Study on Suitability of Reclaimed Asphalt Pavement Aggregate (RAPA) in Hot Mix Asphalt Production

Abstract

Currently, a huge amount of reclaimed asphalt pavement is produced each year worldwide due to different reasons. These materials are generated when asphalt pavements are removed for reconstruction, resurfacing, or to obtain access to buried utilities. However, there are some concerns and uncertainties about the actual environmental, economic and mechanical performance resulting from the incorporation of recycled aggregates in asphalt mixtures. The main objective of this study was to evaluate the suitability of recycled asphalt aggregate with crushed aggregate in hot mix asphalt production. This research study was supported by experimental laboratory investigations. Also, Non-probable sampling techniques were adopted to collect samples from study areas such as crushed aggregate and fillers from Shandong Highway Engineering Construction Group Co. Ltd located at SNNP, Gurage zone in Gunchire site. RAPA and bitumen from Ethiopian road works construction corporation construction site found in Deneba. The engineering properties of extracted Reclaimed asphalt pavement aggregate and the crushed aggregate were identified based on standard specification before starting the Marshall Mix design. Then, the Marshall Stability test was conducted on crushed aggregate with three different aggregate gradation size (5.0%, 5.5% and 6.0%) by weight of aggregate and with five different bitumen content (4.0%, 4.5%, 5.0%,5.5% and 6.0%) by weight of total mix. Depending on the selected aggregate gradation Marshall Stability test was conducted for reclaimed asphalt pavement aggregate with a replacement rate of (5.0%, 15%, 25%, 35%, 45%, 55%, and 65%) by weight of crushed aggregate to determine its optimum bitumen content according to National Asphalt Pavement Association method (NAPA). A total of 64 mix designs and 190 specimens were prepared. Hence, Marshall Stability and Moisture Susceptibility test with 3-trials, and rutting test with 2-trials. From 190 specimens, 45 were for the control mix, 105 were for replacement proportion, 36 were for Moisture Susceptibility and 4 were for Rutting. Based on the Marshall test results and comparison with standard specification their performance tests such as Moisture Susceptibility and Rutting was performed to maximum allowable replacement percentage and also compared with standard specification. The optimum bitumen content result obtained in percent was (5.1, 5.04, 4.98, 4.87, 4.81, 4.74, 4.67 and 4.53) for 0 %( control), 5.0%, 15%, 25%, 35%, 45%, 55% and 65%, respectively. The obtained value of Tensile Strength Ratio, proportional rut depth and mean rut depth on 45% RAPA replacement was 85.42% and 4.48 %, 2.24 mm respectively. Finally, the test result obtained from the marshal stability and performance testes indicates that up to 45% replacement of aggregate by reclaimed asphalt pavement aggregate in hot mix asphalt production satisfies the standard specification.