Materials: 2% of total building materials cost consist of rapidly renewable materials.
* Credit 621 – Low Emitting Materials: VOC content of adhesives and sealants are limited to 150 g/L; paints, coatings and flooring systems are limited to 100 g/