Initial setting time marks the transition of concrete from a plastic, workable state to a solid mass. It is typically measured in a lab by penetration resistance (ASTM C403) and dictates the window crews have for placing, consolidating, and finishing the mud. Once initial set is reached, the concrete cannot be remixed or moved without damaging its internal structure.
The mix design says we've an initial setting time of 90 minutes, so we need that second pump truck on site fast.
Hot weather drastically reduces initial setting time, catching inexperienced crews off guard with unworkable mud.
Also heard as
- Initial set
Do not mix it up with
- Final setting time: Initial set means the concrete is unworkable, final set means it has gained enough strength to bear light loads.
Related terms
Final setting time
The point at which fresh concrete has completely lost its plasticity and can bear some load.
Hydration
The heat-releasing reaction of cement with water that turns the paste into solid binder.
Initial set
The point at which fresh concrete stops being workable and begins to stiffen into a solid.
Retarder
An admixture that delays setting, used in hot weather, on long hauls and for big continuous placements.
Slump
How far a cone-shaped sample of fresh concrete sags, the standard field measure of consistency.