Structural Concrete - Hassoun

2.13 Models for Predicting Shrinkage and Creep of Concrete 59
Calculation of J(t, t 0 ):
J(t, t 0 )= 1 + ψ(t, t 0 )
E c E c
1
=
4665.4 + 0.512
4665.4 = 324 × 10−6 psi −1
Example 2.8 (SI Units)
Calculate the shrinkage strain and creep compliance and coefficient for the concrete specimen given
below. Use the ACI 209R-92 model.
Given factors:
Humidity = 75%
h e = 2V/S = 2Ac/u = 76 mm
f cm28
= 45.2MPa
w = 207.92 kg/m3
w/c = 0.46
a/c = 3.73
t = 35 days
t 0 = 28 days
t c = 8days
γ = 2405 kg/m3
Cement type III
Moist-cured concrete
Solution
Shrinkage Calculation
ε sh (t, t c )=
t − t c
f +(t − t c ) K ss K sh ε shu
ε shu = 780 × 10 −6 mm∕mm
According to Table 2.4, f = 35.
V
= 38 mm
S
( ) V
K ss = 1.23 − 0.006 = 1.23 − 0.006(38) =1.002
S
For H = 75%,
K sh = 1.40 − 0.01H = 1.40 − 0.01(75) =0.65
t − t
ε sh (t, t c )= c
f +(t − t c ) K ss K sh ε shu
=
35 − 8
35 +(35 − 8) (1.002)(0.65)(780 × 10−6 )=221.3 × 10 −6 mm∕mm
Creep Calculation
J(t, t 0 )= 1 + C c (t)
E cmt0