• Construction Dry-mix Calcium Sulfate (Plaster, Gypsum and Anhydrite)

Calcium Sulfate, Anhydrous – Synthetic (Anhydrite)

• Calcium Sulfate, Anhydrous (Synthetic Anhydrite), is a common ingredient in many pre-packaged dry-mix compounds. In the construction industry, typical applications like road repair patches, screeds, SLU underlayment, self-leveling flooring, tile adhesive, industrial grouts, and anchors, where Anhydrite is used as a binding material for replacing cement and offers benefits like enhanced fluidity for self-leveling, improved dimensional stability, excellent mechanical strength, and superior thermal conductivity. Additionally, Anhydrite applies to other industrial fields like cement production and fertilizer.

  Two primary methods of Synthetic Anhydrite production are Flue Gas Desulfurization (FGD) and Hydrofluoric Acid (HF) production. FGD anhydrite is a high-purity and consistent product that may have a slower setting time. In contrast, HF anhydrite is a fast-setting product that may have higher impurities and inconsistent quality.

  The differences between the two methods and their effects on pre-packaged dry-mix materials are explained below:

  Flue Gas Desulfurization (FGD) Anhydrite:
  FGD is a process used to remove sulfur dioxide (SO2) from the flue gases of power plants that burn coal or oil. FGD anhydrite is a byproduct of this process and is created when calcium sulfate is precipitated out of the flue gas.

  Benefits:

  • High purity: FGD Anhydrite has a very high purity level, which makes it an excellent ingredient for pre-packaged dry-mix materials.
  • Low impurities: FGD Anhydrite has common contaminants, such as heavy metals, making it safe for construction applications.
  • Consistency: FGD Anhydrite is consistent in quality, which makes it easier to use in pre-packaged dry-mix materials.

  Deleterious effects:

  • Slow setting: FGD Anhydrite may have a slower setting time than other types of Anhydrite, which may affect the drying time of the pre-packaged dry-mix material.

  Hydrofluoric Acid (HF) Anhydrite:
  HF Anhydrite is produced through a chemical reaction between calcium carbonate and hydrofluoric acid.

  Benefits:

  • Fast setting: HF Anhydrite has a fast-setting time, which can be beneficial for pre-packaged dry-mix materials that require a short drying time.
  • High compressive strength: HF Anhydrite has a high compressive strength, which makes it an excellent ingredient for pre-packaged dry-mix materials.

  Deleterious effects:

  • Higher impurities: HF Anhydrite may have higher contaminants, such as heavy metals, making it less safe for construction applications.
  • Inconsistent quality: HF Anhydrite may have inconsistent quality, making it more challenging to use in pre-packaged dry-mix materials.