## 4 Conclusions  
1. Among the three retarders, after compounding \(\beta\)-CD and PCE, the initial fluidity of the HBCSA paste is not much different from that when PCE is used alone, and the dispersion performance is relatively stable. For the incorporation of CA or B, the initial fluidity and Zeta potential of the cement paste decreased due to the competitive adsorption with PCE. When CA and B were, respectively, mixed with \(\beta\)-CD, the fluidity was improved. The addition of a retarder improves the fluidity loss and makes the cement paste plastic within a certain period of time.
2. The three retarders have different degrees of retardation effect on the HBCSA paste, and after the two retarders are mixed together (\(\beta\)-CD+CA, \(\beta\)-CD+B), the retardation effect is more obvious. When B is added alone, the maximum setting time is only 31 min and 37 min. Compared with the other two retarders, the setting retardation effect is not obvious enough, but after the synergistic effect with \(\beta\)-CD, the setting time is prolonged.
3. Retarders \(\beta\)-CD and CA, whether they are single-mixed or mixed together, sustainability reduce the early strength of HBCSA. When B is added alone, it not only improves the early strength of the cement paste but also does not affect the long-term mechanical properties of the cement. When it is mixed with \(\beta\)-CD, it reduces the early strength of cement. However, with the increase of age, the strength of cement motor grows gradually, and it has a more positive effect on the strength of cement.
4. Through the analysis of XRD and SEM microscopic tests, it is further verified that the combination of retarder and PCE will delay the early hydration of HBCSA, and the development of hydration products will be slow, thus changing the morphology of hydration products, but not changing the type of hydration products.
5. The Zeta potential of the HBCSA paste within 30 min after adding different retarders was compared. The addition of \(\beta\)-CD will increase the Zeta potential (absolute value). After the addition of \(\beta\)-CD and B, the Zeta potential of the cement paste is basically the same as that of the blank group, and the Zeta potential of other retarder components is decreased, which further characterized that the addition of the retarder would affect the dispersion performance of PCE in the cement paste.  
Figure 16: Zeta potential of different retarders and cement paste hydration within 30 min.  
In view of the results, it is feasible to mix the two retarders, \(\beta\)-CD+CA or \(\beta\)-CD+B, to improve the workability of HBCSA. They can effectively inhibit or delayed the initial formation of ettrinigite. However, considering the intensity development, the combination of \(\beta\)-CD+B is more appropriate. The dosage of \(\beta\)-CD can be 0.3-0.5%, and that of B can be 0.7-0.9%. At the same time, the setting time and fluidity of HBCSA can be regulated by adjusting the amount of \(\beta\)-CD in the composite admixture. Further studies will focus on the correlation between the effect of compounding retarders on macroscopic properties and microstructure development on HBCSA, to modify the properties of HBCSA products applied in engineering.  
Conceptualization, H.J. and M.G.; methodology, H.J. and M.G.; validation and formal analysis, M.X.; data curation, M.L. and S.D.; writing--original draft preparation, M.X.; writing--review and editing, M.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Key R&D and Promotion Special Program of Henan Province (Research in Science and Technology) (No. 222102320092) and the Innovative Funds Plan of Henan University of Technology (No. 2021 ZKCJ17).  
The study did not require ethical approval.  
Not applicable.  
The authors acknowledge Tangshan Polar Bear Building Materials Co., Ltd. (Tangshan, China) for the high-belite sulphoaluminate cement.  
The authors declare no conflict of interest.