Thermal concrete (also called thermocrete) was a building material like concrete that was mostly silicon. It was used by various races to build quick shelters. The Klingon research facility on Zeta Aurigae IV was built using reinforced thermocrete. Starfleet Intelligence agent Bridget McLellan was able to escape past the thermocrete wall by blasting a hole in the wall with her phaser. (VAN - Declassified novella: The Stars Look Down)