## 2 Experimental Program  
### Details of the Specimens and Test Set-Up  
Eight push-out specimens were prepared for testing. These specimens were divided into two series based on concrete strength. The first series was normal strength concrete specimens, and the second one was high-strength concrete (HSC) specimens. Based on the ACI 363 [72], the compressive strength of HSC varies between 41 and 82 MPa. In this study, the compressive strength of normal specimens was 38.2 MPa, while two compressive strengths of 63 MPa and 82 MPa were adopted for the HSC specimens. Air-dry condition aggregates were used in HSC mixes. Fine aggregate was graded silica sands with a maximum nominal size of 4.75 mm, and coarse aggregate was crushed granite with a maximum nominal size of 10 mm. The used cement in all the mixes was type II Ordinary Portland Cement [73] according to ASTM C150 [74]. To attain the acceptable workability, superplasticizer (SP) was added in the mixes [75]. The SP was Rheobuild 1100 with a specific gravity of 1.195, and a pH within the range of 6.0-9.0. For the normal specimens, standard sand and gravel were used, and all the other materials were the same. All of the push-out specimens were cast in a horizontal position similar to the site situations. The reliable quality of concrete for both sides of the concrete blocks was assumed as well. All the specimens were cured in water for 28 days before testing. Standard cylinders with a diameter of 150 mm and length of 300 mm and standard cubes with a length of 100 mm were cast together with the push-out specimens to measure the compressive strength of the concrete blocks. All cylinders and cubes were cured in water until the day of testing. The concrete strength was achieved from the cylinder and the cube compression tests together. The requirements of the ASTM C39 [76] were used for the compressive strength test procedure, and the mean values of the compressive strengths were used in the calculations. Table 1 illustrates the mixture proportion of concrete materials in which Hh and Hl represent HSC specimens with higher (82 MPa) and lower (63 MPa) strengths, respectively, and N refers to normal strength concrete specimens in which ordinary materials were used. Four types of channel shear connectors with the dimensions of 100 and 75 mm in height and 30 and 50 mm in length were used. The 100 mm height channels had a flange thickness of 8.5 mm and a web thickness of 6 mm, while the 75 mm channels had a flange thickness of 7.5 mm and a web thickness of 5 mm. The geometric properties of the channel connectors are presented in Table 2. In this table, the first letters of the specimens' name imply the type of concrete as mentioned before; the other numbers following the first letters also represent the height, length, web thickness, and flange thickness of the channel shear connectors, respectively. Push-out specimens consisted of a steel I-beam with two slabs attached to each flange of the beam. One channel was welded to each flange of the beam, and two layers of steel bars with four 10 mm diameter steel bar hoops were applied in two perpendicular directions in all the slabs. Details of the test set-up can be seen in Figure 1. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Mix** & **Cement** & **CA** & **FA** & **SF** & **Water** & **SP** & **E\({}_{\text{c}}\)** & **\(f_{\text{c}}\)** \\
**No.** & **(kg/m3)** & **(kg/m3)** & **(kg/m3)** & **(kg/m3)** & **(kg/m3)** & **(\%)** & **(\%)** & **(GPa)** & **(MPa)** \\ \hline Hh & 460 & 910 & 825 & 40 & 168 & 0.37 & 0.5 & 39 & 82 \\ Hl & 360 & 940 & 870 & - & 180 & 0.5 & 1 & 32 & 63 \\ N & 350 & 750 & 1100 & - & 133 & 0.38 & 1 & 19 & 38.2 \\ \hline \hline \end{tabular}  
* CA = Coarse aggregate; FA = Fine aggregate; SF = Silica Fume; W = Water; C = Cement; SP = Superplasticizer; E\({}_{\text{c}}\) = Modulus of elasticity; \(f_{\text{c}}\) = Compressive strength.  
\end{table} 
Table 1: Mixture proportioning of the concrete materials. Figure 1: Set-up of the push-out test: (**a**) Side view; (**b**) Top view.