Compressive strength of concrete?

We design the structural components with C20, C30 & C35A concrete and cast accordingly with ready mix concrete. Later we find that the respective 7day, 14 day, 28 day compressive strengths are exorbitantly high (cube crushing strength) compared to what we expected (we expected 2/3 of 28 day strength for 7day, 90% of 28day strength for 14day & so on with the specified limitations). Can you guess what happened & what will happen if such higher strengths are allowed instead?

Update:

We actually conducted the trial mix and found this.

3 Answers

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  • 8 years ago
    Favourite answer

    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.

  • Anonymous
    4 years ago

    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.

  • 8 years ago

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

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

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