Gypsum

0.05-0.5 usd/kg
Circularity potential
Medium
Strength
Low
Production energy
Ultra low
Stiffness
Low
Embodied CO2
Ultra low
Density
Medium

Gypsum mineral is heated to produce materials useful for building. It is a soft sulphate mineral composed of calcium sulphate dihydrate (CaSO4·2H2O) commonly found in sedimentary rock. Its water content is essential to its unique properties. When heated it undergoes a process of calcination, whereby it gradually loses its water content. This yields a very cheap material suitable for building products, such as board, plaster of Paris and stucco.

It is soft and easily scratched, and naturally bright white, like the White Sands Desert, New Mexico, which is an incredible gypsum dune field. Colours are the result of impurities. As well as building products, gypsum is used in agriculture for soil conditioning and as a fertiliser, concrete making, dental moulds, casts for broken bones and sculpture, for example.

Gypsum is recyclable and new plasterboard panels typically contain a proportion of recycled material. Sources include construction waste and unused boards, and post consumer waste from renovation and demolition work. While pure gypsum can be recycled indefinitely, contaminated waste is less straightforward and care must be taken to ensure the fire performance of new products made of recycled material is not compromised.


Sustainability concerns
Non-renewable ingredients
Raw material generates polluting by-products
Low circularity potential


Plaster of Paris (POP) is a brittle material, but it has a fine crystal structure which provides excellent casting and coating properties. This makes it useful for mouldings, such as used in architecture and sculpture, as well as wall coating (plaster). Its mechanical properties depend on the ingredients, but are also affected by curing process and temperature. It is reinforced with fibres, such as cotton and jute, to increase tensile strength and make it suitable as a cast material for medical applications to hold broken bones in place.


Design properties
Cost usd/kg
0.05-0.1
Embodied energy MJ/kg
6.75
Carbon footprint kgCO2e/kg
0.4
Density kg/m3
1000-2760
Tensile modulus GPa
0.95-2.9
Tensile strength MPa
2-3.5
Flexural strength MPa
1-2
Compressive strength MPa
4-16
Hardness Mohs
2
Poissons ratio
0.34
Thermal conductivity W/mK
0.24-0.43
Temperature min-max °C
-40 to 100
Thermal
insulator
Electrical
insulator