Civil Engineering Reference
In-Depth Information
Table 4.16 28-day compressive strength of concrete with two types of rubber aggregates
(Benazzouk et al.
2003
)
Volume of rubber (%)
Size of rubber aggregates
Compressive strength (MPa)
CRA
ERA
0
-
82.5
82.5
5
1-4
68.0
59.0
4-8
63.0
54.0
8-12
60.5
51.0
10
1-4
55.0
42.0
4-8
48.0
36.0
8-12
43.0
32.0
25
1-4
26.0
15.0
4-8
20.0
13.0
8-12
15.0
11.0
50
1-4
6.5
3.4
4-8
5.0
2.6
8-12
3.5
2.0
CRA compacted rubber aggregates; ERA: expanded rubber aggregates
The rubber particles are less stiff than the surrounding cement paste which lowers
the compressive strength of concrete. The cracks are initiated around the rubber
particles, which accelerates the failure in the matrix. Larger incorporation of
rubber particles in the concrete mix creates difficulty in the packing of lightweight
rubber particles, and therefore voids are introduced in the matrix. The trend is
slightly influenced by aggregate size; e.g. for a given amount of rubber, finer
aggregates lead to lower losses in compressive strength than coarse aggregates.
Similar effect of particle size on the strength behaviours of rubberized concrete
was also reported in other studies (Topcu
1995
; Son et al.
2011
; Khatib and
Bayomy
1999
; Ali and Goulias
1998
; Ali et al.
1993
). Khatib and Bayomy (
1999
)
showed that rubberized concrete made with coarse chipped rubber replacing coarse
aggregates has less strength than concrete made with fine crumb rubber. Ali and
Goulias (
1998
) and Ali et al. (
1993
) also observed higher reduction in compressive
strength due to the addition of coarse sized rubber aggregates than of fine rubber
particles. This is due to the high compressibility of rubber particles, which gen-
erates localised stresses and bonding problems between them and the cement
matrix. According to Topcu (
1995
), the interfacial bond in a coarse tyre rubber
chips cement paste is weaker than in a fine tyre rubber chips cement paste, which
ultimately affects the compressive strength. However, in some studies such as that
of Emiroglu et al. (
2007
) the exact opposite effect of particle size is reported
(Table
4.15
).
Li et al. (
2004
) reported that the compressive strength of concrete with rubber
chips replacing 15 % by volume of coarse NA was lower than that of concrete with
an equal volume percentage of elongated or fibre type coarse rubber aggregates
(Table
4.15
). According to the authors, this is possibly due to the difference
between their load transfer capabilities. Once debonded from the concrete matrix,
