Question

Hardening of plaster of paris is because of

Answer 1

Rajesh Panda, B.tech Civil Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, India (2020)

Answered Aug 22, 2017 · Author has 57answers and 655.7k answer views

The first thing which comes to my mind , when i hear the word Plaster of Paris is,that paste like substance which is used to wrap the externalbody part during fracturing .

I think,the reason you know better.

Already laid the foundation of question,lets initiate with a picture…



Image source:google

This is what plaster of Paris(POP)looks like.

Image source:google

What POP is ?

POP, quick-setting gypsum plaster consisting of a fine white powder (calcium sulfate hemihydrate,CaSO4. 1/2H2O), which hardenswhen moistened and allowed to dry. Known since ancient times, POP is so called because of its preparation from the abundant gypsumfound near Paris.

POP+WATER = ?



Image source:google



So the product;Gypsum is the staple reason forhardening of POP when it blended with water.

How hard Gypsum is?(Mohs’ scale of hardness)

Mohs' hardness is a measure of the relative hardness and resistance to scratching between minerals.This scale is a chart of relative hardness of the various minerals (1 - softest to 10 - hardest). Since hardness depends upon thecrystallographic direction (ultimately on the strength of the bonds between atoms in a crystal), there can be variations in hardness depending upon the direction in which one measures this property.



image source:google image

So from the above chart its so clear,in the scale of 1 to 10,Gypsum is 2.

That’s why,we can treat Gypsum as one of the hardest minerals.(except these mentioned 8*Calcite to Diamond*)



Gypsum mineral,Image source:google image

Hope it will help you.

Thanks for reading.

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