Evaluation of dissolved organic carbon released from aged asphalt binder in aqueous solution

Abstract

Asphalt binder which is usually used in pavement construction, is a kind of organic material. Dissolved organic carbon (DOC) will be released from asphalt by rainfall wash and runoff, resulting in potentially environment influence by transferring such hazardous matters into aqueous and soil system. By simulating the aging process of asphalt binder in laboratory, this work presented the results of a study addressing release of DOC from different aged asphalt binders. Leaching behavior, characteristics of aged asphalt after leaching, chemical composition and carbon speciation of leachates were discussed. Leachability and factors were analyzed by grey relation theory method. The concentration of DOC ranged from 3.95 mg/L to 23.6 mg/L for all leachates. Aging enhanced the leachability of DOC released from asphalt. Combined with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analysis indicated that the polar matters containing hydroxyl and carbonyl group increased by aging treatment and then enhanced the leachability of DOC from aged asphalt. Meanwhile, a significant increase and decrease of oxygen content was obtained for asphalt binders respectively after aging and leaching. As a result, the organic matters in leachates significantly increased and mainly consisted of hydrocarbons and oxygen containing compounds. The proportion of fulvic acids (FA) and hydrophilic organic carbon (Hy) fraction was dominate while a small percentage of humic acids (HA) was obtained. Grey incidence analysis showed absolute grey index (AGI) value varied from 0.5107 to 0.7064, which indicated that DOC leaching was likely pH-dependent for thin film oven test (TFOT) and ultraviolet (UV) aged asphalt while time was main influential factor for pressure aging vessel (PAV) aged asphalt.