Silica fume, ground granulated blast furnace slag (GGBFS), metakaolin, ground glass pozzolan, and fly ash are supplementary cementitious materials (SCMs). Meaning they replace some of the cement content in a specific mix. Each of these materials are used to improve different qualities. Below we discuss what the material is, and why you might consider using a specific SCM in your mix.
Silica Fume:
Silica fume, or microsilica, is a byproduct of silicon metal or ferrosilicon alloy production. It consists of amorphous, ultrafine particles of silicon dioxide (SiO2). Silica fume is known for its high pozzolanic reactivity and ability to improve concrete's strength, durability, and resistance to chemical attack.
Typical Conditions for Use:
· High-performance concrete or when enhanced strength and durability are desired.
· Applications where resistance to water penetration, chemical attack are necessary, like marine structures, bridge decks, and industrial flooring.
Additional information:
Ground Granulated Blast Furnace Slag (GGBFS):
GGBFS is a byproduct of the iron-making process in blast furnaces. Molten slag is quickly cooled to produce granulated amorphous silicates and aluminosilicates. These granules are ground into a fine powder.
Typical Conditions for Use:
· Can improve workability, durability, and long-term strength.
· Suitable for mass concrete applications, tends to reduces the heat of hydration and improves resistance to alkali-silica reaction.
Metakaolin: Metakaolin is a calcine-activated form of kaolin clay. Because of metakaolin’s high amorphous silicate and aluminosilicate content, when ground fine enough, it can result in highly pozzolanic material.
Typical Conditions for Use:
· Metakaolin can improve concrete's strength, durability, and workability.
· Applications requiring high early strength development or reduced drying shrinkage.
· High-strength concrete, precast, applications for reducing alkali-silica reaction (ASR) potential.
· White or lighter-colored concrete.
Additional information:
Ground Glass Pozzolan:
Ground glass pozzolan (GGP) is made from post-consumer or post-industrial waste glass. When processed and ground into a fine powder it can achieve strengths greater than regular portland cement. GGP is primarily amorphous silica and other oxides.
Typical Conditions for Use:
· Ggp enhances concrete's strength, durability, and sustainability.
· It can improve the workability of concrete and when ground fine enough it can reduce ASR.
· Ggp is suitable for applications where a high level of pozzolanic activity is required.
· White or light-colored concrete: ggp is often used in architectural concrete, producing white or light-colored concrete.
Additional information:
Fly Ash:
Fly ash is a byproduct of coal combustion power plants, typically is composed of silicon dioxide (SiO2), aluminum oxide (Al2O3), and iron oxide (Fe2O3).
Typical Conditions for Use:
· Enhance its workability, durability, and resistance to sulfate attack.
· Improve concrete's long-term strength.
· Fly ash is suitable for various applications, including general construction, pavement, and mass concrete structures.
Additional information:
In closing, each SCM has its own unique properties and benefits. Silica fume can improve strength and reduce porosity, GGBFS can improve workability and durability, metakaolin provides early strength and shrinkage control, ground glass pozzolan increases strength and offers sustainability benefits, and fly ash is used for its performance-improving characteristics. The material selection depends on the project's specific requirements, such as strength, durability, workability, and environmental considerations. Ternary, or quaternary cement systems can be even more beneficial by having some of the desired characteristics of each selected material. In any case, it's essential to consult industry guidelines and conduct testing to determine the appropriate SCM and dosage for optimal concrete performance in a given set of conditions.
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