Sustainable asphalt production using reclaimed asphalt pavement (rap) with waste engine oil (WEO) as chemical rejuvenator: environmental and economic benefits for Sri Lanka’s road transportation

Abstract

Reclaimed Asphalt Pavement (RAP), also known as milling asphalt, is generated in large quantities in Sri Lanka as roads deteriorate rapidly due to heavy traffic and harsh weather conditions. This results in massive wastage of bitumen and aggregates, accelerating the depletion of natural aggregate sources through overexploited quarries and heavy reliance on imported bitumen (over 90% of demand). Currently, the common practice of complete pavement removal and relaying leads to enormous waste of aggregates, bitumen, machinery, and labor, with virtually no recycling processes existing in the road construction industry. This study investigates sustainable asphalt production by developing an optimized hot mix incorporating 30% RAP using Waste Engine Oil (WEO) as a chemical rejuvenator. Laboratory results confirmed a well-balanced combined gradation within the job mix formula limits. Marshall stability and volumetric properties of the 30% RAP mix were highly comparable to the conventional virgin asphalt mix. Waste Engine Oil (WEO) was effectively used as the chemical rejuvenator. Due to its rich content of aromatic hydrocarbons, saturates, and maltene fractions, WEO restores the colloidal balance in aged bitumen by peptizing and redispersing asphaltenes, which reduces viscosity, improves ductility and workability, and recovers the original rheological and mechanical properties of the binder. This 30% RAP approach offers approximately 30-40% savings in asphalt production costs, reduces carbon emissions by up to 30%, alleviates landfill pressure, and minimizes ecosystem damage (e.g., deforestation in the Central Highlands). It will strongly support Sri Lanka’s resource conservation, economic recovery and infrastructure growth (including Colombo’s smart city projects), and Paris Agreement commitment to carbon neutrality by 2050.