The effect of processed cooking oil (PCO) on the characteristics of cement pastes

The construction sector nowadays investigates sustainable waste-derived admixtures to enhance the physical and microstructural properties of cementitious systems while reducing environmental impact. This paper investigates the effect of a partially saponified processed cooking oil (PCO) (80% surfactants, 20% triglycerides) as an admixture on air content, density, compressive strength, water absorption, thermal conductivity, and microstructure. Five cement pastes with PCO dosages (0-5%) were evaluated. The result obtained shows that PCO increased air content (0-29.5%) while reducing density (2.0-1.41 g/cm³) and thermal conductivity (0.72-0.23 W/m•K), achieving a 68% insulation improvement. However, as the porosity of the matrix increased, the compressive strength declined (72.7-31.0 N/mm²). On the other hand, water absorption decreased by 69% at 1%. PCO outperforms traditional foam cement due to PCO-mediated hydrophobicity. Microstructural analysis (SEM) shows a homogeneous distribution of air voids in the cement paste matrix (~63.1 µm). The results showed that the optimum performance was at a concentration of 1-1.5% of PCO, which maintained an effective balance between thermal efficiency (0.27-0.33 W/m•K) and maintaining an acceptable compressive strength (55.2-70.2 N/mm²), which indicates the practical and environmental impact of using PCO as an admixture in construction applications.