set retarder is a type of admixture that delays the setting time of concrete. This is typically done in the production of ready-mixed concrete or on-site to extend workability.
A typical use of a set retarder is to offset the temperature acceleration effect that occurs during placement or transportation, allowing the concrete to be placed safely at higher temperatures. Temperature is a significant factor in all aspects of concrete production, including the rate at which concrete sets.
Most commonly, regular retarders are used to place concrete during hot weather when long travel times or emergency situations exist. They are also often used for mass concrete pours to prevent cold joints.
Extended-Set Control Admixtures
The most common extended-set control admixture is a retarder/water reducer system that slows hydration and increases the workability of the concrete. Depending on the amount of retarder added, this can add as much as several hours to the setting time.
Fritz-Pak manufactures retarders, accelerators, and water reducers (superplasticizer) in packets that can be added on site to provide additional workability and delay the setting time. They are safe for use on concrete, masonry, and plaster.
Mini Delayed Set
Fritz-Pak’s Mini Delayed Set is a dry powdered set retarder that is packaged in ready-to-use water-soluble bags. It is formulated to stabilize residual concrete wash water or extending the setting time of concrete without adding calcium chloride, nitrates, or nitrites to the mix.
The adsorption of the set retarder by the C2+, OH- and Si ions prevents them from precipitating. The resulting complexes are not soluble and inhibit the growth of the hydration products.