Effect Of Interface Treatment On The Cracking Behaviour Of Hybrid SHCC (Strain Hardening Cementitious Composite) Concrete Beams

Strain Hardening Cementitious Composite (SHCC) is applied on the tension side of a flexural member in order to improve crack-width control of reinforced concrete and its effectiveness is investigated for varying treatment of the interface between SHCC and concrete. A four-point bending test configuration is used and the interface is varied locally within the constant bending moment region as smooth, partially debonded, completely debonded and profiled surface. The aim is to investigate the influence of interface on the cracking behaviour and the development of maximum crack-width in the hybrid SHCC beams with varying interface profile. Therefore, all the beams are designed to have a similar load carrying capacity by providing mechanical anchorage through the interface outside the constant bending moment region using stirrups. The cracking behaviour is analysed by measuring the maximum crack-width in SHCC layer using Digital Image Corelation (DIC), Linear Variable Differential Transformers (LVDTs) and visual inspection with a microscope. The effectiveness of the interface treatment is then judged by comparing the load at which the maximum crack-width in SHCC layer exceeds 0.3 mm, corresponding to the maximum allowable crack-width for most structural applications. It is observed that the relatively stronger interfaces (smooth and profiled) show better crack-width control when compared to partially debonded and completely debonded (weak) interfaces, probably because with weaker interface the hybrid action of the beam is reduced resulting in higher stresses and early crack localization in SHCC.