Structural performance evaluation of composite concrete slabs that were constructed using partially precast concreting system\nwhich utilized Hybrid Fiber-Reinforced Lightweight Aggregate Concrete (HyFRLWAC) as stay in-place formwork and selfcompacting\nconcrete (SCC) as topping layer was conducted in this research. This paper focused on determining the appropriate\nstrength limit criteria of interface between two different concrete layers. The tensile strength was tested using pull-off test, while\nconcrete cohesion was investigated based on modified bisurface shear test, and dual L-shaped shear test was used to determine the\neffect of normal force on the shear strength of concrete interface. Sample variants were designed based on the substrate surface\nconditions, compressive strength of the topping layer, and magnitude of perpendicular normal force acting on interface area.The\nsubstrate surfaces were prepared in as-placed and grooved conditions for tensile test, cohesion, and shear strength test. Test results\nindicate that tensile strength, cohesion, and shear strength of the concrete interface are affected by surface condition of the substrate,\ncompressive strength of the topping layer, and the normal force acting perpendicularly on the concrete interface area. Proposed\nformulation for bond strength prediction between HyFRLWAC as substrate and SCC as topping layer is also presented in this\npaper.
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