Why the concrete cube test always done at seven and twenty eight days why not six and twenty nine?

Because after week (7 days) concrete is catching 70% of strength and after 4 weeks (28 days) almost 100%

Because the concrete test after7 days give you% from concrete resistance and this result gives you an initial idea about success concrete test after days

Hi Elgeli,

The norm its7,14,28 day for test.

At7 days the concrete is until to maimum result of resistance. more less50 %, see more

At28 days the concrete don't moove to level resistance , more less95 %, minimum.

I hope to have answered to your question.

Best Regards.

Jean Marie