Structural Concrete - Hassoun

28 Chapter 2 Properties of Reinforced Concrete
where
t = age of concrete after casting (days)
t c = age of the concrete drying commenced (days)
f = constant in determining shrinkage strain, depends on curing method shape and size factors
according to Table 2.4
K ss = shape and size correction factor for shrinkage according to Eq. 2.11
K sh = relative humidity correction factor for shrinkage according to Eq. 2.12
ε shu = ultimate shrinkage strain 780 × 10 −6 (in./in.) or (mm/mm) (for both moist- and steam-cured
concrete)
where
Shape and size correction factor for shrinkage should be calculated as follows:
For t − t c ≤ one year
( )
⎧
⎪
1.23 − 0.152 V
(in. − lb)
S
K ss = ⎨
( )
⎪1.23 − 0.006 V
(SI)
⎩
S
For t − t c > one year
( )
⎧
⎪
1.17 − 0.116 V
S
K ss = ⎨
( )
⎪1.17 − 0.00456 V
⎩
S
V = volume of the specimen (in. 3 or mm 3 )
S = surface of the specimen (in. 2 or mm 2 )
(in. − lb)
(SI)
(2.11a)
(2.11b)
Relative humidity correction factor for shrinkage is
{ 1.40 − 0.01H for 40% ≤ H ≤ 80%
K sh =
3.00 − 0.03H for 81% ≤ H ≤ 100%
where
H = relative humidity (%)
(2.12)
Table 2.4
Values of Constant f as a Function of Curing
Method
Conditions
Moist-cured concrete (7 days min.) 35
Steam-cured concrete (3 days min.) 55
If shape and size effects are
26e [0.36(V/S)] (in.−lb)
considered for both curing condition
26e [1.42×10−2(V∕S)] (SI)
Note: In practice, f = 35 and f = 155 are commonly used.
f