Slag cement is a gelling agent created through the process of granulating slag and grinding it. It is commonly used as a component in concrete and mortar, alongside other common ingredients such as Portland cement (the most common type of cement), air-entraining agents, aggregate, water, plasticizers and pozzolans.The use of slag cement in combination with Portland cement dates back to the early 1900s. The first recorded use of slag cement in the United States was in 1909 at Lehigh University for a concrete pavement. Since then, slag has proven to be an effective component of concrete, providing numerous benefits to your next project:

* Slag cement can improve the durability and performance of concrete by reducing permeability, decreasing alkali-silica reactivity potential and reducing explosive spalling potential due to fire or high temperatures.

* Slag cement can be used as an addition to concrete in combination with Portland cement or part of a separate SCM blend.

* Slag can be used at higher replacement levels than fly ash.

* Slag cement can contribute towards LEED credits for Green Building projects.*

We’ve all heard the debriefing. “Mix X concrete and you get Y results.” That’s how most of us were taught, but it’s oversimplified and leaves out important details that make all the difference in your final project.

Slag cement, for example. What is it and why should you care?

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.

There are many advantages of using slag cement in concrete including:

• Increased strength at all ages

• Improved durability characteristics

• Reduced permeability

• Better workability (slump retention)

• Improved finishability

• Reduced alkali-silica reactivity (ASR) potential

Slag cement can be added to concrete as an SCM in the same manner as fly ash, silica fume or other pozzolans. Using slag

Slag cement has been used for over 100 years to make high-performing concrete, and today, its availability and versatility makes it one of the most common supplementary cementitious materials (SCM) in the United States.

The ratio of slag in the cement mix is typically 30% or less, but can be increased up to 80%. The higher the ratio of slag, the more dramatic and beneficial are its effects on concrete performance.

Performance benefits from slag cement include:

Increased strength and durability

Reduced permeability

Reduced heat of hydration

Less cracking and shrinkage

Improved workability**

Slag cement reduces both the amount of materials required for every project, as well as greenhouse gas emissions. Using slag cement to replace a portion of Portland cement in a concrete mixture reduces carbon dioxide emissions by 8 percent on average. Slag also reduces energy consumption by 40 percent during production and improves concrete’s resistance to chemical attack and weathering.

From its earliest beginnings in ancient Rome, cement has been essential for world development. The production of cement provides employment for millions and is a key element in the demand for other commodities, including steel, coal, limestone and sand.

Cement is a hydraulic binder that when mixed with sand, stone or other aggregates and water produces either ready-mix concrete or mortar. With global population rising, urbanisation increasing and standards of living improving around the world, the manufacture and use of cement is increasing at an unprecedented rate.

The growing demand for construction projects around the world has led to greater demand for cement. Cement plants have limited resources to meet this demand by way of expanded production facilities, so there is a need to find alternative sources to incorporate into the mixture along with Portland cement to produce blended cements that can help reduce cost while meeting performance requirements.

Slag Cement: Slag cement is produced by finely grinding granulated blast furnace slag, a glassy by-product of iron production, and blending it with Portland cement to create a product that has a number of advantages over mixes that do not include slag cement. Blended cements that include slag can be used at the same levels as Portland cement and can reduce costs due to lower amounts

Portland cement, the foundation of concrete, is used around the world to make concrete for bridges, buildings, pavements, walls and many other structures. It is created by heating limestone and clay minerals in a kiln to form clinker.

Portland cement blends are often interground with blast furnace slag, a nonmetallic coproduct of iron production. The ground granulated blast-furnace slag (GGBFS) is a byproduct of steel manufacturing.

Benefits:

GGBFS provides durability and performance improvements to concrete that cannot be achieved with ordinary Portland cement (OPC). Adding GGBFS can extend the service life of concrete in many marine environments where chloride ion penetration can cause serious rebar corrosion problems. GGBFS stops or greatly reduces this problem because it combines with free lime in concrete to form calcium silicate hydrate (CSH), the active ingredient in most durable concretes.

In addition to its superior chemical resistance, slag cement also has a lower carbon footprint than OPC due to its reduced energy requirements during manufacture and the fact that it is manufactured from an industrial waste product.

The concrete industry is a major user of slag cement. It’s been used for years to increase strength, reduce permeability, improve resistance to chemical attack and enhance durability. 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 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 using slag cement, a few are highlighted below and detailed information sheets are located here.

Slag cement is a hydraulic binder and a cementitious material used in concrete for hundreds of years. Slag cement is a by-product of the metal refining process. It’s used to increase the strength and durability characteristics of concrete containing it.

Slag cement, usually ground granulated blast furnace slag (GGBFS), is also sometimes referred to as “ground granulated blast-furnace slag” and “slag cement.”

How does slag cement work?

The basis for the performance of slag cement in concrete is the chemical composition and physical properties of the material. The physical properties can be divided into hydration properties, like initial and final setting times, heat of hydration, autoclave expansion resistance, etc., which affect the early age performance and volume stability; mechanical properties, like compressive strength; durability properties, like sulfate resistance, alkali-silica reactivity (ASR), chloride resistance and permeability; plus freeze-thaw durability and abrasion resistance. These are important because they affect long-term performance.

Slag cement has many benefits. For one thing, it can improve performance characteristics that contribute to LEED accreditation. But it also has environmental benefits that help improve concrete’s