Rebound-Based Diagnosis of Tile Detachment Near the Boundary of Detached Area for the External Tile Finishing Wall

Abstract

In Japan, periodic inspections of external tile walls are mandated by the Building Standards Act. Conventional hammering inspections are influenced by environmental noise and rely on human judgment. To address these limitations, a solenoid tapping device has been developed to evaluate tile detachment quantitatively based on rebound characteristics. However, previous studies mainly focused on the center of detached areas, without examining behavior near detachment boundaries.This study investigates how the rebound ratio varies with tapping position relative to the detachment boundary using pseudo-void specimens with 200 mm and 300 mm square detached areas. Results show that as the tapping position approaches the boundary, the rebound ratio increases and becomes closer to normal tiles, indicating a transitional zone. This behavior was observed in the range of (X=-40) to -5 mm from the boundary. A comparison between threshold-based detachment classification and actual detachment geometry confirmed that misclassification occurs within this zone. To address this, margins were quantified as +20 mm for 5 mm-thick mortar and +15 mm for 10 mm and 15 mm. An empirical equation was proposed to estimate the width of this zone as a function of mortar thickness. These findings improve the spatial accuracy of automated detachment diagnosis systems.