Development of composite-phase change microcapsule coating and numerical investigation on its effect in ballastless track slabs

•A composite phase change microcapsule particle with both heat reflection and thermal storage is developed.•An indoor solar simulation system that simulates both solar heat radiation and air heat convection is developed.•The heat reflection and energy storage effect of the developed coating is analyzed.•The cooling effect of the developed coatings is quantitatively simulated and investigated. To solve the problems of interlayer cracking, up-arching and warping of ballastless track slab of high-speed railway under temperature load, a composite phase-change microcapsule (MPCM) was developed, and a series of physical and chemical experiments was conducted. The practicality and functional advantages of composite phase-change microcapsules were investigated by SEM, FTIR, DSC and other material tests. The cooling effects of the coating were evaluated and simulated by indoor tests and numerical simulations. The results show that the developed MPCM exhibits both strong reflectivity of TiO2 and the phase change energy storage property of paraffin, which can reflect 59%-63% of the near-infrared radiation in solar radiation. Moreover, 1 g MPCM can absorb and store 98.3–112.5 J of heat when the ambient temperature exceeds 40 °C. The MPCM coating can reduce the rate of temperature rise of the test specimen, and also decrease its overall temperature difference to 12–15 °C. Furthermore, it can reduce the longitudinal temperature gradient of the test specimen at least by 50%, and its surface temperature by 18%-28%. The temperature regulation ability of coating is positively correlated with the content of MPCM, and its cooling effect reaches the best when the content of MPCM is 20%. The coating reduces the vertical deformation of track slab by 25%-59.6% and the temperature difference inside the track slab by 12.2 °C under high-temperature condition.