Wet Blue Fiber and Lime from Leather Industry Solid Waste as Stabilizing Additive and Filler in Design of Stone Matrix Asphalt

In India about 1, 00,000 tons of raw hides and skins are converted into leather from which around 60,000 tons of different kinds of solid wastes are generated per annum from the leather industry in India. Chrome shavings (CS), the chrome laden collagenous scrap generated as waste during levelling of chrome tanned pelt called wet blue. The Calcium salt in the form of CaSO₄, a byproduct by neutralization of spent lime solution using alkaline protease (protolytic enzyme) in solid state fermentation (SSF) technology. In this study, CS is used as stabilizing additive and CaSO₄ as filler has been used in design of Stone Matrix Asphalt (SMA) mixture. Various micro-structural analysis such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermo Gravimetric Analysis (TGA)/Differential Scanning Calorimetric (DSC) were carried out on both additive and filler. Based on the experimental investigations on SMA mixtures showed good stone on stone contact. The Drain Down values were in the range of 0.12–0.22% by weight of mix. The values of Creep Modulus, rutting and Tensile Strength Ratio exhibited superior performance in terms of durability and moisture susceptibility of SMA mixture. From this research study, it is recommended that the design SMA may be designed with 6% Viscosity Grade bitumen (VG-30), 0.3% leather fiber and 5% spent lime to fulfill the mix design criteria as per IRC SP:79–2008.