## 3 Results and Discussion
### Sem  
The strength of the cement mixed with water-reducing agent H is low after one day, but it increases rapidly in 7 days and demonstrates the same characteristics in concrete, mortar, and cement. According to Figure 4, the flowability of sample H gradually increases with time, which is in line with the performance trend of the other groups. The fluidity of the cement slurry increases over time, and it plays a role of slow-releasing because water-reducing agent H has a small molecular structure with polyoxyethylene and ester functional groups and the branched chains penetrating into the liquid phase to disperse particles. The formation of the water film increases the stability of the hydration layer, delays/inhibits the cement hydration, and prevents the formation of the cement structure to a certain extent; thus, the cement slurry remains plastic for a certain period of time, which leads to the low early strength of the cement. The water reduction rate of water-reducing agent H is lower than that of superplasticizers J and Z; therefore, because of its property of delaying hydration, the hydration of superplasticizer H is not as good as that of water-reducing agents Z and F after the same age of 28 days (compare Figure 15 with Figure 14). When the SEM image is magnified 5000 times, you can see that some fibrous CSH gel and some irregular needle/rod AFt are staggered on the CSH gel, which means that the structure is not dense and contains some pores at this time. Therefore, the porosity, total pore area, and pore volume of the concrete mixed with the sample H water-reducing agent are higher than the concrete mixed with the samples Z and F (as shown in Table 4). According to the XRD images shown in Figures 8-10, the AFt and CH peaks of the cement slurry mixed with the superplasticizer H are the weakest, indicating that the CH crystal form of the cement slurry mixed with the sample H is not as good as that of the J and Z superplasticizers. The CH crystal form of the cement slurry is good, which is mainly due to the short molecular side chain of the H superplasticizer, which can extend the setting time of the cement. In addition, the ester group in the H superplasticizer is slow under the alkaline environment of the cement system. Hydrolysis into carboxyl water-reducing functional groups can further delay the hydration of cement. Therefore, compared to J and Z superplasticizers, H superplasticizers can delay cement hydration. More unhydrated cement particles lead to a slower rate of strength development. It can be seen from Figures 5-7 that the early strength and the later strength of cement mortar, and cement mortar and concrete mixed with H water reducer are relatively lower than those of superplasticizer J and Z. Compared to superplasticizer H, the structure of water-reducing agent J includes longer side chains; nonetheless, its side chains are shorter than those of superplasticizer Z. It can be inferred from the flow rate of the cement (see Figure 4) that, under similar water consumption, superplasticizer J initially has high fluidity and the lowest rate of fluidity loss over time in each group, indicating that water-reducing agent J can adsorb the water on the surface of cement particles. Thus, the water molecules are released to the maximum extent, providing high fluidity and enhancing water retention. In terms of compressive strength, the cement mixed with superplasticizer J is stronger than the one mixed with the standard C40 group. In fact, the proper dispersion of the cement can greatly enhance the reaction between cement and water. It can be seen in Figure 16 that the cement mixed with standard C40 can have many tiny pores and can form a nonuniform structure containing both dense  
Figure 15: SEM images of the concrete mixed with water-reducing agent H.  
and loose/porous areas. The pore structure of sample NF is denser than that of the standard C40 sample but far looser than that of sample J.