Fly ash containing unburned carbon of at least 10 wt % is pelletized using water as a binder without substantial addition of an inorganic binder, into unsintered particles each having an average diameter of 2 mm to 30 mm. The unsintered particles pelletized are sintered at a temperature which allows...http://www.google.com.au/patents/US20050130828?utm_source=gb-gplus-sharePatent US20050130828 - Porous landscape pebble and method of manufacturing the same
