FIBER REINFORCED GEOPOLYMER – MECHANICAL PERFORMANCE

For the last two centuries, Ordinary Portland Cement (OPC) is the most popular building material in the world due to its high mechanical properties, ease of handling and low cost. However, the concrete industry is known to leave an enormous environmental footprint. Therefore, the development of sustainable materials that could replace the OPC is essential. One of such recent development is an aluminosilicate based material that can be activated in an alkaline medium to form a hardened sustainable material, known as ‘Geopolymers’. Geopolymers exhibit equal or better engineering properties as compared to conventional concrete with better environmental foot print. However, geopolymer`s main disadvantage, as concrete, is its brittleness and low tensile properties. One way to overcome this limitation is by addition of fibers, as they can control cracking by crack bridging, resulting in increase of the fracture toughness of the geopolymeric matrix.

The purpose of this research was to develop high performance geopolymer composites by addition of short fibers. Different fiber types (PVA, PP and Carbon) were added to the matrix and their influence on the geopolymer flexural behavior was examined. The microstructure of the composite at the fracture surface was also studied to better understand the role of the fibers. An increase in the flexural strength was recorded with the higher fiber contents, for all examined fibers. The greatest flexural strength was obtained for the carbon fiber composite. Different failure mode was observed – fiber pull-out for the PP and carbon composites and fiber rupture for the PVA fiber composite. This can be explained based on the different chemical nature of the fibers which produce a different matrix-fiber interface.