#concrete  a strong hard building material composed of sand and gravel and cement and water
  supertype:  #building_material  #paving_material
  substance:  #cement.building_material  #sand
  subtype:  #cement.concrete  concrete pavement is sometimes referred to as cement; "they stood on the gray cement beside the pool"
  subtype:  #reinforced_concrete__ferroconcrete  concrete with metal and/or mesh added to provide extra support against stresses

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