The Thesis is focused on methodology development for microstructure assessment of plain and fiber-reinforced geopolymer composites after long-term property determination in compression, tension and three-point bending. Plain and reinforced with steel, polyvinyl alcohol, polypropylene and carbon fibers geopolymer composites have been tested for long-term properties in compression, tension and three-point bending. Creep properties have been determined in a linear state. Shrinkage properties have been determined simultaneously with the creep strains. For microstructure assessment, polished section specimens have been used and assessed in a scanning electron microscope. As a result, one national patent and one patent application have been developed that show microstructure assessment and long-term determination.