Adding an additive to make concrete set faster can be useful when pouring new concrete during cold weather. This can help reduce the set time of the concrete and decrease the chances of cracking from ice crystals formed during the curing process.

Accelerators, like water reducers, retarders and plasticizers, are one of the most common types of chemical admixtures. They are often added to a concrete batch either immediately before or during mixing.

Calcium Chloride – This is the most commonly used cement accelerating admixture. It can accelerate the set of concrete as much as two-thirds and promote early strength development.

Nonchloride based accelerators, on the other hand, have been shown to be more effective in accelerating set times. They also can improve mix workability, reduce bleeding and improve air-entrained concrete.

Retarding admixtures are usually used when concrete is being poured during hot weather. This helps to slow down the curing process so you can have more time to level the concrete and prepare for foot traffic or other construction activities.

The amount of retarding admixture needed to offset temperature increases is dependent on the dosage and mix design, but typically provides a 30-minute delay at a 1 oz/cwt dosage with ambient temperatures of 70-75deg F.

Fast-setting concrete is a special mix that will set hard in 20 to 40 minutes after it’s poured, giving you plenty of time to level the surface and prepare for foot traffic or other projects. This versatile mix can be used for a wide variety of general-purpose applications, from setting a post to fixing a concrete slab.