A dormant period (from the French ‘dormant’ = sleeping) is a rest time during which a mixed product such as adhesive, mortar or a chemical anchor must not be worked or loaded before it can react further or be used. In construction, the dormant period is particularly important for chemical fixings and certain cementitious or adhesive products.
When does a dormant period apply?
Manufacturers prescribe the dormant period to ensure the desired product properties. Examples include:
- Chemical anchors — after injecting the mortar, the bolt may not be loaded until the curing time has passed
- Adhesives and sealants — some two-part adhesives need a rest after mixing, before they can be applied
- Self-levelling compounds and epoxy mortars — often require a specific rest time after mixing
- Levelling compounds — the mix may need to ‘mature’ before being poured
Difference between open time and curing time
It is important to distinguish the dormant period from two related terms:
- Open time — the period in which a mixed product remains workable
- Curing time — the time needed before a product reaches its final strength
- Dormant period — a rest period during which nothing may be done to the product
Points to watch
When working with products that have a dormant period:
- Read the product datasheet — the manufacturer specifies exact times
- Temperature and humidity — influence the length of the dormant period
- Wait it out — loading or working too early gives reduced final strength or a failed bond
- Marking — on larger jobs, chalk or label the area to track when the wait is over
Related terms
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