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Updated: Jul 16, 2026
08:59
Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)
Published on: December 16, 2019
Interfacial Characteristics of a Fly Ash-Based Artificial Aggregate.
Xiaoxing Zeng1, Qijun Yu1, Jiangxiong Wei1
1School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.
Materials (Basel, Switzerland)
|July 15, 2026
Summary
Fly ash-based artificial aggregates were developed for concrete applications. While initial concrete strength was lower than with natural aggregates, the interfacial transition zone (ITZ) improved over time, showing potential for high-strength concrete.
Area of Science:
- Materials Science
- Civil Engineering
- Concrete Technology
Background:
- Fly ash, a byproduct of coal combustion, is an abundant pozzolanic material.
- Developing sustainable construction materials from industrial byproducts like fly ash is crucial.
- The interfacial transition zone (ITZ) significantly influences concrete's mechanical properties.
Purpose of the Study:
- To prepare and characterize fly ash-based artificial aggregates.
- To compare the mechanical properties and ITZ characteristics of concrete made with artificial aggregates versus natural aggregates.
- To investigate the influence of matrix materials and curing conditions on ITZ performance.
Main Methods:
- Cement and alkali activation methods were used to prepare artificial aggregates (>75% fly ash).
- Concrete specimens with artificial and natural aggregates were prepared and tested for compressive strength.
- Scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and nanoindentation were used to analyze the ITZ structure and composition.
Main Results:
- Concrete with artificial aggregates showed 19.0-27.6% lower compressive strength than with natural aggregates.
- The ITZ in artificial aggregate concrete was initially looser (30-40 µm) but became denser over time (90 d).
- Hydration products like C-S-H gel and calcite (cement matrix) or N-A-S-H and C-A-S-H (alkali-activated matrix) were identified in the ITZ.
Conclusions:
- Fly ash-based artificial aggregates can be produced with high compressive strength.
- The ITZ in artificial aggregate concrete matures over time, improving its structure and density.
- Artificial aggregates, particularly in alkali-activated matrices, offer a promising route for developing durable, high-strength concrete with reduced cracking potential.
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