IGC. 50 th. 50 th INDIAN GEOTECHNICAL CONFERENCE COMPRESSIBILITY AND STRENGTH CHARECTERISTICS OF SOFT CLAY TREATED WITH BOTTOM ASH

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1 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India COMPRESSIBILITY AND STRENGTH CHARECTERISTICS OF SOFT CLAY TREATED WITH BOTTOM ASH Manicka Priya N 1, Dr. K Rangaswamy 2 ABSTRACT It is well-known fact that the construction of foundation for any infrastructure in soft clay soils is not possible without an improvement. Due to lack of availability of soil deposits with sufficient bearing capacity, it is mandatory to utilize the soft clay soils for constructing the facilities after stabilizing in improving the engineering properties. Now-a-days, the demand is increasing drastically to produce electricity power from thermal power plants. Each power plant is releasing a huge amount of fly ash and bottom ash as a waste by-product and it poses difficulties for storing and preventing the environmental pollution. Hence, the present work focuses to utilize such waste bye product bottom ash as a stabilizing material to improve the properties of clay soil. Bottom ash is the heavier burnt particle settled on the bottom part of a furnace in thermal power plant. It is dark greyish black in color with sand like texture. In present work, the laboratory tests were carried out on clay and bottom ash treated clay samples including index properties tests, compaction, and consolidation and UCS strength tests. The highly compressible soft clay soil is collected from local region of Calicut city in Kerala. The soil is dried in air and pulverized to utilize for experimental programme. The bottom ash is obtained from Ennore Thermal Power Plant, Chennai. The bottom ash treated clay samples i.e. soil combinations are prepared after adding different amounts of bottom ash to the soil in dry state in the percentages of 10%, 20%, 30%, and 40% by weight and mixed thoroughly. The tested materials of clay and bottom ash were characterized after conducting all basic properties tests. Further the compaction tests were carried out on bottom ash treated clay samples to determine the OMC corresponding to its maximum dry density of each soil combination. The effect of bottom ash amount on maximum dry density and OMC was studied in order to develop the relation. The OMC and maximum dry density of each soil combination obtained from compaction tests were used to make the UCS samples. The UCS tests were carried out on all soil combinations to determine the optimum dosage of bottom ash which one exhibiting the maximum UCS strength and estimate the quantitative improvement. The UCS strength of samples has been tested for various curing periods up to 1 compressibility and strength characteristics of soft clay treated with bottom ash _N.Manicka priya, Department of Civil Engineering, Student, Calicut, India, manickapriya91@gmail.com 2 compressibility and strength charecteristics of soft clay treated with bottom ash _Dr.K.Rangaswamy, Department of Civil Engineering, Assiatant Professor, Calicut, India, ranga@nitc.ac.in

2 N.Manicka priya & Dr.K.Rangaswamy seven days. In the next phase, the soil combinations are tested for compressibility characteristics after conducting consolidation tests on soil samples. The test results show that the compaction densities are decreases and corresponding optimum moisture contents are increases with an increase in bottom ash amounts. The maximum UCS strength is obtained at an optimum bottom ash level of 10% added to the clay soil and further the strength is decreases. The strength of 10% bottom ash treated clay at 7 days of curing is increased about 3.5 times the strength of 10% bottom ash treated clay without curing. It is noticed that the value of coefficient of consolidation is increases with the addition of bottom ash up to 10%. The consolidation of sample is too quick, the rate of settlement was faster and the time required for 90% consolidation is less. This may be due to the size of bottom ash which is grainy in nature and allows water to dissipate more quickly than of the parent clay. Keywords: Soft clay, Bottom ash, Consolidation, Unconfined Compressive Strength

3 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India COMPRESSIBILITY AND STRENGTH CHARACTERISTICS OF SOIL TREATED WITH BOTTOM ASH N. Manicka Priya, Student, National Institute of Technology, Calicut, Dr.K. Rangaswamy, Assistant Professor, National Institute of Technology, Calicut, ABSTRACT: Construction of foundation on clayey soil is always a challenging task. In a site with clay soil of low strength, the bearing capacity is low on such sites there is a necessity of improving the soil. There are various methods available for ground improvement. All the available methods require new materials and sound in cost wise. An attempt has been made in this research to utilize the by- product from thermal power plant which is bottom ash to study the property of soil randomly mixed with bottom ash. Namely compaction, consolidation and shear strength properties are studied. The tests are done for all mix of soil with bottom ash. There was a noticeable improvement in strength and consolidation properties of treated soil. INTRODUCTION There is a rapid increase in requirement of land for construction in recent times as a result the engineer is force to construct on the available land however the soil condition is thereby leading to ground improvement techniques if the available ground is having very low strength. In this research an attempt has been made to improve the soil strength using bottom ash. Bottom ash is a by-product from thermal power plant along with fly ash. These are heavier particles settling down in the furnace after escape of fly ash. The bottom ash is collected from Ennore thermal power plant, Chennai. MATERIALS AND ITS PROPERTIES The materials used are soil and bottom ash. The bottom ash obtained is of dark grey coloured and having sand like texture. The bottom ash is collected from Ennore thermal plant Chennai. The obtained bottom ash is taken for SEM image and X-Ray diffraction studies to determine the morphology and chemical constituents. Fig.1SEM image of bottom ash Table 1 percentage of chemical present in bottom ash Compound Percentage (%) SiO Al 2 O Feldspar 1.67 Calcium 0.68 Titanium 1.60 Iron 1.89 Soil is obtained locally from Kunnamangalam, Calicut. The soil is collected below 10 m in a residential place. The soil is tested for all basic properties including moisture content, atterberg limits, Unconfined Compressive Strength (UCS), and Consolidation.

4 N.Manicka priya & Dr.K.Rangaswamy Table 2 Properties of soil Property Value Natural moisture 16 content, % Specific gravity 2.70 Liquid limit, % 73 Plastic limit, % 41 Plasticity index, % Optimum moisture 29 content, % Maximum dry 1.33 density, g/cm 3 Coefficient of consolidation, cm 2 /minute UCS strength, EXPERIMENTAL PROGRAMME The soil is treated with four percentages of bottom ash which were 10%, 20%, 30% and 40% by weight of soil respectively. The soil treated with the above dosages is tested for compaction, consolidation and Unconfined Compressive Strength. The UCS is carried out for curing time of about 1 day, 3 days and 7 days. The mix having maximum UCS strength is taken for optimum dosage to be added. Compaction Test Various standard proctor compaction tests were carried out on each fresh soil-bottom ash mixture sample added with different water contents to obtain the optimum moisture content corresponding to maximum dry density. The values of optimum water content corresponding to its maximum dry density of each soil-bottom ash mixture are listed in Table 2. Unconfined Compressive Strength To obtain the shear strength values of each soilbottom ash mixture, various UCS tests were performed on samples prepared at its maximum dry density by controlling the optimum water content. The samples were tested for different curing periods in order to examine the effect of curing on strength properties. The UCS tests were carried out on three similar fresh clay samples molded at OMC corresponding to maximum dry density. The average UCS strength of three samples is reported to actual value of clay soil strength Consolidation Test The samples were prepared at maximum dry density of each soil-fly ash mixture by maintaining its optimum water level. The samples were compacted in the consolidation ring and placed inside the consolidation chamber to allow the drainage for full saturation. One dimensional odometer tests were performed on several samples of soil-bottom ash mixtures as per the standard test procedure given in the IS code 2720: Part V. Each sample was loaded by 0.5 kg/cm2 up to 24 hours of duration. The square root of time plots were drawn based on the test data of four combinations of soilbottom ash mixture. RESULTS AND DISCUSSIONS The outcome of the tests done are presented in the form of graph and table for all the test done Compaction Test The compaction curves obtained for all soil-bottom ash combinations are shown in Figure.1. It was found that the maximum dry densities (MDD) are decreases with increasing the bottom ash amount added to the soil. This trend may result due to the replacement of lighter material with the soil exhibiting more unit weight. It also found that the optimum water content is increases significantly in the range of 32 % to 36 %. Each soil-bottom ash mixture possesses the different compaction properties of OMC and MDD. The values of optimum water content corresponding to its maximum dry density of each soil-bottom ash mixture are listed in Table.2. Given below.

5 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India Table 3 compaction properties of soil mixed with bottom ash Bottom ash Maximum Dry (%) Density g/cc Optimum Moisture Content (%) Table 4UCS strength of treated soil sample Bottom ash (%) UCS at 1 day curing UCS at 1 day curing UCS at 1 day curing Fig. 2 Typical compaction curve for clay treated with various dosage of bottom ash Unconfined Compressive Strength For each soil-bottom ash mixture, three similar UCC specimens were prepared and tested to report the average value of UCC strength. Shear strength is the half of the UCC strength. After arrival of strength values from Figure, the relation was drawn in between UCC strength and curing time in days as shown in figure.2. To examine the sustainability of strength values and study the effect of curing time on strength values.figure...2. Shows that the UCC strength is generally increases while increasing the curing time from 1 day to 7 days irrespective of any soil-bottom ash mixture. The increase in strength may be possible due to the strong cementation property of bottom ash in the presence of continuous moisture. Table 3 gives the values if the UCS strength of soil treated with various percentages of bottom ash. Fig. 3 Variation of shear strength with curing for treated clay Consolidation Test The consolidation test is done on clay sample treated with various dosages of bottom ash with a single load of 0.5 for 24 hours. Square root of time curve is plotted from which the coefficient of consolidation and time required for 90% consolidation is found out. Table 5: Consolidation parameters for treated soil Bottom ash Coefficient of (%) consolidation Time required for 90%consolidation min cm 2 /min

6 N.Manicka priya & Dr.K.Rangaswamy Fig. 4 variation of coefficient of consolidation on addition of various bottom ash dosages It is observed that the coefficient of consolidation is increases drastically with the addition of bottom ash up to 20% into the clay soil. Further, there is no significant change in the value of c v. The increase trend of c v may be due to the nature of sand size of bottom ash particles which makes the soil more permeable and allows faster drainage and hence lowering the time required for 90% consolidation. CONCLUSIONS This study mainly concentrated on the potential use of thermal power plant by-product, bottom ash as a raw material for improvement of low strength clay soil. For this purpose, compaction, UCS and consolidation test were carried out. The major findings of the research are listed below. 1. The untreated clay is having UCS strength of 0.5 which corresponds to soft clay nature 2. The compaction characteristics reveal that the Maximum Dry Density decreases and the Optimum Moisture Content increases 3. This is due to addition of lighter denser particle to highly denser particle 4. The maximum strength was reported to 1.53 at 7 days of curing time for the soil added with 10 % bottom ash 5. Quantitatively, the strength was improved about 200 % over the strength of clay soil 6. The consolidation test revealed that there was an increase in coefficient of consolidation, which implies that the bottom ash leads for improvement in drainage of the water leading to increased permeability 7. There was a noticeable decrease in time required for 90% consolidation due to faster dissipation of water The study shows that there is a significant increase in strength and compressibility characteristics of the soil treated with fly ash addition of 10% BA is taken as optimum dosage for the maximum strength for the given soil. The study can be further done for Column studies can be done by installing bottom ash columns on soil specimen and tests can be done by varying different parameters like column depth and spacing The study can be extended to determining the engineering and geotechnical properties of soft clay with bottom ash on field density and field moisture content Other parameters like permeability and CBR tests can be done on soil treated with bottom ash. REFERENCES 1. Muzamir Bin Hasan, Aminaton binti Marto, Masayuki Hyodo, Ahmad Mahir bin Makhtar (2011), The Strength Of Soft Clay Reinforced With Singular And Group Bottom Ash Columns, Electronic Journal Of Geotechnical Engineering,, volume 16, Sanjeev Kumar and James Stewart, (2003), Evaluation of Illinois Pulverized Coal Combustion Dry Bottom Ash for Use in Geotechnical Engineering Applications, J. Energy engineering ASCE, Do Thanh Hai and Tran Xuan Tho,(2011), Particle Size Effect on Shear Properties of Bottom Ash Added-Geocomposite Soil, Journal of Civil Engineering and Architecture, ISSN , USA, Hashim Mohammed Alhassan*, Ahmed Musa Tanko,(2012), Characterization of Solid Waste Incinerator Bottom Ash and the Potential for its Use,IJERA,