Civil Engineering Reference
In-Depth Information
Table 3.9
Impact value of CDW aggregate along with normal aggregate
Reference
10 % crushing value (%)
CDW aggregate
Normal coarse aggregate
Rao et al. (
2011
)
35.0
17.37
Wong et al. (
2007
)
17.89
10.25
Limbachiya et al. (
2000
)
23.7
19.7
Table 3.10
Shape parameters of CDW and natural aggregate
Reference
Parameters
CDW aggregates
Natural aggregates
Etxeberria et al.
2007b
Shape index (%)
28
25
Gomez-Soberon (
2002
)
Shape coefficient
10-20 mm: 0.363
10-20 mm: 0.364
5-12 mm: 0.444
5-12 mm: 0.576
Elongation index
10-20 mm: 6
10-20 mm: 15
5-12 mm: 8
5-12 mm: 19
Gonzalez-Fonteboa et al. (
2011
)
Flakiness index (%)
4-20 mm: 7
8-20 mm: 7
4-12 mm: 14
Gonzalez-Fonteboa and
Martinez-Abella (
2007
)
Flakiness index (%)
4-12 mm: 9
4-12 mm: 25
10-25 mm: 7
10-25 mm: 11
Tam et al. (
2008
)
Flakiness index (%)
10 mm: 10.44-17.82
-
20 mm: 5.70-12.96
Vieira et al. (
2011
)
Shape index (%)
22.3
14.0-18.3
Fonseca et al. (
2011
)
Shape index (%)
24.3
11.1
Ferreira et al. (
2011
)
Flakiness index (%)
10
9
et al. (
2003
), CDW aggregate presents a cracked surface which contributes to an
increase in water and air flows into the aggregates and between the cement paste and
the aggregates. The natural and CDW aggregates used in Gonzalez-Fonteboa and
Martinez-Abella (
2008
) study were angular with multiple cracking faces.
The shape and flakiness indices of various CDW aggregates reported in the
literature are not much different from those of natural aggregates used in the same
studies. Table
3.10
shows some shape parameters for CDW and natural aggregates
reported in various studies. Chen et al. (
2003
) analysed the particle shape of CDW
and natural coarse aggregates by measuring several types of axis lengths of both
types of aggregates and found similar particle shapes for both types of aggregates.
On the other hand, through the analysis of shape indices of natural and CDW
aggregates, Vieira et al. (
2011
) concluded that CDW aggregate is sharper than the
normal coarse aggregate since the shape index of CDW aggregate is about 34 %
higher than that of the normal aggregate. Etxeberria et al. (
2007b
) reported the
shape indices of CDW and conventional aggregates as 0.28 and 0.25, respectively.
According to the author, the better shape of the CDW aggregates facilitated their
use for concrete production.
