Experimental Evaluations of Stabilization Methods for High Sulfate Soils in Iran Desert Roads

In this paper, the approach proposed methods for soil stabilization in road construction projects has been explored in the literature. Geological studies, chemical status and soil salinity, along with relevant tests, analyze data and present the results of theoretical studies, field and laboratory tests have been done. As a case study, Khur- Arababad Desert Road (KADR) is used. KADR is located in South Khorasan province, which has a desert climate and the plain- hills are evaluated in terms of topography. The annual average daily traffic volume of the road between 8500 to 9000 has fluctuated. A total of 11 soil samples were taken for studies of soil chemistry. In this context soil samples to determine the texture, pH, Electrical Conductivity (EC), the percentage of lime and plaster were tested. Results showed that most samples are placed in the category of saline soils. Defining what type of soil salinity that the region is facing, to determine the exact concentration of sodium, calcium and magnesium ions in the samples, advanced atomic absorption method was used. The soil is very high sulfate content at all stations. To study the physical and mechanical properties of soil 7 samples were chosen. The experiments included sieve test, the sand equivalent, the determination of specific gravity, determine the plastic limit and liquid limit, proctor compaction, California Bearing Ratio (CBR) and swelling test. The results showed that the use of lime for soil stabilization with respect to the necessary CBR number is quite responsive. It also seems that even in relation to the amount of lime, Lime 2% would suffice, although higher percentages such as 5 percent of lime will obtain more reliable results. The volume changes average with increasing the percentage of lime almost showed an increasing trend. Soil stabilization options including limestone, blast furnace lump slag and Ground-Granulated Blast-Furnace Slag (GGBFS), copper and magnesium oxide tailings. To determine the optimal amount of lime, examples of the 2, 5 and 10 percent of lime was prepared. The addition of four other factors, according to previous studies was 5% and 2% lime was added to half of the samples as a catalyst. Three modes including lime 5%, fine-grained magnetite 5% with lime 2% and copper tailings 5% showed the best performance in terms of increasing the CBR, uniform effect on all the samples, and a little swelling in treated samples in 7 days. Iron slags, especially when they are combined with lime, have demonstrated effective performance to CBR increasing, But this performance fluctuated sharply and not uniform in different sampling stations. Another reason was that the exclusion of iron slags was the economic disadvantage due to the long transport distance. There is also concern regarding the use of fine-grained magnetite that Inflationary in the long run to the formation of the mineral magnesium sulfate (MgSO4) in soil. Copper tailings and lime performance in preventing soil volume changes in processed samples approximately the same and a small amount of swelling has been observed in some samples. Therefore, the use of two additives including lime 5% or copper tailings 5% more is recommended.