Mechanical properties and microscale changes of geopolymer concrete and Portland cement concrete containing micro-encapsulated phase change materials

The effect of micro-encapsulated phase change materials (MPCM) in solid and liquid states on the mechanical properties and microstructure of geopolymer and Portland cement concretes is investigated. Geopolymer concrete (GPC) and Portland cement concrete (PCC) containing different amounts of MPCM were prepared and cured at both 20 °C and 40 °C. The results revealed that the compressive strength of both GPC and PCC decreases with the addition of MPCM. Whether the PCM is in solid (20 °C) or liquid (40 °C) state did not significantly affect the mechanical properties of GPC, while melting the PCM was found to reduce the strength of PCC. X-ray tomography imaging was utilized to examine the effect of MPCM on the porosity of the samples. SEM imaging reveals that air gaps are formed between the microcapsules and the surrounding concrete matrix.