Slag cement (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 properties when ground into powder.

Slag cement is commonly found in ready-mixed concrete, precast concrete, masonry, soil cement and high temperature resistant building products. While there are many applications and benefits of slag cement, a few are highlighted below and detailed information sheets are located here.

Uses of Slag Cement

Concrete: Slag cement can contribute to achieving LEED points to help your project attain this globally-recognized sustainability certification. The use of slag cement has demonstrated longer set times during hot weather placing, reduced heat generated during hydration and increased resistance to alkali-silica reaction.

Precast Concrete: Precast producers choose slag cement for its proven performance in precast concrete applications including architectural and structural products as well as infrastructure components such as box

Slag cement (also called ground granulated blast furnace slag) is a hydraulic cement produced during the reduction of iron ore to iron in a blast furnace. During this process, the iron ore is melted and a large amount of slag is generated. The molten slag floats on top of the molten iron from which it is continuously tapped off and air-cooled. Once cooled, it can be stored indefinitely. GGBFS has been used in concrete for over 100 years due to its consistent performance record and reputation for quality.

Slag cement (also known as slag aggregate) produces concrete with a lower permeability, higher strength and improved resistance to chemical attack when compared with ordinary portland cement concrete. 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 fine powder.

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 provides superior performance in both plastic and hardened concrete through reduced permeability, higher strength, improved resistance to both chemical and freeze-thaw attack, reduced heat of hydration, reduced alkali silica reactivity and self-consolidating properties.

Increased Durability: Lower permeability and increased strength improve durability providing increased resistance to aggressive environments such as deicing salts, sulfates, chlorides and carbonation resulting in longer service lives for concrete structures.

Higher Strength: The use of slag cement

Slag cement, or ground granulated blast-furnace slag (GGBFS), has been used in concrete projects in the United States for over a century. Earlier usage of slag cement in Europe and elsewhere demonstrates that long-term performance is enhanced in many ways. Most notably, concrete containing slag cement develops stronger, more durable concrete than 100 percent portland cement concrete. Increasing the percent replacement of portland cement with slag cement will further improve the long-term durability and performance of concrete.

Slag cement is commonly found in ready-mixed concrete, precast/prestressed concrete, masonry, shotcrete and structural concrete. 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.

Chemically, slag is a non-crystalline substance which contains mainly oxides of calcium, magnesium, silicon and aluminum. Slag cement is often called “ground granulated blast furnace slag” (GGBFS). When used as part of the cementitious material in concrete, the slag enhances durability and reduces life cycle costs and environmental impacts.

Since its introduction in 1904, no construction material has contributed more to the durability of concrete pavements than slag cement. Slag cement is a partial replacement for ordinary Portland cement that can improve concrete performance in both plastic and hardened states. In addition to its significant contribution to strength, slag cement has been proven to:

* Increase resistance to freeze-thaw cycles

* Improve workability

* Reduce permeability

* Increase abrasion resistance

* Increase volume stability

In general, the use of slag cement results in stronger, more durable, and easier-to-place concrete.

“Slag cement (Ground granulated blast furnace slag) and fly ash are the most common SCMs used in concrete. Fly ash is a pozzolanic material that reacts with calcium hydroxide at ordinary temperatures to form strength-bearing compounds.

Slag cement is a hydraulic binder, i.e., it becomes a cement when mixed with water. It is similar to Portland cement, except for its physical appearance, color and the fact that it does not contain clinker or free lime. Slag cement is manufactured by grinding granulated blast furnace slag (a by-product of iron manufacturing) to a suitable fineness. Slag cement meets ASTM C989 requirements in Types IP and IS.”

In the early times of cement industry, slag was not considered as a waste material and it was used as a raw material in the manufacture of clinker. The success of using slag cement in concrete depends on the combination of its properties such as pozzolanic activity, grinding ability, proper fineness and chemical composition.

The desire to make use of slag cement in concrete is mainly due to its pozzolanic properties and its ability to increase durability. Several investigators have reported that the use of slag cement in concrete has resulted in improved resistance to sulfate attack and reduced permeability.

Slag cement, now commonly called ground granulated blast-furnace slag (GGBFS), is a byproduct of steel production. When a molten blast-furnace slag is rapidly chilled as granules by quenching with water, it forms particles similar to Portland cement upon grinding. Since about 1990, GGBFS has been used as a supplemental cementitious material (SCM) for concrete at levels ranging from 5% to 40% by mass of total cementitious material content.