## 3 Test Results and Discussions
### Bond-Slip Relationship  
The applied load and end-slip were continuously recorded, until the composite slab specimen could not withstand any load. A comparative analysis was conducted to investigate the load slip behaviour of the SCGC composite slab compared to the normal concrete composite slab with compressive strength of 40 MPa and 60 MPa, respectively. Table 7 presents the results from the push tests on six specimens that demonstrate chemical adhesion breaking loads, interface connection stiffness, ultimate loads and toughness. The mechanism of shear load transfer in the composite slab system is profoundly dependent on the composite interaction between the profiled steel sheet and the hardened concrete. The concrete chemical adhesion bond and mechanical and frictional resistance developed at the concrete-profiled steel sheet interface are responsible for transferring shear loads to the beam elements. The maximum load concrete can withstand before the chemical break occurs is the chemical adhesion break load. A sudden drop in load happens once the chemical adhesion is broken, followed by a proportional increase between the applied load and end-slip, due to the mechanical interlock and frictional resistance. The interface connection stiffness can be expressed based on the slope of the linear graph drawn up to the ultimate load. The composite slab toughness can withstand inelastic deformation without a rapid deterioration in its ultimate strength. The composite slab toughness can be described as the total area under the load-slip curve to the rupture (failure load). The failure load can be considered 80% of the ultimate load at the descending branch of the load-end slip curve. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **SCGC** & **NC40** & **NC60** \\ \hline Slump (mm) & 680 & 95 & 85 \\ \hline Compressive strength (MPa) & 36.65 & 39.6 & 61.45 \\ \hline Indirect tensile strength (MPa) & 2.53 & 3.4 & 4 \\ \hline Modulus of elasticity (GPa) & 15 & 19 & 32 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Concrete mechanical properties. Figure 14: High precision laser sensor. Load-end slip curves of NC40, NC60 and SCGC composite slabs are shown in Figure 15. It is to be noted that a cracking sound was heard early at the first recorded end slip during the test at loads that varied between 1 and 2.5 MPa, which indicated that the chemical adhesion bond was broken. NC40 reported a 25% better average chemical bond strength than NC60. On the other hand, SCGC showed a 31% better average chemical adhesion bond than NC40 and 64% better average chemical adhesion bond than NC60, respectively. The higher chemical adhesion bond observed in the SCGC composite slab could be due to the higher moisture content in the mixture that interacted with the binder material and resulted in better flowability and distribution over the profiled sheet contact surface. The findings indicate that the geopolymer binder has better chemical adhesion than normal concrete. It is also possible to interpret that neither compressive nor tensile strength influences the chemical adhesion bond between the profiled sheet and concrete, as NC40 and NC60 have higher compressive strength and tensile strength than SCGC, but a lower chemical adhesion bond. Once the chemical adhesion bond between concrete block and profiled steel sheet is broken, a sudden drop in load occurs, followed by a gradual increase in the load proportional to the end slip, as shown in Figure 15b. The slip resistance load is attributed to the combined effect of mechanical interlock (embossment) and frictional resistance at the concrete-profiled steel sheet interface. The ascending load-end slip graph slope represents the interface connection stiffness (m). The stiffness of the composite slab is due to the composite interaction between the concrete and profiled steel sheet surface. NC60 specimens have a high average shear connection stiffness value equal to 21.50 MPa, which is approximately five times higher than NC40.