cinder

This term evokes the image of residual heat and charred remains. It is most commonly associated with the aftermath of a fire, where the material is no longer actively flaming but remains dangerously hot to the touch. In construction contexts, the word shifts from a natural byproduct of fire to an industrial material. Cinder blocks are a specific architectural staple, referring to the porous, lightweight concrete blocks made from volcanic ash or blast-furnace slag.