Civil Engineering Reference
In-Depth Information
Fig. 2.15 Grading curves of
natural and tyre aggregates
(Khaloo et al.
2008
)
Table 2.34 Properties of
rubber aggregates
(Benazzouk et al.
2003
)
Properties
CRA
ERA
Unit weight (kg/m
3
)
1,286
1,040
Hardness (shore)
85
35
Modulus of elasticity (Mpa)
68
12
from truck tyre recaps was less expensive than that from the whole tyre because the
tread is free from any fibrous material. The used crumb rubber aggregate was
coarser than the ASTM C 33-02A specified limit for concrete sand. The crumb
rubber used in this study was in dry state. However used crumb rubber aggregate
can absorb a small amount of water equal to 2.4 % of its dry weight in the saturated
surface dry condition that was higher than that of concrete sand, which is normally
about 0.5 % or less. The bulk specific gravity of the crumb rubber aggregate varied
between 0.53 and 0.60, which is nearly five times less than sand. Crumb rubber can
thus be considered a lightweight aggregate source due to its low specific gravity.
The authors compared some properties measured during the investigation
including cost of crumb rubber aggregate with some lightweight aggregates
available in the markets and they are presented in Table
2.35
.
The authors concluded that the cost of crumb rubber aggregate compared
favourably with that of other lightweight aggregates and were lower than the costs
of microlite and perlite.
Sukontasukkul and Chaikaew (
2006
) reported the use of crumb tyre rubber as a
partial replacement of aggregate to produce concrete paving blocks. The crumb
rubber particles passing ASTM sieve No. 6 and ASTM sieve No. 20 were used
separately as aggregate in concrete. The specific gravity and fineness modulus of
both crumb rubber aggregates are presented in Table
2.36
and their particle size
distributions were presented in Fig.
2.16
. According to the authors, the higher
water requirement of concrete mix containing rubber aggregate than that of a
conventional concrete mix was due to the low specific gravity and high specific
surface area of rubber crumb.
