What Is Slag Cement

What is Slag Cement

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 characteristics when ground into cement fineness.

Once the slag has been cooled and ground to a usable fineness it is stored and shipped to suppliers throughout the United States. 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.

Slag Cement - SCIC #1 
Slag cement, or ground granulated blast furnace slag (GGBFS), has been incorporated into concrete projects in the U.S. for over a century to improve durability and reduce life cycle costs. Among its measurable benefits in concrete are better workability and finishability, higher compressive and flexural strengths, and improved resistance to aggressive chemicals. SCIC #1, Slag Cement, provides an introduction to the material's benefits, manufacturing process, and relevant terminology, and makes an excellent primer for those new to the cement and concrete industry.
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Slag Cement and Fly Ash -SCIC #11 
Slag cement and fly ash are supplementary cementitious materials often included in contemporary concrete mixes. SCIC #11, Slag Cement and Fly Ash, compares the two materials, explaining that while chemical similarities exist between them, they exert different influences in concrete applications. Slag cement is a hydraulic cement while fly ash is a pozzolan. This information sheet lists the properties slag cement can bring to concrete in both plastic and hardened form. For example, the addition of slag cement usually results in reduced need for water, faster time of set, improved pumpability and finishability, higher 28-day strength, lower permeability, resistance to sulfate attack and alkali-silica reactivity (ASR), and lighter color.
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Blended Cements - SCIC #21 
According to ACI 116, blended cements consist "essentially of an intimate and uniform blend" of a number of different materials. Slag cement can be used to produce blended cement that complies with ASTM C 595, Standard Specification for Blended Hydraulic Cements, and as a constituent in hydraulic cements produced under ASTM C 1157, Standard Performance Specification for Hydraulic Cement. SCIC #21, Blended Cements, explains how materials are blended, and the role slag cement can play in blended cement. Blended cement may allow some concrete producers to take advantage of the benefits of slag cement despite storage constraints.
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