Applied Clay Mineralogy Phần 9 ppt

goethite, the firing temperature and degree of vitrification, the propor- tion of alumina, lime, and magnesia in the clay material, and the com- position of the fire-gases during burning (Butterworth, 1953). The best white firing clays contain less than 1% Fe 2 O 3 . B tan-burning clays con- tain between 1% and 5% Fe 2 O 3 , and red-firing clays contain 5% or more Fe 2 O 3 . Common clays occur in a variety of environments and in many differ- ent rocks across all time periods of the geologic record. The source clay material can be glacial clay, soils, alluvium, loess, shale, weathered and fresh schist, slate, argillate, and underclays or seat earths. 2. LIGHTWEIGHT AGGREGATE Certain common clays are used to produce lightweight aggregate. The American Society for Testing Materials has published a standard spec- ification governing lightweight aggregates for concrete (Code No. C330- 53 T, 1955). The unit weight of fine lightweight aggregate cannot exceed 70 lb/ft 3 and the unit weight of coarse lightweight aggregate cannot exceed 55 lb/ft 3 . Clay and/or shale, which is a common clay, is used as the raw ma- terial to make lightweight aggregate. The raw material is crushed and fed into a rotary kiln or sintering machine. The raw material is heated rapidly up to the range between incipient and complete fusion. The bloating and vesiculation require the presence of substances that release gas after fusion has developed a molten jacket around the particles to prevent the escape of the gas. The molten jacket must be viscous enough to prevent the escape of the expanding gas. Conley et al. (1948) and Riley (1951) have investigated the causes of bloating. Several factors are important, most of which are based on chemical and mineralogical composition. Shales and clays containing illites, chlorite, some montmorillonite, and mixed-layer clays are the most promising sources to make lightweight aggregate. A close relationship exists between the chemical composition and the bloating characteristics of clay and shale. Riley (1951) concluded that the viscosity of the melt produced by firing is determined essentially by the bulk chemical composition based on SiO 2 ,Al 2 O 3 , and the total of CaO, MgO, FeO, Fe 2 O 3 ,K 2 O, and Na 2 O in which optimum viscosity of the molten jacket might be expected. Fig. 19 shows the limits of bloating established by Riley (1951). This was verified by Murray and Smith (1958) in their study of some Indiana shales. Clays and shales of various Applied Clay Mineralogy144 geologic age and from many formations are used to make lightweight aggregate (Cole and Zetterstrom, 1954; Greaves-Walker et al., 1951; Mason, 1951; Plummer and Hladik, 1951; Burwell, 1954). REFERENCES Burwell, A.L. (1954) Lightweight Aggregate from Certain Oklahoma Shales. Oklahoma Geological Survey, Mineral Report 24, pp. 1–20. Butterworth, B. (1953) The Properties of Clay Building Materials in Ceramics— A Symposium. Green, A.T. and Stewart, G.H., eds. British Ceramic Society , London, England, pp. 824–877. Cole, W.A. and Zetterstrom, J.D. (1954) Investigation of Lightweight Aggregates of North and South Dakota. US Bureau Mines, Report of Investigation 5065, 1043pp. Conley, J.E., Wilson, H., and Klinefelter, T.H. (1948) Production of Lightweight Concrete Aggregates from Clays, Shales, Slates and Other Materials. US Bu- reau of Mines, Report of Investigation 4401, 121pp. Greaves-Walker, A.F., et al. (1951) The development of lightweight aggregate from Florida clays. Eng. Ind. Exp. Station Bull. Ser., 116, 1–24. Holdridge, D.A. (1953). The Colloidal and Rheological Properties of Clays in Ceramics—A Symposium. Green, A.T. and Stewart, G.H., eds. British Ce- ramic Society, London, England, pp. 60–93. Hyslop, J.F. (1953) The Action of Heat on Clays in Ceramics—Symposium. Green, A.T. and Stewart, G.H., eds. British Ceramic Society, pp. 186–200. Mason, R.S. (1951) Lightweight Aggregate Industry in Oregon. GMI Short Pa- per 21, 23pp. Murray, H.H. (1994) Common clay. Chapter in Industrial Minerals and Rocks, 6th Edition. Carr, D.D., ed. Society for Mining, Metallurgy and Exploration, Littleton, CO, pp. 247–248. Murray, H.H. and Smith, J.M. (1958) Lightweight Aggregate Potentialities of Some Indiana Shales. Industrial Geological Survey, Report of Progress 12, 42pp. Norton, F.H. (1948) Fundamental study of clay, VIII, a new theory for the plasticity of clay–water masses. J. Am. Ceram. Soc., 31, 236. Plummer, N. and Hladik, W.B. (1951) Manufacture of lightweight concrete aggregate from Kansas clays and shales. State Geol. Surv. Kansas Bull., 91, 1–100. Ries, H. (1927) Clays, Their Occurrence, Properties and Uses. John Wiley and Sons, New York, 613pp. Riley, C.M. (1951) Relation of chemical properties to the bloating of clays. J. Am. Ceram. Soc., 34, 1–20. Chapter 8: Common Clays 145 This page intentionally left blank Appendix Appendices A–D describe the test procedures for identifying and evaluation of kaolins, ball clays, bentonite, palygorskite–sepiolite, and common clays. The following tests apply to all the above-mentioned clays: 1. X-ray diffraction to determine the mineral content of the crude and degritted sample. 2. Percent grit (+325 mesh). 3. pH. 4. Particle size distribution of the degritted sample. The identification of the clay minerals and the non-clay minerals is necessary to determine the amount and type of clay and non-clay minerals present. For example, generally the quartz and micas are concentrated in the grit (+325 mesh) portion of the clay. Also, the grit is generally removed from the clay during processing so that the percent recovery of the portion which is À325 mesh can be calculated. The pH of the sample gives an indication of the presence of soluble salts, which may be deleterious to the final product. Some kaolins have an alkaline pH which may indicate the presence of calcium and sodium salts which if they cannot be removed by processing will cause high viscosity for paper use and cause a lower temperature of vitrification in ceramic utilization. Also, in the use of kaolins in paint there is a conductivity maximum and the presence of soluble salts may cause a conductivity which exceeds the specification. In ceramic kaolins and ball clays, the presence of montmorillonite can cause excess shrinkage, slow casting rate, and a short and low temperature vitrification range. In bentonites it is necessary to identify whether or not the clay is a sodium, calcium, or magnesium variety. This can generally be identified by the c-axis d-spacing as sodium montmorillonite has a 12.2 A ˚ spacing and calcium and magnesium montmorillonites have a 14.2–14.8 A ˚ d-spacing. In kaolins, ball clays, bentonites, and palygorskite–sepiolite clays, a high grit per- centage is detrimental. In common clays depending on the type of structural clay product for which it is used, a higher grit percentage may be tolerated. 147 This page intentionally left blank Appendix A COMMONLY USED TESTS AND PROCEDURES FOR EVALUATING KAOLIN SAMPLES Commonly used tests and procedures for evaluating kaolin samples are as follows: 1. Crude clay X-ray diffraction 2. Crude clay moisture 3. Percent grit (+325 mesh) (screen residue test) 4. Degritted X-ray diffraction 5. Crude clay pH 6. Crude clay brightness 7. Degritted clay brightness 8. Crude clay particle size 9. Crude clay Brookfield viscosity 10. Crude clay settling procedure 11. Leaching and brightness test 12. Magnetic separation 13. High shear (Hercules) viscosity 14. Processed clay Brookfield viscosity 15. Processed clay particle size 16. Processed clay brightness 17. Conductivity measurement 1. X-ray diffraction: Pulverize about 2 g of sample to À325 mesh. Press the pulverized clay in the sample holder. Follow operating procedures of the X-ray diffraction unit. 2. Crude clay moisture 2a. Apparatus Balance sensitive to 0.1 g Ceramic dish Drying oven to operate at 105721C 2b. Procedure Weigh 200 grams (to the nearest 0.1 gram) of crude clay into a ceramic dish of known weight. Place in an oven set at 1051731C and allow to dry overnight. Remove from oven and weigh to the nearest 0.1 gram. 2c. Calculation % moisture ¼ weight loss initial weight of clay  100 3. Percent grit: material coarser than 325 mesh 3a. Apparatus 325 mesh (44 mm) US standard sieve Ceramic dish 149 Balance sensitive to 0.1 g Drying oven to operate at 105721C Sodium hexametaphosphate Soda ash Small brush Waring blender 3b. Procedure Dry approximately 200 g of crude clay overnight at 105 1C. Mix 5 lb/ton equi- valent calgon and 1 lb/ton equivalent soda ash in 500 ml water and mix on the Waring blender. Add 100 g oven dried clay to the mixer cup and mix on low speed for 3 min.Sieve the slurry through a 325 mesh sieve. If a crude particle size is needed, collect screened slurry in a bucket. Rinse screen until all clay has been washed through the sieve. Closely observe residue remaining on sieve. If a significant amount of unblunged clay remains, rinse residue back into Waring container with 500ml water and mix an additional 3 min. Screen the sample as above. Place screen in oven until dry. Brush residue from screen using small paintbrush into a tared ceramic bowl. Weigh residue to the nearest 0.1 g and record. After sample is degritted, the À325 mesh portion should be X-rayed to determine the mineral content of the degritted sample. 4. Degritted x-ray diffraction: Pulverize about 2 g of sample to À325 mesh. Press the pulverized clay in the sample holder. Follow operating procedures of the X-ray diffraction unit. 5. Crude clay pH test 5a. Apparatus pH meter Balance sensitive to 0.1 g 250 ml beaker Deionized water Spatula 5b. Procedure Weigh 40 g of pulverized clay into a 250 ml beaker. Add 160 ml of deionized water and stir well with a spatula until free of ‘‘lumps.’’ Measure pH. 6. Crude clay brightness 6a. Apparatus Brightness meter Ceramic dish Drying oven to operate at 105721C Brightness ring and press Micro-pulverizer Balance sensitive to 0.1 g 6b. Procedure Grind the sample to a fine powder (o100 mesh) in a pulverizer. Degritted kaolin should be pulverized for 2 min. Do not use the mortar and pestle. Pack the sample in the brightness meter holder using 32.65 lb of pressure. 7. Degritted clay brightness: Dry the degritted clay and follow the procedure described in item 6. Applied Clay Mineralogy150 8. Crude clay particle size 8a. Apparatus Balance sensitive to 0.1 g Waring blender and container Deionized water Plastic 250 ml bottle 250 ml flask 1000 ml beaker 8b. Procedure Using the sample from the crude residue test, determine the percent solids using a 250 ml flask. Determine dry clay content in the 250 ml flask. Dilute percent solids to 7% using a 1000 ml beaker and mix for 3 min in a mixer. Weigh 200 g slurry (14 g dry clay) into a 250 ml plastic bottle labeled with the sample iden- tification. Submit sample for Sedigraph testing. 8c. Sedigraph procedure 8c.1. Sample preparation Prepare a 7% by weight solution of clay in water totaling 200 g. (For dry clay use 14 g in 186 ml of water; for slurry clay determine the percent solids and calculate the necessary amount of water to add to reach a 7% solution at 200 g of total weight.) Mix on medium speed for 8 min in Hamilton Beach blender. Agitate for 2–3 min using Lightnin mixer and pour sample into the Sedigraph cup. 8c.2. Sample analysis Follow procedure provided by Sedigraph. 8d. Apparatus Bouyoucos hydrometer 1 l graduated cylinder (2.5 in. diameter) (a larger cylinder may be used, i.e. 1205 ml soil sample cylinder) Rubber stopper to fit graduated cylinder Thermometer Constant temperature water bath (19.41C) (a constant temperature room may be used if a water bath is not available) High-speed mixer (Hamilton Beach Model 936) Table 1: Temperature correction values for hydrometer reading Table 2: K N correction coefficients for variation in viscosity of suspending me- dium Table 3: Maximum particle size equivalents Table 4: K L correction coefficients for a given hydrometer number 8.1. Particle size test, hydrometer method 8.1a. Apparatus Bouyoucos hydrometer 1 l graduated cylinder (2.5 in. diameter) (a larger cylinder can be used, i.e. 1205 ml soil sample cylinder) Rubber stopper to fit graduated cylinder Thermometer Constant temperature water bath (19.41C) (a constant temperature room may be used if a water bath is not available) High-speed mixer (Hamilton Beach Model 936) Table 1: Temperature correction values for hydrometer reading Table 2: K N correction coefficients for variation in viscosity of suspending medium Appendix A 151 Table 3: Maximum particle size equivalents Table 4: K L correction coefficients for a given hydrometer number 8.1b. Procedure Particle size distribution is checked by adding 700 ml of deionized water to 50 g of clay (if a larger cylinder is used, the test specimen should be increased accordingly) and agitating it in the Hamilton Beach Model 936 or other high-speed mixer for 8 min on medium speed. Transfer sample to a 1 l grad- uated cylinder and dilute to the 1000 ml mark. Stopper and shake the cylinder to mix the sample and place it in a controlled temperature bath. Gently immerse the hydrometer into the cylinder, allow it to stabilize, and take reading. Re- cord the temperature as well. This is made easier by using a stopper to suspend the thermometer in place. (If testing more than one sample at a time, be sure to wipe off both the hydrometer and thermometer before placing them into the next sample to avoid contamination.) Read the hydrometer to 0.2 g/l and the temperature to 0.2 1C at 1, 3, 10, 20, 60, 100, 200, 300, and 400 min settling time. 8.1c. Calculations To find the correct grams per liter, add or subtract the appropriate amount shown in Table 1 to or from the actual hydrometer reading. To find the percent in suspension, divide each of the corrected grams per liter by the highest reading. Use the following equation to determine the corrected particle diameter at each sampling time: D t ¼ D a ÂK L ÂK N where: D t ¼ particle diameter in microns D a ¼ maximum particle diameter in microns from Table 3 K L ¼ hydrometer correction coefficient from Table 4 K N ¼ correction coefficient from Table 2 8.1d. Theory To determine particle size with a Bouyoucos hydrometer, use is made of Stokes’ law. The maximum diameter of particles in a suspension, based on Stokes’ law for assumed conditions, is expressed by the following equation: D a ¼ ffiffiffiffiffiffiffiffiffiffiffi 30nL p 980ðG À G 0 ÞT where: D a ¼ maximum particle diameter in millimeters (equivalent spherical diameter) n ¼ coefficient of viscosity of suspending medium in poise (in this case, 671F ¼ 0.0102) L ¼ distance in centimeters through which the particles settled (32.5 cm) G ¼ specific gravity of clay particles (2.65 assumed for this formula) G 0 ¼ time period, in minutes, of sedimentation The above equation gives only the apparent diameter since it assumes that L is a constant. In order to use Stokes’ law to determine the diameter of the particle, it is necessary to know the distance through which the particle falls. Applied Clay Mineralogy152 The correction coefficient, K L , for a given hydrometer is computed as follows: K L ¼ ffiffiffiffiffiffiffiffi H R p L where: H R ¼ H 1 þ 1 2 h À volume of hydrometer bulb area of graduate  L ¼ distance in centimeters through which the particles settled (32.5 cm) Further: H 1 ¼ distance from the top of the bulb to the reading h ¼ length of the bulb Variation in viscosity of water at temperatures other than 671F (19.41C) is accounted for by the use of the correction coefficient, K N , and is expressed by the equation: K N ¼ ffiffiffiffiffi n 1 n r where: n 1 ¼ viscosity coefficient at a given temperature n ¼ (0.102) viscosity coefficient of water at 671F (19.41C) Thus making the final equation for the ‘‘equivalent spherical particle diameter’’: D t ¼ D a ÂK L ÂK N Appendix A 153 [...]... À0.7 À0.3 +0.1 +0.4 +0.8 +1.1 +1.5 +1 .9 +2.2 +2.6 +2 .9 +3.3 +3.7 +4.0 À0 .9 À0.6 À0.2 +0.1 +0.5 +0 .9 +1.2 +1.6 +1 .9 +2.3 +2.7 +3.0 +3.4 +3.7 +4.1 Table 2 KN correction coefficients for variation in viscosity of suspending medium Temperature (1C) 19. 0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29. 0 30.0 KN 1.00 0 .99 2 0 .98 0 0 .97 0 0 .95 7 0 .94 6 0 .93 5 0 .92 5 0 .91 5 0 .90 5 0. 895 0.885 Table 3 Maximum particle size... 37 38 39 40 41 42 KL 0.6 09 0.605 0.601 0. 597 0. 592 0.588 0.583 0.5 79 0.574 0.5 69 0.565 0.560 0.556 0.551 0.546 0.542 Reading 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 KL 0.537 0.533 0.528 0.523 0.5 19 0.514 0.510 0.505 0.500 0. 495 0. 491 0.486 0.481 0.476 0.471 0.467 0.462 0.457 K-values will vary with each hydrometer 8.1e Reference Tappi Method T-6 49 9 Crude clay Brookfield viscosity 9a Apparatus... 3 .92 Appendix A 155 Table 4 KL correction coefficients for a given hydrometer number* Reading À5 À4 À3 À2 À1 0 1 2 3 4 5 6 7 8 9 10 * KL 0.736 0.732 0.728 0.725 0.721 0.717 0.713 0.7 09 0.705 0.701 0. 697 0. 693 0.6 89 0.685 0.681 0.677 KL Reading 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 0.673 0.6 69 0.665 0.661 0.657 0.653 0.6 49 0.645 0.641 0.637 0.633 0.6 29 0.625 0.621 0.617 0.613 Reading 27 28 29. . .Applied Clay Mineralogy 154 Table 1 Temperature correction value for hydrometer reading 1C 0.0 0.2 0.4 0.6 0.8 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 À1.2 À0 .9 À0.5 À0.1 À0.2 +0.6 +0 .9 +1.3 +1.7 +2.0 +2.4 +2.7 +3.1 +3.5 +3.8 À1.1 À0.8 À0.4 À0.1 +0.3 +0.6 +1.0 +1.4 +1.7 +2.1 +2.4 +2.8 +3.2 +3.5 +3 .9 À1.1 À0.7 À0.4 0.0 +0.4 +0.7 +1.1 +1.4 +1.8 +2.2 +2.5 +2 .9 +3.2 +3.6 +4.0 À1.0... Mineralogy 9c Brookfield procedure 9c.1 In Hobart mixer, add 5#/ton equivalent TSPP solution and 1.5#/ton equivalent soda ash in 251 ml total water (221 ml water+30 ml TSPP solution) 9c.2 Add 600 g clay and mix on speeds 1 and 2 until large lumps of clay disperse and sample becomes fluid 9c.3 Stop mixing and scrape dry clay from sides of bowl Replace bowl, cover, and mix on high for 10 min 9c.4 Check... solution 9c.5 Pour sample into a container that can be covered or sealed to prevent moisture loss Check oven dried solids 9c.6 In a Hamilton Beach mixer cup, weigh 500 g dry clay equivalent and adjust to 70.5% solids 9c.7 Place on mixer and mix for 5 min Mix on the highest speed possible being careful as not to lose any clay 10 Crude clay settling procedure (to classify a sample to a coating clay grade)... determine the sulfate content of a clay slurry and the percent transmission of the filtrate from the slurry 2a Apparatus Visible spectrophotometer Laboratory mixer Baroid filter press Whatman #42 filter paper Applied Clay Mineralogy 162 2b Sample preparation 2b.1 Clay: The equivalent of 300 g of dried clay is added to 510 g of distilled water The slurry is mixed until all of the clay is dispersed Slurry or slip:... soft clays or 5 lb/ton equivalent of TSPP solution and 1 lb/ton soda ash for fine, hard clays Add 2500 g of crude clay dry clay basis (38% solids) Mix with a Cowles mixer at 4000 rpm for 5 min Test the pH of the suspension and adjust, if necessary, to 6.5–7.5, targeting 7.0 with 10% soda ash solution Visually inspect the slurry to insure proper surface tension and that no unblunged clay remains If clay. .. 600 ml beaker Thermometer Balance sensitive to 0.1 mg 9b Procedure Determine moisture content in the clay (see procedure 2) Weigh out a sample of 500 g equivalent of dry clay Add enough water for a 70% solids slurry to a Waring blender along with 5#/ton TSPP and 1#/ton soda ash Start blender and slowly add one-third of total amount of crude clay If clay is noticeably flocculated, check pH and adjust to... speed possible without losing clay Repeat steps 14c.1–14c.5 until viscosity minimum is reached Minimum is signified by an increase in viscosity after the addition of more dispersant 15 Processed clay particle size 15a Sedigraph procedure 15a.1 Sample preparation Prepare a 7% by weight solution of clay in water totaling 200 g (For dry clay use 14 g in 186 ml of water; for slurry clay determine the percent . suspending medium Temperature (1C) K N 19. 0 1.00 20.0 0 .99 2 21.0 0 .98 0 22.0 0 .97 0 23.0 0 .95 7 24.0 0 .94 6 25.0 0 .93 5 26.0 0 .92 5 27.0 0 .91 5 28.0 0 .90 5 29. 0 0. 895 30.0 0.885 Table 3. Maximum particle. 0.7 09 18 0.645 34 0.5 79 50 0.505 3 0.705 19 0.641 35 0.574 51 0.500 4 0.701 20 0.637 36 0.5 69 52 0. 495 5 0. 697 21 0.633 37 0.565 53 0. 491 6 0. 693 22 0.6 29 38 0.560 54 0.486 7 0.6 89 23 0.625 39. 0.6 69 28 0.605 44 0.533 À3 0.728 13 0.665 29 0.601 45 0.528 À2 0.725 14 0.661 30 0. 597 46 0.523 À1 0.721 15 0.657 31 0. 592 47 0.5 19 0 0.717 16 0.653 32 0.588 48 0.514 1 0.713 17 0.6 49 33 0.583 49