## 4 Conclusions  
This study systematically evaluated the activity changes of volcanic rock powders under physical refinement, chemical activation, and thermal activation conditions, and the following main conclusions were obtained:  
1. Through the \"microaggregate\" effect of physical refinement, the early activity (3 d) was significantly enhanced, the 28 d activity increase was only 4%, and the long-term activity (90 d) leveled off. With the increase in specific surface area, the flexural and compressive activity indices were improved by 6-12% and 4-10%, respectively, throughout the age period, and the optimal economic fineness range was 560-640 m\({}^{2}\)/kg.
2. By optimizing the exciter ratios (6% CaO, 2% CaCO\({}_{3}\), and 2% CaCO\({}_{4}\)-2H\({}_{2}\)O), the 28-day flexural and compressive activity indices of the volcanic rock powders reached 88% and 82%, respectively. CaCO\({}_{3}\) promoted the hydration of C\({}_{3}\)S, CaSO\({}_{4}\) 2H\({}_{2}\)O reacted with C\({}_{3}\)A to form AFt, and CaO maintained the concentration of Ca(OH)\({}_{2}\) and the alkaline environment, thus enhancing the generation of hydration products and material strength.
3. In the low-temperature heat treatment from 300 \({}^{\circ}\)C to 700 \({}^{\circ}\)C, the volcanic rock powder showed an activity index gain of 10% to 20%, reaching 80.4% at 28 days. However, in the high-temperature heat treatment from 800 \({}^{\circ}\)C to 1400 \({}^{\circ}\)C, the crystallization of the composition, the reorganization of the glassy phase, and a loss of active oxides led to a decrease in the activity index of 8% to 15%.
4. The composite activation method demonstrated the highest activation efficiency with an activity index of 86% within 28 days. The order of activation efficiency was as follows: composite activation, chemical activation, low-temperature heat treatment (300 \({}^{\circ}\)C to 700 \({}^{\circ}\)C), and mechanical milling. The economic and environmental considerations were combined to balance the process complexity and energy consumption issues, and the appropriate activation strategy was preferred.  
Our results show a significant difference in the pattern of variation of the physical activation process compared with previous studies. This difference provides a direction for future research to explore the intrinsic mechanism of the two different activation patterns. Despite the limitations of this study in terms of content, such as the enhancement effect of physical milling, the cost of chemical activators, and the energy consumption of the heat treatment process, which were not fully considered, these preliminary methods are sufficient to demonstrate the feasibility of utilizing volcanic rock powders in Hotan, Xinjiang. The experimental results are expected to provide a theoretical basis and practical guidance for the application of volcanic rock powder.  
S.Y.: Data curation, Formal analysis; Y.W.: Project administration, Writing--original draft, Writing--review and editing; H.W.: Investigation, Methodology; G.Y.: Resources, Software; X.D.: Funding acquisition, Supervision; Z.X.: Validation, Visualization. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Central Government Guiding Local Science and Technology Development Fund Project (ZYYD2023B04).  
Not applicable. This study did not involve any human or animal subjects requiring ethical approval.  
Not applicable. The study does not involve any human participants or personal dat.  
Data Availability Statement: Data will be made available on request.  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.