## 3 Results and Discussion
### Level Analysis of Influencing Factors of SSCFC's Fluidity and Compressive Strength
#### 3.4.3 Effect of Ceramsite Substitution Rate on Fluidity and Compressive Strength of SSCFC  
Figure 8a elucidates the influence of the ceramics replacement rate on SSCFC paste's fluidity. The experimental data reveal nonlinear fluidity enhancement: a 0.9% increase when the ceramics substitution rises from 20% to 25%, followed by a dramatic 8.9% surge at 30% substitution, representing a tenfold acceleration in growth rate. Contrary to [PERSON] et al.'s findings [69] that ceramicsite's rough surface and high water absorption increase frictional resistance and reduce fluidity, our results show the inverse behavior. Two key mechanisms explain this discrepancy: (1) Thorough pre-wetting of ceramics during preparation substantially diminished its water absorption capacity during mixing, preventing foam destabilization through water competition [69], which typically degrades flowability. (2) Synergistic physico-dosage effects: 20-25% substitution enables localized friction reduction via discrete spherical particles, while 25-30% substitution facilitates percolating lubrication networks through optimized particle alignment and surface-bound water films. Furthermore, particle size gradation between ceramicsite and cement improves the packing efficiency, minimizing frictional contacts and enabling fluidity leap.  
Figure 8b-d systematically reveal the evolution of compressive strength in SSCFC specimens with ceramicsite replacement rates across the 7d/14d/28d curing periods. The experimental data demonstrate a strong correlation in strength development across curing ages, leading to the selection of the 28d compressive strength as the key parameter for final performance evaluation. Tests reveal a parabolic strength trend with ceramics substitution: both the 7d and 28d compressive strengths initially increase then decrease, peaking at 25% ceramsite replacement. This strength behavior stems from dynamic equilibrium between aggregate-matrix interfacial effects and load transfer mechanisms. Below 25% substitution, dispersed ceramicsite particles fail to establish efficient stress transfer networks, causing localized stress concentration at ITZ regions. The cementitious matrix predominantly bears mechanical loads under this condition, while ceramicsite's reinforcement potential remains underutilized [70]. At 25% substitution, an optimal spatial distribution of spherical ceramic-site enables stress homogenization and enhances the ITZ's properties through mechanical interlocking, establishing a synergistic matrix-aggregate bearing system. Exceeding 25% substitution induces dual detrimental effects: (1) the reduced binder content compromises matrix continuity, weakening the ITZ's integrity; (2) increased ceramicsite contact probability forms rigid skeletons that generate stress-shielding effects, restricting the matrix plastic deformation capacity. Both under- and over-substitution scenarios are attributed to incompatibility between ceramicsite content and foam concrete formulation ratios [71]. Theoretical analysis suggests that the ideal failure mode combines matrix microcrack propagation with gradual ceramicsite fragmentation, a balanced state that is only achievable within specific substitution ranges (25% in this study).  
Given the focus on compressive behavior of SSCFC, the comprehensive analysis prioritizes the 7d, 14d, and 28d compressive strengths. Through in-depth analysis of SSCFC performance versus factor levels, the optimal parameter combination A1B1C2 was determined.