Development of pumice based geopolymer concrete for hydraulic structures

Due to the large amount of energy consumption and high CO2 emission in the production of Portland Cement, the search for binders that can be an alternative to these cements has gained importance. Among the alternative binders, geopolymers, which have superior properties such as good fire resistance, early high strength, resistance against acid attack and environmental friendliness, stand out. Geopolymers are produced by using pozzolan and alkali activators instead of cement and water. In this study, pumice obtained from Iğdır as natural pozzolan and solution consisting of sodium hydroxide and sodium silicate as alkali activator were used. The aim of this thesis study is to develop pumice-based geopolymer concretes with sufficient resistance against the destructive effects that hydraulic structures are exposed to. In this context, geopolymer pastes, mortars and concretes were prepared by substituting fly ash and calcium aluminate cement to pumice, and their properties in fresh and hardened state were investigated. Considering the results of the work done with geopolymer pastes, parameters such as alkali activator content and curing conditions were kept at constant levels in mortar and concrete mixtures. Accordingly, the workability, physical and mechanical properties, durability and microstructures of the mortars and concretes produced were examined in detail. Methods such as XRD, BET, FTIR and SEM-EDX were used for microstructure investigations. The study showed that pumice-based geopolymer binders achieved sufficient workability and strength thanks to the admixture of fly ash and calcium aluminate cement. With these additives, it has been determined that the pumice-based geopolymer concretes have sufficient durability against effects such as wetting-drying, freezing-thawing, sea water, abrasion and acid, which water structures are also frequently exposed to. In addition, it has been determined that pumice-based geopolymers complete their setting and reach sufficient strength in acceptable times even at room temperature with the addition of calcium aluminate cement.