## 3 Test Results
### Variation Patterns of Various Factors on Mechanical Properties  
The mechanical properties of EAC are important technical indicators that determine its application scenarios. The strength of EAC designed in this study should meet the C40 compressive strength grade (\(\geq\)40 MPa) and the requirements for concrete flexural strength (\(\geq\)5 MPa) under heavy and above traffic load grades specified in the Specifications for Design of Highway Cement Concrete Pavement (JTG D40-2011) [38]. The variation patterns of average 28-day compressive and flexural strength under different factor levels are shown in Figure 10.  
As shown in Figure 10, as the water-binder ratio increases, both the 28-day compressive and flexural strengths gradually decrease. This is mainly because an increase in the water-binder ratio affects the hydration reaction of cement, and excess water easily forms blisters or pores after concrete hardening, resulting in excessive pores inside the concrete, which, in turn, reduces the strength of the concrete.  
As the sand ratio increases, the 28-day compressive strength gradually increases, while the 28-day flexural strength first increases and then decreases. When the sand ratio increases from 28% to 31%, the fine aggregates continuously fill the voids between the coarse aggregates, making the concrete structure denser and the stress distribution between the aggregates more uniform, thereby improving both the compressive and flexural strengths. When the sand ratio increases from 31% to 34%, the interlocking effect of the microscopic engagement structure between the fine aggregates is further enhanced, increasing the compressive strength. However, at this point, an increase in the sand ratio increases the specific surface area of the aggregates, and insufficient coating of the aggregates by the cement paste leads to a decrease in the flexural strength of the concrete interface.  
As the coarse aggregate volume ratio increases, the 28-day compressive strength gradually increases, while the 28-day flexural strength first decreases and then increases. For compressive strength, an increase in the coarse aggregate volume ratio increases the \"point-to-point\" contact between coarse aggregates, improving the interlocking force between them, and thus gradually increasing the compressive strength. For flexural strength, when the coarse aggregate volume ratio is 40%, the flexural strength reaches a maximum value of 5.31 MPa, which is only an increase of 1.5% compared to the minimum value, indicating that the coarse aggregate volume ratio has a small impact on the 28-day flexural strength.  
As the proportion of aggregates > 9.5 mm increases, the 28-day compressive strength first increases and then decreases, while the 28-day flexural strength gradually increases. For compressive strength, when the proportion of aggregates > 9.5 mm is 50%, the aggregates form a skeleton-dense structure, resulting in the highest overall compressive strength of the concrete structure. For flexural strength, the larger the proportion of aggregates > 9.5 mm, the smaller the specific surface area of the aggregates, the higher the proportion of cement mortar at the cross-section, and the smaller the area of the interface weak zone composed of mortar and coarse aggregates, thus resulting in higher flexural strength.  
Figure 10: The variation patterns of 28-day compressive and flexural strength.