حميدرضا محبي

The effect of geopolymer stabilization on the behavior of different soil types was investigated by performing UCS and wind tunnel tests as indirect and direct testing methods, respectively, for eva‎luating the soil susceptibility to wind erosion. Sandy soil sample (having 30 percent of non-plastic silt as fine content) is selected as the main soil sample. Many methods have been studied to alleviate soil wind erodibility. Employment of different kinds of chemical stabilizers to create a crusted surface is a popular one to mitigate wind induced soil erosion. Geopolymers are inorganic, amorphous polymers producing from alkaline activation of aluminosilicate materials. The feasibility of surface stabilization of a highly wind erodible soil sample using alkaline activated volcanic ash is studied in this research. The unconfined compressive strength test is employed as an indirect method to clarify the mechanisms of developing the geopolymeric bonds between soil particles. The 28-day compressive strength of cylindrical samples treated by 5 percent volcanic ash and 15 percent alkaline activator and cured at heated condition having 65 ̊ C temperature (as the nominated geopolymer mix design), reached a value of around 2 Mpa. By means of surface treatment of a volcanic ash-based geopolymer, soil surface crusted layers are developed against wind flow. Increased efficiency of the soil-geopolymer mixture (from both the wind tunnel and UCS tests) as a result of the reduction of fines content indicated that geopolymeric treatment is more effective for non-plastic soils with fewer fines contents. According to the order of adding different geopolymer elements to the soil, three different methods were examined for the preparation of the soil samples. The 3-phase method (in which water is added to a mixture of soil, volcanic ash and solid powder sodium hydroxide) was selected based on the result of the mechanical strength tests. Moreover, using the latter method yielded higher compressive strength and advanced soil surface crust. The impact of crust thickness, activator solution quantity, and curing conditions on the erodibility and friction velocity of three different soil types (clean sand, silty sand, and silty soil specimens) are measured by wind tunnel experiments. The results show that treatment with the geopolymer can notably increase the threshold friction velocity and reduce the soil wind erodibility. It is concluded that proper determination of the geopolymer mix design requires consideration of the soil type, maximum wind speed, and ambient conditions. Advanced performance of geopolymer cured under heated curing condition comparing the ones cured at room curing condition, demystify the suitability of using geopolymer for soil stabilization against wind erosion.

تثبيت خاك , ژئوپليمر , خاكستر آتشفشاني , فرسايش بادي , ماسه سيلتي

soil stabilization , Geopolymer , volcanic ash , wind erosion , Silty sand

Hamidreza Mohebi

Dr. Shariatmadari