Concrete Modulus of Elasticity Ec (ACI 318-19 19.2.2)
How stiff concrete is at a given strength, the number every deflection and drift check starts from.
Example
You enter
- Concrete strength f'c (psi) 4000
- Unit weight wc (pcf, 145 normalweight) 145
You get
- Ec (psi) 3644147
- Ec normal (psi) 3604997
Details, formula, and sources
Ec = wc^1.5 x 33 x sqrt(f'c) psi (ACI 19.2.2.1), the stiffness behind every deflection, drift, and short-column calculation; the normalweight shortcut is 57000 x sqrt(f'c). 4000 psi at 145 pcf -> 3,644,000 psi (3644 ksi); a 115 pcf lightweight deck is only ~70% as stiff. A design aid; the engineer of record's stamped design governs.
Ec = wc^1.5 x 33 x sqrt(f'c) psi (90 <= wc <= 160); normalweight shortcut Ec = 57000 x sqrt(f'c).
The ACI 318-19 19.2.2.1 modulus of elasticity of concrete, by name.
ACI 318 is readable free through the ACI online reading room at concrete.org; the 19.2.2 modulus provisions are in the published code.
Estimate. AHJ and licensed professional govern.
Field names used by the API: fc_psi, wc_pcf, ec_psi, ec_normal_psi
- Secant modulus Ec = wc^1.5 x 33 x sqrt(f'c) psi for 90 <= wc <= 160 pcfACI 318-19 19.2.2.1(a)
- Normalweight shortcut Ec = 57000 x sqrt(f'c) psiACI 318-19 19.2.2.1(b)
- Design value code secant modulus; the in-place value varies with aggregate and mixscope of this tile