Evaluation of strength characteristics of recycled bituminous pavement materials

There is a long history of natural resources exploitation without accounting for their limitations. One of the greatest challenges is to find new ways of saving natural resources to create a long-term and stable green environment for generations to come. Research in past decades has uncovered that reclaimed asphalt pavement (RAP) is a valuable part of hot mix asphalt. Primary reasons of using the reclaimed asphalt in asphalt pavements are both environmental and economic. The key purpose of this project is to investigate the strength characteristics of recycled proportioned asphalt pavement materials through determining the resilient modulus of asphalt. Resilient modulus is an important design parameter for pavement structures, as it represents the structural strength of pavement layers through which the thickness design is based. After reviewing past research and current Austroad practices, dense grade 20 (DG20)mix design prepared with 0%, 15%, 30%, 40%, 50% and 60% reclaimed asphalt-proportioned composition with C600 and C320 binder material formed the base specimens. To verify previous experimental work and current Austroad guidelines, the indirect tensile test method was used to determine the resilient modulus of the specimens. After analyzing the results, it was concluded that with an increasing amount of reclaimed material, the resilient modulus also increased. This confirmed the results of previous studies. However, the resilient modulus for the 15% proportioned mix was very high and40% RAP result was similar to 0% RAP, which did not comply with current guidelines. There was an initial concern to lower the binder grade as a lowered grade binder can compensate the RAP aged binder. However, doing so comes at the potential risk of soft pavement production, which in turn could lead to an increased risk of rutting. From the results of this study the Austroad guidelines, in their current form, are not sufficient to attain the best performance for high proportioned Reclaimed asphalt pavements materials. The major recommendation from these results is to conduct a larger scale experiment to find the optimal mix design of reclaimed asphalt and thus use these results to help inform a review of the current Austroad guidelines concerning such mixes