Preparation and water sorption properties of novel SiO₂-LiBr microcapsules for water-retaining pavement

Novel SiO₂-LiBr microcapsules for water-retaining pavement were prepared and firstly characterized by scanning electron microscope (SEM), particle size analysis, and Fourier transform infrared spectroscopy (FT-IR). The water vapor sorption and desorption of the formulated microcapsules was then experimentally studied using dynamic vapor sorption (DVS), with the results fitted to three kinds of adsorption kinetics models. In addition, the specific surface area (SSA) was also calculated based on BET theory; and the thermal performance was investigated by laser flash analysis (LFA). Experimental results show a change of 103% in mass of the microcapsule sample under 90% relative humidity (RH) at 30 °C after water vapor sorption. The fitting of results indicates that the adsorption process is mainly governed by the intra-particle diffusion mechanism, followed by the pseudo-first-order adsorption process. In comparison with most conventional pavement materials, it is found that the SSA of the formulated microcapsules is much larger while the thermal conductivity is lower. The unique properties of the formulated SiO₂-LiBr microcapsules have significant potential to take the edge off the urban heat island effect and reduce rutting when applied to water-retaining pavement materials.