Plastering Problems Essay

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Plastering problems A common scenario for fast or slow setting plaster. you turn up to carry out some plastering and you have been told the plastering materials are already on site you check the use by date on the bags and oops the plaster is out of date the nearest builders merchants is an hour away and it's rush hour. Do you risk using the plaster? To know why your plaster sets too fast or not at all you will need to understand the fundamental basics of plaster and plastering conditions In some parts of the world the Term Plaster is used to describe sand and cement render, but not here in theSri Lanka we call sand and cement render (sand and cement render) Plaster is calcium sulphate hemihydrates.  Gypsum is the dehydrate Gypsum is heated to extract the water of crystallization and ground to a powder. Some plasters contain additives to improve the texture and or adhesion etc Out of date plaster is best disposed of, as it either sets very fast (Flash sets) or doesn't set at all. 2CaS04.2H2O (heat)»»» 2(CaSO4).H2O + 3H2O The reaction operates in reverse when water is added and the plaster sets. Old out of date plaster would appear to have taken atmospheric moisture in and the traces of the dehydrate seem to act as seed crystals, causing flash set. Another reason for this is badly stored materials, your plaster should be stored in a completely dry environment off the ground. The RHL for the storage room should be checked with a hygrometer if you are in doubt as to the moisture level present in the room. The conditions for plastering on site should be controlled by you as much as is possible, this we call controlling your environment If your working in domestic properties you should be aware that people in the winter do like to have the heating up as high as possible Turn off the heating, don’t be bullied into working

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