Laboratory-Based Correlation Analysis of Volumetric Properties in Asphalt mixtures Using Recycled Asphalt Pavement (RAP) Aggregate as Partial Replacement of Crushed Aggregate

Abstract

The road network is the backbone for the socio-economic development of the countries over the world. In Ethiopia, most of the leading road network is flexible pavement. The construction and maintenance of those pavements are needed construction materials such as aggregate, bitumen, and fillers. Because of the increasing price of those virgin materials, it's challenging to construct the road network as well. So that, the use of the available Recycled Asphalt Pavement (RAP) aggregate in hot mix asphalt (HMA) as partial replacement of crushed aggregates, is the best alternative. The purpose of this research was focused on using and evaluating the effect of Recycled Asphalt Pavement (RAP) aggregate on the volumetric parameters by determining the relationship between volumetric properties and RAP aggregate percentage using linear regression technique. For the achievement purpose of this study, the previous research was reviewed, and the experimental program was designed and conducted. After study materials such as RAP, bitumen, crushed aggregate, and fillers, are collected, the quality test was conducted on all the selected materials. Next, the Marshall Stability test was conducted on six mix samples containing a different percentage (0%, 10%, 20%, 30%, 40%, and 50%) of RAP aggregate and mixed with five different bitumen content of (4%, 4.5%, 5%, 5.5%, and 6%).A total of 40 mix designs with 3- trials and a total of 120 mix specimens were prepared, From 120 specimens, 45 were for the control mix, and 75 were for RAPA proportion. OBC was determined from the Marshall Stability Test conducted on all mixes with six different RAPA proportion according to Asphalt Institute (2003) method, and the result obtained in percent was (5.08, 5, 4.71, 4.67, 4.35 and 4) respectively. The Marshall Properties of each mix was also determined at each of OBC, and analysis was conducted by using correlation with regression. From final analysis, some volumetric properties of HMA such as OBC, Air void and VMA has a good negative correlation with recycled percentage, by correlation coefficient (R 2 ) of (0.948, 0.736 and 0.743) respectively. Whereas, Void filled with asphalt has a positive correlation with R 2 of 0.961. Based on the result obtained the values of volumetric parameters of HMA are changed by RAP aggregate content in mix and recommended maximum use of RAP aggregate in HMA for this study is up to 40% only