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dư lượng Red Từ Quặng Bauxite - dự án tại Lâm Đồng, Việt Nam
Inorganic Composite Material based on Fly Ash, Red Residue From Bauxite Ore for Road Building Projects in Lam Dong Vietnam Nguyen Van Chanh, 2Mitsuhiro Shigeishi, 3Tran Quoc Tho 1Department of Civil Engineering HCM City University of Technology, Vietnam Department of Civil and Environmental Engineering, Kumamoto University, Japan Department of Civil Engineering, HCM City University of Technology, Vietnam e-mail: nvchanh@hcmut.edu.vn ABSTRACT The paper present solidifying technology based on geopolymer theory of inorganic composite materials from bauxite, red residue from bauxite ore, fly ash and activators for road building projects in Vietnam This study describes physical properties and chemical compositions of bauxite, red residue, fly ash and the effects of bauxite-red residue-fly ash-activator mixes on the geotechnical properties of inorganic composite materials Mixture design and testing procedures for inorganic composite materials For mix proportion using 10-20% fly ash, red residue/bauxite ratio is 30/70, 6-8ml alkaline activator/100gr powder, maximum dry density 1.75-1.81 g/cm3 together with optimum water moisture 19-21% Plastic limit of bauxite modified by fly ash in range of 11-17%, liquid limit 19-25%, swelling of inorganic composite materials 0.5-1.0%, water absorption gets 6.5-8.5%, compressive strength in range of 55-80 kgf/cm2, compressive strength in dry condition/compressive strength in water-saturated condition ratio 0.85-0.90, splitting tensile strength 13-19 kgf/cm2, modulus of elasticity 5800-8000 kgf/cm2 New inorganic composite materials have high durability and ability to water resistance in dry-wet cycle The presentation also show microstructure analysis of inorganic composite materials based on bauxite residue, fly ash and activators by X-Ray CT Analysis, X-ray diffraction analysis, differential thermal analysis/Thermogravimetric Analysis (DTA/TG), transmission electron microscopy (TEM) display high density, modified microstructure of inorganic composite materials Construction method of road using inorganic composite materials will be presented Keywords: Bauxite; Red residue; Fly ash; Inorganic composite materials; Mix proportions; Road construction; Geopolymer technology INTRODUCTION Researching in composite materials from bauxite, red mud, fly ash and activators for building up rural road of highland region in Vietnam Research is based on the mechanism of composite materials stabilization with bauxite, red mud, fly ash and alkaline activators The method of study is based on examining factors that influence in physico-mechanical properties of composite materials Since then, we find out the proper proportions of materials for rural road construction Bauxite is an heterogeneous material composed mainly of aluminum hydroxide minerals (gibbsite which is the trihydrate, diaspore and boehmite which are the monohydrates) The principal impurities common to nearly all known deposits of bauxite are aluminum silicates (clays), iron and titanium oxides The quantity of impurities varies from one deposit to another as does the proportion of trihydrate to monohydrates [1] [2] Chemical composition of bauxite soil consist of much sesquioxide of ferrite and aluminum and other compositions Sesquioxide ratio is different from the layers In some cases, ferrite is up to 90%, while aluminum is less than 5%, in other cases, ferrite is less than 4%, while aluminum is up to 60% Silica is in the chemically bound phase and is present in kaolinite [1] [2] Figure Raw bauxite deposit in Vietnam [1] Figure Chemical composition of bauxite [1] Characteristics of red mud: The most noticeable impacts of bauxite mining and alumina production is red-mud Red mud is mainly a by-product of the Bayer process, composed of the impurities in the bauxite that are not dissolved in the refining process The amount that is generated per ton of alumina produced varies between 0.3 tons to 2.5 tons, depending on the grade of bauxite used [2][3] It is a mixture of compounds originally present in the parent mineral, bauxite, and of compounds formed or introduced during the Bayer cycle It is disposed as a slurry having a solid concentration in the range of 10-30%, pH in the range of 13 and high ionic strength A chemical analysis would reveal that red mud contains silica, aluminum, iron, calcium, titanium, as well as an array of minor constituents, namely: Na, K, Cr, V, Ni, Ba, Cu, Mn, Pb, Zn etc Typical values would account: Fe2O3 = 30-60wt%, Al2O3 = 10-20wt%, SiO2 = 350wt%, Na2O = 2-10wt%, CaO = 2-8wt%, TiO2 = trace-25wt% [2] [3] Mineralogically, red mud has a very high number of compounds present The more frequent addressed are: hematite (Fe2O3), goethite Fe(1-x)AlxOOH (x=0-0.33), gibbsite Al(OH)3, boehmite AlO(OH), diaspore AlO(OH), calcite (CaCO3), calcium aluminum hydrate (x.CaO.yAl2O.zH2O), quartz (SiO2), rutile (TiO2), anatase (TiO2), CaTiO3, Na2TiO3, kaolinite Al2O3.2SiO2.2H2O, hydroxycancrinite (NaAlSiO4)6.NaOH.H2O, sodalites, aluminum silicates, chantalite CaO.Al2O3.SiO2.2H2O, hydrogarnet cancrinite (NaAlSiO4)6.CaCO3, Ca3Al2(SiO4)n(OH)12-4n [2] [3] Red mud is a very fine material in terms of particle size distribution Typical values would account for 90 volume % below 75µm The specific surface (BET) of red mud is around 10m2/g [3] GEOPOLYMER ACTIVATION MECHANISM OF INORGANIC COMPOSITE MATERIALS The purpose of composite materials stabilization is: to create stable molecule structure like inorganic materials in natural condition If elements of material bind together through certain methods or chemical reactions, materials will possess good property of natural stone With presence of fly ash (containing SiO2 and Al2O3) and bauxite, red residue (containing Al2O3 and Fe2O3), Al and Si can combined together through coordination linkage with oxygen when activated by alkaline and suitable temperature [5] Polymerization reactions are conducted as following: Geopolymerization is a modification of microstructure in materials to form stable silicate skeletons Reaction conditions are presence of alkali catalyst and a temperature range 40100oC, atmospheric pressure condition [4] Geopolymerization involves a chemical reaction of Al-Si materials under highly alkaline conditions, yielding polymeric Si-O-Al-O bonds Its chemical structure can be described by Mn{-(SiO2)z – AlO2}n wH2O, where “M” is a cation such as potassium, sodium or calcium, “n” is a degree of polymerization, and “z” is 1,2 or [4] Depend on Si/Al ratio, lattices are formed as following: (-Si-Al-O-) poly(sialate), (-Si-OAl-O-Si-O-) poly(sialate-siloxo, (-Si-O-Al-O-Si-O-Si-O-) poly(sialate-disiloxo) [4] Figure Some lattices formed by polymerization [4] EXPERIMENT ON PROPERTIES OF BAUXITE, RED RESIDUE AND FLY ASH Bauxite and red residue after selection of bauxite ore were taken from Bauxite Company in Lam Dong province, Vietnam Fly ash from Formosa Company, Dong Nai province Alkaline activator: Natri silicate solution, density of 1.440, Na2O = 10%, SiO2 = 28%, concentration of 12M, modulus silicate of 2.4 A Chemical Composition Analysis of Bauxite and Red Residue Bauxite and red residue have high content of Al2O3, respectively 37.6% and 34.2% The amount of SiO2 is rather low (9.8% and 16.7% respectively) Especially, Fe2O3 is high in bauxite and red residue (44.3% and 41.9%, respectively) TABLE CHEMICAL COMPOSITION OF BAUXITE AND RED RESIDUE Samples Bauxite Red residue Chemical composition (%) Al2O3 SiO2 Fe2O3 TiO2 CaO L.O.I 37.60 9.80 44.30 7.00 0.05 1.25 34.20 16.70 41.90 6.00 0.10 1.10 B X-Ray and Scanning Electron Microscopy of Bauxite Figure SEM of bauxite The results in X-ray analysis of bauxite and red residue show that they have the same mineral composition of gibbsite 54.70-45.15%, goethite 27.22-28.84%, hematite 6.45-10.08%, quartz 1.52-1.08% Through SEM and TEM analysis, shape of minerals in bauxite exists in layer and flake, condensed tube-shape Quartz Rutile Hematite Gibbsite Goethite Mullite 2:1 Anatase Titanomagnetite Perowskite 70,000 60,000 50,000 40,000 30,000 20,000 1.52 % 1.35 % 6.45 % 54.70 % 27.22 % 2.61 % 1.66 % 2.33 % 2.16 % 10,000 -10,000 -20,000 -30,000 -40,000 10 15 20 25 30 35 40 45 50 55 60 Figure X-ray diffraction of bauxite Figure TEM analysis of bauxite C Sieve Analysis of Bauxite soil Group of grading particles contribute compaction capacity of soil Fine particles (less than 0.075mm) have properties such as: high specific surface area, water-retaining property, water absorption, volume change and shrinkage, flexibility; these properties cause instability of bauxite attacking to water [7] 100 90 Percent passing (%) 80 70 60 Red residue Bauxite 50 40 30 20 10 10 0.1 0.01 0.001 Particle size (mm) Figure Grading curve of bauxite and red residue D Atterberg limit of bauxite and red residue TABLE ATTERBERG LIMIT OF BAUXITE AND RED RESIDUE Atterberg limit, % Sample Liquid limit Plastic limit Plastic Index Density Bauxite Red residue 34.25 45 23.29 26.83 10.96 18.17 Bulk density (g/cm3) 2.51 - 1.52 - E Physico-Chemical and Mineral Composition Analysis of Fly Ash Test results show that fly ash have high total content of SiO2 Al2O3 (88.4%) and high value of fineness passing 0.05mm screen is 93.5%, density 2.4 g/cm3, active index 90.7% Test result of X-ray analysis of fly ash proved the present of specific peak SiO2 in unidentified form and peaks mullite, quartz TABLE CHEMICAL COMPOSITION OF FLY ASH SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O TiO2 P2O5 (%) (%) (%) (%) (%) (%) (%) (%) (%) 53.9 34.5 4.0 0.4 0.7 0.3 1.7 0.06 d=3.35201 150 1.0 140 130 120 110 90 80 d=1.22551 d=1.38295 d=1.37278 d=1.82171 d=2.21060 d=2.12612 d=1.54423 d=1.52469 20 d=2.28569 d=2.88432 30 d=2.69550 40 d=2.54964 d=5.39393 50 d=2.46126 60 d=3.43584 d=3.40314 70 d=4.26195 Lin (Counts) 100 10 11 20 30 40 50 60 70 2-Theta - Scale 29_MAU_QUOC THO_5 - File: 29_MAU_QUOC THO_5.raw - Type: 2Th/Th locked - Start: 10.000 ° - End: 79.990 ° - Step: 0.030 ° - Step time: s - Temp.: 25 °C (Room) - Time Started: 16 s - 2-Theta: 10.000 ° - Theta: 5.000 ° - Chi: 0.00 00-015-0776 (I) - Mullite, syn - Al6Si2O13 - WL: 1.5406 - Orthorhombic - a 7.54560 - b 7.68980 - c 2.88420 - alpha 90.000 - beta 90.000 - gamma 90.000 - Primitive - Pbam (55) - 167.353 - I/Ic PDF - F30= 60(0.0135,37) 00-046-1045 (*) - Quartz, syn - SiO2 - WL: 1.5406 - Hexagonal - a 4.91344 - b 4.91344 - c 5.40524 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primitive - P3221 (154) - - 113.010 - I/Ic PDF 3.4 - F30=539(0.0018,31) Figure The result of X-ray diffraction analysis of fly ash EXPERIMENT ON PHYSICO-MECHANICAL PROPERTIES OF INORGANIC COMPOSITE MATERIAL The method of study is based on examining factors that influence in physico-mechanical properties of composite materials The objective is to find out the proper proportions of materials for rural road construction through parameters such as: compressive strength, flexural strength and splitting tensile strength, water absorption and water resistance, Proctor compaction test, modulus of elasticity [6], [8], [9] After casting, specimen is kept in the ambient condition, then specimens are dried Time for drying : hours Drying temperature: 105oC After drying, specimens are cured into air condition and water saturated condition Figure Sampling process in laboratory A Moisture-Density relationships and Swell values Figure 10 show considerable improvement on compaction properties of inorganic composite materials with presence of fly ash Mix proportion using bauxite, 10-20% fly ash, 6-8% activators, max dry density 1.72-1.78 g/cm3, optimum moisture 21% 8%Quicklime (Bauxite/Red residue =70/30) 1.8 1.85 1.6 1.4 Expansion (%) DRY DENSITY (g/cm3 ) 1.80 1.75 1.70 1.65 1.2 0.8 0.6 0.4 1.60 1.55 18.0 19.0 20.0 21.0 MOIS TURE (%) 22.0 0.2 23.0 24.0 Figure 10 Moisture-Density relationships of bauxite + 20% fly ash combined with (1) 4%, (2) 6%, (3) 8% and (4) 10% alkaline silicate activators 10 20 % Fly ash Figure 11 Swell values of inorganic composite materials Incorporation of Class F fly ash reduced soil plasticity and reduced the potential for swelling Use of fly ash for stabilization could be sufficient to improve soil properties to desired levels B Compressive Strength and Splitting Tensile Strength With an increase of 10-20% fly ash, 8-10% activators, compressive strength of inorganic composite materials get 70-80 kgf/cm2, splitting tensile strength 10-20 kgf/cm2 Increasing in strength is due to geopolymer activation mechanism of inorganic composite materials based on bauxite and fly ash Figure 12 Compressive strength test and sample damaged Figure 13 Splitting tensile strength and modulus of elasticity test 18 16 14 12 10 20 2 10 (kgf/cm ) 28 day compressive strength 28 day splitting tensile strength (kgf/cm ) 22 85 80 75 70 65 60 55 50 45 40 35 30 25 11 4 10 11 % Activators % Activators Figure 14 The relationship between activators and compressive strength, splitting tensile strength (1/ 0% Fly ash +8% quicklime ; 2/ 10% Fly ash +8% quick lime; 3/20% Fly ash +8% quicklime ; 4/10% Fly ash; 5/20% Fly ash) Bauxite incorporated of class F fly ash and activators significantly improves the strength very quickly This benefit is particularly important because the heaviest loads to be placed on the subgrade often occur during construction of the road and the development of associated properties C Modulus of Elasticity 28 day modulus of elasticity (kgf/cm ) 9000 8000 7000 6000 5000 4000 3000 2000 1000 10 11 % Activators Figure 15 The relationship between activators, fly ash and modulus of elasticity (1/ 0%Fly ash +8% quicklime; 2/ 10% Fly ash +8%quicklime; 3/20%Fly ash+8%quicklime; 4/10% Fly ash+; 5/20% Fly ash) Presence of activator, fly ash influences in compressive strength When using of 4-10ml activator/100gr powder and 10-20% fly ash, modulus of elasticity (6000-8000 Kgf/cm2) increase up to 20% D Water absorption and water resistance factor: 0.92 0.90 0.88 0.86 Water absorption (%) Water resistance factor 0.94 0.84 0.82 0.80 0.78 10 12 11.5 11 10.5 10 9.5 8.5 7.5 6.5 5.5 5 11 4 10 11 % Activators % Activators Figure 16 The relationship between activators and water absorption, water resistance factor (1/ 0%Fly ash +8%quicklime; 2/ 10%Fly ash +8%quicklime; 3/20%Fly ash +8%quicklime; 4/10%Fly ash; 5/20%Fly ash Mix proportion using bauxite combined with 10-20% fly ash, 6-8ml activator/100gr, water absorption 6.5-8.0% With an increase of fly ash and activator, water resistance factor increase dramatically Compressive strength of materials in water-saturated condition get 85-90% compared to of materials in dry condition EXPERIMENT ON CHEMICAL COMPOSITION AND MICROSTRUCTURE ANALYSIS OF INORGANIC COMPOSITE MATERIAL A X-ray diffraction and Infrared spectroscopy (IR) Result of mineral composition of composite : quartz 9.48%, sodalite 1.23%, hematite 9.33%, gibbsite 40.76%, goethite 22.52%, mullite 5.52% (Figure 17) Infrared spectroscopy (IR) can yield information concerning structural detail of the material are show in figure 18 Quartz Sodalite Hematite Gibbsite Goethite Mullite 2:1 Gypsum Titanomagnetite Perowskite 35,000 30,000 25,000 20,000 15,000 10,000 9.48 % 1.23 % 9.33 % 40.76 % 22.52 % 5.52 % 7.80 % 1.71 % 1.66 % 5,000 -5,000 -10,000 -15,000 -20,000 10 15 20 25 30 35 40 45 50 55 60 Figure 17 X-ray diffraction result of composite (red residue 22% + Bauxite soil 50% + lime 8% + fly ash 20% + alkaline activator 8%) Figure 18 IR result of composite red residue 22% + Bauxite soil 50% + lime 8% + fly ash 20% + alkaline activator The intense bands occur at 420, 434, 473, 532, 558 cm-1 for mode of the O-Si-O, at 663, 735, 798 877 cm-1 mode of O-Si-O or Si-O-Al in zeolite The intense bands occur at 9501000 cm-1 mode of gel aluminosilicat Si-O and Al-O, at 1400-1700 cm-1 for mode of geopolymer Si-O-Al The absorbance band in between the wave number 950-1400 cm-1 in the IR spectrum of fly ash – bauxite – alkaline activator composite represent the presence of substituted Al atoms in the forms of silica frame work Geopolymerization involves a chemical reaction of Al-Si materials under highly alkaline conditions, yielding polymeric Si-O-Al-O bonds B Transmission Electron Microscopy (TEM) Important component of the binder phase is formed in the geopolymer process of the crystal structure is nanoscale Nano-crystalline aluminosilicate materials in the form of gel is amorphous in bauxite soil, red sludge also contributes to forming a binder with high performance Microstructure of geopolymer with inorganic nanometer level are given in Figure 19 C X-ray CT Analysis This method allows assessment of the extent of the compact structure and material composition of each solid phase Which can demonstrate the ability to create a compacted form, the combination creates fusion materials compact structure, thereby enhancing the physical properties of materials and capabilities for water resistence well improved In one section of composite materials (Figure 20), we can see the consistency of synthetic soil material bauxite, fly ash Xray diffraction diagrams corresponding CT has changed the type of diffraction at a location containing fly ash is micro porous structure Figure 19 Microstructure of inorganic composite materials based on bauxite, red residue and fly ash activated by alkaline activator for at 105oC Figure 20 X-ray CT analysis of inorganic composite materials EXPERIMENTAL CONSTRUCTION OF ROAD IN SITE USING INORGANIC COMPOSITE MATERIAL Preparing the base layer: Using motor grader to windrowing along the center of road, the base layer need to be smooth, horizontal slope is as designed and the base is compacted with compacting factor ≥0.95 [6], [10], [11] Figure 21 Preparation of subgrade Figure 22 Mixing process of materials for road Figure 23 Grader for leveling work Figure 24 Road roller for compaction Fly ash, bauxite, red residue, dry quicklime, alkaline activator are mixed Spread out the mixture of the specific content into the thin layer by using grader Using road roller and watering during compacting Finishing After compaction is finished, the pavement is dried by sun shining The compaction on a small area is carried out for compacting factor Then, determine the number of compaction of each roller to get the maximum compaction capacity The required compaction is 0.95 γ k max ( γ k max is maximum dry density, determined by Proctor compaction test) [6] [10] CONCLUSION Residue from bauxite ore can be successfully solidified by the geopolymer technique by blending fly ash as active filler with alkaline activator The effective requirement of blending fly ash is generally 20% and more Inorganic composite materials based on bauxite, fly ash and red residue have high strength and ability to water resistance Geopolymerization involves a chemical reaction of Al-Si materials, modifying structure of composite material with stable skeleton based on formation of stable frameworks in materials with -Si-O-Al-O- geopolymer sequence For mix proportion using 10-20% fly ash, red residue/bauxite ratio is 30/70, 6-8ml alkaline activator/100gr powder, maximum dry density 1.75-1.81 g/cm3 corresponding with optimum water moisture 19-21% Plastic limit of bauxite modified by fly ash in range of 11-17%, liquid limit 19-25%, swelling of inorganic composite materials 0.5-1.0%, water absorption gets 6.58.5%, compressive strength in range of 55-80 kgf/cm2, compressive strength in dry condition/compressive strength in water-saturated condition ratio 0.85-0.90, splitting tensile strength 13-19 kgf/cm2, modulus of elasticity 5800-8000 kgf/cm2 Inorganic composite materials showed good properties for construction of road surface and increased the durability of road ACKNOWLEDGMENT We wish to thank Japan International Cooperation Agency (JICA) and Ho Chi Minh city University of Technology for supporting to this research through SUPREM-HCMUT Program REFERENCES [1] Vietnam National Coal – Mineral Industries Group – Vinacomin, Conference in sustainable development of aluminum industry in highland, Vietnam, September (2009) [2] W Kurdowski, F Sorrentino, in "Waste Materials Used in Concrete Manufacturing", Edited by Satish Chandra, William Andrew Publishing/Noyes, (1997), pp 290-308 10 [3] A R Hind, S K Bhargava, Stephen C Grocott, "The surface chemistry of Bayer process solids: a review", Colloids and Surfaces Physicochem Eng.(1999), pp 359–374 [4] Joseph Davidovits, “Geopolymer chemistry and applications”, (2008) [5] A Ferna´ndez-Jime´nez, A Palomo*, M Criado, “Microstructure development of alkaliactivated fly ash cement: a descriptive model”, Cement and Concrete Research 35, (2005) [6] Vietnam Standard and acceptance of soil stabilized by lime 22TCN 229-95 [7] Vietnam Standard TCVN 4198-95, “Soil for construction, methods for determination of grade curve, Atterberg limits of soil in laboratory”, (1995) [8] Modified Proctor compaction Test AASHTO T180-90 [9] R L Parsons and E Kneebone, Department of Civil and Environmental Engineering, University of Kansas, Lawrence, “Field performance of fly ash stabilised subgrades”, Ground Improvement 9, No 1, USA, (2005), pp.33–38 [10] Department of the army, the navy, and the air force, “Soil stabilization for pavements”, October (1994) [11] M A Rahman, Department of Civil Engineering, University of Ife, “Effects of Cement-Lime Mixes on Lateritic Soils for use in Highway Construction”, Building and Environment, Vol 22, No 2, Nigeria, (1987), pp 141-145 11 ... Si/Al ratio, lattices are formed as following: (-Si-Al-O-) poly(sialate), (-Si-OAl-O-Si-O-) poly(sialate-siloxo, (-Si-O-Al-O-Si-O-Si-O-) poly(sialate-disiloxo) [4] Figure Some lattices formed by... 16 s - 2-Theta: 10.000 ° - Theta: 5.000 ° - Chi: 0.00 0 0-0 1 5-0 776 (I) - Mullite, syn - Al6Si2O13 - WL: 1.5406 - Orthorhombic - a 7.54560 - b 7.68980 - c 2.88420 - alpha 90.000 - beta 90.000 - gamma... 90.000 - Primitive - Pbam (55) - 167.353 - I/Ic PDF - F30= 60(0.0135,37) 0 0-0 4 6-1 045 (*) - Quartz, syn - SiO2 - WL: 1.5406 - Hexagonal - a 4.91344 - b 4.91344 - c 5.40524 - alpha 90.000 - beta