The incorporation of PCMs in energy piles holds significant potential for revolutionising thermal management in construction, making them a crucial component in the development of next-generation systems. The existing literature on PCM-integrated energy piles largely consists of isolated case studies and experimental investigations, often focusing on specific aspects without providing a comprehensive synthesis to guide future research or practical applications. To date, no review has been conducted to consolidate and evaluate the existing knowledge on PCMs in energy piles, making this review the first of its kind in this field. Up until now, this gap in research has limited our understanding of how PCM configurations, thermal properties, and integration methods impact the thermal and mechanical performance of these systems. Through thoroughly analysing the current research landscape, this review discovers key trends, methodologies, and insights. The methodology used here involved a systematic search of the existing SCI/SCIE-indexed literature to ensure a structured review. Based on the SLR findings, it is evident that current research on PCMs in energy piles is focused on improving thermal efficiency, heat transfer, and compressive strength. Furthermore, precise adjustments in melting temperature significantly impact efficiency, with PCM integration boosting thermal energy extraction by up to 70 % in some cases, such as heating cycles, and saving up to 30 % in operational costs. PCMs also reduce soil temperature fluctuations, improving structural integrity through minimising axial load forces. However, challenges remain, including reduced mechanical strength due to voids and weak bonding, high costs, and complexities such as micro-encapsulation. We acknowledge that there are gaps in addressing certain key factors, including thermal diffusivity; volume change during phase transitions; thermal response time; compatibility with construction materials; interaction with soil, creep, and fatigue; material compatibility and durability; and the long-term energy savings associated with PCM-GEP systems.

Alkali-silica reaction (ASR) is a chemical reaction between alkaline ions (Na+, K+), silicon phases and aluminum phases in the aggregate, causing volume expansion and cracking of the concrete, leading to a deterioration in the mechanical properties of the structure. In previous studies, microbially induced carbonate precipitation (MICP) technology had been demonstrated to be effective in inhibiting ASR. In this study, in order to explore better inhibition effect, MICP treatments of alkali active aggregates under different saturation degrees were tested. The results showed that when treated at a low-saturation degree (35 %), the inhibition effect of ASR was better comparing with that obtained at higher saturation degrees in the presence of same CaCO3 content. When the CaCO3 content was about 6 %, mortar bar specimens made of low-saturation treated aggregates possessed a 75 % reduction in the expansion and a 37 % increase in the compressive strength compared to the control group. In addition, through microstructure and component analysis of the aggregate surface, it was found that under the low-saturation treatment, the CaCO3 layer could be formed on the surface of the aggregate more uniformly and efficiently, with a higher binding strength to the aggregate and a greater Vickers hardness. Thus, it could better block the invasion of external alkaline ions to react with the active SiO2 inside the aggregate, leading to a better inhibition of ASR.