Study of heavy metal release characteristics of asphalt pavement surface prepared by drilling residue

Objective In order to further promote the resource utilization of oil-based rock debris deoiling residue, the feasibility of preparing asphalt pavement from deoiling residue is studied by using deoiling residue, mineral powder and gravel as raw materials.

Methods JTG/T F40-2004 Technical specification for construction of highway asphalt pavement, GB/T 30810-2014 Method for determination of leachable heavy metals in cement mortar and EA NEN 7375-2004 Standard for leaching characteristics of molded or integral block materials were used to investigate the product quality of asphalt surface test blocks prepared by replacing mineral powder with residual solid phase, and the effective releasable amount and releasing characteristics of heavy metals in asphalt surface were analyzed.

Results The performance of the prepared asphalt pavement surface test block could meet the requirements of JTG/T F40-2004 when the content of residual solid phase is not higher than 4.8%(mass fraction).The releasing rates of 11 heavy metals (arsenic, barium, cobalt, copper, chromium, manganese, molybdenum, nickel, lead, vanadium and zinc) in the leaching solution of asphalt surface test block were less than 1%.The releasing mechanism of each heavy metal in the asphalt surface test block is different.The releasing mechanism of arsenic and chromium is mainly due to dissolution and the release mechanism of barium, cobalt, manganese, nickel and lead is mainly ascribed to surface scouring while the remaining heavy metals are controlled by diffusion.The releasing rate of each heavy metal was in the following order: barium < cobalt < zinc < manganese < nickel < chromium < arsenic < lead < copper.

Conclusions The deoiling residue of oil-based rock cuttings can replace mineral powder to prepare asphalt surface test block.The prepared asphalt surface test block has a low risk of groundwater environment contamination caused by the migration of heavy metals.It is suggested that waste generation enterprises and the road construction industry could jointly formulate the product quality standard and pollution control requirements for the preparation of asphalt mixture from oil-based rock debris deoiling residue, so as to promote the popularization and application of oil-based rock debris deoiling residue in the road construction industry.