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Perlite is naturally occurring rock.Since it contains significant amount of water, it can be expanded in specially designed furnaces.After expandation, lightweight expanded perlite is obtained.Unfortunately during both production as well as processing of expanded perlite, some fine grained waste perlite is being formed.Due to its extremely low bulk density, waste expanded perlite is difficult to handle, utilize and causes dust formation.Paper presents results on the investigations on the properties of ground waste expanded perlite used as supplementary cementitous material.Waste expanded perlite was ground in ball mill.Ground waste expanded perlite was characterized.Tests were performed using OPC mortars containing various amounts of ground waste expanded perlite.Results showed, that addition of ground waste expanded perlite leads to strength increase up to even 50% for 35% addition of perlite.Detailed investigations showed, that waste expanded perlite is pozzolanic in its nature.Due to its very high specific surface (caused by cellular microstructure of expanded perlite) as well as chemical composition (sum of SiO2 and Al2O3 close to 90%) ground waste expanded perlite exhibits very good pozzolanic activity.In addition, ground waste expanded perlite is almost white.It makes it valuable pozzolanic additive in special applications like white cement based materials.It can be also used as anti-efflorescence additive in special masonry mortars.