A Critical Review on Enhancing Thermal Conductivity of Sandy Soils Using Nano Aluminum Oxide (Al₂O₃) under Different Moisture Conditions

Abstract

This review synthesizes up-to-date research on enhancing thermal conductivity in natural sandy soils, a key parameter for improving the utility of Ground Source Heat Pump (GSHP) systems and many geotechnical applications. The review is structured around four key research areas that capture the interdisciplinary context of this research. These areas of study include: the studies, which incorporate mineral and non-mineral synthetic additives into sandy soils to improve thermal connectivity and density with particle contact during loading; the other research area included moisture, which was found to improve thermal connectivity with particle contact, and therefore thermal transfer, when all air voids were filled; there were also studies that investigated the effects of nanomaterials, with a strong emphasis on nano aluminum oxide (Al₂O₃), that focused on mechanical properties for sandy soils, such as; strength, and cohesion. Al₂O₃ improved these properties of sandy soils which were factors indirectly assisting enhanced thermal pathways; and lastly, there are other studies that looked at the applications of Al₂O₃ as a heat transfer medium in nanofluids, and phase change materials (PCMs), which provide consistent improvements in thermal performance and superior thermal management. The challenge is that, while areas of investigation have been explored, substantial gaps remain in our understanding of how nano-Al₂O₃ and moisture variability interact to affect the thermal conductivity of sandy soils, particularly in tropical weather and conditions. This study discusses the gap identified above, addresses its applicability, and identifies potential experiments for future work.