California Bearing Ratio and Unconfined Compressive Strength of Soil-Fly Ash-Glass Fiber Mixture

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1 California Bearing Ratio and Unconfined Compressive Strength of Soil-Fly Ash-Glass Fiber Mixture Yachang Omo Assistant Professor Central Institute of Technology Kokrajhar Ajanta Kalita Assistant Professor North Eastern Regional Institute of Science and Technology, Nirjuli ABSTRACT A study was conducted on sandy soil-fly ash-glass fiber mixture to determine the improvement in strength characteristics. The soil was treated with fly ash of 10, 30, 50 and 70% by dry weight of soil sample. To improve the shear strength the soil-fly ash mixture was further reinforced with glass fiber of 0.25, 0.5, 0.75 and 1% by dry weight of soil. Each specimen of soil-fly ash-glass fiber mixture were subjected to California bearing ratio (CBR) and unconfined compression tests at curing period of 7, 14 and 28 days, to determine the strength characteristics of the mixture. The effect of fly ash and glass fibers in improving the strength of soil was studied and has been presented here. The percentage increase in CBR value was 29 to 304% when the percentage of fly ash and glass fiber were increased from 0 to 70% and 0 to 1% respectively. The maximum percentage increase in unconfined compressive strength (UCS) of the soil was 1417, 1463 and 1555% after curing period of 7, 14 and 28 days, respectively with addition of 50% fly ash and 1% glass fibers. A considerable increase in strength of the soil-fly ash-glass fiber mixture was observed, thus making it suitable for civil engineering construction works. Keywords Sandy Soil, Fly ash, Glass fiber, CBR, UCS. INTRODUCTION Fibers, when distributed randomly improves the strength and stability of weak soil and natural slopes. This can be observed in plant roots that act as natural means of incorporating randomly oriented fiber inclusions in the soil. One of the main advantages of randomly distributed fibers is that it maintains the strength parameters and absence of potential failure plane that can develop parallel to oriented reinforcement fibers (Mali and Singh, 2013). A wide varieties of reinforcing materials such as metal strips (Fatani et al.,1999), geosynthetic fibers (Consoli et al., 2002, Michalowski and Cermak, 2003;Yetimoglu and Inanir, 2005; Rao et al., 2006 and Chandra et al., 2008), discontinuous multioriented polypropylene elements (Lawton et. al., 1993) and glass fibers (Mali and Singh 2013, Ahmad et al. 2012, Patel and Singh 2015) have been used to reinforce soil and shown that the addition of randomly distributed elements to soil contributes to the increase in strength and stiffness. Gary and Ohashi (1983) studied the fiber reinforcement of beach sand and concluded that fibers improve shear strength characteristics of beach sand. Consoli et al. (1998) studied the use of glass fibers with silty sand and indicated that inclusion of glass fibers in silty sand effectively improves peak strength. The use of fly ash reinforced with geogrid sheet and jute geotextile as sub grades was studied by Choudhary and Verma (2003), they reported that the CBR value of reinforced fly ash increases with increasing number of reinforcing layers and it is significant upto four numbers of reinforcing layers placed within the specimen at equal vertical spacing. Kumar et. al. (2007) studied the use of stabilized fly ash layer as sub-base course in flexible pavement construction and reported that the load carrying capacity of the flexible pavement was significantly increased for cement stabilized fly ash sub-base with respect to the lime stabilized fly ash and fly ash sub-base stretch on sand subgrade and expansive soil subgrade. Jadhao and Nagarnaik (2009) studied randomly reinforced fly ash with polypropylene fibers withdifferent length and varying amount. The optimum dose of fiber added to fly ash was determined to be 1% by weight of 12 mm fibers. The CBR value was observed to have increased considerably. 347

2 Jiang et al. (2010) conducted a test on the effect of short discrete polypropylene fiber on the engineering properties of soil, their findings indicate that the UCS, cohesion, and internal friction angle of fiber-reinforced soil were greater than those of the parent soil; the UCS, cohesion, and internal friction angle of fiber reinforced soil experienced an initial increase followed by a decrease with increasing fiber content and hence the optimal fiber content was found to be 0.3% by weight of the parent soil. With an increase in fiber length, the UCS, cohesion, and internal friction angle of fiber-reinforced soil gently increase at first and then rapidly decrease and the optimal fiber length for the study is observed at about 15 mm and also concluded that the presence of polypropylene fiber could effectively contribute to the improvement in the strength and stability of the parent soil.liu and Starcher (2012) studied the effects of curing conditions on UCS of cement-fiberimproved soft soils and it was concluded that although specimens have higher UCS when a longer curing time is experienced, the magnitude of UCS change is not very sensitive to curing time. UCS can only be increased approximately from 30-40% when curing time changes from 28 to 120 days.fiber increases the ductility of cement-soil mixture and postpone the development of crack formation during UCS tests.ahmad et al. (2012) studied the mechanical properties and behavior of recycled glass fibers based on laboratory tests. The findings from this research show that the presence of recycled glass fiber reinforcement in soil leads to a significant increase in the shearing resistance and internal friction angles of soil media. Jian Li et al. (2014) studied the effect of discrete fiber reinforcement on soil tensile strength and concluded that a very small dosage of fiber inclusion can significantly enhance soil tensile strength. The tensile strength increases with increasing fiber content. As the fiber content increases from 0% to 0.2%, the tensile strength is increased by 65.7%. They also suggested that the fiber reinforcement is a favorable ground improvement technique, and has the potential to increase soil cracking resistance and the stability of earth structures. Patel and Singh (2015) studied the strength behavior of clayey silt soil reinforced with glass fibers by conducting a series of CBR test on clayey silt soil with glass fibers and concluded that the CBR improvement in unsoaked soilis much significant in magnitude than that of soaked sample. The CBR improvement increases with an increase in fiber length and fiber content upto 0.75% for all moisture content. This paper presents the results of the study carried out to analyze the strength characteristics of soil-fly ashglass fiber mixture and its improvement. Effect of fly ash content, glass fiber content and curing period have been discussed. METHODS AND MATERIALS The soil sample was obtained from national highway, Karsingsa, Arunachal Pradesh, India, which is a hilly area prone to landslides. The index and compaction properties of the soil was determined and are tabulated in Table 1 and grain size distribution curve is shown in Figure 1. The soil was characterized as sandy soil having 21, 67 and 8% of coarse, medium and fine sand, respectively and a small amount 3.59% of silt and clay. The soil was found to be poorly graded having co-efficient of uniformity C u=4.61, which is designated as SP as per IS Fly ash used for the study was obtained from Farakka, thermal power plant, India. The fly ash was found to be class F fly ash with low lime (CaO) content (Sridharan et al., 2000).It reveals that the fly ash predominantly consists of silt-sized particles 71%, sand-sized particles 21% and clay-sized particles 8%. Grain size distribution of fly ash is shown in Figure 2. The uniformity coefficient, C u and coefficient of curvature, C c of the fly ash were 3.75 and 0.96, respectively. The specific gravity of the fly ash was The chemical compositions of the fly ash were, SiO 2=43.94%, Al 2O 3=33.60%, Fe 2O 3=4.40%, CaO=12.73%, MgO=0.21%, loss on ignition 2.32%. Different percentages of fly ash content used for this study were 0, 10, 30, 50 and 70% by dry weight of the soil sample.to add shear strength to the soil-fly ash mixture, glass fibers were used throughout this investigation as soil reinforcement. The fibers were kept 30 mm in length and was 0.55 mm in diameter, with specific gravity of 2.55, tensile strength of 1950 MPa, elastic modulus of 72 GPa. The percentage of fiber contents used in the experiments were 0, 0.25, 0.5, 0.75 and 1% by dry weight of the soil sample. Glass fiber is shown in Figure 2. Potable water was used for molding specimens for both compression test and characterization test. 348

3 The soil and fly ash both were subjected to standard proctor compaction test as per IS 2720 (Part VII)-1980 to determine the water content-dry density relationship. The optimum moisture content (OMC) and maximum dry density, γ d(max) was 13.69%, kn/m 3 and 18.34%, kn/m 3 for soil and fly ash, respectively. The grain size distribution analysis of soil and fly ash were conducted as per IS 2720 (Part-IV) Table 1. Index and compaction properties of Soil and Fly ash Soil Fly Ash Properties Value Properties Value Specific Gravity 2.68 Specific Gravity 2.48 Liquid limit Liquid Limit NP Plastic limit NP Plastic Limit NP MDD, γ d(max) (kn/m 3 ) MDD, γ d(max) (kn/m 3 ) OMC (%) OMC (%) % Gravel (>4.75 mm) - % Gravel (>4.75 mm) 0 % Coarse sand (2 mm- 21 % Sand ( mm) 21 % Medium sand ( mm) % Silt ( mm) 71 % Fine sand (.075 mm % Clay (< mm) 8 % Silt and Clay (<0.075 mm)) 3.59 Effective size, D 10 (mm) Effective size, D 10 (mm) 0.13 C u 3.75 C u 4.61 C c 0.96 C c 1.15 Figure 1: Grain size distribution curve of soil and fly ash The soil was stabilized with fly ash by mixing them thoroughly with hand to ensure a homogeneous mixture. Different percentages of fly ash used were 0, 10, 30, 50 and 70%. The soil-fly ash mixture was further reinforced with varying percentages of glass fibers of 0, 0.25, 0.50, 0.75 and 1%. CBR tests for both soil-fly ash and soil-fly ash-glass fiber mixture were conducted for both soaked and unsoaked specimens. Similar method of sample preparation was followed for unconfined compression tests. UCS for both soil-fly ash and 349

4 soil-fly ash-glass fiber mixture were conducted after curing period of 7, 14 and 28 days. In this paper, the mixes are designated in the tables and graphs with a common coding system consisting of three terms. The first term, S stands for soil; the second and third terms show the percentages of fly ash, F, and glass fibers, G, respectively. For example, a mix of soil, fly ash and glass fibers containing 10% fly ash and 0.25% glass fibers is designated as S+10F+0.25G. Total of 21 mixes were used in the present study: S+0F+0G, S+10F+0G, S+30F+0G, S+50F+0G, S+70F+0G, S+10F+0.25G, S+30F+0.25G, S+50F+0.25G, S+70F+0.25G, S+10F+0.5G, S+30F+0.5G, S+50F+0.5G, S+70F+0.5G S+10F+0.75G, S+30F+0.75G, S+50F+0.75G, S+70F+0.75G, S+10F+1G, S+30F+1G, S+50F+1G, S+70F+1G. Figure 2: Glass Fiber Figure 3:Standard Compaction Curve for fly ash and Soil with different percentages of fly ash MOISTURE-DENSITY RELATIONSHIP OF STABILIZED SOIL SECTIONS Standard Proctor compaction tests were conducted in accordance with IS 2720 (Part VII) Moisture content-dry density relationships curve obtained from the tests for the soil mixes containing 0, 10, 30, 50 and 70% fly ash are presented in Figure 3. The optimum moisture content (OMC) varied from to 16.29% and the maximum dry density, γ d(max) ranged from 15 to kn/m 3. It was observed that the optimum moisture content increases with the increase in percentage of fly ash from 0 to 70% whereas maximum dry density, γ d(max) decreased with the increase in fly ash content. Such behaviour of compaction curve has been reported earlier by other researchers (DiGioia and Nuzzo, 1972, and Indraratna et al., 1991). Kumar et al., 350

5 2007 reported that with the addition of fly ash in expansive soil-lime mixture, there is further decrease in maximum dry density, γ d(max) and increase in optimum moisture content. The presence of fly ash having a relatively low specific gravity may be the cause for this reduced dry density. The increase in optimum moisture content can be attributed to the increasing amount of fines which require more water content because of their larger surface area. Kumar et al., 2007 also reported that fibers had no significant effect on maximum dry density, γ d(max) and optimum moisture content of fly ash-soil-lime-fiber mixtures. PREPARATION OF SAMPLE FOR CBR AND UCS TESTS Soil, fly ash and glass fibers were mixed thoroughly in dry state to prepare a homogeneous mixture and water was added and mixed thoroughly. Water was added to its optimum moisture content corresponding to its maximum dry density of the respective samples obtained from compaction tests. The prepared specimens were kept inside CBR mold and compacted as per standard procedure given in IS: 2720 (Part-16) CBR tests were carried out for both unsoaked and soaked samples. Unsoaked specimen gave higher CBR values than the soaked specimen. Soaked samples were kept inside water tank for 96 hours, which was then taken out and exposed to air for half an hour to let the excess moisture escape. The CBR values of the test samples of unreinforced and reinforced soil were determined corresponding to plunger penetrations of 2.5 mm and 5 mm. Unconfined compression tests were conducted in accordance with IS 2720 (Part 10) To study the effect of fly ash and glass fiber content and curing time on UCS, specimens were cured for 7, 14 and 28 days. Only unsoaked specimens were tested for UCS. Many researchers have also conducted unconfined compression tests after soaking the specimens inside water for 24 hours after curing (Chu et al. 1955; Lo and Wardani 2002). Depending on the mix proportions, required amount of materials were mixed thoroughly in dry state by hand, making sure to give a homogeneous mixture. All specimens were prepared to achieve maximum dry density corresponding to its optimum moisture content of the respective mixes and unconfined compression tests were conducted. The values of dry density and molding water content used for specimen preparation for the mixes of soil and fly ash with glass fibers were the same values for mixes with corresponding fly ash content obtained from standard Proctor compaction test. The specimens were compacted in layers into a split mold of size 38 mm diameter and 76 mm height. Each specimen were carefully extracted from the split mold after compaction. Immediately after preparation, the specimens were kept inside desiccator. RESULTS AND DISCUSSION The CBR values of soil and soil-fly ash mixes reinforced with different contents of glass fibers are shown in Table 2. The interpretation of tests results such as effects of fiber content on CBR value of soil and soil-fly ash have been compared and discussed. Table 2. Percentage increase in CBR value of soaked and unsoaked specimen of soil-fly ash-glass fiber mixture Mix CBR (Soaked) Percentage increase in Mix CBR (Soaked) CBR (Unsoaked) CBR (Unsoaked) Percentage increase in CBR CBR S+0F+0G S+0F+0G S+10F+0G S+50F+0G S+10F+0.25G S+50F+0.25G S+10F+0.5G S+50F+05G S+10F+0.75G S+50F+0.75G S+10F+1G S+50F+1G S+30F+0G S+70F+0G S+30F+0.25G S+70F+0.25G S+30F+0.5G S+70F+05G S+30F+0.75G S+70F+0.75G S+30F+1G S+70F+1G

6 EFFECT OF GLASS FIBER CONTENT It was observed that the CBR value of soil when reinforced with glass fibers, increases significantly upto fiber content of 0.75% after which the increase in CBR value is very nominal. From Table 2 it can be seen that when the percentage of glass fiber is increased from 0 to 1%, the CBR value also increases from 5.69 to 22.98% with 50% fly ash content. The maximum increase in CBR value was obtained for soil with 50% fly ash and 1% glass fiber, with 304% increase in CBR over that of parent soil. Unconfined compressive strength also increased from 13 kpa to 215 kpa when fiber content is increased from 0 to 1% after 28 days of curing. The improved behavior of reinforced soil is due to properties such as soil-fiber interfacial friction and apparent cohesion induced due to moistening of the soil-fiber mix. As the fiber content increases, the contribution of the interfacial friction becomes greater. Moreover, due to soil-fiber interlocking, stress is transferred from soil to the fibers leading to the mobilization of tensile strength of fibers which in turn imparts this resisting force to the soil. EFFECT OF FLY ASH CONTENT It is observed from Table 3, 4, 5 and 6 that addition of fly ash increases the shear strength of the stabilized soil-fly ash mixes due to increase in availability of fly ash for pozzolanic reaction. The rate of gain in shear strength is high for higher fly ash content. However the increase in strength is significant upto 50% fly ash content and beyond which the increase is very marginal. Table 3 shows the percentage increase in unconfined compressive strength, q u due to addition of varying percentage of fly ash and glass fibers in soil specimens without curing. It was observed that the percentage increase in unconfined compressive strength, q u were 31, 285, 447 and 115% with fly ash content of 10, 30, 50 and 70% respectively without curing. Table 3 and 6 shows that with 50% fly ash content, unconfined compressive strength, q u increases from 13 to 71 kpaand 13 to 115 kpa for no curing and 28 days curing, respectively. It was also observed that the unconfined compressive strength had a nominal decrease when fly ash content was increased to 70%. Similar trend of increase in unconfined compressive strength, q u was reported by Ghosh and Subbarao, 2006; Kumar et al., The percentage increase in q u due to addition of 50% fly ash were 524, 616, 785% over that of parent soil after curing period of 7, 14 and 28 days respectively. This increase in shear strength of soil-fly ash mixes is due to the pozzolanic property of fly ash, which binds the soil particles together when mixed with water. Table 2 gives the CBR values with curing and without curing. The CBR value increases with increase in fly ash content upto 50% but decreased with 70% fly ash content. The increase in strength of soil is due to the pozzolanic property of fly ash which binds the soil particles together by filling in the voids when mixed with water thus making it a more hardened medium. Fly ash also acts as a binding agent between soil and fiber, giving a more effective interfacial friction, more tensile strength to glass fibers and more lateral strength to the soil- fly ash-glass fiber mix. When the percentage of fly ash is increased upto 70%, it surpasses the volume of the soil itself. Since the fly ash is more spherical in shape than soil particles, it leads to a lower interfacial friction and weaker lateral strength. Thus, a decrease in strength is observed at higher percentage of fly ash. EFFECT OF CURING PERIOD The rate of gain in shear strength with curing period for fly ash stabilized soil mixes has been compared in Figure 4. It was observed that the increase in q u is uniform till curing period of 21 days. Gosh and Subbarao, (2006) studied till 90 days curing period and observed that it increases significantly after 45 days curing up till 90 days of curing period. Similar type of behavior was reported by Consoli et al. (2001) for soil fly ash carbide lime mixture, where rate of gain in strength increased appreciably after 90 days of curing. Maher and Gray,(1990) suggested that the low shear strength gain at lower curing period may be due to low ph values of the pore fluid in the first few days. The pozzolanic reaction accelerates at a later stage of curing. In this study the maximumgain in strength was achieved for soil with 50%fly ash and 1% glass fiber at 28 days of curing, which is equal to 215 kpa that is 1555% increase in shear strength than that of plain soil. 352

7 Figure 4. Increase in UCS of soil with fly ash content from 0 to 70% at curing period of 7, 14 and 28 days Table 3. Percentage Increase in Unconfined Compressive Strength q u of Fly Ash stabilized Soil due to addition of varying percentage of Glass Fibers without Curing Mix q u (kpa) Percentage increase in q u Mix q u (kpa) Percentage increase in q u S+0F+0G 13 - S+0F+0G 13 - S+10F+0G S+50F+0G S+10F+0.25G S+50F+0.25G S+10F+0.5G S+50F+0.5G S+10F+0.75G S+50F+0.75G S+10F+1G S+50F+1G S+30F+0G S+70F+0G S+30F+0.25G S+70F+0.25G S+30F+0.5G S+70F+0.5G S+30F+0.75G S+70F+0.75G S+30F+1G S+70F+1G

8 Table 4. Percentage Increase in Unconfined Compressive Strength qu of Fly Ash stabilized Soil due to addition of varying percentage of Glass Fibers after 7 Days Curing Mix qu (kpa) Percentage increase in qu Mix qu (kpa) Percentage increase in qu S+0F+0G 13 - S+0F+0G 13 - S+10F+0G S+50F+0G S+10F+0.25G S+50F+0.25G S+10F+0.5G S+50F+0.5G S+10F+0.75G S+50F+0.75G S+10F+1G S+50F+1G S+30F+0G S+70F+0G S+30F+0.25G S+70F+0.25G S+30F+0.5G S+70F+0.5G S+30F+0.75G S+70F+0.75G S+30F+1G S+70F+1G Table 5. Percentage Increase in Unconfined Compressive Strength qu of fly ash stabilized soil due to addition of varying percentage of Glass Fibers after 14 Days Curing Mix qu (kpa) Percentage increase in qu Mix qu (kpa) Percentage increase in qu S+0F+0G 13 - S+0F+0G 13 - S+10F+0G S+50F+0G S+10F+0.25G S+50F+0.25G S+10F+0.5G S+50F+0.5G S+10F+0.75G S+50F+0.75G S+10F+1G S+50F+1G S+30F+0G S+70F+0G S+30F+0.25G S+70F+0.25G S+30F+0.5G S+70F+0.5G S+30F+0.75G S+70F+0.75G S+30F+1G S+70F+1G Table 6. Percentage Increase in Unconfined Compressive Strength qu of fly ash stabilized soil due to addition of varying percentage of Glass Fibers after 28 Days Curing. Mix qu (kpa) Percentage increase in qu Mix qu (kpa) Percentage increase in qu S+0F+0G 13 - S+0F+0G 13 - S+10F+0G S+50F+0G S+10F+0.25G S+50F+0.25G S+10F+0.5G S+50F+0.5G S+10F+0.75G S+50F+0.75G S+10F+1G S+50F+1G S+30F+0G S+70F+0G S+30F+0.25G S+70F+0.25G S+30F+0.5G S+70F+0.5G S+30F+0.75G S+70F+0.75G S+30F+1G S+70F+1G

9 Figure 5: Relation between CBR and UCS with 10 to 70% fly ash and 0.25 to 1% glass fiberwithout curing Figure 6: Relation between CBR and UCS with 10 to 70% fly ash and 0.25 to 1% glass fiberafter 7 days curing period 355

10 Figure 7: Relation between CBR and UCS with 10 to 70% fly ash and 0.25 to 1% glass fiberafter 14 days curing period Figure 8: Relation between CBR and UCS with 10 to 70% fly ash and 0.25 to 1% glass fiberafter 28 days curing period 356

11 CONCLUSIONS The strength characteristics of the soil were studied through CBR and unconfined compression tests. The soil was stabilized with 10-70% fly ash alone or in combination with glass fibers 0.2, 0.5, 0.75 and 1.0%. The specimens for unconfined compression test were cured for 7, 14 and 28 days. Effect of fly ash and glass fibers on CBR and UCS of soil were studied. The following conclusions may be drawn from the test results and the discussions presented herein. Stabilization of a sandy soil with fly ash up to 70%is effective to improve the strength characteristics. However it is effectively only upto 50% fly ash, beyond which the increase in soil strength is very nominal.when the percentage of glass fiber is increased from 0 to 1%, the CBR value of soil-fly ash also increases from 5.69 to 22.98%. The maximum increase in CBR value was obtained for soil with 50% fly ash and 1% glass fiber, which is about 304% more than that of plain soil. Addition of a small percentage of fly ash 0.25, 0.5, 0.75 and 1.0%along with fly ash to soil, enhances the gain in shear strength at curing periods of 7, 14 and 28 days. Addition of glass fibers delays the shear failure when cured. The unconfined compressive strength of soil with 50% fly ash and 1% glass fiber mixes was 215 kpa, which is 1555% more than that of the parent soil after 28 days curing. Soil stabilized with 30% fly ash and 1% glass fiber achieved unconfined compressive strength equal to 1401 kpa and thatof soil stabilized with 10% fly ash and 1% glass fiber was 916% both after 28 days curing. Thus it can be concluded that a sandy soil having low CBR and shear strength value can be stabilized to achieve higher CBR and shear strength. Such stabilized soil may find potential use in highway construction as subgrade and embankments. REFERENCES [1] Ambarish Ghosh and ChillaraSubbarao (2006). Strength Characteristics of Class F Fly Ash Modified with Lime and Gypsum J. Geotech. Geoenviron. Eng., 2007, 133(7): [2] Bureau of Indian Standards (BIS). (1980). Methods of test for soils; determination of water content dry density relation using light Compaction of Indian standard on soil engineering. IS 2720, Part 7, New Delhi, India. [3] Bureau of Indian Standards (BIS), ( 1970). Classification and Identification of Soils for General Engineering Purposes IS 1498: 1970, New Delhi, India. [4] Bureau of Indian Standards (BIS), (1985). Methods of test for soils; Grain Size Analysis IS 2720, Part 4, New Delhi, India. [5] Bureau of Indian Standards (BIS), (2002). Methods of test for soils; Laboratory determination of California Bearing Ratio (CBR) IS 2720, Part 16, New Delhi, India. [6] Bureau of Indian Standards (BIS), (1991). Methods of test for soils; Determination of Unconfined Comp ressive Strength IS 2720, Part 10, New Delhi, India. [7] Choudhary A. K. and Verma B. P. (2003), Shear Strength Characteristics of Reinforced Fly ash. Proceedings of Indian Geotechnical Conference, 2003, pp [8] Chandra S., Viladkar, M.N. and Nagrrale P.P., (2008). Mechanistic Apporoach for fiber reinforced flexible pavements Journals of Transportation Engineering, Vol. 134: [9] Chu, T. Y., Davidson, D. T., Goecker, W. L., and Moh, Z. C., (1955). Soil stabilization with lime -flyash mixtures: Preliminary studies with silty and clayey soils. Highway Research Board Bulletin, 108: [10] Consoli, N. C., Prietto, P. D. M., Carraro, J. A. H., and Heineck, K. S., (2001). Behavior of compacted soil-fly ash-carbide lime mixtures J. Geotech. Geoenviron. Eng., 1279: [11] Consoli, N.C., Montardo, J.P., Prietto, P.D.M., and Pasa, G.S., (2002). "Engineering behavior of sand reinforced with plastic waste" J. GeotechGeoenviron. Eng., ASCE, 128(6): [12] DiGioia, A. M., and Nuzzo, W. L., (1972). Fly ash as structural fills. J. Power Div., 98(1):

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