The investigation of bitlis pumice based alkali activated hybrid binders production

The environmental impact of CO2 gas generated during the production of Portland cement has led to the search for alternative binders. Alkali activated cements (geopolymers) produced by the activation of aluminosilicate materials with alkali solutions are one of these alternatives. Pumice based alkali activated hybrid binders produced with a small amount of Portland cement, while benefiting from the material properties of traditional cement and inorganic geopolymers, attract attention of researchers due to their environmental impacts and improved strength properties. In this thesis, the use of pumice from Bitlis region in alkali activated systems and effect of the addition of Portland cement at low rates (up to 20%) on these materials was investigated. Sodium silicate (Na2SiO3) and potassium hydroxide (KOH) solutions were used as alkali activators. Material proportions and curing conditions of alkali activated paste samples with and without Portland cement were determined and then alkali activated hybrid mortars were produced. The optimum proportions of paste mixes were evaluated over Portland cement content (%0, %5, %10, %15 and %20), alkali solution/binder ratio (0.47, 0.50 and 0.53) and Na2SiO3/KOH ratio (1, 2 and 3). UPV, compressive strength, density, total water absorption and porosity tests were performed. Also, SEM/EDX and FTIR analyzes were performed to examine the microstructure of the materials produced. After the mixing proportions were determined, the curing conditions were examined at different oven temperatures (20˚C, 40˚C, 60˚C, 80˚C, 100˚C and 120˚C), different waiting time in the oven (24, 48, 72 and 96 hours) and different curing ages (3, 28 and 90 days). UPV, flexural and compressive strength, density, total water absorption and porosity values of the alkali activated hybrid mortars prepared in different binder dosages were obtained as a result of the tests. Mortar samples with optimum binding dosage were exposed to 200˚C, 400˚C, 600˚C, 800˚C and 1000˚C to examine their behavior against high temperatures. In addition, UPV values, compressive strengths and weight losses were determined. SEM/EDX and FTIR analyzes were performed to examine the microstructure properties. Experiments have shown that satisfactory compressive strength results can be obtained from samples cured under ambient conditions. 28 days compressive strength of pumice based alkali activated hybrid paste samples, which kept in the oven at a temperature 100˚C for 72 hours, is 91.09 MPa while mortar samples is 43.66 MPa. As high temperatures increase, the compressive strength of mortar samples decreases. The loss of compressive strength at 800˚C was %49.32. These results have shown that the pumice of Bitlis region can be used in alkali activated hybrid systems.