SETTING TIME OF CEMENT

SETTING TIME OF CEMENT FOR CONSTRUCTION USE

Cement is a hydraulic binder, i.e. a finely ground inorganic material which, when mixed with water,
forms cement paste, cement paste has a plasticity property, get  hardened and to achieve strength within a short period of a time. It is therefore very important for us to know in how much time cement will lose its plasticity and start hardening, and how much time we will have to use the cement in concrete mixing and casting  during construction before hardening, this early time of the hardening of cement paste is known as setting time.

Setting time of cement is defined as a specified time required for cement paste to change from liquid state to plastic state and plastic state to solid state so that surface becomes sufficiently rigid to withstand an external pressure onto it.

Setting time of cement is the one which bring setting time of cement concrete, the type of cement you are using for concrete preparation and mixing determine the setting time of concrete produced for a construction work.

The setting time of cement is divided into two categories which are initial setting time and final setting time.

1.      Initial setting time

Initial time of cement is the time to which cement can be moulded in any desired shape without losing its strength, this is the time available for mixing the cement with water to form paste for concrete making and placing it in position, if further delayed, cement loses its strength and produce weak concrete.

2.      Final setting time

Final setting time is the time at which cement completely loses its plasticity and became hard is a final setting time of cement, when this time reaches the cement loose all its plasticity property, attain its moulded shape of which it is casted, cement sufficiently hardened and gain its strength in such a way that formwork can be removed.

Setting time of cement is the one which bring setting time of cement concrete, the type of cement you are using for concrete preparation and mixing determine the setting time of concrete produced for a construction work.

The following is the table showing the type of cement and their initial and final setting time

S/N	Cement Type	Initial Setting Time, min (min.)	Final Setting Time, min (max.)
1.	OPC(33)	30	600
2.	OPC(43)	30	600
3.	OPC(53)	30	600
4.	SRC	30	600
5.	PPC	30	600
6.	High alumina	30	600
7.	Super sulphated	30	600
8.	PPC	30	600
9.	Low heat	60	600
10.	Masonry cement	90	1440
11.	RHPC	30	600

IMPORTANCE OF KNOWING SETTING TIME OF CEMENT

Knowing the setting time of cement is very important as it help in planning different works that use different kind of cement as one its materials  such as masonry work, plaster work and concrete work.

Knowing setting time of cement help to know the time required to work (play) with cement in different work during constructing which involve mixing, transportation and casting, also help to know at what time we can remove formwork.