Pumice has a bulk density of 500–900 kg/m³ and is the only natural light weight aggregate used widely. The unit also notes a historical use of pumice concrete in:

1. The unit traces pumice's use beyond modern construction. 2. It calls pumice one of the oldest light weight aggregates, even used in Roman structures. 3. Roman use leveraged pumice's low density to lighten upper-storey concrete. 4. The unit does not credit Mesopotamian, Mughal or Inca contexts in its discussion. 5. So Roman is the historical context highlighted by the unit. _Source: IGNOU Concrete Technology, Unit 11 "Special Concrete" (Light Weight, Aerated, No-Fines, High Density, Fibre Reinforced, Polymer Concrete)._