Mechanical and thermal properties of phase change microencapsulated foam concrete

The thermal performance of the building envelope directly affects indoor thermal comfort. Meanwhile, maintaining indoor thermal comfort in buildings consumes massive amounts of energy, which further leads to increased greenhouse gas emissions.Lightweight foam concrete blocks with excellent insulating properties can improve envelope thermal performance, though these cannot adapt to dynamic temperature changes nor manage thermal energy. In this study, paraffin@microporous-cenosphere microcapsules were fabricated via a physical method. These microcapsules were then incorporated into foam concrete with different density grades, aiming to enhance the thermal performance of foam concrete blocks and optimize their thermal energy utilization and management efficiency. The corresponding effects on the physical, mechanical, and thermal properties of the foam concrete were investigated. A scaled experimental house constructed with phase change material (PCM) energy-storage foam concrete blocks was further used to evaluate the temperature-control performance of the PCM foam concrete under realistic environmental conditions. The test results demonstrate that the prepared paraffin@microporous cenosphere microcapsules possess favorable thermal stability and energy-storage properties. Specifically, the microcapsules show no thermal decomposition below 193.69 °C, and their phase change latent heat reaches 69.02 J·g⁻¹ .After incorporating into the foam concrete, the microcapsules exhibited good overall integrity with the foam concrete matrix. The dry density of the modified foam concrete rises with the increase in microcapsule content, with a maximum increase of 111.04% observed at 25% microcapsule addition. In contrast, the porosity and water absorption of the foam concrete decline gradually, reaching maximum reduction rates of 40.86% and 85.75% respectively under the same addition ratio. In addition, the paraffin@microporous cenosphere microcapsules significantly improve the mechanical strength of foam concrete. The maximum strength improvement reaches 316.38% at 25% microcapsule content, which confirms that the microcapsules act as an effective strength enhancer for foam concrete. The strength enhancement was more pronounced in specimens with lower dry density grade. Although incorporating the microcapsules moderately increased the thermal conductivity of the foam concrete, the relatively high phase change latent heat (16.74–18.18 J·g −1 ) and a suitable phase change temperature range compensate for the increased thermal conductivity. Also, relative to the outdoor environment and to an ordinary foam concrete test house, the PCM energy-storage foam concrete test house reduced the daytime maximum temperature by 13.98 °C and 2.84 °C, respectively. The temperature difference between the inner and outer surfaces of the PCM foamed concrete walls validates the temperature-regulating capability of the developed paraffin@microporous cenosphere microcapsules.This study elucidates that the microcapsule-modified foam concrete has excellent comprehensive physical, mechanical and thermal properties. It can effectively mitigate dynamic indoor temperature fluctuations by cutting temperature peaks and compensating temperature troughs, thus showing promising application potential in controlling building thermal loads and reducing building energy consumption.