Setting Time of Cement vs Performance of Concrete

Initial setting time 

In Short:

Time delay from point of water addition to the point when the cement paste begins

to stiffen considerably

in other words, it is that time period between the time water is added to cement and time at which 1 mm square section needle fails to penetrate the cement paste (1:3), placed in the Vicat’s mould 5 mm to 7 mm from the bottom of the mould.

Final setting time 

In Short: 

Time delay from point of water addition to the point

When the cement paste has hardened to the point at which it can sustain some load

in other words, it is the time period between the time of water addition to cement and the time at which 1 mm needle makes an impression on the paste in the mould but 5 mm attachment does not make any impression.

For all the cement in India except (Masonry cement & Railway Sleeper cement),

BIS Specifications are:

Initial Setting Time         : 30 Minute (Min)

Final Setting Time           : 600 Minute (Max)

Masonry Cement 

Initial Setting Time    : 90 Min (Min)

Final Setting Time      : 1440 Min (Max)

Railway Sleeper Cement 

Initial Setting Time    : 90 Min (Min)

Setting Time of cement depends on

1. Cement fineness   

2. Especially Gypsum content 

Ie : 

*Gypsum quality 

*Chemistry of Gypsum with clinker

Some Facts : 

But Practically, Cement companies set their values as 120 - 180 min as initial setting time and 200 -280 min as final setting time. 

** Setting time values are just arbitrary points are only used to characterize cement

** Setting time values do not have any relation to fundamental chemical significance of cement

** Setting time values are not tied to the setting time of concrete (which is different)

** Setting time values only give a rough idea about how much time the concrete will be workable for.

Strength development of concrete 

depends on :

1. Water – Cement Ratio

2. Type of Cement and its shelf age

3. Cement content in concrete

4. Cement-Aggregate Ratio

5. Physcal&Chemcl proprties of mterial

6. Particle Size Distribution of materials

7. Gradation of Aggregate

8. Quality of water

9. Impurities in aggregate & water

9. Compaction of concrete (Packing)

10. Curing of Concrete

11. Atmospheric Conditions & etc

So, 

Judging the Performances of cement or concrete with setting time values of cement, does not make any sense .