Civil Engineering Reference
In-Depth Information
chips do not have enough length to transfer the applied load through interfacial
frictional force, while fibres have longer length to transfer the applied load,
resulting in higher strength.
In a few studies, the effect of chemical or physical treatments of rubber
aggregates on the compressive strength behaviour of the resulting concrete was
also reported. This type of technique is generally adopted to improve the weak ITZ
between rubber aggregates and cement paste. Li et al. (
2004
) reported that the
surface treatment of fine rubber aggregates by NaOH solution increased the
mechanical performance including compressive strength. However, this technique
could not improve the properties for coarse rubber aggregates. The same author
also tried to improve the mechanical performance by making holes in the rubber
aggregates but it did not improve the studied properties. Naik and Singh (
1991
)
also reported that the surface treatments of rubber particles could enhance the
hydrophilicity of the rubber surface and therefore could improve mechanical
performance including compressive strength.
4.7.2.3 Tensile Strength
Just like for compressive strength, the addition of rubber aggregates decreases the
splitting tensile strength of the resulting concrete. The development of microcracks
due to weak interfacial binding of rubber aggregates and cement paste as well as a
surface segregation between rubber aggregates and cement paste due to the exerted
stress are the major causes that lower the tensile strength of concrete due to the
incorporation of rubber aggregates (Ganjian et al.
2009
). However, for a given
substitution ratio the reduction in splitting tensile strength of concrete with rubber
aggregates is less prominent than that observed in compressive strength (Eldin and
Senoucci
1993
; Mavroulidou and Figueiredo
2010
). The reduction in splitting
tensile strength of concrete with fine rubber aggregates is also smaller than that
with coarse rubber aggregates.
Ganjian et al. (
2009
) reported that the percentage reduction of tensile strength
in concrete using chipped rubber as a partial replacement of NA was about twice
than that in concrete using ground rubber particles for the same replacement level.
The reduction in tensile strength with 7.5 % replacement was 44 % for concrete
with chipped rubber and 24 % for concrete with ground rubber as compared to the
control mix. In the Topcu (
1995
) study, the splitting tensile strength of C 20 type
conventional concrete was 3.21 MPa, while it was 2.17, 1.53 and 1.13 MPa for
concrete with fine rubber chips and, 1.50, 1.06 and 0.82 MPa for concrete with
coarse rubber chips at the replacement ratios of 15, 30 and 45 %, respectively.
Instead of the brittle failure usually exhibited by conventional concrete speci-
mens under compression, specimens with rubber aggregates generally show duc-
tile failure due to the plastic behaviour of the rubber aggregates. Topcu (
1995
)
found that the failed specimens withstood measurable post-failure loads during
tensile strength test and underwent significant displacement, which was partially
recoverable. Therefore, concrete specimens with rubber aggregates showed high
