Performance Evaluation of Reclaimed Asphalt Pavement as a Fine Aggregate Substitute in Dolomite Base Layers

Abstract

The extensive use of natural quarry materials in pavement base layers raises growing concerns regarding resource depletion and environmental sustainability, particularly in Egypt, where dolomite aggregate is widely used in base course construction. This study evaluates the potential use of Reclaimed Asphalt Pavement (RAP) as a sustainable partial replacement for natural aggregate in pavement base course mixtures. Conventional dolomite aggregate was used as the control material, while RAP was incorporated at contents of 0%, 10%, 20%, and 30% by total mixture weight. Modified Proctor compaction and California Bearing Ratio (CBR) tests were conducted to investigate the influence of RAP content on compaction characteristics and load-bearing capacity. The experimental results showed a consistent reduction in compaction and strength parameters with increasing RAP content. The maximum dry density (MDD) decreased from 2.23 g/cm³ for the control mixture to 2.19, 2.13, and 2.10 g/cm³ at 10%, 20%, and 30% RAP, respectively. Similarly, the optimum moisture content (OMC) decreased from 5.99% to 5.25%, 4.41%, and 3.94%. A comparable trend was observed in CBR, which decreased from 96.9% for the control mixture to 77.2%, 67.1%, and 58.3% at 10%, 20%, and 30% RAP, respectively. These results demonstrate that increasing RAP content progressively influences both the compaction characteristics and load-bearing capacity of the RAP–aggregate mixtures. Regression analysis was conducted to quantify the influence of RAP content on the measured engineering properties. The developed linear relationships indicated that each one-percentage-point increase in RAP content resulted in an approximate decrease of 0.0045 g/cm³ in MDD, 0.073 percentage points in OMC, and 1.259 percentage points in CBR within the investigated range. These relationships provide a useful means of describing and estimating the performance trend of RAP–aggregate mixtures at intermediate RAP contents. Despite the observed reductions in density, moisture demand, and load-bearing capacity, the results demonstrate the potential for incorporating controlled proportions of RAP into granular pavement materials, subject to the performance requirements of the intended pavement layer. The findings support the partial replacement of natural aggregate with RAP as a sustainable approach for reducing the consumption of virgin quarry materials while promoting the reuse of reclaimed pavement materials in Egypt.