How to calculate cube test result for 7 and 28 days?

Cube test result after 7 and 28 days: –

• Make mortar of cement sand and aggregate of different ratio for different grade of concrete.
• Make at least 3 concrete cube of size 150mm×150mm×150mm each in mould.
• Use tamping rod for compacting and levelling the surface of mould.
• It is kept for 24 hours setting after mixing with water in concrete and after 24 hours it is kept in water for curing.
• After curing for 7 days. And taken out just 30 minutes prior to start of test.

Calculation: –

• Now concrete cube test by Compression Testing Machine (CTM).
• 14N//minute load is applied on concrete cube specimen of different grade till the cube break.
• The maximum load at which the specimen collapse is taken as a compressive load.
• Now following results are obtained for compressive strength of different grade of concrete at 7 and 28 days of curing given in list below:

Compressive strength of concrete after 7 and 28 days: –

Conc. Grade          After 7 days           After 28 days

M10             –         6.5 MPa       –         10 MPa

M15             –         9.75 MPa     –         15 MPa

M20             –         13 MPa        –         20 MPa

M25             –         16.25 MPa   –         25 MPa

M30             –         19.25 MPa   –         30 MPa

M35             –         22.75 MPa   –         35 MPa

M40             –         26 MPa        –         40 MPa

M45             –         29.25 MPa   –         45 MPa

M50             –         32.5 MPa     –         50 MPa