Civil Engineering Reference
In-Depth Information
Fig. 5.63 Shrinkage of
concrete containing untreated
and polyvinyl alcohol treated
coarse RCA and conventional
concrete (Kou and Poon
2010
)
higher than the standard specifications' limit. An OPC blended with 8 % SF was
used as binder in this investigation. Fathifazl et al. (
2011
) observed lower
shrinkage strain of NAC and RCAC when both types of concrete were prepared by
the EMV method than when they were prepared by the normal method. They also
observed lower shrinkage strain in concrete containing RCA originated from a
concrete made with river bed gravel than from one made with limestone gravel.
5.4.2 Permeability Properties
The durability of concrete is greatly influenced by its permeability behaviour. A
concrete with low permeability has better durability performance. Lower perme-
ability means lower void content in concrete, and therefore water and some other
corrosion agents cannot penetrate easily into concrete. Several properties such as
water absorption, gas permeability and chloride penetration are evaluated to
determine the permeability performance of concrete. Alexander et al. (
1999
)
classified concrete according to its performance in various permeability tests. This
classification is presented in Table
5.21
.
The types of pores present in concrete also influence the permeability behaviour
of concrete: discontinuous capillary pores are desirable for low permeable con-
crete. Thus the evaluation of porosity of concrete can provide data on the per-
meability behaviour of concrete. The factors, which improve concrete porosity,
Table 5.21
Concrete durability classification based on permeability parameters (Alexander et al.
1999
)
Durability class
Oxygen permeability
index (log scale)
a
Sorptivity (mm/Hh)
Chloride conductivity
(mS/cm)
Excellent
[10.0
\6
\0.75
Good
9.5-10.0
6-10
0.75-1.50
Poor
9.0-9.5
10-15
1.50-2.50
Very poor
\9.0
[15
[2.50
a
Negative logarithm of oxygen permeability coefficient
