Enhancing the engineering performance of lightweight limestone calcined clay cement concrete using used engine oil as a foam stabilizer

Abstract

Lightweight foam concrete is an appealing thermal insulation material with great potential for decarbonizing the building sector, given that its superior thermal insulation and reduced material usage promote energy-efficient and low-carbon constructions. However, traditional foam concrete largely depends on carbon-intensive ordinary Portland cement (OPC) and costly foam stabilizers, e.g., nanomaterials. To address these issues, this study developed an eco-friendly foam concrete formula incorporating limestone calcined clay cement as a low-carbon cement substitute and used engine oil (UEO) as a foam stabilizer. The viability of this formula was confirmed by assessing foam stability performance of UEO-enhanced foam and crucial engineering performance – thermal conductivity and compressive strength – of foam concrete. Experiments demonstrate that 1 % UEO notably boosts foam stability, with prolonged stable time by 75 % and enhanced remaining foam fraction by 43 %. Additionally, 1 % UEO-containing foam concrete exhibits superior compressive strength of 3.2 MPa and reduced thermal conductivity of 0.162 W⋅m-1K-1, outperforming foam concrete without UEO. The mechanisms of macroscopic performance changes were revealed through scanning electron microscopy (SEM), which disclosed a uniformly established UEO-enhanced pore system and UEO-driven hydration process as the microscale origins. These findings provide waste-enhanced foam stabilizers and present an environmentally appealing alternative to traditional foam concrete, with implications for clean waste management and building decarbonization.