Investigation of the use of fiber-reinforced geopolymer columns in soil stabilization

In this thesis, the use of steel fiber-reinforced geopolymer composites, in which blast furnace slag and silica fume were used as binding materials, in soil stabilization was investigated. In the first stage of the thesis, silica fume was substituted into blast furnace slag at three different rates (5%, 10% and 15%). Geopolymer paste samples, the binder part of which was produced in this way, were activated by preparing 8, 10 and 12 M NaOH solutions. Alkali/binder ratios were determined so that the mixture had normal consistency. 7 and 28-day compressive strength tests were carried out on the geopolymer paste samples produced in this way, and after determining the sample group with the highest compressive strength, the second phase of the thesis was started. In the second stage of the thesis, 0.5%, 1% and 1.5% steel fiber was added to the sample group prepared by substituting 10% silica fume into blast furnace slag and activated with 8 M NaOH. 7 and 28 day bending strength values were examined on the samples produced in this way. After determining the sample group with 1.5% steel fiber addition in which the highest bending strength was observed, the final phase of the thesis was started. In the final stage of the thesis, geopolymer piles with a diameter of 50 mm and three different lengths (100 mm, 150 mm and 200 mm) were produced and the usability of these geopolymer piles in the ground stabilization process was investigated. In the third stage of the thesis, geopolymer dough with the optimum mixture ratio was prepared and geopolymer piles of different lengths were formed. Ground stabilization values of model foundation, cast-in-place geopolymer piles and driven geopolymer piles subjected to ground loading tests were investigated. As a result of the ground loading tests of the model foundation and cast-in-situ geopolymer piles, it was concluded that the cast-in-situ geopolymer piles had better soil bearing capacity than the model foundation. In addition, it has been observed that the ground bearing capacity of driven geopolymer piles is higher than cast-in-place geopolymer piles. One of the main reasons why driven and cast-in-place geopolymer piles increase the ground bearing capacity is that they enable the loads on the ground to be transferred deeper. In addition, the friction forces on the side surfaces of the piles and their ability to resist the load thanks to their end resistance are other factors that increase the soil bearing capacity. Keywords: Geopolymer, steel fiber, soil stabilization, compressive strength