### The 28-Day Myth - National Precast Concrete Association

Specified concrete compressive strength is the minimum compressive strength at which the concrete should fail in standard tests of 28-day-old concrete cylinders. A typical concrete compressive strength specification requires 4,000 to 5,000 psi at 28 days.

### Relationship between compressive strength and modulus of ...

expressed as a function of compressive strength, σB, and unit weight, γ. Since it is self-evident that the concrete with a compressive strength of 0 MPa has modulus of elasticity of 0 MPa, the basic form of the equation is expressed as Eq. 2. b c E =aσB γ (2) The parameters examined are compressive strength, modulus of elasticity, and unit ...