Synergistic Effects of Alkali Activator Dosage on Carbonation Resistance and Microstructural Evolution of Recycled Concrete: Insights from Fractal Analysis and Optimal Threshold Identification
The synergistic mechanism between alkali activation and carbonation in fly ash recycled aggregate concrete (FRAC) remains a critical challenge for enhancing durability and promoting solid waste utilization. This study systematically investigates the effects of CaO-based alkali activator dosages (0%,...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
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| Series: | Buildings |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-5309/15/10/1742 |
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| Summary: | The synergistic mechanism between alkali activation and carbonation in fly ash recycled aggregate concrete (FRAC) remains a critical challenge for enhancing durability and promoting solid waste utilization. This study systematically investigates the effects of CaO-based alkali activator dosages (0%, 4%, 8%, 12%) on carbonation resistance, compressive strength, and pore structure evolution. The results demonstrated 8% CaO maximized compressive strength (48.6 MPa, 10.76% higher than the control group) and minimized porosity (22.87% vs. 39.33% in untreated samples), with enhanced carbonation resistance (35% depth reduction after 28 days). Fractal dimension (FD) analysis revealed that 8% dosage optimized pore complexity (FD > 1.9), forming a dense C–S–H/AFt network that suppressed CO<sub>2</sub> diffusion. CaO addition introduces embodied carbon (9.84 kg CO<sub>2</sub>/m<sup>3</sup>), and the synergy between fly ash’s cement replacement (120 kg CO<sub>2</sub>/m<sup>3</sup> reduction) and extended service life (theoretically, 15–20 years) ensures a net carbon benefit. These findings establish 8% as a critical threshold for optimizing alkali activation efficiency and durability in low-carbon concrete design. These findings offer theoretical and technical foundations for low-carbon concrete design and sustainable solid waste recycling in construction. |
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| ISSN: | 2075-5309 |