equations

Equations

As the figure from ACI 363 above shows, the equation ACI 318 lists to calculate the modulus of elasticity overestimates the value for a concrete having a compressive strength greater than 6000 psi. Therefore, a different equation must be used to calculate the modulus for high performance concrete.

The general equation to compute the elastic modulus for normal concrete from ACI 318 is:

E_c = 33 w_c^1.5 (f’_c)^1/2 psi

where:

w_c= the unit weight of concrete

f’_c = the compressive strength of concrete

The general equation to compute the elastic modulus for high performance concrete from ACI 363 is:

E_c = 40,000 (f’_c)^1/2 + 1.0 x 10⁶ psi

For 3,000 psi < f’_c < 12,000 psi