Assessment on the heterogeneity and roughness of fracture surface of steel fiber reinforced concrete

The characterization of fracture morphology in steel fiber reinforced concrete (SFRC) remains an area of limited study. This research investigates the influence of heterogeneity on fracture surfaces in SFRC across various surface sizes, sampling intervals (δ), and directions. Utilizing point-cloud matching technique, fracture morphologies are characterized to analyze damages in the heterogeneous fracture process zone. Four roughness parameters, i.e., root mean square deviation (Sq), arithmetic average height (Sa) distribution, surface area to projective area (RS) and root mean square of directional derivatives (Z2–3D), are used to quantify morphology. Results reveal that as surface size arises, Sq and Sa increase with their ratio (Sq/Sa) approaching 1.25, while the ratios of Sq and Sa to size length decrease following a double-exponential decay model, indicating a size scale dependence. Meantime, roughness anisotropy, characterized by coefficient of variations in directional Z2–3D values, declines. RS and Z2–3D exhibit higher sensitivity to textural features than surface size, showing a δ-dependence. As δ rises, RS and Z2–3D sharply decrease, whereas Sq, Sa and Sq/Sa stabilize. This analysis highlights the significance of Z2–3D in providing insights into fracture morphological features and heterogeneity of SFRC. •A double-exponential decay model (y=A1e−x/T1+A2e−x/T2+y0) is proposed to elucidate the deterioration mechanisms of relative 3D amplitude roughness with increasing normalized area.•A point-cloud-matching technique is introduced to characterize fracture morphology within steel fiber reinforced concrete.•Fracture process zone is digitized and quantified by morphological characterization to examine heterogeneity of steel fiber reinforced concrete.•Demonstration of the superior ability of textural roughness parameters over amplitude roughness parameters in evaluating fracture morphology of steel fiber reinforced concrete.