Structure-property correlation of thermally activated nano-size phase change material in the cementitious system

Abstract

Recently, energy-efficient building design has emerged as a prominent research focus for maximizing energy savings. In light of this, various attempts are made to improve the thermal mass of buildings. Increasing the heat capacity of construction materials with the incorporation of phase change material (PCM) has been considered an easy and effective technique to increase the thermal mass of concrete structures. However, the incorporation of microencapsulated phase change material (MPCM) into cementitious system possesses drawbacks of weaker hydration activity and leakage problems. Therefore, this study has been aimed to explore the chemical and morphological evolution of thermally activated nanoencapsulated phase change material (NPCM) with principal hydrated phase of ordinary Portland cement (OPC) at 60 °C. With an average size of ∼450 nm, silica encapsulated paraffin-based NPCM is synthesized via facile in-situ polycondensation method. 1% NPCM has boosted the hydration reaction with the occurrence of a low quantity of C3S + C2S, whereas a denser cement matrix with minimum pore structures has been accomplished due to better pozzolanic activity and existence of CaCO3 on the surface of NPCM. The emergence of needle-shaped CaCO3 polymorph on the NPCM surface proves that NPCM acts as secondary nucleation sites for the formation of additional C–S–H, which has manifested pore-filling effects as well as further leakage protection. The activation of NPCM at high-temperature curing has ascertained excellent structural and durability performances over an extended period. Thus, this study may bring out better insight to the researchers toward the direction of energy storage materials applications in building structures.