Experimental and theoretical study on flexural behaviour of a new UHPC sandwich slab

Abstract

In this study, a new type of prefabricated ultra-high performance concrete (UHPC) sandwich slab is proposed, which is composed of UHPC layer at the top and bottom, short UHPC columns and extruded polystyrene foam board (XPS) in the middle layer. The load-bearing and thermal-insulation integrated sandwich slab shows much lower self-weight and less reinforcement than traditional concrete slab, which are very beneficial for construction of precast structures. This paper first presents a reasonable and reliable casting method for the new sandwich structure. Then four-point bending tests on five slabs are conducted to reveal their flexural performance. The investigated parameters include the thickness of the UHPC layer, reinforcement ratio, short column spacing and XPS layout. Test results demonstrate that this type of sandwich slab, with 4500 mm span length, 150 mm thickness and one-way simply supported condition, has excellent anti-cracking and flexural performance, which can sustain an additional uniformly distributed load more than 9 kN/m2 before cracking even without reinforcement. A small ratio of reinforcement 0.13% in the bottom layer can further improve the ultimate bearing capacity by 20% and ultimate deformation by 61%. Finally, the calculation methods of cracking load, peak load and stiffness are proposed, together with design suggestions for typical slab dimensions, which offers valuable guidance for practical engineering.