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Damage and Recovery Behavior of Low-Replacement-Rate Fly Ash Concrete after Different High-Temperature Exposures
Lin Mi1,2, Bowen Kuang1,2, Daixin Fu1,2
1Failure Mechanics and Engineering Disaster Prevention Key Laboratory of Sichuan Province, College of Architecture and Environment, Sichuan University, Chengdu 610207, China.
Materials (Basel, Switzerland)
|September 14, 2024
Summary
This study examined fire-damaged fly ash concrete (FAC). Post-fire curing aided strength recovery at 400°C due to pozzolanic reactions, but higher temperatures and low FAC content limited long-term durability.
Area of Science:
- Materials Science
- Civil Engineering
- Concrete Technology
Background:
- Fire damage significantly compromises concrete strength and durability.
- Fly ash concrete (FAC) offers potential for improved performance, but its behavior post-fire requires detailed investigation.
- Understanding microstructural changes is crucial for predicting strength recovery in damaged concrete.
Purpose of the Study:
- To investigate the strength recovery of fire-damaged fly ash concrete (FAC) with 10% fly ash substitution after post-fire curing.
- To analyze the chemical and microstructural alterations in FAC subjected to elevated temperatures.
- To elucidate the role of fly ash in mitigating fire-induced damage and promoting strength regain.
Main Methods:
- Fire exposure of concrete specimens to temperatures of 400 °C, 600 °C, and 800 °C.
- Post-fire curing to assess strength recovery.
- Chemical and microstructural analysis using X-ray diffraction (XRD), derivative thermogravimetry (DTG), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and nitrogen adsorption.
Main Results:
- Low substitution (10%) fly ash concrete showed slight strength enhancement at 400 °C due to enhanced pozzolanic reactions.
- Higher temperatures (600 °C, 800 °C) negated the benefits of fly ash, with strength recovery limited by microstructural damage.
- Fly ash influenced crystal morphology (calcium carbonate, calcium silicate hydrate), potentially due to its high aluminum content.
Conclusions:
- Post-fire curing can facilitate strength recovery in FAC damaged at moderate temperatures (400 °C) via pozzolanic reactions.
- The low fly ash content limits its efficacy in preventing long-term microstructural damage and strength loss at higher temperatures.
- Fly ash's aluminum content may act as a crystallization-guiding agent, affecting the morphology of hydration products in fire-damaged concrete.
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