Evaluation of adhesion characteristics of joint in concrete by tension softening properties

This study intends to reveal some clues for improving mechanical properties of joint in concrete. The authors conducted fracture mechanics test of nine types of specimens as the models of vertical construction joint. Along with the investigation on fracture mechanics parameters, SEM analysis was made from the samples on detached and fractured surfaces of specimens. The resulted fracture mechanics parameters and tension softening diagram showed clearer difference of performance in joint than flexural strength does. There are many pores and fragmental layers of Ca(OH) 2 observed in smooth part of ligament after the test, which could be the main cause of detaching without fracturing of the surface.