## 3 Results and Discussion
### SEM Analysis  
Due to the bonding and interlocking effects between ettrinigite crystals [29], it has a great contribution to the early strength of cement. Therefore, the dosage consistent with the above XRD test was selected, and the SEM morphology of different retarders at 1 d and 28 d was observed (Figures 14 and 15). It can be seen that most of the AFt generated by the blank group (Figure 14a) has a slender rod-like structure with a staggered distribution, and a small amount of AH\({}_{3}\) gel around it adheres to the AFt, which makes the structure relatively dense. After the incorporation of CA (Figure 14b), the development of ettrinigite 1 d was relatively slow, and the shape of the needle bar was not obvious enough. However, the number of ettrinigites formed by incorporating \(\beta\)-CD was significantly reduced, and plate-like AFm appeared, with a sparse distribution and more pores. This shows that the formation rate and development of ettrinigite are delayed after the addition of CA and \(\beta\)-CD, which also verifies the conclusion that the above two will be detrimental to the early strength development of cement. It can be seen from Figure 14d that, after adding B, compared with the blank group, the hydrated product ettrinigite has a thick and short shape, and the generated AH gel is significantly increased, and filled in the pores, making the structure more stable due to an increase in density. This shows that the incorporation of borax improves the early strength of HBCSA and further indicates that borax cannot effectively inhibit the hydration of HBCSA. It can be seen from Figure 14e,f that after the remixing of \(\beta\)-CD and CA retarders, the ettrinigite morphology is mostly thin and short, and it is attached to the unhydrated cement particles, so the structure is relatively loose; after the cyclodextrin and borax are mixed together, some ettrinigites are needle-shaped, and some are short and thin, and AH\({}_{3}\) gel is distributed around. After the two retarders are re-mixed, the dosage increases and the two have a synergistic retardation effect, so the amount of ettrinigite generated is significantly lower than that of single mixing, which will make the early hydration rate of HBCSA cement slower. Figure 13: XRD patterns of hydration products of cement paste hydrated for 1 d and 28 d: (**a**) 1 d and (**b**) 28 d.  
with the morphology of 1 d, the grain size is obviously refined and radially grown. The hydration products can be tightly connected. After the incorporation of CA (Figure 15b), thick rod-shaped ettringite was formed, and the growth of small ettringite in the figure was inhibited. Some rods were stacked together, and the gap between the two rods was large, which also caused the structure to be looser. Similarly, with the addition of \(\beta\)-CD (Figure 15c), the resulting ettringite has an uneven morphology and a small amount of AH\({}_{3}\) gel. Therefore, the better retardation effect of the retarders CA and \(\beta\)-CD can effectively inhibit the hydration of cement, so that the hydration of cement is insufficient, and the number of ettringites of hydration products is reduced, thereby reducing the strength development of cement mortar. In addition, the addition of B (Figure 15d) does not affect the formation of hydration products and has a certain promotion effect on cement hydration. The morphology of ettringite is relatively consistent, which is similar to that of the blank group, and the structure is compact. However, in these three samples, it can also be clearly seen that petal-like AFm is formed and interspersed in ettringite. Since AFt and AFm are unstable phases, they can be converted into each other under certain conditions. When the solution is insufficient in sulfate and calcium ions, AFt can be naturally converted into AFm [30], which also shows that the addition of a retarder may consume sulfate and calcium ions in the cement paste and promote the generation of AFm.