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concrete accelerator products accelerate the hydration of cement. Typically used in cold weather, these products reduce the curing and setting time of concrete to provide a faster, more efficient construction process.
HYDRASET® is an easy-to-use, ready-to-use liquid admixture that accelerates the initial setting time of mortar and concrete one to three times faster than without the use of an admixture. It also improves workability and increases strength.
Accelerating admixtures are typically dosed according to the weight of the cement in a batch, though some non-chloride accelerators have more variable dosages. Admixture manufacturers list a recommended dosing rate on their product data sheets.
Chloride-based accelerators act as a catalyst for hydration reactions in cement. These reactions occur in a temperature and time-dependent manner, which means the reaction is quicker as temperatures increase.
Inorganic salt-based accelerators contain nitrates, nitrites or thiocyanates instead of chlorides. They may be more effective at accelerating the hydration of cement, but they can cause corrosion issues in steel reinforcements.
Soluble organic compounds and quick-setting admixtures also speed the hydration of cement. These accelerators can also cause a loss of plasticity and workability in concrete, so they’re not typically used in precast or ready-mix applications.
Retarders counteract the accelerated hardening of concrete caused by hot weather. They work as water reducing agents and delay the initial setting of concrete.
Most of these admixtures are custom blends, so they do what the precaster needs them to do with the specific cement. Some are a combination of accelerating and water-reducing admixtures (ASTM C494 Type E chemical admixtures). Others include components that help offset shrinkage, which is a concern for precasters.