## 3 Performance Prediction of a Cement-Chemically Inert Quartz Filler Binary Mixture
### Experimental Overview
#### 3.2.1 Calibration of Input Parameters of Quartz Powder-Portland Cement Binary Blends
In this section, we maintain the assumption that the water availability coefficient is equal to 1 and examine whether this assumption holds true for chemically inert quartz filler concrete with a water-to-(cement + quartz) ratio of 0.2. The calculated results are shown in Figure 2. As illustrated in Figure 2a, the reaction level increases as the amount of chemically inert quartz filler rises due to the nucleation and dilution effects of the quartz filler. However, when comparing the calculated results with the experimental values for the hydration heat (Figure 2b), chemically combined water (Figure 2c), and portlandite content (Figure 2d), a common pattern emerges: the calculated results are generally higher than the tested values. We believe this discrepancy arises because the assumption that the water availability coefficient is 1.0 is not realistic. In ultra-high-strength concrete with a very low water-to-(cement + quartz) ratio, the consumption of capillary water during hydration reduces the size of the saturated capillary pores [15], which can lower the reaction level. As the proposed model does not account for this factor, the calculated results tend to be overestimated. Performance Prediction of Chemically Inert Quartz Filler Concrete with a Water/(Cement + Quartz) Ratio of 0.2 (Water Availability Coefficient \(wr>\) 1)  
In our previous study, we analyzed the calculated results for chemically combined water in concrete mixed with fly ash and assumed that the water availability coefficient decreased as the water-to-(cement + fly ash) ratio decreased [15]. This specific relationship is expressed in Equation (7):  
\[\begin{array}{l}\mathrm{wr}=2.6\,-\,4*\mathrm{W0/(C0+FA0)}\qquad\mathrm{(W0/ (C0+FA0)<0.4)}\\ \mathrm{wr}=1\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad \qquad\qquad  
the cement also increases as the chemically inert quartz filler substitution amount rises (Figure 3b). Figure 3c,d show the separation of the dilution and nucleation effects: the solid line represents both effects, the dotted line shows only the dilution effect, and the difference between the two lines indicates the nucleation effect. For concrete with a water-to-(cement + quartz) ratio of 0.2, the solid and dashed lines are relatively close, suggesting that the nucleation effect is minimal. In this case, the chemically inert quartz filler primarily acts as a diluting agent. When the water availability coefficient is set to 1.8, the calculated results for the hydration heat more closely match the tested values (Figure 3e). The calculated values for the chemically combined water and portlandite are also more consistent with the experimental data (Figure 3f,g). For concrete with a low water-to-(cement + quartz) ratio of 0.2, the changes in the amounts of chemically combined water and portlandite are minimal when the substitution rate of the chemically inert quartz filler varies from 10% to 20%. Our simulation results successfully reproduce this experimental observation. Additionally, on day one, the tested values are slightly higher than the calculated results. This discrepancy may be because our simulation did not consider the delaying effect of the superplasticizer on the cement hydration reaction [5]. Figure 3: _Cont._