Shear strength of different connection and concrete types for Timber Concrete Composites (TCC)

Timber Concrete Composite (TCC) is a sustainable system that presents increasing potential for utilisation in construction. Bonding the timber and concrete is one of the most essential aspects of TCC. Hence, this research aims to investigate the shear performance of various innovative connections for TCC. Moreover, in order to increase the environmental 'friendliness' of the novel TCC system, fly ash was utilized to partly substitute Portland cement. A new kind of bonding method; micro-notch connection, for which continuous shear is transferred by interlocking with micro-notches and additional fasteners are not needed, was investigated. Furthermore, to mitigate shrinkage and cracking caused by hydration process of concrete in early ages, Superabsorbent Polymers (SAP) were introduced as internal curing agent in concrete. Overall 15 types of samples, including 45 specimens were tested, and slip modulus and connection shear strength were determined from push-out test. Performance of different connection types (nails, adhesive and micro-notches) for different configurations and using different concretes (reference concrete, FA concrete and SAP concrete) were compared. During the course of this study, it was established that workability of concrete has huge influence on TCC connection. Concrete with higher workability fully fills into timber grooves, which leads to timber and concrete notches combine tightly. Furthermore, epoxy resin has adequate strength to bond timber and concrete and shear strength of adhesive connection depends on the concrete strength. On the other hand, usage of concrete mix of high plasticity impair the combination between wet concrete and adhesive. Finally it was determined that micro-notch connection with slope zigzag notches can effectively link the two components of TCC and transfer the shear force through their interlocking without other fasters. Moreover, shear strengths for such connections are much higher than for nails connectors, reaching that of adhesive connections.