Cracking resistance and fracture toughness of rice husk ash SFRSCC with varied W/C ratios analysed via ENDB and ANN-UPV prediction

This study investigates the crack resistance of rice husk ash (RHA)–incorporated SFRSCC, with RHA contents from 2.50% to 15.00% and water–cement ratios (W/C) from 0.35 to 0.50. ENDB samples were tested under mode I, mode III, and combined III/I loading to enable a comprehensive fracture-resistance assessment. Results show that increasing W/C from 0.35 to 0.50 raises workability by 50.71%, while the same tests with RHA reduce it to about 15.00%. Moreover, for each increment of RHA from 2.50% to 15.00% within a 0.40–0.50 W/C range, maximum load improves by 62.35%. At W/C = 0.35, 15.00% RHA slightly lowers compressive strength by 2.83% and UPV by 2.43. In contrast, at W/C = 0.40 and 0.50, strengths rise by 27.41% and 27.61%, indicating improved microstructure and pozzolanic activity. The greatest fracture toughness under mode I occurs for a mix with 7.50% RHA and W/C = 0.35, 25.42% above the reference; at higher W/C, increases reach up to 97.51%. The ANN model predicts fracture toughness with R = 0.993 and errors under 15%. SHAP analysis identifies loading condition, W/C, and UPV as dominant influences on toughness. Overall, optimizing RHA and W/C enhances SFRSCC fracture toughness for real projects.