Volume 9, Issue 2 (February 2012)
Sawdust Ash Stabilization of Reclaimed Asphalt Pavement
Pavement rehabilitation and reconstruction generates large volume of reclaimed asphalt pavements (RAP) aggregates. Also, large quantities of sawdust are generated by logging industries worldwide. This paper presents results of the laboratory evaluation of the characteristics of sawdust ash (SDA) stabilized RAP with a view to determine its suitability for use as subbase and base material in flexible pavements. The RAP-SDA 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 with SDA treatment. The particle grading improved from 99 % coarse aggregate and 1 % fines, with AASHTO classification of A-1-a for 100 % RAP to 29–95 % coarse aggregate and 5–71 % fines, with AASHTO classification that range from A-1-a (granular materials), for the various RAP-SDA mix proportions to A-4 (silty materials) for 100 % SDA. Maximum dry density (MDD) and optimum moisture content (OMC) increased with higher SDA content in the mixes. The CBR values initially decreased with higher SDA content to a minimum value of 11 % recorded for 30%RAP/70%SDA mix and thereafter increased. With the potential of time-dependent increase in strength in view, the 90%RAP/10%SDA mix that recorded a CBR value of 26 % (soaked for 24 h) can be used as subbase material in flexible pavements. This research provides an initial lead to the evaluation of SDA stabilized RAP as highway construction material, as it is based on CBR determination, a limited parameter that does not provide information concerning all important solicitations that bases and subbases are subjected to. Further work may be encouraged to assess resilient modulus of this material under cyclic load, as well as the assessment of permanent deformation of SDA stabilized RAP. Insignificant expansion and insignificant water absorption were observed.