61 STUDIES ON SOIL STABILIZATION USING BLAST FURNACE SLAG Abhlilash Devanoor 1 and Dr. M. S. Nagakumar 2 1 M. Tech Student in Highway Technology, R. V. College of Engineering, Bangalore 2 Professor P. G. Studies in Highway Technology, R. V. College of Engineering, Bangalore ABSTRACT Soil stabilisation may be defined as the alteration of the properties of an existing soil to meet specified engineering requirements. The main properties that may require to be altered by stabilisation are strength, volume stability, durability and permeability. In India, the black cotton soil covers an area of about 0.8 million sq. km. which is about 20% of the total land area. It is considered as problematic soil due to detrimental volume changes with variation in moisture content. When it comes in contact with water it shows immense swelling whereas it shrinks with the decrease in water content and develops cracks on drying. Now-a-days the utilization of waste products with soil has gained attention due to the shortage of suitable soil and increasing problems of industrial waste management. Expansive soil samples were collected from Badanavalu, Chamarajanagar district. This soil was classified as CH as per Indian Standard Classification System (ISCS). Different dosages of blast furnace slag i.e. 10,20,30,40 and 50% were used to stabilize the expansive soil. The performance of blast furnace slag stabilized soil was evaluated using physical and strength performance tests namely; plasticity index, specific gravity, compaction, California bearing ratio (CBR) and Unconfined compressive strength Test (UCS). Based on strength performance tests, it was observed that replacement of blast furnace slag increases the strength of expansive soils. It can be seen that the CBR value has increased by 700% when compared with native soil and the unconfined compressive strength increased by almost 400% compared with native soil. Keywords Blast furnace slag, Back cotton soil, CBR, UCS 1. INTRODUCTION: In India, the black cotton soil covers an area of about 0.8 million sq. km. which is about 20% of the total land area. It is considered as problematic soil due to detrimental volume changes with variation in moisture content. When it comes in contact with water it shows immense swelling whereas it shrinks with the decrease in water content and develops cracks on drying. Now-a-days the utilization of waste products with soil has gained attention due to the shortage of suitable soil and increasing problems of industrial waste management. In any highway engineering work the construction of the embankment or the sub grade is a very important activity. The earthwork constitutes 30% of the cost of the road project. The pavement directly rests on the artificially prepared soil sub grade and thus derives considerable strength from it. The adequate design and construction of embankments is therefore the key to the successful performance of the pavement. Soil stabilization may be defined as the alteration of the properties of an existing soil to meet specified engineering requirements. Soil stabilization is broadly utilized as a part of road development to enhance sub-bases and sub-grades for rail, road and landing strip development, as landfill and waterway linings, for development of soil underneath establishment piece. 2. EXPERIMENTAL WORK: The black cotton soil was procured from Badanavalu village in Chamarajanagar district at a depth of 20cm. Manual labour method was used for the procurement of the soil. Top vegetation and dry soil crust was removed for the depth of 20cm with crow bars. The soil was pulverized and then it was oven dried for 24 hours at 105 c to 110 c. The properties of black cotton soil are presented in Table 1. Blast furnace slag was procured from Nava Karnataka steel industry, Bellary for a thesis work by Mr.Ravishankar which was used in this project work also. The chemical composition of blast furnace slag is presented in Table 2.
62 Table 1- Properties of black cotton soil PROPERTIES VALUE 1. Specific Gravity (IS 2720: Part 3) 2.59 2. Grain Size Distribution (IS 2720: Part 4) a) Gravel b) Sand c) Silt and Clay 1.95 13.13 84.92 3. Liquid limit (%) (IS 2720: Part 5) 60 4. Plastic limit (%)(IS 2720: Part 5) 33.82 5. Plasticity Index (%)(IS 2720: Part 5) 27.18 6. Free Swell index (%) 65 7. IS classification of soil CH 8. HRB classification A-7-6 9. Proctor/Compaction test (IS 2720: Part8) a) Maximum Dry Density (g/cc) b) Optimum Moisture content (%) Table 2 Chemical composition of Blast furnace slag PROPERTIES (%) BY MASS 1. CaO 35.20 2. SiO2 34.90 3. Al2O3 19.00 4. MgO 8.76 5. MnO 0.14 6. FeO 0.039 1.610 20 Source: Nava Karnataka steel industry, Bellary Black cotton soil used in this study was replaced with Blast furnace slag in different proportions i.e. 10, 20, 30, 40, and 50% by weight of the soil to obtain the optimum amount for stabilization. Physical and strength properties of the blended mix was evaluated in the laboratory and compared with the properties of the black cotton soil to obtain the optimum amount of blast furnace slag. 3. RESULTS AND DISCUSSIONS: Basic tests like Specific gravity, wet sieve analysis, Atterberg limits and free swell index. Strengthen properties like compaction, California bearing ratio and unconfined compressive tests were conducted. Below indicates the test results, 3.1 Atterberg limits Atterberg limits of the blended soil were determined as per IS2720: Part 5-1985. Liquid limit and plastic limit both decreases with increasing percentage of blast furnace slag. Variation of plasticity index with various percentage of blast furnace slag is shown in Fig 1, it was inferred that plasticity index decreases with increasing percentage of blast furnace slag. 3.2 Compaction properties Compaction properties of the blended mixes were determined as per IS2720: Part 8 1983 and variation of MDD and OMC is shown in Fig. 2 and 3 respectively. From the Fig 2 and Fig 3 it is inferred that MDD increased and OMC decreased with increasing percentage of blast furnace slag. 3.3 California bearing ratio (CBR)
63 CBR is one of the important tests to evaluate the optimum amount of stabilizer for stabilizing the black cotton soils. Soaked CBR test were conducted on the black cotton soil as well as on blended material with various BFS percentages for evaluating the optimum amount of BFS. The soaked CBR tests were conducted on samples compacted at OMC, for 96 hours as per IS2720: Part 16 1987. Variation of the soaked CBR values with BFS mixes is shown in Fig 4. It was observed that CBR value increases with increase in percentages of BFS. The increment in the CBR can be attributed to the gradual formation of the cementitious compounds and Cao present in the Blast furnace slag. 3.4 Unconfined compressive strength The UCS tests were conducted on black cotton soil and blended material in accordance with IS2720: Part 10 1991. Variation of strength with respect to curing days is shown in Fig 5. It was observed that UCS value increases with increase in percentages of BFS. 3.5 X-Ray diffraction This method was carried out to know the presence of the mineral montmorillonite in the native soil and calcium mineral in soil stabilized with Blast furnace slag. To confirm the presence of montmorillonite mineral XRD tests were conducted and the results obtained are presented in Fig 6. The scanning range for montmorillonite mineral was found to be 3º to 60º. From the graph it can be seen that the peak intensity is at 26 which shows the presence of montmorillonite clay mineral present in the soil sample. Due to the addition of Blast furnace slag to the native soil, the main mineral composition of Blast furnace slag is checked for confirmation of calcium mineral mixed with native soil. The scanning range provided was 5 to 40. The diffract meter diffracts at angle of 26 and it is noted down in the acquisition system. From the graph it can be seen that the peak intensity is at 26 which shows the presence of calcium oxide. Therefore from Fig 7, it is clear that the presence of calcium mineral participated in stabilizing the native soil. Fig 1 Variation in PI with increase in BFS content Fig 2 Variation of MDD due to the replacement in BFS content Fig 3 Variation of OMC due to the replacement Of BFS Fig 4 Variations in CBR values with respect to dosages of BFS
64 Fig (5) Variation of strength with respect to curing days Fig 6 X-ray diffraction pattern for montmorillonite mineral Fig 7 X-ray diffraction pattern for calcium mineral 4. CONCLUSIONS: From all the above tests conducted it is clear that Blast furnace slag can be used as a stabilizer in subgrade for road construction. Blast furnace slag was found to be very effective especially in California bearing ratio and unconfined
65 compressive strength tests. This effect is mainly attributed to the hydration reaction of Blast furnace slag were the pores are filled by crystalline growth. 1. The reduction in plasticity index of the Blast furnace slag treated soil decreased from 26.18% to 17.24% showed a decrease of 51.85% was found to be encouraging. 2. Optimum moisture content decreased and maximum dry density increased due to the replacement of the Blast furnace slag when compared with native soil. 3. There was a drastic change in soaked CBR of treated soil. CBR changes were found to be significant at 30% BFS content after 4 days of curing. It can be seen that the CBR value has increased by 700% when compared with native soil. 4. Unconfined compressive strength increased by almost 400% compared with native soil. Stability of the soil will increase due to increase in unconfined compressive strength. 5. X-ray diffraction studies were proved significant to identify the mineral present in native and stabilized soil. REFERENCES 1. Laxmikant Yadu and Dr.R.K.Tripathi, Effects of Granulated Blast Furnace Slag in the engineering behavior of stabilized soft soil, Procedia Engineering 51( 2013 ) pp125-131. 2. H.N. Ramesh, K.V. Manoj Krishna, and H.V. Mamatha, Compaction and strength behavior of lime-coir fiber treated Black Cotton soil, Geomechanics and Engineering, Vol.2, No.1, 2010, pp 19-28. 3..Nuno Cristelo, Stephanie Glendinning, Lisete Fernandes, Amândio Teixeira Pinto, Effect of calcium content on soil stabilization with alkaline activation, Construction and Building Materials 29(2012) pp 167-174. 4. Bernardo Celauro, Antonio Bevilacqua, Dario Lo Bosco, Clara Celauro, Design Procedures for Soil-Lime Stabilization for Road and Railway Embankments, Procedia - Social and Behavioral Sciences 53 ( 2012 ) pp 755 764. 5. Rafael Alavez-Ramirez, Pedro Montes-Garcia, Jacobo Martinez-Reyes, Delia Cristina Altamirano-Juarez, Yadira Gochi-Ponce, The Use of Sugarcane bagasse ash and lime to improve the durability and mechanical properties of compacted soil blocks, Construction and Building Materials 34(2012) pp 296 305. 6. Kiran R.G, Kiran L, Analysis Of Strength Characteristics Of Black Cotton Soil Using Bagasse Ash and additives as Stabilizer, International Journal of Engineering Research & Technology, Vol. 2 Issue 7, July 2013 pp 2240-2246. 7. Pankaj R. Modak, Prakash B. Nangare, Sanjay D. Nagrale, Ravindra D. Nalawade, Vivek S. Chavhan, Stabilisation of Black Cotton Soil Using Admixtures, International journal of civil and structural engineering, Volume 1, Issue 5, May 2012 pp 01-03. 8. VinayAgrawal and Mohit Gupta, Expansive Soil Stabilization Using Marble Dust, International Journal of Earth Sciences and Engineering Volume 04, No 06, October 2011, pp 59-62. 9. Takeshi Kamei, Aly Ahmed,ToshihideShibi, The use of recycled bassanite and coal ash to enhance the strength of very soft clay in dry and wet environmental conditions, Construction and Building Materials 38 (2013) pp 224 235 10. AmaiaLisbona, Iñigo Vegas, Javier Ainchil3 and Carolina Ríos, Soil Stabilization with Calcined Paper Sludge: Laboratory and Field Tests, Journal of Materials in civil engineering, American society of civil engineers, June 2012 pp 666-673. 11. Noorina Tarannum, R.K. Yadav, Influence of Blast Furnace Slag on the Consistency Limits of the Black Cotton Soil, International Journal of Scientific & Engineering Research, Volume 4, Issue 4, April-2013 pp 456-458. 12. Chun-YangYin, Hilmi Bin Mahmud, Md Ghazaly Shaaban, Stabilization/solidification of lead-contaminated soil using cement and rice husk ash, Journal of Hazardous Materials B137 (2006) pp 1758 1764. 13. Nurhayat Degirmenci, Arzu Okucu, Ayse Turabi, Application of phosphogypsum in soil stabilization, Building and Environment 42 (2007) pp 3393 3398. 14. Achmad Fauzi, Wan Mohd Nazmi, Wan Abdul Rahman, Zuraidah Jauhari, Utilization Waste Material as Stabilizer on Kuantan Clayey SoilStabilization, Procedia Engineering 53 ( 2013 ) pp 42 47