Properties of cementitious mortar and concrete containing micro-encapsulated phase change materials

• Microencapsulated PCM in substitution of sand increase heat capacity of concrete.
• Fineness of PCM involves a filler effect and increase cement hydration.
• Low density of PCM compared with fine aggregates reduces compressive strength.
• Microencapsulated PCM remain intact in the cementitious matrices during mixing.
• Blend of 20% v/v is proposed as optimum PCM replacement in cement-based materials.

More efficient energy usage in buildings with increased thermal mass and better thermal insulation has attracted considerable attention in recent years. As one the most widely used construction materials in the building industry, concrete has a great potential to be converted to a high performance thermal storage material by using phase change materials (PCMs). To demonstrate this, mortar and concrete mixes were blended with microencapsulated PCM as part replacement of fine aggregates and assessed for improved thermal performance. Specimens with varying amount of microencapsulated PCM were tested using calorimetry, differential scanning calorimetry (DSC), thermogravimetry (TGA), scanning electron microscopy (SEM), compressive strength and thermal conductivity. Results show that high specific surface of microencapsulated PCM particles has induced an acceleration of the cement hydration. However, the compressive strength at 28 days is still decreased when fine aggregates were substituted by PCM. Contrary to past observations, microencapsulated PCM is observed to remain intact in the cementitious matrices and contributed significantly to improve the heat capacity as well as to reduce the thermal conductivity of the mixes tested. A blend with 20%·v/v replacement was identified as the optimum PCM replacement.