From the results given in Fig. 8, it was noticed that the depth of
carbonation of the mixes with 2.5–12.5% crumb rubber were less
than or equal to that of control mix concrete. Gradual decreasing
trend in the depth of carbonation was noticed up to 10% substitution
with crumb rubber. Beyond 10%, there was gradual
increase in the depth of carbonation up to 20% substitution with
crumb rubber. At 91 days, the depth of carbonation in control
mix was 11 mm, It was 14 mm (the maximum value) in the mix
with 20% crumb rubber. Minimum depth (10 mm) was observed
in the mix with 5%, 7.5% and 10% crumb rubber. When we study
the carbonation coefficient given in Fig. 9, all the mixes with 0%
to 20% crumb rubber showed a flattening trend in the carbonation
coefficient at 91 days.