## 3 Results and Discussion
### Conclusions  
This paper presented the results of an experimental program conducted to evaluate the structural behavior of quarry rock dust (QRD)-incorporated FA/SG-based fiber-reinforced geopolymeric concrete columns tested under concentric and eccentric loading. In this study, a total of 20 columns were cast and divided into three groups depending upon their mix proportions, i.e., CC, GC, and GCD. The first group (Group CC) comprised of four square cross-section conventional concrete specimens, whereas the second and third comprised of 16 GPC columns. In the second group (GC), all the specimens were prepared with FA (50%) and SG (50%) as the source materials. In the third group (GCD), QRD was incorporated as a partial replacement (20%) of SG, along with SG (30%) and FA (50%) contents. The following key conclusions have been drawn from this study:  
* Quarry rock dust is a suitable material that can be used as a source material in GPC to manufacture structural concrete members with satisfactory performance. * The axial load-carrying capacity of plain GPC columns in the GCD group incorporating QRD (20%) is 8-15% lower in comparison to the corresponding plain specimens of the GC group (without QRD). However, the peak axial load attained by the fiber-reinforced columns in the GCD group was 7-15% more than the corresponding plain specimens in the GC group. * The specimens (without fibers) of GC and GCD groups had lower peak load values than their counterparts in CC group. The load-carrying capacity of concentrically loaded plain columns in GC and GCD groups was 10% and 16% lower, respectively,  
Figure 15: The ductility index of CC, GC, and GCD columns. than their counterpart in CC group. However, the peak axial load achieved by the fiber-reinforced GC and GCD specimens was 20-30% more than their corresponding plain specimens in the same group. The load capacities of fiber-reinforced GC specimens were about 5-7% higher than their counterparts in CC group. * Increasing the eccentricity of the applied axial load resulted in reduction of load carrying capacity and ductility of columns. * The spalling of concrete cover at failure was observed in all plain CC, GC, and GCD columns tested under concentric and eccentric loading. On the other hand, all fiber reinforced GC and GCD specimens experienced no spalling. The cover concrete of all specimens (without fibers) spalled-off in between a region of 200-300 mm from the ends of columns, and core concrete was intact. However, the failure modes of all fiber-reinforced columns of GC and GCD groups were characterized by surface cracking, leading to disintegration of the concrete cover. * The general performance of the GPC columns incorporating QRD (20%) is observed to be similar to that of GPC columns (without QRD) and conventional concrete columns; the peak axial load and axial deformation at peak axial load decreased with an increase in the loading eccentricity. On the other hand, the lateral displacement tends to increase with the increase of eccentricity due to the tendency of columns to buckle under eccentric loading. * The fiber reinforced specimens of GC and GCD groups exhibited more deformation than the corresponding plain columns in the same group. The addition of steel fibers significantly improved the load-carrying capacity, ductility, and post-peak load-displacement behavior of the tested columns. The addition of steel fibers softens the descending phase of the axial load-displacement response and restricts the sudden failure of the tested specimens. The specimens (without fibers) of GC and GCD groups had lower ductility index than their counterparts in CC group. The addition of fibers in GC and GCD specimens resulted in improving the ductility by 50% compared to the corresponding CC specimens. In view of the results of the present study, it is evident that QRD is a promising material to be used as a replacement for SG, in FA- and SG-based GPC columns.