What Information Does Tg-Dtg Provide For Aasc? Analyze Thermal Stability And Hydration Products

Thermogravimetric Analysis (TG-DTG) provides a quantitative profile of the thermal stability and phase composition of Alkali-Activated Slag Cement (AASC). By subjecting samples to a controlled heating rate—typically 10 °C per minute under a nitrogen atmosphere—the equipment records precise mass loss data. This process distinguishes between the evaporation of free water, the dehydration of minerals like ettringite, and the decomposition of stable phases such as hydrotalcite or calcium hydroxide.

TG-DTG does not merely measure weight loss; it acts as a diagnostic tool to quantify specific hydration products based on their unique decomposition temperatures. This allows for an exact assessment of how different additives influence the total volume of hydration products within the cement matrix.

What information does TG-DTG provide for AASC? Analyze Thermal Stability and Hydration Products

The Mechanics of Thermal Analysis

Controlled Environmental Conditions

To ensure accuracy, AASC samples are heated in a nitrogen atmosphere. This inert environment prevents unwanted oxidation reactions from skewing the results.

The heating rate is strictly controlled, often at 10 °C per minute. This steady rise allows for the distinct separation of thermal events, ensuring that rapid decomposition does not blur the data.

Quantifying Mass Loss

The core output of the analysis is a record of weight changes over time and temperature. These changes correspond directly to the release of volatile components or the breakdown of chemical bonds.

Deciphering Decomposition Stages

Low-Temperature Range (40–220 °C)

Significant mass loss occurs in the lower temperature bracket of 40–220 °C.

This range is primarily associated with the evaporation of free water trapped within the pore structure.

Crucially, this temperature window also captures the dehydration of ettringite. Distinguishing between free water and chemically bound water in this phase is essential for understanding early-age properties.

Mid-Temperature Range (260–300 °C)

As temperatures rise to the 260–300 °C range, the analysis reveals the stability of more durable phases.

This window allows for the quantitative distinction of hydrotalcite decomposition.

It also identifies the breakdown of calcium hydroxide. The presence and quantity of these phases are key indicators of the cement's reaction progress and long-term stability.

Understanding Analytical Boundaries

Resolution of Overlapping Phases

While TG-DTG provides detailed ranges, distinct thermal events can sometimes overlap.

For example, the loss of free water may transition seamlessly into the dehydration of hydration products.

Dependence on Heating Rate

The clarity of the decomposition peaks is heavily dependent on the heating rate (e.g., 10 °C/min). Deviating from this standard can shift the temperature ranges, making comparisons with established data difficult.

Applying TG-DTG Data to Material Evaluation

Measuring Hydration Product Volume

The total mass loss within specific ranges serves as a proxy for the volume of hydration products.

By summing these losses, you can calculate the extent of the reaction. A higher volume of hydration products generally correlates with better mechanical development.

Assessing Additive Influence

TG-DTG is vital for comparative studies. It provides the data needed to assess how additives alter the microstructure.

You can observe if an additive suppresses the formation of calcium hydroxide or promotes the growth of hydrotalcite by monitoring shifts in their respective temperature windows.

Interpreting Results for Your Project

To effectively utilize TG-DTG data for your Alkali-Activated Slag Cement projects, focus on these specific analytical goals:

If your primary focus is early-age curing: Monitor the mass loss in the 40–220 °C range to quantify the ratio of free water to early hydration products like ettringite.
If your primary focus is structural stability: Analyze the 260–300 °C window to measure the formation of robust phases like hydrotalcite and calcium hydroxide.

By isolating these thermal events, you transform raw weight-loss data into a precise metric for the chemical maturity of your cement paste.

Summary Table:

Temperature Range	Phase Identification	Thermal Event
40–220 °C	Free Water & Ettringite	Evaporation and dehydration of early-age products
260–300 °C	Hydrotalcite & Calcium Hydroxide	Decomposition of stable hydration phases
Total Range	Hydration Product Volume	Quantitative assessment of chemical maturity

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