## 7 Conclusions  
This paper proposes a hydration kinetic model of the cement-eggshell powder binary system, which considers the dilution and nucleation effects of eggshell powder. Through this hydration model, the development of the thermal/mechanical/chemical/durability properties of the cement-eggshell powder binary system concrete is predicted. The specific contents of the proposed model are as follows:  
First, based on the cumulative hydration heat of the binary system from the beginning of mixing to the age of 7 days, the parameters of the cement hydration model and the nucleation parameter of eggshell powder are calibrated. These parameters do not change with the change in water-binder ratios or eggshell powder contents. Second, the cumulative hydration heat of the binary system at the age of 28 days is calculated using the hydration model. It was found that at 28 days, for the specimens with 0%, 7.5%, and 15% eggshell powder replacement, the cement hydration degrees were 0.832, 0.882, and 0.923, respectively, and the cumulative hydration heat based on each gram of cement was 402.69, 426.88, and 446.73 J/g cement, respectively. With the increase in eggshell powder replacement, the heat release based on unit mass of cement increased due to the physical effect of eggshell powder. Third, it was found that at 28 days, for the specimens with 0%, 7.5%, and 15% eggshell powder replacement, the cumulative hydration heat based on each gram of binder was 402.69, 394.86, and 379.72 J/g binder, respectively. When the hydration heat is expressed as the result per gram of binder, with the increase in eggshell powder replacement, the cumulative hydration heat at 28 days decreased. This is because in the later stage of hydration, the dilution effect of eggshell powder played a dominant role, reducing the cumulative hydration heat. Fourth, the hydration model was used to calculate the chemically bound water and calcium hydroxide contents of the binary system at 28 days. At 28 days, for samples with 0%, 7.5%, and 15% eggshell powder, the chemically bound water was 0.191, 0.188, and 0.180 g/g binder, respectively. The calcium hydroxide at 28 days was 0.183, 0.179, and 0.173 g/g binder, respectively. In the later stage of hydration, the dilution effect makes reducing the chemically bound water and calcium hydroxide contents. Fifth, the calculated hydration heat and a power function were used to regress the relationship between the cumulative hydration heat and compressive strength, and the cumulative hydration heat and surface electrical resistivity. For compressive strength, the correlation coefficient is 0.8474. For surface electrical resistivity, the correlation coefficientis 0.9714. This is because eggshell powder is relatively soft compared to other solid components, which is equivalent to the weak point in the strength experiment. The weak point effect of eggshell powder has little effect in the experiments of hydration heat and surface electrical resistivity, but has a significant effect in the strength experiment. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14135775/s1](https://www.mdpi.com/article/10.3390/app14135775/s1)]([https://www.mdpi.com/article/10.3390/app14135775/s1](https://www.mdpi.com/article/10.3390/app14135775/s1)), Figure S1. Particle size distributions of cement and eggshell powder [24]. Figure S2. XRD patterns of cement and eggshell powder [24]. Figure S3. Test results of compressive strength [24]. (a) Compressive strength results of ES0, ES7.5, and ES15 at different ages. (b) Compressive strength based on ES0 normalization. Figure S4. Resistivity test results of ES0, ES7.5, and ES15 [24]. Figure S5. Curves of ES0, ES7.5, and ES15 for 1 day. (a) TGA; (b) DTG [24]. Figure S6. Curves of ES0, ES7.5, and ES15 for 28 days. (a) TGA; (b) DTG [24]. Table S1. Chemical compositions of cement and eggshell powder [24]. Table S2. Mixtures of samples [24]. Table S3. Combined water and portlandite of ES0, ES7.5, and ES15 for 1 day and 28 days [24]. L.-N.Z.