Study on Mode I Fracture Characteristics and Fracture Surface Morphology of Concrete–Sandstone Under Different Loading Rates

ABSTRACT This paper studies the effect of various loading rates (0.02, 0.05, 0.5, and 1 mm/min) on the fracture characteristics of Mode I concrete–rock composites. Digital image correlation (DIC) and acoustic emission (AE) techniques are used to analyze cracked straight‐through Brazilian discs (CSTBD). Significant changes in Shannon entropy were observed before fracture failure, suggesting it as a reliable precursor indicator. The study found that as loading rates increased, the time for CSTBD to undergo plastic deformation decreased, leading to more transgranular and intergranular fractures. Surface morphology analysis revealed that fractal dimensions and surface roughness (Rrms) increased with higher loading rates. A MATLAB program, using power spectral density (PSD) to evaluate the joint roughness coefficient (JRC), demonstrated greater efficiency and accuracy compared with traditional visual assessment methods. This highlights the PSD method's superior performance in determining JRC values.