Thermal, mechanical and microstructural properties of sustainable concrete incorporating Phase change materials

Abstract

Over the past two decades, there has been a significant increase in Buildings’ energy consumption. This rise led to a noticeable leap in operating costs. Subsequently, a need to find novel ways to lower the energy demand in buildings was crucial. Advances in material technology have proven that incorporating phase change materials (PCM) into concrete is one of the ways to tackle energy consumption problems. Depending on the temperature that PCM is exposed to, energy can be absorbed and released easily. This study introduces a set of experiments adopting different quantities of microencapsulated paraffin wax; 1%, 3%, 5%, 7%, and 10% incorporated into normal strength concrete (NSC), high strength concrete (HSC), normal lightweight concrete (LWC) and high strength lightweight concrete (HSLWC). Hence, fresh, hardened, and thermal properties of produced concrete were explored. The hardened properties comprise both strength and sorptivity tests. Additionally, microstructure analysis was investigated. Concrete thermal performance was identified by both thermal conductivity (K-Value) and analyzing the heat transfer rate. The results showed that increasing PCM amount led to reducing the thermal conductivity and increasing heat capacity, which in turn enhanced concrete thermal performance. However, the microstructural analysis showed that many capsules are damaged during the mixing process, releasing their paraffin wax filling into the surrounding matrix, which consequently causes a significant reduction in strength. Anyhow, the prevention of PCM leakage during mixing and improving ITZ in concrete were both achieved using HSC.