Machine spraying of lightweight gypsum plaster

Gypsum mortar (calcium sulfate). The construction steps required for gypsum plaster are more complex and time-consuming than cement plaster, and the proportions are also more complex. The main thing is to correctly adjust the retardation time so that workers can complete all construction steps before the surface condenses or dries. Because the construction environment differs in many countries, adjustments must be made to accommodate different work procedures, with the main difference being the final finishing step after secondary leveling. In Central Europe, a particularly smooth surface was obtained by moistening the surface with water and wiping the water slurry off the surface with a sponge and then scraping it smooth with a knife. In southern Europe and the UK, surface wetting is not performed, which results in a rougher surface. In order to obtain the required smoothness, the surface needs to be scraped with putty. 

Lightweight gypsum mortars containing perlite and vermiculite are commonly used. In these formulations, methylcellulose ether plays a very important role in increasing production and saving lightweight aggregate costs. In machine-sprayed lightweight gypsum mortar, a suitable MC can save 100-200 liters of perlite per ton of mortar compared to MC without any additional thickening effect for the same coverage area. This MC can increase the coverage area of ​​mortar by 10%. 

The true throughput of machine sprayed lightweight gypsum plaster can only be measured in mortar spray trials. For gypsum-lime mortar, the typical German gypsum mortar output is 80 liters per 100 kg of dry mortar, while for machine-sprayed lightweight gypsum mortar, the output is up to 120 liters per 100 kg of dry mortar.

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