Combined experimental and theoretical investigation of pore characteristics effect on thermal conductivity of light-weight aggregate concrete including microencapsulated PCM

Pore characteristics of concrete material have a significant impact on its thermal conductivity, however, very little pays attention to the impact of pore characteristics on thermal conductivity of light-weight aggregate concrete including microencapsulated phase change materials (MPCM-LWAC). In this paper, the experimental investigation was carried out to reveal the thermal conductivity and pore characteristics of LWAC including different MPCM dosage. The quantitative analysis on pore characteristic parameters (Porosity, Flatness, Spherical degree) that were extracted based on stereology theory has proved a clear relationship of pore characteristics in regard to MPCM dosage. On the basis of experimental investigation, the theoretical investigation was performed to establish the theoretical model suitable for the effective thermal conductivity (ETC) of MPCM-LWAC. To consider the impact of pore characteristics on ETC of MPCM-LWAC, two-step method was proposed to improve the common theoretical model. Results shown that the addition of MPCM caused the increasing of porosity of MPCM-LWAC, while little impact on the Flatness and Spherical degree. Regardless of the MPCM dosage embedded into LWAC, the data sets of Flatness and Spherical degree follow the Lognormal Distribution and Normal distribution respectively. The position parameter of Normal distribution was determined as the shape factor in improved H-C model by using retrograde method. The ETC of MPCM-LWAC getting from the improved H-C model were in better agreement with the experimental results. Hence, the improved H-C model was recommended as the theoretical model to predict the ETC of MPCM-LWAC.