Plain Geopolymer Concrete Cross-Section Surface Analysis After Creep and Shrinkage Tests in Compression and Tension

Low calcium alkali-activated cement composite known as geopolymer has been around for more than 40 years. The main benefit of geopolymer based composites is the environmental aspect—it is partially made by utilizing waste products, such as fly-ash, slags, and others. It has been estimated that geopolymer binder production makes up to 6 times less CO₂ than the production of Portland cement. Due to the polymerization or in other words nature of the geopolymer binding process, there are some differences in creep and shrinkage development. Because of this microstructure of the specimen could be dissimilar to ordinary Portland cement. There has been an absence of investigations regarding the geopolymer composite long-term properties and micro-analysis. Also, the conditions affecting the long-term properties of the geopolymer composites have been little studied. The subject of the research is geopolymer concrete that has been tested for creep and shrinkage in compression and tension. The specimens for microstructure analysis were acquired from the cylindrical shape (compression) and compact tension (tension) specimens. Polished sections were used for SEM microanalysis. Acquired polished section image cross-sections were analyzed by determining the amount of geopolymer binder, filler, and air void in the analyzed cross-section. The results were cross-referenced with creep and shrinkage test results. After creep and shrinkage tests in compression and tension specimen cross-section zones that have been subjected to the highest stresses were chosen and analyzed. The article’s main aim is to determine the geopolymer composite microstructure and applied load influence on long-term properties.