Mete COŞKUNTUNA
Sales and Marketing Manager
Cega Yapı Kimyasalları
As we all know, if the amount of water-soluble chrome (IV) is over 2 ppm in cement during the hydration of cement it can cause irritation on skin. This article aims to mention about some basic points known to everyone regarding this matter and offer a general summary.
The reason for irritation disappears when chrome VI is reduced to chrome III and the amount of chrome IV is decreased to a value below 2 ppm. Cega Building Chemicals has long been working on this matter with the German MIG company – its strategic partner.
The Turkish cement factories have long been working in this area and, with the start of the restricting regulation, they have been trying to complete all kinds of infrastructures and technical studies regarding the production of cement low in chrome IV. At Cega Building Chemicals we have been maintaining our parallel studies. As it is known, there are three different types of materials used in Europe and in the world as chrome IV reducers.
1) Tin sulfate
2) Iron sulfate
3) Antimony trioxide
In brief, they have the following differences when it comes to the reason of use, costs, and the shelf life of the final product.
1) When the EU brought a limitation to the use of lead as a solder in computers due to its emission, Chinese computer producers opted for tin instead of lead. This increased the use and the prices of tin and that very increase raised the costs in the cement sector, making the use of tin difficult even though it is the most suitable material in terms of shelf life and stability. The shelf life of the cement produced with tin sulfate (chrome III) is a minimum of 12 months and, it can be said that it is the best solution due to its low usage dosing when compared to other options. When used as liquid the dosing system cost turns out less and when used as powder the feeding system cost becomes high but the efficiency becomes higher with powder use and, thus, unit cost turns out low. Considering these, the preference takes shape according to factory needs.
2) Iron sulfate is another alternative. There are two types of uses, namely Hepta and Mono Hydrates. They offer different advantages, and the need can vary from factory to factory.
In Europe if the current chrome IV ppm value is below 5, FeSO4 Mono Hydrate is used considering the cost advantage. A chrome value of over 5 ppm, on the other hand, increases the amount of the use of iron sulfate and, thus, the possibility of iron stain formation in exposed concrete. In addition, based on the increasing amount of use, a freezing time delay formation is also increasingly possible. Hepta Hydrate use reduces such risks a little. Chrome III value shelf life is three months when iron sulfate (mono) is used. This time period is also considered in preference.
Again in Europe, 3 months were previously found sufficient for low chrome cement but then this was changed to 6 months. And within 2-3 months, it was decided that the shelf life be 12 months. The reason for that is the time period when cement and cement based products stay in stock, in other words, on shelves in DIY stores.
3) (ATO) Antimony trioxide use is another option as an alternative to increasing tin costs as a previously known method. It can be used as powder and liquid. Chrome reducing performance becomes 10 percent more when used during the grinding of cement, that is, when a powder product is used in mills. It is also a different alternative for factories having difficulties to find powder product silos. Adding a powder product directly to cement in an amount about 10 percent more than its normal dosing efficiently reduces its chrome IV value.
Average dosing is 50 g/ppm in liquid and 35 g/ppm in powder and its shelf life is about 12 months. They, on the other hand, are sensitively fed through gravimetric weighing systems with a domestic production of about 10,000 Euros while liquid ATO-based chemicals can be used through a simple pumping system.
At Cega Building Chemicals, we use these three different types of products and offer services and generate solutions for cement factories according to their own special terms. The research and production works that we carried out in collaboration with our partner company MIG have brought results. We will start to produce a liquid-based chrome (VI) reducing product with 100 percent domestic capital in the last quarter of this year at our new factory established in Düzce. We are already very happy that we will offer an added value to our country thanks to the cost advantage that we will provide factories through our new production technology.
