Investigation of freezing-thawing behavior of soils improved with geopolymer based on construction and demolition waste

As a result of construction activities, waste materials (brick, concrete, glass, etc.) generated from buildings that have reached the end of their service life cause significant environmental problems. This situation paves the way for critical issues such as environmental pollution. For a sustainable environment, both the preservation of natural resources and the recycling of construction demolition waste for reuse in buildings are of great importance. Within the scope of this study, the feasibility of using a geopolymer binder derived from recycled concrete, brick, and glass powder was investigated, and its effects on the physical and mechanical behaviors of clayey soils were examined. In this context, unconfined compressive strength (UCS) tests were conducted to determine the consistency limits, compaction parameters, and UCS of the soil. As a result of the UCS test, consistency tests, and compaction tests, it was observed that the construction demolition waste reduced the plasticity of the soil, but it was determined that it improved the compaction parameters. To examine the effect of construction demolition waste-based geopolymer binder on the UCS of clayey soil, the binder was added to the soil in increasing percentages of 4%, 8%, 12%, 16%, 20%, and 30%. The UCS test was conducted on the improved samples after 7 and 28 days of curing. Additionally, to determine the freeze-thaw resistance of the samples, freeze-thaw cycles were applied after the 28-day curing period, including 1, 3, 5, 7, 9, and 11 cycles, and the strength behavior of the samples was examined both before and after the freeze-thaw process. As a result of the experiments, it was determined that the UCS of clayey soils improved with the geopolymer binder based on recycled brick, concrete, and glass powder was significantly higher compared to the unimproved soil. Specifically, when 30% CDW and 12M NaOH were used, the UCS of the soil increased from 190 kPa to 1832 kPa. However, in freeze-thaw tests, this value decreased to 1023 kPa after 11 cycles. This finding revealed that the UCS of soil samples subjected to freeze-thaw cycles decreased.