With increasing concern over the excessive exploitation of natural aggregates, synthetic lightweight aggregate produced from environmental waste is a viable new source of structural aggregate material. The uses of structural grade lightweight concrete reduce considerably the self-load of a structure and permit larger precast units to be handled. BS EN 12504-4. 2004. Testing concrete. Determination of ultrasonic pulse velocity. The mechanical properties of a structural grade lightweight aggregate made with fly ash and clay will be presented. Indicated that water absorption of the green aggregate is large but the crushing strength of the resulting concrete can be high. The 28-day cube compressive strength of the resulting lightweight aggregate concrete with a density of 1590 kg/m^3 and respective strength of 34 MPa. Experience of utilizing the green lightweight aggregate concrete in the prefabrication of concrete elements is also discussed.