Laboratory investigation of RAP for various layers of flexible and concrete pavement

The present study investigates the potential of RAP for various layers of flexible and concrete pavements. Natural aggregates were replaced in different proportions by the coarse RAP and fine RAP, for preparations of granular subbase, wet mix Macadam, dry lean concrete, dense bituminous Macadam and Plain concrete mixes. Utilisation of both fractions of RAP resulted in reductions in the optimum moisture content (OMC) and maximum dry density of granular subbase and wet mix Macadam mixes, whereas, incorporation of the same was found to increase the OMC of dry lean concrete mixes. Incorporation of coarse RAP doesn't affect much the engineering properties of base and subbase layers in comparison to fine RAP. Improving the gradation of fine RAP was found to increase its suitability in all the considered mixes. Similarly, utilisation of coarse RAP was found to improve the workability of concrete mixes, however, significant reductions in strength properties were noted. It was observed that as the strength requirement of layer increases, the negative impact of RAP on strength properties also increases linearly, suggesting incorporating a higher fraction of RAP in lower layers and a lower usage of the same for wearing course of the pavement.