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Sulphur content of recycled aggregates applied in concrete production 503

Figure 17.3 Specimen of mortar (v40) with S 8 sulphur.

concrete of 5% 10% for 20% replacement and 20% 30% for the 100% substitution
(Evangelista and de Brito, 2010; Marinkovi´ c et al., 2010; Abbas et al., 2009; de Juan
and Gutie ´rrez, 2009; Lo ´pez-Gayarre et al., 2009; Tabsh and Abdelfatah, 2009;
Etxeberria et al., 2007) basically due to the adhered mortar of the aggregate (Thomas
et al., 2018). Also, 20% incorporation of coarse aggregate containing sulphur implies
a non-significant loss of properties, but the 100% replacement (sand included) causes
a loss of the compressive strength slightly higher than the value observed for the RA.
The sulphur concentration is higher in the finer aggregates, due to the higher fri-
ability of the sulphur phase of the aggregate. These indicate that it is possible to
obtain a RC with a higher compressive strength than the original one if the coarse
fraction of the aggregate is used (Thomas et al., 2013; Ajdukiewicz and
Kliszczewicz, 2002). This result supports the hypothesis that sulphur acts as an
impurity or a lightweight aggregate (Lo et al., 2007) and does not cause any nega-
tive effects. The negative effect of the incorporation of the RA with the correspond-
ing percentage of sulphur is more significant in the case of the tensile strength, with
a reduction of between 25% and 35% when compared with the natural aggregate.
It is observed, similarly as in mortars, that the sulphur aggregate is a CDZ
(Markeset and Hillerborg, 1995) that affects the resistance in proportion to the size
(Miled et al., 2004) as a lightweight aggregate or equivalent to air porosity.

17.3.2 Durability

The carbonation depth found in specimens of mortar with sulphur cured directly
exposed to a marine environment was about 4 mm (Thomas et al., 2013)(Fig. 17.3)
and no influence of sulphur on the carbonation process is observed.