Building plaster
Building plaster is a collective term for binding agents which are mainly used for plastering, stucco and screed work . It is also used in the manufacture of plasterboard .
Manufacturing
Gypsum stone ( anhydrite and gypsum ) is used as raw material . It occurs naturally as calcium sulfate Ca [SO 4 ] • 2 H 2 O containing water of crystallization . The gypsum stone is burned in rotary kilns . The water of crystallization is partially or completely withdrawn from the gypsum stone . At temperatures up to 573 Kelvin , plaster of paris (a bassanite ) is formed, which still contains small amounts of bound water. Anhydrite gypsum is formed at temperatures between 300 and 1000 ° C.
These products are finely ground and packed in bags or provided in containers. By adding water on the construction site, gypsum stone is created again.
About 80% of the calcined gypsum is used for the production of plasterboard and only about 20% for the production of plaster of paris and other gypsum products.
Types of building plaster according to DIN V 18550
Building plaster is used in the construction sector for various applications.
Types of plaster without additives
Plaster of paris
Fast curing and is used for stucco ornaments as wall, ceiling and facade stucco . Plaster of paris achieves a minimum pressure capacity of 6 N / mm 2. Plaster of paris consists mainly of calcium sulfate hemihydrate and is burned in a low temperature range.
Plaster of paris
Does not harden as quickly as stucco and can therefore be used longer. It is used as hand and machine plaster. Plaster of paris is used for interior plastering and rabitz work. Firing takes place in high and low temperature ranges.
Types of plaster with additives
Plaster of paris
Adding retarders significantly increases the processing time. Is used, for example, to fasten electrical sockets.
Adhesive plaster
Particularly good surface adhesion. Used to fasten components. Electrician's plaster is very strong and is used for laying cables and fastening boxes. It has a short setting time of about ten minutes. This means that switches and sockets can be connected a short time later.
Machine gypsum plaster
In addition to longer workability, machine gypsum plaster can be machine processed and is used as wall and ceiling plaster .
Joint plaster
Ability to retain water and delay hardening. For grouting building boards and cracks.
Plaster of paris
Ability to retain water and delay hardening, mostly very fine-grained. Used to level uneven walls.
Screed plaster
It is characterized by slow curing and high strength and is usually very coarse-grained. Used as a screed (also called anhydrite screed).
Ready-made plaster
Slow stiffening and indoor use.
processing
There is a short period of time between the start of mixing and the time of hardening. Depending on the type of plaster, hardening begins between 5 and 90 minutes after the start of processing. Plaster of paris bandages and plaster of paris have the shortest processing time. The building plaster can be processed until it has hardened. The plaster of paris reaches around 40% of its final strength when it begins to stiffen. From this point on, the plaster of paris may no longer be processed, even with the addition of water. The start of hardening can be delayed by adding chemical additives or adding air lime . Warm added water and old plaster residues from partially set plaster on the tools and mortar boxes shorten the processing time considerably.
Building plaster of paris takes 1–20 hours to fully harden. Excess added water diffuses and the plaster surface is enlarged by the hardening process. The subsequent drying of gypsum plaster depends on the temperature, ventilation and the layer thickness and can take several weeks. Layers of more than five centimeters can form cracks, in such cases the gypsum plaster is applied in several layers. Gypsum reacts with iron and galvanized iron and leads to rust formation in a short time. For this reason, plasterboard is fastened with black phosphated screws.
properties
| Gypsum plaster | Water gypsum value |
Gross density (set, dry) [kg / m³] |
Pore volume [% by volume] |
Modulus of elasticity [N / mm²] |
Compressive strength * [N / mm²] |
|---|---|---|---|---|---|
| Plaster of paris | 0.75 | approx. 1,000 | 57 | approx. 4,800 | |
| Plaster of paris | 0.80 | approx. 1,050 | 54 | approx. 5,200 | |
| Machine plaster | 0.48 | approx. 1,110 | 52 | approx. 2,800 | 2.5 - 5 |
| Adhesive plaster | 0.62 | approx. 900 | 61 | 2.5-4 | |
| Ready-made plaster | 0.62 | approx. 950 | 58 | 2.5-4 | |
|
* data based on the water gypsum value |
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literature
- DIN EN 12860, gypsum adhesive for gypsum blocks - terms, requirements and test methods . Beuth Verlag, Berlin 2001.
- DIN EN 13279, gypsum binders and dry gypsum mortar . Beuth Verlag, Berlin November 2008.
- Structural engineering expertise in construction . Expertise for bricklayers, concrete and reinforced concrete builders, concrete and reinforced concrete builders, carpenters, carpenters and architectural draftsmen, [with CD]. In: European reference book series for construction technology . 12th, revised edition. Europa-Lehrmittel Nourney, Vollmer 2007, ISBN 978-3-8085-4462-4 .
- Otto Henning, Dietbert Knöfel : building materials chemistry . An introduction for civil engineers and architects. 5th updated edition. Bauverlag Wiesbaden / Verlag für Bauwesen, Berlin 2001, ISBN 3-7625-3247-8 (or ISBN 3-345-00611-1 ).
Web links
- Federal Association of the Gypsum Industry
- Stucco / building plaster material archive - extensive material information and pictures
Individual evidence
- ^ GIPS data book. (PDF; 1.73 MB) Bundesverband der Gipsindustrie eV, May 2013, accessed on March 10, 2017 .