The anisotropy of the capillary absorption coefficient is critical to moisture transport modeling and durability prediction, whereas reliable on-site assessment methods remain scarce. Herein, a new anisotropy index based on drilling resistance was proposed. An extruded fired-clay brick and Portland cement mortar were chosen as target materials. Leeb hardness, P-wave velocity, capillary absorption coefficient, and drilling resistance were tested and analysed in different directions. The influence of anisotropy on the capillary absorption coefficient was investigated. The results indicate that: (1) The new index effectively reflects anisotropy by comprehensively accounting for multi-directional drilling data. (2) Extrusion moulding significantly impacts clay brick anisotropy; drilling resistance shows that layered compaction yields denser mortar in lower sections, more distinct at higher water-cement ratios. (3) Multivariate regression models estimating capillary absorption coefficient with Leeb hardness, P-wave velocity, and drilling resistance have been developed. Research results can be applied to on-site investigations of buildings. • A new anisotropy index was proposed based on drilling resistance. • The extrusion moulding process significantly affects the anisotropy of clay bricks. • Multivariate regression models to assess capillary absorption coefficient were developed. • Combining the drilling resistance method with non-destructive testing techniques.
Zhang et al. (Sun,) studied this question.