TGA PT 1600 – Gypsum plaster decomposition

Gypsum plaster – carbonate content – organic content – decomposition

Gypsum plaster is a commonly used material for protecting brick walls, both on the exterior and interior, against the effects of weather and environmental factors. This plaster is typically composed of minerals, silicates, carbonates, and water. It is mixed with water to form a slurry, applied to the wall, and allowed to dry and harden, resulting in a durable solid finish intended to withstand the test of time. However, the precise application procedure and composition of the gypsum can significantly impact its longevity and robustness.

The following measurement example illustrates a damage analysis of gypsum plaster that exhibited cracks and structural deterioration following a cycle of exposure to summer and winter conditions. The manufacturer suspected improper application and utilized thermogravimetric analysis (TGA) to compare the damaged section of the wall with a reference gypsum sample that remained crack-free after heating and cooling cycles.

The measurement revealed that the carbon and organic content of the “flawed” samples (represented by the green and blue curves) closely resembled that of the reference samples (indicated by the red and black curve). All samples displayed a similar level of mass loss, approximately 2%, in the temperature range around 500°C. However, a notable discrepancy emerged in the weight loss occurring at temperatures between 800°C and 900°C, where carbonates in the gypsum release carbon dioxide. In the case of the reference samples, there was a substantial 30% mass loss due to the released CO2, whereas the wall samples with cracks exhibited only 11% and 13% mass loss. This discrepancy suggests that the gypsum on the damaged wall had a lower carbon content than expected, implying that there was indeed an issue with the mixing of the gypsum plaster.

Interestingly, the analysis also unveiled differences in carbon content between the wall’s west-facing (weather-exposed) side and the east side of the building, further highlighting the critical role of gypsum composition in its performance and longevity.

App. Nr. 02-003-001 TGA PT 1600 – Gypsum plaster decomposition – TGA

Related instruments

TGA PT 1600

  • Modular high temperature thermobalance (TGA)
  • Numerous options and upgrades: sample robot, gas dosing system, vacuum, etc.
  • Temperature range: -150 to 1000/1400/1600/ 1750/2000/2400°C
Scroll to Top