## 3 Results and Discussion
### Analysis of Hydration Characteristics of Composite Mortar  
The heat of hydration is an essential parameter for evaluating the hydration process of gelling materials, which can well reflect the dynamic process of slurry hydration [16]. Usually, the hydration reaction process of gelling materials is divided into five stages [17; 18]: dissolution period, induction period, acceleration period, deceleration period, and stabilization period. Figure 4 shows the exothermic rates of hydration and accumulated exothermic heat of the composite net slurry for 72 h. The characteristic values of the hydration exothermic behavior are shown in Table 4. The exothermic rate diagram in Figure 4a shows that the first exothermic rate peak is formed rapidly after contact with water, which is caused by the exothermic dissolution of aluminates and sulfates in the cementitious material in contact with water [19]. Subsequently, the hydration reaction of the slurry enters the induction period, and small amounts of hydration products AFt and Ca(OH)\({}_{2}\) are generated. Compared with the induction period of the OPC group, the induction period of the A0 group was prolonged, while the induction period of the A1-A6 group was shortened after the redoping of appropriate amounts of RM and EMR. In addition, during the acceleration phase, the peak of 3.32 \(\times\) 10\({}^{-3}\) mW/g was reached at 10.0 h for the OPC group and 4.20 \(\times\) 10\({}^{-3}\) mW/g at 10.9 h for the A0 group. In contrast, the induction period of the A1-A6 group was shortened after compounding with appropriate amounts of RM and EMR. With the increase of EMR doping, the appearance of the second exothermic rate peak was gradually delayed, and the peak height showed a trend of first increasing and then decreasing. Meanwhile, the third exothermic rate peak was gradually separated. The formation of the third exothermic rate peak was related to the recrystallization of AFt following sulfate depletion [20; 21]. With the increase in EMR doping, the appearance of the third exothermic rate peak was gradually  
Figure 3: The compressive strength of composite mortar. delayed and the peak height was steadily reduced. The cumulative exotherm plot in Figure 4b shows that the cumulative hydration exotherm of the composite system decreased to different degrees compared with the OPC system because of the dilution effect of SS, RM, and EMR doping. The hydration exotherm of the A0 group was significantly lower, with a cumulative hydration exotherm of 225.0 J/g at 72 h, which was 87.0% of that of the OPC group (258.5 J/g). After the blending of RM and EMR, with the increase of EMR, the cumulative heat release of hydration showed a trend of increasing first and then decreasing. It can be inferred that the incorporation of SS will inhibit the hydration reaction of the slurry, slow down the rate of hydration exotherm, and reduce the cumulative heat release of the slurry, while the compounding of RM and EMR in appropriate proportion can promote the hydration reaction of the slurry, accelerate the rate of hydration exotherm, and increase the cumulative heat release. Figure 4: Hydration exothermic curve of composite mortar: (**a**) hydration heat evolution rate; (**b**) cumulative hydration heat. Figure 5 presents the XRD of the net slurry at 3 d and 28 d age. The figure shows that the main hydration products of the composite mortars of each group, except for the C-S-H gel, are mainly Ca(OH)\({}_{2}\) and AFt and dicalcium silicate (C\({}_{2}\)S) and tricalcium silicate (C\({}_{3}\)S), which are not involved in the hydration reaction, with the appearance of a new material phase aluminous carbonate aluminate (Ca\({}_{4}\)Al\({}_{2}\)O\({}_{6}\)CO\({}_{3}\)\(\cdot\)11H\({}_{2}\)O) at the age of 28 d There was no difference in the types of hydration products among the OPC, A0, and A1-A6 groups at each age, but only the peak intensities of the hydration product diffraction peaks were varied.