# Effect of Coupled Mechanical-Chemical Activation on Hydration Activity of Copper Slag Powder
## 4 Conclusions  
1. The specific surface area of the copper slag powder increased by 27.84%, 20.14%, and 10.92% when the grinding time increased from 30 min to 120 min. The particle size  
Figure 9: Mechanism of coupled mechanical–chemical activation of copper slag.  
distribution of the copper slag powder after grinding for 90 min and 120 min was superior to that of cement.
2. The strengthening effect of the copper slag powder on the composite cement-hardened paste at 3 d of age mainly had a \"filling effect,\" and the strengthening effect of the copper slag powder on the composite cement-hardened paste at 28 d of age showed a \"pozzolanic effect.\" The chemical activator CaO further stimulated the hydration activation of the copper slag and promoted the development of the compressive strength of the copper slag powder-based composite cement at various ages.
3. The incorporation of the copper slag powder prolonged the induction period and the occurrence time of the second exothermic peak and reduced the total heat release of the composite cementitious system. The reduction ratio of the hydration heat was lower than the mass ratio of the copper slag in the hydration reaction system. With the same content of copper slag powder, the addition of alkaline activator CaO improved the hydration heat and the hydration heat of the copper slag powder-based composite cement.
4. Micro measurements demonstrated that the hydration products of the copper slag powder-based composite cementitious system mainly included calcium hydroxide, ettringite, hydrated calcium silicate gel, and unhydrated cement particles. The incorporation of copper slag powder reduced the compactness of the composite cementitious system. The new hydration product of calcium iron oxide was detected in the hardened paste of the copper slag powder-based composite cement.
5. Mechanical grinding increased the fineness and specific surface area of the copper slag powder and exposed the active mineral components to the alkaline environment of cement-based materials. The copper slag underwent hydration reactions such as dissociation of glass body structure, precipitation of internal ions, C-S-H gel formation, and hardening in the alkaline environment of cement-based materials.  
Writing--original draft, J.Z.; data curation, Q.L.; formal analysis, X.L.; investigation, Y.Z.; methodology, F.L.; funding acquisition, J.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Natural Science Foundation of Jiangxi Province (20202 BABL204063), the 2018 Decision Consulting Project of Jiangxi Association for Science and Technology (17), the Fund of Jiangxi Provincial Department of Education (21 YB230, GJJ212002), and the Key Research and Development Projects of Jiangxi Provincial Science and Technology Department (20192 BBHL80006).  
The article does not cover human research, so it does not cover this item.  
The authors declared that they have no conflict of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.