Recycling pyrolysis residues from oily sludge in cement-based materials: Workability and microstructural analysis

Oily sludge pyrolysis residues (OSPR), a solid waste from the petroleum industry or oil-contaminated wastewater/sediment treatment, hold significant environmental value when repurposed as a resource. This study evaluates the specific surface area (SSA), mineral composition, and environmental leaching characteristics of OSPR, as well as its performance in cement-based materials, assessing its feasibility as a supplementary cementitious material (SCM). Results show that OSPR has a high SSA and a more dispersed particle size distribution, with leachate pollutants well below hazardous waste thresholds. Incorporating OSPR into cement enhances paste densification, shortens the setting time, and improves workability. The chloride ions introduced by OSPR influence the formation and coexistence of ettringite. The secondary hydration of minerals in OSPR leads to the formation of a denser gel, optimizing the pore structure and improving the later-stage strength. With 10 % OSPR content, a balance between filling, dilution effects, and pozzolanic effects is achieved, optimizing the overall performance of the cement-based material.