Volcanic tuff ash as quartz replacement in autoclaved aerated concrete: microstructure modification and performance enhancement

The energy-intensive quartz milling process dominates the environmental impact of autoclaved aerated concrete (AAC) manufacturing. This study examines volcanic tuff ash as a quartz replacement (0–100%) in AAC production, evaluating fresh properties, hardened state performance, and microstructural characteristics. Improved compressive strength (11.6% increase to 3.61 MPa) and A-value (13% increase) are achieved at 20% replacement, attributed to enhanced tobermorite crystallinity and pozzolanic reactivity. The formation of hydrogarnet was observed in tuff ash samples, contributing to hazardous element immobilization. Thermal conductivity decreases to 0.080 W/(m·K) with increasing tuff ash content, while maintaining structural integrity. These findings demonstrate the feasibility of tuff ash incorporation for both improved material performance and reduced environmental impact.