Lightweight Gypsum Materials with Potential Use for Thermal Insulations

Area of Science:

• Materials Science
• Construction Materials
• Gypsum Composites

Background:

• Gypsum-based materials are widely used in construction.
• Optimizing porosity is key for thermal insulation properties.
• Controlling pore structure influences mechanical and thermal performance.

Purpose of the Study:

• To investigate the impact of hydroxyethyl methyl cellulose (HEMC), sodium bicarbonate, and flue gas desulfurization (FGD) gypsum on the porosity of gypsum-based materials.
• To achieve a microstructure with numerous closed pores for enhanced thermal insulation.
• To evaluate the effects of these additives on material density, strength, and thermal conductivity.

Main Methods:

• Gypsum binder modified with varying percentages of HEMC (0.3 wt.%) and sodium bicarbonate (0.5-2 wt.%).
• Incorporation of FGD gypsum to counteract setting delays caused by sodium bicarbonate.
• Analysis of porosity, geometrical density, flexural and compressive strengths, and thermal conductivity.

Main Results:

• HEMC addition increased porosity by stabilizing entrained air.
• Sodium bicarbonate addition formed pores via CO2 entrapment, delaying setting.
• FGD gypsum addition mitigated the setting delay.
• Geometrical density decreased up to 13% with increased porosity.
• Flexural and compressive strengths decreased by 33-75%.
• Thermal conductivity decreased by 9-18%, indicating improved thermal insulation.

Conclusions:

• The combination of HEMC and sodium bicarbonate effectively creates a porous microstructure in gypsum-based materials.
• The resulting materials exhibit improved thermal insulation properties at the expense of reduced mechanical strength.
• The use of FGD gypsum is a viable strategy to manage the setting behavior of gypsum modified with sodium bicarbonate.