Multi-physics analyses on a passive radiative cooling coating for performance improvement of high-speed railways in hot regions

With the rapid expansion of modern high-speed rail networks and the increasing occurrence of extreme high-temperature events, thermal issues such as cracking and upwarping gaps in ballastless track slabs are becoming more frequent. Currently, cooling tubes and radiative cooling coatings are the primary strategies for mitigating these thermal-induced damages. Cooling tube systems, which dissipate heat through fluid-filled conduits embedded within the track slab, have proven effective but pose significant challenges due to their complex installation and maintenance requirements. In contrast, radiative cooling coatings, as a zero-energy, environmentally friendly, and energy-efficient passive cooling solution, have demonstrated great potential in improving the thermal conditions of ballastless track slabs and mitigating heat-related deterioration. This study investigates the application of a novel radiative cooling coating which composed by TiO2, SiO2, PDMS, and glass microspheres to mitigate thermal stresses and temperature-induced deformation in ballastless track slabs. The three-dimensional heat-stress coupling model of track slab with passive cooling coating is developed to simulate the influence of coatings on the temperature and mechanical fields of track slabs. And a full-scale ballastless track slab experiment is set up to test and validate the model. Results show a maximum surface temperature reduction of 28.27 °C in summer, with an annual average reduction of 5.14 °C. Additionally, the cooling effect led to a 65 % reduction in surface thermal stress compared to uncoated slabs, and a 50 % reduction in surface strain. The coating demonstrated optimal performance in summer and autumn. Additionally, a cost-effectiveness analysis confirms the coating's feasibility for large-scale application in high-speed rail systems. The findings suggest that the novel radiative cooling coatings present a sustainable, low-maintenance solution for managing thermal conditions in ballastless track slabs, with promising potential for future implementation in railway infrastructure.