Influence of the granulometric fractions of recycled sands on the mechanical properties of Portland cement mortars

Abstract

This research study is based on the assumption that the granulometric fractions of recycled small aggregates present different characteristics and, therefore, these characteristics would influence the mechanical behaviour of mortars differently. This paper proposes the study of the granulometric fractions of two recycled sands: SD1 (sand from construction waste and demolition) and SD2 (sand from concrete waste). The recycled sands were submitted to physical characterisation and FRX tests, and subsequently incorporated in mortars. The results showed that the recycled sands form two groups with different characteristics and tendencies: (1) the "coarse fractions” group, formed by the coarse fractions and (2) "fine fractions” group, formed by the fine and fine- medium fractions. The study demonstrated that the diversity of the source materials of the SD1 sand led the cement paste to dilute in its fractions, whereas in the SD2 sand, it concentrated mainly in the "fine fractions". Thus, the "fine fractions" of the SD1 sand are similar to the IPT sand (used as reference) and more adequate than those of the SD2 sand. The study concluded that the mechanical behaviour of mortars differ as the granulometric fraction is replaced, increasing the possibilities of application of recycled small aggregates in the design of cement mixtures.

Keywords:
Recycled small aggregates; Construction waste and demolition; Concrete waste; Granulometric fractions; Mechanical behaviour