Rice Husk Ash Stabilization of Reclaimed Asphalt Pavement

The use of a reclaimed asphalt pavement (RAP) and rice husk ash (RHA) mixture in the construction of pavements has benefits in not only reducing the amount of waste materials requiring disposal but can also provide construction materials with significant savings over new materials. The paper presents results of the laboratory evaluation of the characteristics of RAP stabilized with sawdust ash (RHA) with a view to determine its suitability for use as a subbase and base material in flexible pavements. The RAP-RHA mixtures were subjected to British Standard light, BSL (standard Proctor) compactive effort to determine the compaction characteristics and California bearing ratio (CBR). Test results show that the properties of RAP improved when treated with RHA. The particle grading improved from 99.8 % coarse aggregate and 0.2 % fines, with an AASHTO classification of A-1-a for 100 % RAP to 92.5–99.5 % coarse aggregate and 0.5–7.5 % fines, with an AASHTO classification that ranges from A-1-a (granular materials) to A-3 (nonplastic fine sand) for the various RAP-RHA mix proportions to A- 4 (silty materials) for 100 % RHA. Generally, maximum dry density (MDD) decreased and optimum moisture content (OMC) increased with higher RHA content in the mixes. The CBR values decreased with higher RHA content. However, the values increased from 35 (unsoaked) and 23 % (soaked for 24 h) for 100 % RAP to peak values of 41 (unsoaked) and 34 % (soaked for 24 h) for a 70 %RAP/30 %RHA mix that can be used as a subbase material in flexible pavements.