Retrofitting methods are widely used to reinforce existing concrete structures and frames. Strengthening becomes necessary when building codes mandate a higher load carrying capacity originated from, for example, changes in earthquake zone mapping. A haunch conclusively relocates the formation of plastic hinges away from the beam-column-joint. Geopolymer concrete is an environmentally friendly material, based on fly ash. Utilizing a haunch with this material is effectual and sustainable. The low workability of geopolymer concrete was in this study improved by adding a superplasticizer, which effectiveness was trigger by the presence of low volume Portland cement and water creating a Self-Compacting-Geopolymer-Concrete (SCGC). This SCGC ensured easy fabrication in the field, and improved the compaction and homogeneousness of the haunch. A full-scale experiment based on water-loading was conducted on an existing building to analyze the behavior of a SCGC haunch. The research concluded that the SCGC resulted in a high-performance haunch with good compatibility to the structure, the integrity of the haunch and the structure was maintained up to working-loading conditions. The load carrying capacity and the serviceability greatly improved. Analytical comparison to the prismatic section showed that the SCGC haunch reduced the deflection at mid-span to 77%.