Synthesis and characterization of release agent from used cooking oil at the concrete/formwork interface.

For this preliminary study, the lubricating properties of six formulations containing used cooking oils were tested. The physicochemical properties involved were determined by measuring viscosities at temperatures between 0 and 40 °C as well as by calculating adhesion energies. The formwork/concrete interface was then studied on the steel surface by means of both tribological measurements and analysis of facing quality at 1 day and 7 days after stripping. The results obtained were compared with a marketed vegetable-based oil. The physicochemical results revealed attractive parameters despite a viscosity that remained high. The liquid/vapor surface tensions and wettabilities measured satisfied the recommendations, i.e., greater than 30 mN/m and less than 30°. The selected formulation offered the best compromise between composition and the physicochemical recommendations. At the formwork/concrete interface and for a scraped application, satisfactory criteria were derived, with a 35% reduction in friction and an acceptable facing quality for this initial study. [ABSTRACT FROM AUTHOR]