Fly ash (FA) is the main solid waste emitted from coal-fired power plants. Due to its high yield, low utilization rate, and occupation of a large amount of land, it exerts enormous pressure on the Earth’s environment. With the deepening of the concept of sustainable development, exploring the reuse of industrial waste such as FA has become a key strategy. If FA can be combined with commonly used jewelry in people’s lives, it will be of great significance to promote the high-net-worth utilization of FA. Therefore, this study synthesized a fly-ash-based composite material with color-changing function and combined it with necklaces as the main material. In the first stage, after blending fly ash and slag, an alkaline activator with a total mass of 10% was added. When the proportion of fly ash was 60%, the compressive strength of the prepared fly-ash-based composite material reached 10.1 MPa. This was attributed to the reaction between sodium silicate in the alkaline activator and free CaO, MgO, and other substances in the fly ash to form hydrated silicate colloids, which solidify the fly ash and transform it into a complex three-dimensional network skeleton. In the second stage, a UV resistant coating with thermochromic function was obtained by blending acrylic resin, TiO2, and a thermosensitive color-changing agent. It was applied to the surface of fly-ash-based composite materials, and the results showed that as the content of the color-changing agent increased, the number of pores on the surface of the coating gradually decreased. When the content of color-changing agent was 10%, the prepared 10%FAB not only had good surface color but also had good thermal stability, UV absorption ability, superhydrophobicity, and mechanical properties. Therefore, 10%FAB was selected as the basic material for jewelry design. In the third stage, the traditional Chinese technique of “gold inlaid with jade” was utilized to develop jewelry applications for the FA composites. As such, 10%FAB was processed into necklaces, which not only had modern design aesthetics but also had good color-changing effects above 30 °C. And after a long period of UV aging experiments, the necklace did not show any wrinkles, bubbles, or other phenomena. Due to the excitation of TiO2 hole–electron pairs, the necklace’s UV absorption ability was further improved. This study demonstrates the potential application of industrial waste in decorative products, expands the high-end utilization of fly ash as a low-cost material, and provides new ideas for building a low-carbon lifestyle.
