Civil Engineering Reference
In-Depth Information
Fig. 4.49 Stress-strain
behaviour of concrete with
various percentage of rubber
aggregates (Batayneh et al.
2008
)
Fig. 4.50
Brittleness index of various types of concrete (Benazzouk et al.
2003
)
this rubber content. The decrease in BI values with rubber content over 10 %
reflected an increase in plastic deformation energy. This increase became even
greater as the rubber size increased. For the same rubber content, the BI was lower
for expanding type rubber aggregates than for compacted rubber aggregates. The
alveolar character of rubber, therefore, helped to increase the deformability of
cement-rubber composites.
Khaloo et al. (
2008
) observed increasing nonlinearity of stress-strain curves
due to the incorporation of rubber aggregates in concrete. To compare the non-
linearity between the control concrete and the rubber tyre concrete, a nonlinearity
index was defined as the ratio between the slope of the line connecting the origin to
40 % of the ultimate stress and the slope of the line connecting the origin to the
ultimate stress. A higher nonlinearity index implies a more nonlinear stress-strain
curve. The nonlinearity index increases as the rubber content increases for all
mixes. The substitution of rubber for mineral aggregates appears to allow more
uniform crack development and provide gentler crack propagation, compared to
conventional concrete. The authors also determined the toughness indices of the
concrete mixes. Rubber tyre concrete exhibited greater toughness as compared to
conventional
concrete.
Toughness
indices
maximise
as
rubber
concentration
