Suitability of blended recycled asphalt aggregate with fresh aggregate as a base course material

Abstract

Globally, large amount of construction waste is produced each year. Recycled materials offer viable solutions to the concern, which is beneficial to both environment and economy. Recycled Asphalt Aggregate is one of the most commonly used recycled materials. Road construction has become very expensive due to the increase costs on raw materials. Aggregate is one of the main ingredient in asphalt (>95%) and Recent statistics showed the increasing demand of construction aggregate to reach 2.6 million metric tons by the year 2013 in Ethiopia. The production of aggregate materials increased by 31% compare to the year 2012. A study is needed to evaluate the suitability of high percentage (greater than 20%) recycled asphalt aggregate as base course material, without compromising the pavement performance. The main objective of this thesis was to evaluate the suitability of Blended recycled asphalt aggregate with fresh aggregate as a base course material concerning physical and mechanical properties of both fresh and recycled aggregates compare to ERA specification. The thesis was designed to be an experimental study and Recycled and fresh aggregate samples were collected from ERCC, Jimma town. Laboratory tests were performed on fresh aggregate and recycled aggregate samples at a mixture of 0%, 20%, 50% and 100% recycled aggregate by weight of fresh aggregate sample. The tests were Gradation, Flakiness index, Aggregate crushing value, Aggregate impact value, Los Angeles Abrasion value, Compaction and California Bearing Ratio. Then, the results of laboratory experiments were compared to standards to identify the suitability of recycled asphalt aggregate as a base course material by systematic analysis method. The results from this study have shown that the addition of 0 %( Fresh aggregate), 20% and 50% RAA gave the technically qualified results on crushing, impact and abrasion value. The blend gave a ACV of 14.5%, 19.72% and 23.5% (maximum required 25%), AIV of 13%, 17.24% and 22% (Maximum required 24%), LAA value of 21%, 28% and 35%(maximum required 40%) respectively. But in the CBR test only 0% and 20% RAA mix by weight of fresh aggregate gave technically qualified results that is 107% and 92%(minimum required 80%) respectively. The test results by regression analysis to determine the maximum percent or optimum ratio of recycled asphalt aggregate used in base course regards to ERA specifications on crushing ,impact , abrasion and CBR values are 61%,62% ,58% and 40% respectively. This test results confirm that recycled aggregate is a good substitute for fresh aggregate with a limited ratio of 40% by weight of fresh aggregate for a base course material without compromising the pavement performance. Based on the findings in this thesis concluded that Recycled Asphalt Aggregate not waste products and contribute in conserving non-renewable natural resources. As fresh aggregate become more limited and prices rise, the use of recycled aggregate in pavement construction is definitely an eco-friendly alternative