Waste Stone Wool as a Co-Precursor in Natural Pozzolan-Based Alkali-Activated Materials: Balancing Performance, Resource Efficiency, and Carbon Intensity

Sustainability, cilt.18, ss.1-27, 2026 (Hakemli Dergi)

Within the literature reviewed, no systematic study was identified that evaluates waste

stone wool (SW) as a partial replacement for natural pozzolan (NP) while varying both

SW content and NaOH concentration in the same alkali-activated material (AAM) mix-

ture. To address this gap, this study examined SW replacement levels of 0–40 wt.% and

NaOH concentrations of 5, 7.5, and 10 M. Fresh-state behavior, physical and mechanical

properties, drying shrinkage, pore structure, and material-based environmental indica-

tors were evaluated. Increasing SW replacement level reduced flowability, while mixtures

containing up to 30% SW showed improved hardened-state performance. SW30-7.5M ex-

hibited the best overall performance, with compressive and flexural strengths of 16.13 and

3.41 MPa, respectively, total porosity of 15.07%, and ultrasound pulse velocity of 3.19 km/s.

It also showed the lowest 63-day drying shrinkage magnitude, with a reported value of

−1014.9 × 10−6 mm/mm. Mercury intrusion porosimetry (MIP) analysis of this mixture

gave an MIP porosity of 14.03% and an average pore diameter of 0.24 μm. X-ray diffraction

(XRD) and Fourier transform infrared spectroscopy (FTIR) indicated changes in the bond-

ing environment after activation, but did not identify a specific reaction product or a new

dominant crystalline phase. Within the defined material-input boundary, SW replacement

reduced NP consumption and the material-based carbon indicator, with the lowest carbon

intensity per unit compressive strength (0.0113 kg CO2 -eq./MPa) obtained for SW30-7.5M.

The overall performance of the investigated AAMs depended on the combined effects of

SW replacement level and NaOH concentration.