Enhancing thermal energy storage and cement hydration control in concrete: Silica-encapsulated nanometric n-octadecane phase change materials

Abstract

Incorporating phase change materials (PCMs) into concrete mixtures offers a promising solution to the challenges of high heat generation and thermal regulation in large building structures. The suitable selection and post-processing of PCM are crucial before application in cementitious systems. This study focuses on synthesizing nano-encapsulated PCMs (NPCMs) via a single-pot sol-gel method and evaluating their thermal energy storage performance. Silica-encapsulated noctadecane (NOD) NPCMs are synthesized, and the optimized core-to-shell ratio is found 3:1. Characterizations have confirmed the successful encapsulation of NOD by silica, forming distinct core-shell structures without new phase formation. The highest melting (Delta Hm) and solidification (Delta Hs) enthalpies are 186.82 and 183.14 J/g, respectively, with encapsulation ratio and efficiency of 83.72 % and 82.28 %. NPCMs have demonstrated superior thermal stability and leakage resilience against temperature. Congruent heat charging and discharging capabilities are demonstrated by NPCMs over 300 thermal cycles, with negligible changes in enthalpy. According to calorimetry studies, addition of NPCMs ensures a more regulated setting and hardening process by delaying the acceleration and deceleration phases of cement hydration. The potential to improve the mechanical properties and durability of concrete, while lowering the risk of thermal cracking is further indicated by the 9.4 % reduction in total heat output resulting from replacing 5 wt% of OPC with NPCMs.