Structural Concrete - Hassoun

2.13 Models for Predicting Shrinkage and Creep of Concrete 31
Table 2.8
Correction Factor α 1
as
Function of Cement Type
Type of Cement α 1
I 1.00
II 0.85
III 1.10
Table 2.9
Correction Factor α 2
as
Function of Type of Curing
Type of Curing α 2
Steam cured 0.75
Water cured or H = 100% 1.00
Sealed during curing 1.20
where
α 1 = type of cement correction factor according to Table 2.8
α 2 = curing condition correction factor according to the Table 2.9
w = water content (kg/m 3 )or(lb/yd 3 )
f cm28
= mean compressive concrete strength at 28 days (MPa) or (psi)
E cm607 ∕E cm(t+τsh ) = a factor that accounts for the time dependence of ultimate shrinkage of concrete
Type of cement correction factor α 1 can be determined using Table 2.8.
Curing condition correction factor α 2 can be determined using Table 2.9.
Humidity function for shrinkage, K h , should be determined according to Table 2.10.
{ √
57000 fcm28 (in. − lb)
E cm28 =
4735 √ f cm28 (SI)
(2.23)
E cm607 =(1.167) 1∕2 E cm28 (2.24)
(
) 1∕2
t
E cm(tc +T sh ) =
c + τ sh
4 + 0.85 ( ) E cm28
t c + τ sh
(2.25)
⎧ ( ) [ ( )]
⎪
190.8t −0.08 −0.25 V 2
c fcm28 2k s (in. − lb)
τ sh =
S
⎨
[ ( )]
⎪
V 2
⎩
0.085tc −0.08 (f cm28 ) −0.25 2k s (SI)
S
(2.26)
where H is relative humidity (%).
Time function for shrinkage, S(t), should be calculated according to the following equation:
√ t − tc
S(t) =tanh
(2.27)
T sh