Thermal enhancement of concrete by adding bio-based fatty acids as phase change materials

• Binary mixtures of fatty acids were developed as PCMs for building applications.
• PCMs kept their thermal storage properties even after thermal 1000 cycles.
• Leakage-free, thermally enhanced concrete mixture was produced.
• Lower peak temperature during hydration of cement was observed.
• Compressive strength of concrete mix with PCM was kept within allowable limits.

An effective way to enhance the thermal storage capacity of buildings is to incorporate phase change materials (PCM) into building materials. Fatty acids are derivatives of materials readily found in nature and labeled as bio-based. In this study, we tested binary mixtures of capric acid (CA), myristic acid (MA), lauric acid (LA), and palmitic acid (PA) as candidate materials for building applications. The melting points of such fatty acid mixtures may further be adjusted, to agree with human comfort zone temperatures by regulating their compositions. We developed two binary mixtures of CA–LA and CA–MA as candidate PCMs for building applications. Thermal storage capacities were measured to be 109.0–155.4 J/g with a differential scanning calorimeter. Thermal cycle tests showed that both PCMs are thermally and chemically stable. Durabilities of PCM mixtures determined by the thermal gravimetric analysis indicated that degradation started at 120 °C. The compressive strengths of 1 wt.% PCM added to concrete mixtures were reduced by 12%, yet stayed within the desired limits for C35/45 concretes. However, when PCM contents were increased to 2 wt.%, compression strengths were reduced further, to be within the limits of C30/37 concretes. Both PCMs were suitable for self-compacting concrete mixtures used in buildings.