Experimental and numerical assessment of the flexural behavior of UHPC-NC composite slab with UHPC wet joint

In order to study the mechanical performance of the new prefabricated ultra-high performance concrete (UHPC)-normal concrete (NC) composite wet joint slab (NUS slab), four-point bending tests were carried out by designing and making 3 cast-in-situ slabs of different concrete materials and 1 NUS slab, and numerical modelling technique was conducted by ABAQUS software. The results showed that the main cracks of the cast-in-situ slab were mainly located in the mid-span and the loading point. The main crack of the NUS slab was located at the wet joint interface. The application of UHPC layer and UHPC wet joint improved the flexural capacity of slabs comparing with the cast-in-situ NC slab. Through the finite element simulation and parameter analysis, the width of UHPC wet joint had a certain effect on the improvement of the flexural capacity of NUS slab, but the effect was not obvious. 25 cm UHPC wet joint is suggested as a reference for design. The reinforcement ratio has a great influence on the flexural behavior of NUS slab. When the reinforcement ratio exceeded 4.43%, the flexural shear failure occurred in the precast part of the flexural shear section of NUS slab, while the wet joint part had no great damage, and the flexural capacity was good. When the reinforcement ratio was less than 4.43%, the main damaged area was located between the loading points, and the position of the main crack was at the interface of the wet joint. And the flexural capacity and ductility of NUS with 3.25% reinforcement ratio was found better then cast-in-situ NC slab.