Preparation of environment-friendly ultrafine fly ash based superhydrophobic demoulding coating

Abstract The superhydrophobic surface can be used to separate castable concrete materials and moulds instead of waste oil which has the risk of contamination. In this study, a low cost superhydrophobic demoulding coating was prepared using waste materials. Solid waste ultrafine fly ash (UFA) as micron particles. Nano-sized CaCO3 nucleated on the surface of UFA with Ca(OH)2/calcium carbide slag(CCS) slurry under constant CO2 bubbling condition. Fluorosilanes were used to provide low surface energy. Powder coating was used as the base coating to provide intermediate bonding. Through SEM and AFM analysis, it was found that after carbonization, nano-sized CaCO3 particles were distributed on the surface of UFA particles and form large protrusion, and the surface roughness was significantly increased. The contact angle of the coating water was greater than 150° under the optimal condition. Compared with the original UFA, the amount of fluorosilane was reduced from 2% to 0.1%, which reduced the cost. The composite interface between the liquid droplets and the coating surface was formed to intercept air bubbles. The hydrophobic model of the coating met the Cassie theory. The coating can replace the release agent to achieve easy release effect.