Cement stabilization of reclaimed asphalt pavement aggregate for road bases and subbases

Pavement rehabilitation and reconstruction generates large quantities of reclaimed asphalt pavement (RAP) aggregate, and recycling into new asphalt paving mixtures is the predominant application. RAP acceptance in road bases and subbases has been limited, because of the lack of laboratory and field performance data. In the Sultanate of Oman, recycling of pavement materials is not practiced. A previous study conducted at Sultan Qaboos Univ. indicated that RAP-virgin aggregate mixtures could be utilized in the subbase layer rather than in the base course. This paper presents the results of a laboratory evaluation of cement stabilized RAP and RAP-virgin aggregate blends as base materials. Compaction and unconfined compressive strength tests were conducted on the following RAP/virgin aggregate mixtures: 100/0, 90/10, 80/20, 70/30, and 0/100%. Samples were prepared using 0, 3, 5, and 7% Type I portland cement and were cured for 3, 7, and 28 days in plastic bags at room temperature. A pavement design analysis of using various cement stabilized RAP-virgin aggregate mixtures as base materials was also undertaken. Results indicate that the optimum moisture content, maximum dry density, and strength of RAP will generally increase with the addition of virgin aggregate and cement. Longer curing periods will yield higher strength results. The ability of RAP aggregate to function as a structural component of the pavement is more pronounced when it is stabilized with cement rather than when blending with only virgin aggregate. A 100% RAP aggregate should not be recommended for use as a base material unless stabilized with cement. Cement stabilized RAP-virgin aggregate mixtures seem to be a viable alternative to dense-graded aggregate used in road base construction.