Concrete · Materials & serviceability

Creep coefficient calculator

Design creep coefficient from the basic value for f′c, maturity (k2), age at loading (k3) and environment (k4).

Standard: AS 3600 Cl 3.1.8

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Result	Value	Unit
Basic creep φcc.b	3.00
th = 2Ag/ue	375.0	mm
α2 = 1 + 1.12 e^(−0.008 th)	1.06
k2 = α2 t^0.8/(t^0.8 + 0.15 th)	1.02
k3 = 2.7/(1 + log τ)	1.10
φcc = k2 k3 k4 k5 φcc.b	2.19
Effective modulus factor 1/(1 + φcc)	0.313

Diagram for the worked example

Basic creep φcc.b = IF(32<=20,4.5,IF(32<=25,3.8,IF(32<=32,3,IF(32<=40,2.4,IF(32<=50,2,IF(32<=65,1.7,IF(32<=80,1.5,1.3))))))) = 3
th = 2Ag/ue = 2*3.000e+5/1600 = 375 mm
α2 = 1 + 1.12 e^(−0.008 th) = 1+1.12*EXP(-0.008*375) = 1.0558
k2 = α2 t^0.8/(t^0.8 + 0.15 th) = 1.0558*10000^0.8/(10000^0.8+0.15*375) = 1.0196
k3 = 2.7/(1 + log τ) = 2.7/(1+LOG10(28)) = 1.1033
φcc = k2 k3 k4 k5 φcc.b = 1.0196*1.1033*0.65*3 = 2.1936
Effective modulus factor 1/(1 + φcc) = 1/(1+2.1936) = 0.31313
k5 for f′c > 50 MPa is not applied (taken as 1.0); see AS 3600 Cl 3.1.8.3.

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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.