Utilization of oil-based drilling cuttings as asphalt pavement surface: Study on the mechanical characteristics and long-term environmental impact

Abstract

The pollution caused by oil-based drill cuttings (OBDC) is among the major problems affecting the oil industry. In this study, six different mixing proportions of OBDC were used in preparing asphalt pavement surface, and the heavy metal leaching of the pavement surface were studied. The results indicated that with the maximum mixing proportion of OBDC reached to 4.8% (wt./wt.), the Marshall Stability, maximum flexural strain, and dynamic stability met the requirement of the technical specification for construction of highway asphalt pavements standard. Ba, Mn, Pb and Zn were the characteristic heavy metals in OBDC; heavy metal leaching experiment revealed that the cumulative leaching amount of these four heavy metals showed a similar trend, and all of them could reach to leaching equilibrium during 64 days of leaching. Among the four heavy metals, Ba and Pb showed the largest and least cumulative leaching amount, with 445.5 and 0.7 μg/kg, respectively. Overall, the full stage leaching behavior of Ba, Mn, Pb and Zn was affected by surface wash-off, but specifically, the leaching of Ba was dominated by dissolution, while Mn, Pb, Zn was controlled by diffusion at the early leaching stage. During the middle and late leaching stage, all four heavy metals turned into depletion-controlled leaching. The leaching model of Ba, Pb, and Zn were better described by the Elovich equation, while Mn fitted the second order kinetic equation more precisely. The long-term leaching prediction of cumulative leaching amount revealed that the leaching of Ba, Pb, and Zn should be concerned.