Tests on influence of aging time on punching shear strength of HPFRC circular slabs

High Performance Fiber-Reinforced Concrete (HPFRC) is a high-performing material foreseeing new applications especially addressed to get lighter and more durable constructions, and to achieve more ductility. As part of the collaborative research project between University of Firenze and Baraclit, one of the largest Italian precast companies, an extensive study on the behaviour of thin HPFRC slabs has been planned and is presently in progress. The research has been developed in collaboration with Politecnico di Milano. The target was to investigate punching shear behaviour using circular slabs while considering all existing experimental constrains. A free diameter of 500 mm was chosen for the specimens and in addition, to easily obtain and to clearly distinguish a punching shear failure mode from a flexural one, the edge of slabs were clamped. Several tests were performed and are currently being performed in order to investigate the punching shear capacity of thin slabs varying in thickness, punch size, and aging time. The results of early punching tests on 30 mm slabs during aging time of 28 days are preliminarily presented in this present paper.