Evaluation of the Chemical Compounds and Environmental Impacts of Lime Kiln Dust as a Substitute Filler in Bituminous Mixtures

ABSTRACT The viability of lime kiln dust (LKD) as a substitute filler in asphalt paving materials has been assessed to determine its suitability for road surfacing applications. This study compares the chemical composition, environmental impact, and leaching behavior to conventional fillers like ordinary portland cement (OPC) and hydrated lime (HL). Using attenuated total reflectance Fourier transform infrared spectroscopy, it was found that LKD shares almost similar functional groups with OPC and HL, including calcium hydroxide, carbonate, silica, and sulfate, suggesting its suitability for improving asphalt durability. Gas chromatography-mass spectrometry (GC-MS) analysis identified hydrocarbons, esters, brominated alkanes, and phenols in all fillers, with OPC showing higher ester concentrations, whereas LKD and HL exhibited more varied compositions. These differences indicate distinct environmental impacts, with compounds such as 2-Bromododecane and phenols contributing to emissions. Toxicity characteristic leaching procedure tests confirmed that heavy metal concentrations (such as Pb: 0.14 ppm and Cu: 0.05 ppm) in LKD were well below those of OPC (such as Pb: 0.28 ppm and Cu: 2.56 ppm), and HL were within safe regulatory limits, ensuring their environmental safety. Furthermore, GC-MS analysis revealed that LKD contained a lower total concentration of critical organic compounds, such as the bis(2-ethylhexyl) ester (13.45 % in LKD versus 22.89 % in OPC), reinforcing its lower environmental impact profile. Based on the findings, LKD emerges as a viable, environmentally safer alternative filler for asphalt, offering almost similar performance benefits to conventional fillers while lowering environmental risks. The study supports the use of LKD to enhance pavement durability and promote more sustainable construction practices.