Laboratory Investigation on the Likely Usage of Sub-base Course Dust: An Alternative Filler Material Ingredient for Marshall Design Mix

Construction of road asphalt pavement is always considered to be one of the very few challenging endeavors in implementing projects due to the type and content of the filler material ingredient and bitumen. This research study investigated the likely usage of natural Sub-base Course Dust (SCD) as alternative filler material and its effect in the Hot Mix Asphalt (HMA) through laboratory tests. There were forty-eight samples prepared according to ASTM D1559, of which out of fifteen samples used to determine the optimum bitumen content, while the remaining samples utilized to determine the effects of adding varying percentages of SCD to the asphalt mix. Five different bitumen percent contents applied, starting from 4%, 4.5%, 5%, 5.5% & 6%. The aggregate mixtures mixed "with" and "without" Sub-base Course Dust (SCD) filler ingredients evaluated the Marshall properties of Hot Mix Asphalt (HMA). Likewise, four different contents of Sub-base Course Dust (SCD) filler materials considered, ranging from 2% to 8%, with an increment of 1%. On the other hand, the control mix established with 2% Hydrated Lime (HL), 2% Ordinary Portland Cement (OPC), and 4% marble dust ingredients. The Job mix formula used to obtain the percentage of material proportion for the laboratory experiment. The aggregate ratio applied for "without" filler in 3/4 size of 26%, 3/8 size of 23%, and fine of 51%, while for the aggregates "with" Sub-base Course Dust (SCD) filler, 3/4 size of 26%, 3/8 size of 22%, fine sand of 46%, and mineral filler of 6%. Laboratory test results indicated the Optimum Bitumen Content (OBC) of about 5.1% of the total Hot Mix Asphalt (HMA), and the optimum percentage of Sub-base Course Dust (SCD) indicated 6%. The Marshall properties of the Hot Mix Asphalt (HMA), when the 6% Sub-base Course Dust (SCD) filler ingredient applied, it resulted in high stability, low flow, low Voids in Mineral Aggregates (VMA), low Voids Filled with Binder (VFB), and Low Air Voids. These results complied with the Standard Specifications. Therefore, Sub-base Course Dust (SCD) filler ingredient can likely be used as an alternative filler material in Hot Mix Asphalt (HMA) with an optimum filler content of 6%