What are the factors affecting the setting time and compression strength of ordinary Portland cement?

It appears that some have dismissed the possibility of testing cement for setting time and compressive strength, assuming that the OPer really meant concrete.

Not so. Cement plants spend considerable effort on laboratory work to ensure that the cement produced meets necessary levels of performance and national standards. Those tests ensure that the cement you buy (or your client) works as did the last lot, and makes good concrete.

Many other tests are also performed regularly, often several times a day. Those include:

Acid soluble CaO

Normal consistency

Drying shrinkage

Soundness by SO4 bath

Soundness of autoclave

Fineness by Blaine apparatus

Fineness by 45-micron washing

Temperature rise by Langevin method

Water-soluble chromate

Chemical composition and Bogue calculation

Concrete Contractor Company Perth

In addition, QA concrete mixes are done in the cement slab to give assurance that the material made today is the same as yesterday. But that is not at the expense of not doing the tests listed above.

In addition to the fine answers given by Ted Krapkat and Alessandro Fais, one thing that can have an interesting effect on setting time is an excessive dosing of hemihydrate gypsum. Whilst an amount of gypsum is necessary to ward off flash setting, an excess of the hemihydrate variety can itself promote “false set”, merely because that form of gypsum, also known as “plaster of Paris” sets quite quickly.