Page 136 - New Trends in Eco efficient and Recycled Concrete

110 New Trends in Eco-efficient and Recycled Concrete

Experimental results showed that the addition of rubber sand in cement-based
mixes led to an increase of freeze/thaw resistance which increased as the rubber
sand content increases.

4.5.5 Resistance to aggressive environment
Segre et al. (2004) tested the durability of mortar containing 10% rubber
(0 0.2 mm) as natural sand replacement, by weight, exposed to 5% HCl for 6 days.
Rubber mortar showed higher resistance against HCl compared to the control
specimen.
Topcu and Demir (2007) prepared mortar specimens by partially replacing natu-
¸
ral sand with crumb rubber (0 4 mm) at up to 40%, by volume. Some specimens
were cured in NaCl solution for 28 days. A reduction in the dynamic elasticity
modulus in specimens with rubber particles was observed.
Azevedo et al. (2012) investigated the resistance of High Performance Concretes
(HPCs) containing tyre waste rubber as natural sand replacement at up to 15%, by
weight, against sulphuric acid attack. After 56 days of curing, specimens were
exposed to sulphuric acid for 28 days. Results showed that increasing rubber sand
content led to a higher mass loss degree.

4.5.6 Fire and high-temperature resistance
¸
Topcu and Demir (2007) observed a reduction in the residual compressive strength

of mortars containing rubber (1 4 mm) after firing at 150, 300 and 400 C for 3 h.
The reduction in the residual compressive strength increased by increasing rubber
sand content.
Marques et al. (2013) replaced natural aggregates in concrete with shredded rub-
ber at up to 15%, by volume. Specimens were exposed to 400, 600 and 800 C for

1 h. Results showed a reduction in the residual compressive and splitting tensile
strength after exposure. This reduction increased by increasing rubber aggregate
content. At 400 C, the compressive strength, compared to the control specimen

heated at the same temperature, was reduced by 24%, 40% and 55% with the addi-
tion of 5%, 10% and 15% rubber aggregate, respectively. At 800 C, the reduction

of the compressive strength was about 37%, 55% and 69% with the addition of 5%,
10% and 15% of rubber aggregate, respectively. The splitting tensile strength reduc-
tion at 400 C was approximately 6%, 21% and 38% with the addition of 5%, 10%

and 15% of rubber aggregate, respectively. At 800 C, the reduction in the splitting
tensile strength was about 48%, 57% and 63% with the addition of 5%, 10% and
15% of rubber aggregate, respectively.
Guo et al. (2014a,b) reported a reduction in the residual compressive strength
and Young’s modulus of concrete where natural sand was partially replaced with
crumb rubber (0.85 1.4 mm) after being exposed to temperature of 200, 400 and
600 C for 2 h. The residual compressive strength decreased by increasing rubber

sand content.