## 3 Results
### Autogenous Shrinkage Performance of Mortar  
The results of the autogenous shrinkage tests of mortar are shown in Figure 6.  
As can be seen from Figure 6, the mortar without DE exhibited the fastest early autogenous shrinkage and the largest final autogenous shrinkage value. As the amount of DE incorporation increased, the autogenous shrinkage value of the mortar gradually decreased, consistent with the variation in the internal relative humidity of the mortar in Figure 4, that is, the lower the internal relative humidity of the mortar, the greater the autogenous shrinkage value of the mortar. The autogenous shrinkage development of the control group (A1) could be divided into four stages: expansion-shrinkage-expansion-shrinkage, namely ab (brief expansion stage), bc (rapid shrinkage stage), cd (second expansion stage), and de (continuous shrinkage stage). The analysis of the deformation characteristics mechanism of the reference mortar at early ages is as follows. During the ab period, the control group mortar exhibits volume expansion. This is due to the mortar still being in a plastic flow state after pouring, with plastic settlement leading to vertical shrinkage and lateral expansion of the mortar. Moreover, the volume expansion rate caused by the hydration reaction of the cementing materials exceeds the shrinkage rate of the low water-binder ratio cement mortar, resulting in macroscopic volume expansion, with a peak expansion value of 20 \(\upmu\)m/m. After the expansion deformation ends, rapid autogenous shrinkage occurs in the bc stage, with an increasing slope of the autogenous shrinkage curve. This is mainly because, during this period, rapid hydration reactions occur inside the cement mortar paste, releasing hydration heat. However, chemical shrinkage dominates over thermal expansion effects at this time, resulting in rapid shrinkage of the paste, with a peak shrinkage value of 200 \(\upmu\)m/m. After this, the shrinkage curve exhibits a brief decline stage, where the cd stage shows a transient expansion process. This is related to the formation of ettrigite, large-sized calcium hydroxide, and internal C-S-H during the hydration process [36]. The expansion-type hydration products offset some of the shrinkage, resulting in transient expansion. The reason for this brief duration is that the cement mortar with a low water-binder ratio has a dense structure without coarse aggregates, limiting the occurrence of expansion deformation. After the end of expansion deformation, the autogenous shrinkage of the mortar enters a gradual growth stage in the de period. The slope of the autogenous shrinkage deformation curve gradually decreases, becoming flatter, and the shrinkage increases slowly and steadily. The initial shrinkage value in this stage is 196 \(\upmu\)m/m, and the autogenous shrinkage value at 168 h is 442 \(\upmu\)m/m. After adding DE, the self-shrinkage development curve changes significantly, as follows: (1) At the beginning of data collection, i.e., 3 h after adding water to the mortar, the  
Figure 6: Autogenous shrinkage performance of mortar. mortar is in a slightly expansive state, with expansion values of 1.1 \(\upmu\)m/m, 3.143 \(\upmu\)m/m, and 7.416 \(\upmu\)m/m (A2, A3, A4), respectively. (2) Compared to the reference group, the shrinkage time of the bc segment in the diatomic groups (A2, A3, A4) decreases, with shrinkage peaks of 170 \(\upmu\)m/m, 63 \(\upmu\)m/m, and 46 \(\upmu\)m/m, respectively. Subsequently, they enter the cd segment, with extended duration of expansion and expansion peaks of 149 \(\upmu\)m/m, 48 \(\upmu\)m/m, and 23 \(\upmu\)m/m, respectively. (3) The self-shrinkage values in the continuous shrinkage stage (de segment) decrease with the increase in the amount of diatomic added. Compared to the reference group, the final effective reduction rates after 7 days are 36.7%, 46.6%, and 54%, respectively.