I think its 90% of ultimate strenght
It is the grade of concrete which indicates the strength of concrete after 28 days curing. M #) means the strength of concrete after 28 days of curing will be 30 N/mm2 .
The compressive strength of M25 concrete at 7 days will be between 6-7.5 N/mm2 .
how much tensile strength of M20 grade concrete at 28 Days
the strength that it has gained is the main thing, but usually 5 to 7 days as a rough guide.
The strength of M20 concrete for 7days will be 63%( say 12.6) of 28days strength i.e. 20N/sq mm
It is the grade of concrete which indicates the strength of concrete after 28 days curing. M #) means the strength of concrete after 28 days of curing will be 30 N/mm2 .
The compressive strength of M25 concrete at 7 days will be between 6-7.5 N/mm2 .
how much tensile strength of M20 grade concrete at 28 Days
the strength that it has gained is the main thing, but usually 5 to 7 days as a rough guide.
2/3 times the 28 days strength
The strength of M20 concrete for 7days will be 63%( say 12.6) of 28days strength i.e. 20N/sq mm
15
f ′c: concrete compressive strength at 28 days (compression is negative) fcu: concrete crushing strength (compression is negative)
fibre
More than 50 %
minimum curing period of concrete is 21 days and maximum is 28 days
concrete grade and strength are both revalent since if grade increase setting time will be less and curing to be done propely so that concrete strength will reach higher. If concrete grade is low curing to done longer days upto intial setting time to reach proper strength