Comparative study on the thermal insulating potential of rice and wheat straw ash based composite using marble waste

The increasing generation of industrial and agricultural waste—such as marble waste, fly ash, rice straw ash (RSA), and wheat straw ash (WSA)—poses environmental challenges but also offers opportunities for sustainable material development. This study investigates the use of RSA and WSA as silica sources for synthesizing thermally insulating geopolymer composites in combination with marble waste and fly ash. The materials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and BET surface area analysis, along with measurements of thermal conductivity, diffusivity, and specific heat. XRD analysis confirmed the presence of calcium orthosilicate phase and related silicate phases in both materials, with RSA showing slightly higher crystallinity. FTIR analysis confirms the stretching and bending vibrations and similar silicate structures, but, RSA based material had a higher number of amorphous phases. FESEM imaging the microstructure analysis and presence of pores or air gaps in the material. BET analysis confirmed higher surface area and pore width in the RSA based material, contributing to its improved thermal insulation. The thermal conductivity of the WSA-based material was reported as 0.2454 W/mK, whereas the RSA-based material had a slightly lower value of 0.2312 W/mK, indicating better insulation. These findings demonstrate that both materials can be effectively utilized in the development of eco-friendly thermal insulating materials, with the choice depending on application-specific requirements for mechanical strength versus insulation performance.