When discussing chemicals involved in concrete production (where cement is the key binder), the question often refers to chemical admixtures added during the mixing process to modify the concrete's properties. Based on the provided reference, one such chemical is Calcium Chloride.
Calcium Chloride: An Accelerator
Calcium chloride is a chemical commonly added to cement mixes (concrete) because it acts as an accelerator. This means it speeds up the rate at which the concrete sets and gains strength.
- Function: Accelerates the hydration process of cement.
- Benefit: Can be particularly useful in cold weather to reduce the time required for curing and formwork removal.
- Availability: It is available for use in either liquid or flake form.
Usage and Standards
Using calcium chloride in concrete requires adherence to specific standards and limits, especially depending on the type of concrete being mixed.
- Standard Compliance: Calcium chloride used in concrete mixing must meet the requirements of ASTM D98. This standard ensures the quality and suitability of the chemical for its intended use.
- Usage Limit: For concrete mixes that are non-reinforced (i.e., without steel rebar), calcium chloride can be used up to a limit of 2% by the weight of the cement in the mix. This limitation is important because excessive amounts can have detrimental effects, particularly on steel reinforcement (causing corrosion).
In summary, while cement itself is a complex chemical compound, when people ask about a "chemical for mixing cement," they often refer to admixtures like Calcium Chloride, used to alter the setting time and performance of the concrete mix.
