Development of Ca-alginate/nano SiO2 PCC based on waste cooking oil derivative for foamed concrete applied to energy-saving system

Minimizing indoor temperature fluctuations reduces dependence on heating and cooling systems, thereby lowering building energy consumption and carbon emissions and subsequently helping tackle global climate challenges. In this study, phase change capsules (PCCs) based on waste cooking oil derivative, Ca-alginate and nano SiO 2 were developed for foamed concrete (FC). The effects of nano SiO 2 dosage on PCC morphology, durability, thermal stability, and heat storage performance were systematically investigated. The distribution of PCCs within FC and the mechanical and thermal regulation properties of FC containing PCC were evaluated. The experimental results indicate that PCCs with 2 wt% nano SiO 2 exhibit a compressive strength of 26.29 N at 15 °C, the thermal decomposition onset above 200 °C with a notable mass loss of 40 %, and phase change enthalpy and temperature are 68.86 J/g and 20.1 °C, respectively. Ca-alginate/nano SiO 2 PCCs were uniformly dispersed and structurally intact within the FC matrix. Incorporation of 3 wt% Ca-alginate/Nano SiO 2 PCCs led to a 10.8 % reduction in compressive strength while exceeding the minimum strength requirements (>8.13 MPa) and achieving a 3.6 °C reduction in FC temperature variation. This study offers a sustainable strategy for improving building energy efficiency while promoting the recycling of waste cooking oil.