"Lightweight concrete can be produced in three ways: 1. By omitting the fine aggregate. This is called a 'no-fines' concrete. 2. By using lightweight aggragate. 3. By using lightweight aggregate and producing what is generall known variously as 'aerated concrete', 'cellular concrete', 'gas concrete', 'porous concrete', and 'foamed concrete'. This should not be confused with air entrained concrete which has a weight nearly equal to that of ordinary concrete and in which the proportion of air is limited to about 9 per cent."