Hydraulic cement made by burning limestone with clay or shale in a kiln at about 1,450 C (2,640 F) to form clinker, then grinding the clinker with a few percent gypsum to control set. Its calcium silicates react with water, so it hardens underwater as well as in air. Cement is only 10 to 15 percent of a typical mix by weight, yet it is usually the largest material cost in the mix and the source of most of the concrete's embodied carbon.
It's straight portland cement in the footing mix and half slag on the walls, so don't expect the walls to break the same.
Say ready-mix truck, never cement truck, around a finishing crew: cement is an ingredient, not the product.
Also heard as
- cement
- OPC
- ordinary portland cement
Do not mix it up with
- Mud: Cement is only the binder powder; concrete, or mud, is the finished mixture of cement, water, sand and stone.
Related terms
Type I/II cement
The everyday portland cement, certified to meet both general-purpose Type I and moderate sulfate-resistant Type II limits.
Type III cement
High-early-strength portland cement, ground finer so concrete gains strength in days instead of weeks.
SCM
Supplementary cementitious material: fly ash, slag cement or silica fume used alongside portland cement in a mix.
Hydration
The heat-releasing reaction of cement with water that turns the paste into solid binder.
Mud
Jobsite slang for fresh concrete, used by finishers, pumpers and ready-mix drivers alike.