Compressive strength of concrete?

Actually from my experience it was noticed during trial mix the compressive stress of concrete become much higher that my expect ion. It was told by one of my senior that the mix was done under strict control of laboratory so it is expected. During construction the result was also higher. Lastly it was suggested by the consultant to reduce cement consumption.

The strength of concrete is determined using small specimens like 6 X 12 in. cylinders. The test cylinders are cast in steel mould in three layers, each layer being compacted by 25 strokes of a steel rod. The moulded specimens are stored at specified time and condition until the prescribed age of testing, usually 28 days. The compressive strength of the cylinder is the maximum uniaxial load recorded divided by the cross sectional area of the cylinder when tested using hydraulically operated compression machines. The cylinders give the potential strength of the concrete. The compressive strength is influenced by the curing conditions, specimen preparation, age at testing, mode of testing, and mode of failure of the specimen.

You should consider the site factor (1.1 -1.2).

If the strength still high, cut down the cement, make again the trial.