Mechanical behavior and composite action of two-wythe precast concrete sandwich beams via chemically hybridized intermediate layer

摘要

Composite action of two-wythe precast concrete sandwich beams are examined on the premise of an integrated thin intermediate layer that is suggested as a possible substitute candidate for industry-standard extruded polystyrene (XPS) in precast concrete sandwich panels (PCSP). Designable mechanical properties of a carbonfiber reinforced interfacial epoxy-polyurea matrix (C-IEPM) may be tuned via the rate of reaction between epoxide and amine of a thermosetting epoxy network, controlled by the elapsed time of reaction t(c), and its subsequent surface treatment via reaction with isocyanate and amine moieties, resulting in a thin covalently bonded IEPM layer. Thirteen concrete beams were tested under 4-point bending. A two-wythe beam with an intermediate C-IEPM layer (t(c) = 0.5 h) was compared to two-wythe beams that included the following intermediate layers: XPS, conventional carbon-fiber epoxy (CF/E), and no layer, where beams with a C-IEPM layer at lower t(c) showed substantial increase in peak strength and energy absorption: 54% and 97%; 47% and 143%; 27% and 46%, respectively. This indicates that C-IEPM that engenders a high-quality IEPM can substantially improve mechanical performance, energy absorption, and composite action. Finite element analysis of a two-wythe system with an assumed perfectly bonded C-IEPM intermediate layer (t(c) = 24) confirms that IEPM designed at t(c) = 0.5 effectuates a perfect bond between wythes and also provides tremendous resiliency and strength sustainability in accordance with load-deflection response beyond the peak load, making C-IEPM a viable candidate as an intermediate layer in pre-cast multi-wythe constructions.