- Concrete retarder: how does it work?
- In which case are these concrete additives used?
- How to use the concrete retarder?
Concrete retarder is an adjunct for prolonging the fluid texture of concrete. It is generally in the form of a liquid which is poured into the mixing water before being mixed with the other essential elements to create concrete. With this product, the plug can be delayed from 4 hours up to 36 hours depending on the needs and requirements of the professional.
Concrete retarder: how does it work?
Concrete retarder is a specific product that allows a slower hold of the concrete. This adjuvant based on lignosulphonates, carbohydrates or zinc or lead oxides remedies various problems in concreting.
In particular, the retarder prevents the water from evaporating too quickly in very hot weather, while adjusting the heat released when the cement is hydrated. Concrete retarders are essential products for building professionals. Adjuvants must comply with standard NF EN 934.2.
In case of successive castings, this adjuvant makes possible the realization of a concrete block to the homogeneous look even if the pourings are carried out in a deferred manner. In the case of vibrated concrete, the retarder minimizes or even eliminates the needle effect on the hardened material.
In the end, the start of setting is deferred, which makes possible the tweaking of the result or the completion of other complementary works.
In which case are these concrete additives used?
Concrete retarders have many applications. They are particularly essential for the preparation of a BPE or ready-mixed concrete or other materials such as heavy concrete. In addition, this additive allows the concrete mixers to achieve casting continuously and at the highest temperatures. Moreover, if necessary, it is possible to transport concrete over long distances without fear that it will "take".
How to use the concrete retarder?
The self-timer usually fits into mixing water. In general, it is introduced after the other components, in this case cement, water and aggregates. These are ideally wet beforehand for optimal action of the adjuvant. This avoids, indeed, that the additive is absorbed by the aggregates. The dosage varies on average between 0.2 and 0.5%, calculated on the basis of the weight of the cement. The ideal is to use an automatic doser for a meticulous and effective dosage. It is recommended to take the advice of a concrete specialist not to make mistakes because this material is difficult to handle and can be quite "capricious".