Flexural performance of precast geopolymer concrete sandwich panel enabled by FRP connector

Precast concrete sandwich panel (PCSP), consisting of two concrete wythes and a thermal insulation layer in between, can improve greatly the energy efficiency in buildings. This study aims to investigate the structural performance of a new type of PCSP, for which reinforced geopolymer concrete is used as two wythes and connectors made of fiber-reinforced polymer (FRP) composites are used to realize the composition action. Eight so-formed precast geopolymer concrete sandwich panels (PGCSP) were fabricated and evaluated their flexural performance through four points bending test. The experimental parameters included connector type (plate-type and hexagonal tubular), connector spacing (300 and 525 mm), reinforcement type (basalt FRP reinforcement and steel reinforcement) and reinforcement ratio (0.30% and 0.43%). The load vs. mid-span deflection relationships, crack patterns, failure modes, reinforcement strain development relationships, and degrees of composite action of the panels were investigated in details. In addition, two-dimensional (2D) finite element (FE) analysis was conducted to reproduce the test results and to facilitate a better understanding on the panel's performance particularly the connector's behavior at different loading stages. It was concluded that a higher degree of composite action in the panels can be achieved through the use of FRP tubular connectors, besides, all the FRP tubular connectors can retain their load transfer capacities at the ultimate limit state owning to their ductile failure behavior.