Abstract
Oily sludge is a hazardous waste containing emulsified petroleum hydrocarbons, water, heavy metals, and solid particles. The objective of this work is to employ solidification/stabilization (S/S) techniques to utilize oily sludge as a roadbed material with ordinary Portland cement (OPC), fly ash (FA), and silica fume (SF) as binders and phosphogypsum (PG) as a stabilizer. The efficacy of the S/S process is assessed mainly through an unconfined compressive strength (UCS) test and a toxicity leaching test. Road performance, including water stability, freeze-thaw resistance, and volume stability, is also tested on the solidified samples. The mineralogical compositions, microstructures, and pore structure are characterized through X-ray diffractometry (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results show that the addition of 20% binders (OPC : FA : SF = 1 : 0.7 : 0.8) in combination with phosphogypsum to the oily sludge not only increases the 28-day compressive strength of the solidified samples and remarkably decreases the release of heavy metals but also refines the pore structure and compacts the microstructure. The solidified body had sufficient strength and good water stability performance, freeze-thaw resistance, and volumetric stability. This solidification/stabilization (S/S) process, which combines oily sludge treatment and phosphogypsum resource utilization, significantly enhances environmental protection and renders the solidified product economically profitable.
Highlights
In recent years, crude oil production has continued to grow
Plate-like crystals were observed in the PG sample. e binders (OFS) used for S/S treatment included ordinary Portland cement (OPC), fly ash (FA), and silica fume (SF). eir physical properties and chemical compositions are listed in Tables 3 and 4, respectively
(1) e experimental results indicated that the mixtures incorporating di erent proportions of PG had a higher compressive strength and met the limits for a Grade II Highway Subbase (1.5–2 MPa) for a solidi ed body used as roadbed material according to the Speci cation for Construction Technology of Highway Pavement Base (JTJ 034-2000)
Summary
Crude oil production has continued to grow. Crude oil transportation and collection inevitably produce a large amount of oily sludge at the bottom of oil storage tanks [1]. Clay, and lime to immobilize the recalcitrant and hazardous constituents of oily sludge-contaminated soil. E results showed that clay-lime S/S followed by Portland cement was effective to prevent contaminant leaching, and the solidified blocks were safe enough to be used as roadbeds [8]. E purpose of the present study is to investigate the possibility of using phosphogypsum-based cementitious materials, including ordinary Portland cement (OPC), fly ash (FA), and silica fume (SF) as binders and phosphogypsum (PG) as a stabilizer to immobilize oily sludge. To characterize the oily sludge solidified product as a roadbed material, performance evaluation tests were performed, including unconfined compressive strength (UCS), water stability, freeze-thaw cycle, and expansion and leaching tests. It represents a new way to utilize the resource of oily sludge in several engineering applications, which transforms oily sludge into a high-value product
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