Performance of Natural Aggregates and Recycled Aggregates for Unbound Granular Pavement Layers

Abstract

Recycled aggregates from solid waste can be used on pavements to minimize road construction costs and decrease environmental impacts related to the exploitation of natural resources and pollution. Thus, this study aimed to compare the mechanical performance of mixtures composed of natural aggregates, concrete recycled aggregates and polyethylene terephthalate (PET) flakes (in proportions from 0.5 to 4.0%) for application in granular pavement layers. Asphalt mixing, construction and demolition solid waste recycling, and PET recycling plants located in Joao Pessoa/PB, Brazil, provided the material used in this study. Tests such as particle size distribution, compaction with intermediate energy and California Bearing Ratio (CBR) were performed. The results of particle size distribution were useful to determine particle size proportions according to Brazilian DNIT specified standards and to prepare specimens for CBR tests. The compaction results indicated optimum water contents of 8.0 and 14.9%, and maximum dry densities of 2.01 and 1.83 g/cm3, for natural aggregates and recycled aggregates, respectively. Moreover, the optimum water contents increased between 16.4 and 17.7%, while the maximum dry densities decreased from 1.773 to 1.702 g/cm3 in mixtures of recycled aggregates and PET flakes, as PET proportions rose. Assessing mechanical resistance, the CBR value of natural aggregates resulted 45%, while that of recycled aggregates resulted 61%. On the other hand, the CBR results did not show a particular behavior tendency with the addition of recycled PET flakes. Therefore, it was possible to conclude that concrete recycled aggregates are technically viable for use in building granular pavement layers (sub-base and base) with low traffic flow, in spite of the variability of CBR results for mixtures of recycled aggregates and PET flakes.