Use of recycled aggregates in road sub-base construction and concrete manufacturing

This paper investigates the use of construction and demolition waste in road embankment and concrete manufacturing. The aggregates are recycled from the demolition waste of a building and in particular from basalt, sandstone, structural concrete and vibrated concrete blocks. The main physical characteristics of recycled aggregates for road applications and the performance of road sub-base layers containing recycled components are determined and validated on the basis of the latest Italian specifications. The study demonstrates that recycled mixes have sufficient mechanical characteristics and are hence suitable in road sub-base construction, even if only limited to minor technical importance works. Moreover, the mechanical properties of concrete mixtures that use recycled aggregates as replacement for natural aggregates are evaluated and compared to those of standard concrete mixtures. Three types of recycled aggregates are considered (structural concrete, basalt, vibrated concrete blocks) at different replacement ratios. A higher percentage of recycled aggregates than the one prescribed by the current legislations can be effectively used in concrete preparation, especially in the case of aggregates derived from crushed basalt waste or from structural concrete manufactured using basaltic fine and coarse aggregates. The effect of natural fine aggregate replacement with recycled fine fractions on concrete is investigated. The results of the experimental program are significant and encourage the use of 100% recycled basalt aggregate in concrete. Therefore, in areas where the use of basalt stone as primary masonry building material is widespread, the reuse of demolition waste is highly recommended.