## 3 Results and Discussion
### Compressive Strength and Drying Shrinkage of AASC  
#### 3.1.1 Effects of the Water-to-Slag Ratio  
First, the effect of the water-to-slag ratio on the compressive strength and drying shrinkage of AASC was studied, and the results are shown in Figure 6. In Figure 6a, it can be observed that when the sand ratio was 0.59, the late-age (\(\geq\)7 days) compressive strength was smaller at higher water-to-slag ratios, mainly because a higher water-to-slag ratio dilutes the alkaline activator, reducing the compressive strength. Similar results were found by [PERSON] et al. [15], who indicated that the compressive strength decreased as the liquid-to-solid ratio increased from 0.45 to 0.60. However, there was little difference in this trend when observed for water-to-slag ratios from 0.38 to 0.40. Furthermore,the compressive strength of AAS has been previously observed to decrease as the liquid-to-solid ratio increased from 0.50 to 0.60 [31]. The presence of additional water reduced the compressive strength of AASC by causing an increase in the pore volume of the hardened concrete, as reported by [PERSON] et al. [32]. Indeed, the strength of NaOH-activated slag concretes has generally been found to be related to their total porosity [7]. The early-age compressive strength after three days were 41.0, 42.3, and 39.7 MPa for water-to-slag ratios of 0.35, 0.38, and 0.40, respectively, which were 83.5%, 89.4%, and 82.5% of the corresponding compressive strength after 28 days. In other words, a high early compressive strength was obtained for AASC after as little as three days of curing. This is due to the early activation of the slag occurring as a result of the presence of the alkaline solution, causing the early formation of C-S-H gels [33]. The achievement of such high early compressive strength in concretes based on ordinary Portland cement typically requires the addition of chemical and/or mineral admixtures.  
Drying shrinkage results from the removal of pore water from within the hardened binder due to the evaporation loss of internal water to the environment [27]. On the whole, the drying shrinkage of the AASC specimens was greater at higher water-to-slag ratios (Figure 6b). Before the third day, there were only tiny differences in the development of drying shrinkage among the mix specimens. During 3-28 days, the drying shrinkage increased slightly in specimens with higher water-to-slag ratios, from 0.35 to 0.38, and then increased dramatically from the specimen with a water-to-slag ratio of 0.38 to that with a water-to-slag ratio of 0.40. After 28 days, when the water to slag ratios were 0.40 and 0.38, the drying shrinkages of the AASC specimens were 0.040% and 0.028%, respectively, which was 1.63 and 1.14 times that of the AASC specimen with a water-to-slag ratio of 0.35. In general, a higher water-to-slag ratio was found to contribute to the workability of AASC. However, a higher water-to-slag ratio has also been found to result in an increase in drying shrinkage, which may itself lead to shrinkage cracks working as macrodefect points [34]. This inverse relationship between high water-to-slag ratios and drying shrinkage occurs because the presence of more water means that the alkaline activator is diluted, leading to insufficient dissolution of the Si and Al ions and the subsequent failure of continuous polymerization reactions to occur.