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concrete compressive strength

concrete compressive strength

concrete compressive strength

(OP)
Using following mix design

1- cement - 425 kg
2- wrda-90 - 3 liters per M3
3- grevel - 1050 kg
4- sand - 750 kg
5- water - 160 lit

compressive strength at 7 days

range from 28 n/mm2 - 40 n/m2

at 28 days

36 n/mm2 - 44 n/mm2

and in some cases the strength is decreases at 56 days.

my quetion is that why concrete do not gain much strength at 28
days and further in some cases decreases at 56 days.

can anybody help to explain the reason and what are the remedial measures.

Thanks & Regards

kidwai

RE: concrete compressive strength

There may be some complicated technical reasons concerning either the aggregates or the cement. But first I suggest you investigate the following:

1. is your cube crushing machine out of calibration? I suggest you get it recalibrated whether you have a valid certificate of calibration or not.

2. the cubes are not well made. Are there photographs of the cubes before and after crushing? What about cubes now stored at the lab, do they look to be well made?

Is WRDA90 a plasticiser? you could also make sure the admixture is the correct one.

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