Continuous microwave tunnel expansion of vermiculite: a comparative study with thermal/chemical methods for structure-intact performance enhancement

Vermiculite (VMT) expansion technology requires innovation to overcome its low efficiency and limited mechanical properties. Therefore, herein, a tunnel-type continuous microwave method was employed to optimize the VMT expansion process and enhance the performance and industrial value of the expanded VMT (EVMT). The microwave-expanded VMT (M-EVMT) exhibited minimal damage to the raw VMT structure compared with the thermal/chemical expansion methods, and at a 12 kW microwave power and 0.3 m min^-1 conveyor belt speed, the raw VMT with 2.8-8 mm particle size could achieve larger interlayer microwave expansion and maintain its intact structure. Meanwhile, M-EVMT demonstrated unprecedented mechanical flexibility while maintaining a complete layered structure. This microwave method integrated mineral processing with circular economy, enhancing the energy efficiency, material performance, and industrial scalability of sustainable building materials.