Assessment of fibre orientation and distribution in steel fibre reinforced concrete via piecewise density-based spatial clustering of applications with noise algorithm using CT imaging

The distribution of fibres into the concrete matrix greatly influences the mechanical properties of fibre-reinforced concrete (FRC). Assessment of the distribution and orientation of fibres in FRC is essential for predicting its mechanical properties. To date, many robust techniques have successfully analysed straight fibre-reinforced concrete systems but most of them face challenges in analysing fibres that are tortuous or curved within the concrete matrix. To this end, a novel methodology based on the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm was developed to quantify the distribution and orientation of fibre within the concrete matrix using a piecewise scanning approach. This study focused on two types of concrete: one with recycled steel fibres (RSF) obtained from scrap tyres and the other combining RSF with manufactured steel fibres (MSF). The images obtained from X-ray computed tomography (CT) were utilised for post-processing image analysis, generating coordinates that were then employed by a graph-based spatial method for the determination of fibre dispersion across all principal axes. The developed algorithm was then employed to determine the spatial distribution of individual fibres. The research introduced an intuitive algorithm that can accurately capture the complex tortuous geometry of fibre in concrete.