Chemical compositions play an important role in the construction industry. The development and improvement of building materials often depends on the integration of chemical components. A key issue here is chromate reduction in cement. Cement remains an essential material for constructions and buildings. In this article, I will highlight the importance of iron sulfates in this process and show how we at COFERMIN contribute to producing more reliable and environmentally friendly building products.
Hexavalent chromium can be present in cement in concentrations of up to 30 ppm, depending on the raw materials and production conditions. In this water-soluble form, it can penetrate the human skin and trigger allergic reactions such as chromate dermatitis, known as bricklayer’s itch. To minimize these risks, a reduction of the chromate content in cement to less than 2 ppm is required, in accordance with EU Directive 2003/53/EC and Regulation (EC) No. 1907/2006.
Iron sulfate has proven to be an effective agent for reducing hexavalent chromium to its less harmful trivalent form. This chemical reaction occurs immediately after the addition of mixing water to the cement. However, the effectiveness of iron sulfate can vary depending on its form and application. Different types of iron sulfate offer distinct properties, each with its own set of advantages and disadvantages.
We offer various grades of iron sulfate that differ in form, effectiveness, and handling. These variations allow for tailored applications to meet the specific requirements of cement production.
Iron sulfate monohydrate (FeSO₄- · H₂O)
This thermodynamically stable form has low residual moisture, high thermal stability, and a low tendency to build lumps. It is versatile and can be used both before and after grinding, making it ideal for high-temperature applications. However, its slightly lower water solubility might necessitate a higher dosage.
Iron sulfate heptahydrate (green vitriol or FeSO₄·7H₂O)
Iron sulfate heptahydrate (green vitriol or FeSO₄·7H₂O): This form is highly water-soluble and more cost-effective. It is typically dosed as a wet salt or saturated solution and is optimal for applications with low chromium content, up to 5 ppm. However, its higher residual moisture content requires special storage conditions to prevent clumping.
Our iron sulfates are produced from by-products of the steel industry and titanium dioxide production. In this process, diluted sulfuric acid is generated, which reacts with iron compounds to form iron sulfate. This method not only promotes sustainability but also ensures the flexibility of our products, benefiting our customers. We offer iron sulfate monohydrate and iron sulfate heptahydrate in both powder and granulate forms, available in 25 kg bags, big bags, or bulk in tipper trucks.
To recap: Iron sulfate plays a crucial role in the production of cement and other building materials. It effectively reduces chromate levels while contributing to sustainability and flexibility in the construction industry. We place great emphasis on tailoring our products to meet the specific needs of our customers, delivering real added value.
Benjamin Konn
Sales & Marketing Manager