DEVELOPMENT OF MANUFACTURING TECHNOLOGY FOR FLOWABLE SLURRY CONTAINING FOUNDRY SAND AND FLY ASH

Transcription

1 DEVELOPMENT OF MANUFACTURING TECHNOLOGY FOR FLOWABLE SLURRY CONTAINING FOUNDRY SAND AND FLY ASH By Tarun R. Naik, Director Center for By-Products Utilization and Shiw S. Singh, Post-Doctoral Fellow Center for By-Products Utilization Department of Civil Engineering and Mechanics College of Engineering and Applied Science The University of Wisconsin-Milwaukee P.O. Box 784, Milwaukee, WI Ph: (414) FAX: (414)

2 ABSTRACT This project was conducted to establish mixture proportion technology for flowable slurry incorporating foundry sand and fly ash. In this work, two different flowable fly ash slurry mixtures were proportioned for strength levels in the range of psi at 28 days using two sources of ASTM Class F fly ash. The first mixture containing Oak Creek fly ash was proportioned to obtain a flow/spread of 16±1 in., and the second mixture with Port Washington fly ash was proportioned to have a flow of 11±2 in. These mixtures were used as reference mixtures for this study. The other mixtures contained used and clean foundry sand as a replacement of fly ash. For each mixture design, fly ash was replaced with foundry sand at four different levels (30, 50, 70, and 80%). The ingredients of the slurry mixtures such as fly ash, clean foundry sand, and used foundry sand were tested for their physical and chemical properties, and leachate behavior. The leachate results of these materials based on one observation showed that these materials, except the Port Washington fly ash, met the drinking water standards. These materials were found to be appropriate for manufacture of flowable slurry materials. Various flowable mixtures made with and without foundry sand were evaluated for settlement, setting and hardening characteristics, compressive strength, permeability, length change (drying shrinkage), and leachate characteristics. Generally compressive strength of the flowable slurry materials increased with I

3 age and was found to vary between psi for the mixtures tested at 28 days. The permeability of the flowable fill mixtures was negatively affected by increases in either water to cementitious materials ratio or foundry sand content. However, more tests are needed to evaluate environmental impacts of these materials for use in Controlled Low Strength Materials (CLSM). The Oak Creek fly ash mixtures made with and without foundry sand conformed to the requirements of the drinking water standards. However, most of the mixtures made with the Port Washington fly ash fail to do so for solenium. In general, addition of the foundry sands caused substantial reduction in concentration of the elements that are considered hazardous in accordance with drinking water standards. Therefore, the use of foundry may provide favorable environmental impact. II

4 ACKNOWLEDGEMENT The authors express deep sense of gratitude to the UWS Solid Waste Research Council, Madison, WI; Badger Mining Corp., Berlin, WI; Fall River Foundry Company, Fall River, WI; Maynard Steel Casting Corporation, Milwaukee, WI; Pelton Casteel, Inc., Milwaukee, WI; Stainless Foundry & Engineering, Inc., Milwaukee, WI; Wisconsin Aluminum Foundry Company, Fon du Lac, WI; and, Wisconsin Electric Power Company, Milwaukee, WI for their financial support for this investigation. Special thanks are expressed to Mr. Oluwole B. Adebayo for his help in experimental planning, data collection, and analysis for the project. Thanks are also due to the CBU staff, especially Mohammad M. Hossain, Bob Wendorf, Scott Belonger, Michelle Gehrke, and Brian Moen, who directly contributed to the success of this project. The Center was established by a generous grant from the Dairyland Power Cooperative, La Crosse, WI; Madison Gas and Electric Company, Madison, WI; National Minerals Corporation, St. Paul, MN; Northern States Power Company, Eau Claire, WI; Wisconsin Electric Power Company, Milwaukee, WI; Wisconsin Power and Light Company, Madison, WI; and, Wisconsin Public Service Corporation, Green Bay, WI. Their financial support, continuing help and encouragement, and active, continuing interest, is gratefully acknowledged. III

5 CONTENTS Section Page 1 INTRODUCTION GENERAL SCOPE OF THE RESEARCH PREVIOUS INVESTIGATIONS GENERAL CONSTITUENT MATERIALS OF FLOWABLE SLURRY MATERIALS Foundry Sand Properties of Foundry Sand Fly Ash FLOWABLE SLURRY MATERIALS LEACHATE STUDIES Leachate Test Methods Leachate Test Results on Foundry Sand Leachate Characteristics of Fly Ash EXPERIMENTAL PROGRAM GENERAL PROPERTIES OF FOUNDRY SAND PROPERTIES OF FLY ASH PROPERTIES OF CEMENT MIXTURE PROPORTIONS FOR FLOWABLE SLURRY MATERIALS General Oak Creek Fly Ash Mixtures IV

6 3.5.3 Port Washington Fly Ash Mixtures MANUFACTURING TECHNIQUE FOR FLOWABLE SLURRY MIXTURES PREPARATION AND TESTING OF SPECIMENS TEST RESULTS AND DISCUSSIONS GENERAL PHYSICAL AND CHEMICAL PROPERTIES OF CONSTITUENT MATERIALS OF FLOWABLE SLURRY Properties of Foundry Sand Properties of Fly Ash Properties of Cement FLOWABLE SLURRY MATERIALS Fresh Slurry Properties Compressive Strength Permeability Length Change LEACHATE CHARACTERISTICS Slurry Ingredients Slurry Materials SUMMARY AND CONCLUSIONS RECOMMENDATIONS REFERENCES V

7 ILLUSTRATIONS Figure Page 2.1 Iron and Steel Foundry Process Sieve Analysis Envelope for Regular Concrete Sand Sieve Analysis Envelope for Badger Clean Sand Sieve Envelope for Maynard Used Sand Bleedwater Versus Percentage of Foundry Sand (Oak Creek) Compressive Strength Versus Age for Slurry Mixture Containing Oak Creek Fly Ash and Badger Foundry Sand Compressive Strength Versus Percentage of Oak Creek Fly Ash Replacement With Badger Foundry Sand Compressive Strength Versus Age for Slurry Mixture Containing Oak Creek Fly Ash and Maynard Used Foundry Sand Compressive Strength Versus Percentage of Oak Creek Fly Ash Replacement With Maynard Used Sand Compressive Strength Versus Age for Slurry Mixture Containing Port Washington Fly Ash and Badger Foundry Sand Compressive Strength Versus Percentage of Port Washington Fly Ash Replacement With Badger Foundry Sand Compressive Strength Versus Age for Slurry Mixture Containing Washington Fly Ash and Maynard Used Foundry Sand VI

8 4.12 Compressive Strength Versus Percentage of Port Washington Fly Ash Replacement With Maynard Used Foundry Sand Permeability Versus Fly Ash Replacement with Foundry Sand for Slurry Mixture Permeability Versus Water to Cementitious Materials Ratio for the Oak Creek Fly Ash Mixture with and without Badger Sand Permeability Versus Water to Cementitious Mixture with and without Badger Sand Materials Ratio for the Port Washington Fly Ash Permeability Versus Water to Cementitious Mixture with and without Maynard Sand Materials Ratio for the Port Washington Fly Ash Percent Change in Length Versus Age for Slurry Mixtures Containing Oak Creek Fly Ash and Badger Foundry Sand Percent Change in Length Versus Age for Slurry Mixtures Containing Oak Creek Fly Ash and Maynard Used Foundry Sand Percent Change in Length Versus Age for Slurry Mixtures Containing Port Washington Fly Ash and Badger Foundry Sand Percent Change in Length Versus Age for Slurry Mixtures Containing Port Washington Fly Ash and Maynard Used Foundry Sand VII

9 TABLES Tables Page 2.1 Estimated Pounds of Foundry Waste Per Ton of Metal Casting Produced Chemical Oxide Analysis of Foundry Waste Sand ASTM C 618 Chemical Requirements for Fly Ash ASTM C 618 Physical Requirements for Fly Ash Comparison of Backfill Methods Comparison of Laboratory Leaching Tests EPTOX Results for Concrete Samples (a) Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures Containing no Foundry Sand (b) Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures with Foundry Sand (c) Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures with Foundry Sand (d) Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures with Foundry Sand (a) Mixture Proportions and Fresh Slurry Properties for the Port Washington Fly Ash Mixtures Containing no Foundry Sand (b) Mixture Proportions and Fresh Slurry Properties for the Port Washington Fly Ash Mixtures with Foundry Sand (c) Mixture Proportions and Fresh Slurry Properties for the Port Washington Fly Ash Mixtures with Foundry Sand Physical Properties of Sand Samples Sieve Analysis Results for Regular Concrete and Foundry Sand Samples (ASTM C136) VIII

10 4.3 Chemical Elemental Analysis (Short Irradiation) of Foundry Sand Chemical Elemental Analysis (Long Irradiation) of Foundry Sand Physical Properties of Fly Ash Chemical Elemental Analysis (Short Irradiation) of Fly Ash Chemical Elemental Analysis (Long Irradiation) of Fly Ash Physical Properties of Type I Portland Cement Chemical Composition of the Portland Cement (a) Test Data for the Oak Creek Fly Ash Flowable Slurry Mixtures with and without Foundry Sand (b) Test Data for the Oak Creek Fly Ash Flowable Slurry Mixtures with Foundry Sand (c) Test Data for the Oak Creek Fly Ash Flowable Slurry Mixtures with Foundry Sand (a) Test Data for the Port Washington Fly Ash Flowable Slurry Mixtures without Foundry Sand (b) Test Data for the Port Washington Fly Ash Flowable Slurry Mixtures with Foundry Sand (c) Test Data for the Port Washington Fly Ash Flowable Slurry Mixtures with Foundry Sand (a) Compressive Strength Test Results for the Oak Creek Fly Ash Mixtures with and without Foundry Sand (b) Compressive Strength Test Results for the Oak Creek Fly Ash Mixtures with Foundry Sand (c) Compressive Strength Test Results for the Oak Creek Fly Ash Mixtures with Foundry Sand IX

11 4.13(a) Compressive Strength Test Results for the Port Washington Fly Ash Mixtures with and without Foundry Sand (b) Compressive Strength Test Results for the Port Washington Fly Ash Mixtures with Foundry Sand (c) Compressive Strength Test Results for the Port Washington Fly Ash Mixtures with Foundry Sand Permeability of the Oak Creek Fly Ash Mixtures with and without Foundry Sand Permeability of the Port Washington Fly Ash Mixtures with and without Foundry Sand Length Change for the Oak Creek Fly Ash Mixtures with and without Foundry Sand Length Change for the Port Washington Fly Ash Mixtures with and without Foundry Sand (a) Leachate Results (b) Leachate Characteristics of the Oak Creek Fly Ash Mixtures with and without Foundry Sand (c) Leachate Characteristics of the Port Washington Fly Ash Mixtures with and without Foundry Sand X

12 SECTION 1 INTRODUCTION 1.1 GENERAL Large volumes of solid by-product materials are generated by U.S. foundries. Wisconsin alone produces nearly 600,000 tons of foundry by-products. Due to insufficient use, the majority of these by-products find their way to landfills. Landfilling of foundry by-products not only causes loss in resource and energy recovery, but also environmental problems associated with their disposal. Additionally, shrinking landfill space in the country is making landfilling more costly and restrictive. As a result foundries are facing serious challenges in waste product management including regulatory controls, increasing cost and scarcity of disposal options. Due to passage of the Public Law , the Federal Resource Conservation and Recovery Act of 1976, and the Hazardous and Solid Waste Amendments of 1984, many industries are forced to re-evaluate their normal disposal practices (1). Furthermore, governmental mandates calls for elimination of land disposal of untreated wastes (2,3). In the light of the above, it is highly attractive to find innovative applications of foundry by-products, especially in construction materials. The beneficial uses of by-products in construction materials will: (1) reduce or eliminate disposal costs, (2) -1

13 replace expensive virgin material, (3) result in economic gain due to sale of the products, containing foundry by-products, and (4), save valuable landspace. One of the possible uses of foundry sand is production of Controlled Low Strength Material (CLSM). Flowable slurry is a high slump cementitious material that flows like a liquid, supports like a solid, and self-levels without compacting. ACI 229 defines flowable slurry as a "cementitious material that is in a flowable state at placement and has specified compressive strength of 1200 psi or less at the age of 28 days "(3). CLSM is primarily used for nonstructural applications. In the cases where the material may need to be reexcavated in the future, the compressive strength should not exceed 100 psi. In many situations, it provides an economical alternative to conventional granular backfill materials. This material can be used for numerous applications including filling as a backfill materials for utility trenches, pipes, and manholes, excavations in streets and around foundations, and as a fill for abandon tunnels, sewers, and other underground cavities, and for erosion control. It can be used as a good quality base material for foundations and slabs. The major aim of the present research was to develop mixture proportioning technology for the manufacture of Controlled Low Strength Materials (CLSM) incorporating used foundry sand and fly ash. It is anticipated that the use of discarded foundry sand in CLSM will consume large amounts of foundry used sand, and thus will -2

14 provide large savings in disposal costs to foundries. 1.2 SCOPE OF THE RESEARCH This research was carried out to establish mixture proportion technology for flowable slurry containing used foundry sand and fly ash. The properties of the flowable slurry mixtures containing foundry sands and fly ash were determined. These included physical properties, compressive strength, length change, permeability, and leachate characteristics. The work completed had two major parts: literature search and a laboratory investigation. The literature search was focussed toward gathering information on materials used for making flowable slurry and slurry itself. Based on the analysis of the literature information, a comprehensive experimental program was designed and conducted. The laboratory work in this study was concerned with the development and testing of flowable slurry mixtures. A used foundry sand from Maynard Steel Casting Company, a clean foundry sand from Badger Mining Corporation and two sources of Class F fly ash from Wisconsin Electric Power Company were used in this laboratory investigation. The physical, chemical and leachate properties of these by-products were determined. In this study, two fly ash flowable slurry mixtures without foundry sand was used -3

15 as a control mixtures. The flowable slurry mixtures with different percentage of foundry sand (30%, 50%, 70%, and 85%) as a replacement of each fly ash were made and tested. Cylinders (6"x12") were cast to evaluate the compressive strength, bleed water quantity, settlement, condition of setting and hardening, etc. Cylinders (4"x5") were made to determine the permeability of the material, and specimens (2"x2"x10") were used for the length change measurements. All tests were carried out and evaluated in accordance with applicable ASTM standards wherever possible. -4

16 SECTION 2 PREVIOUS INVESTIGATIONS 2.1 GENERAL Considerable amount of work has been directed toward studying behavior of flowable slurry consisting of portland cement, fly ash, regular sand, and water. However, not much work has been done related to flowable slurry made with foundry sand (4,5). A brief review of the literature concerning flowable fill materials is presented. 2.2 CONSTITUENT MATERIALS OF FLOWABLE SLURRY MATERIALS Foundry Sand A summary of foundry wastes generated per ton of metal casting by foundries is given in Table 2.1. The steps that are involved in the production of castings are coremaking, molding, melting, pouring and cleaning, and inspection. Figure 2.1 presents the iron and steel foundry process flow and emission sources. Coremaking and molding usually produce in excess of 75% of solid wastes generated by foundries. The remaining solids are generated primarily from melting operation with minor -5

17 contributions from cleaning and heat treating processes. TABLE 2.1: Produced (6) Estimated Pounds of Foundry Waste Per Ton of Metal Castings Waste Type Foundry Type Malleable Ductile Iron Gray Iron Steel Aluminum Brass and Bronze Refractories System Sand 1,250 2, , Core Sand , Cleaning Room Waste Slag Coke As Dust Collector Discharge Miscellaneous Totals 1,785 2,890 1,38 0 4,13 5 1, In order to produce a casting, the sand is compacted around a pattern similar to the casting to be manufactured. The molten metal is poured into the cavity formed by the pattern for manufacture of a casting. Although many types of molding sands are used in foundries, the most commonly used is the green sand. This sand is made up of sand, clay, sand additives, and water. The found sand consisted of 85 to 95% of -6

18 green sand which is primarily composed of inert silica (7), and sometimes bolivine and zircon sand are also used. Clay (about 4 to 10% of the total mixture) is used as a binder for the green sand which provides strength and plasticity. A finely ground bituminous coal (sea coal), cereal (ground corn starch), oil, and wood flour make up from 2 to 10% of the total green sand mixture. Finally, water is added to Fig 2.1: Iron and Steel Foundry Process (1) -7

19 activate the clay binder in the range of 2 to 5% of the mixture. The dust generated in the molding process is collected by the air pollution system located over the molding process. The large lumps that are screened out of the molding sand recycle system also form a by-product of the molding sand. Internal cavity in the molds are produced by using core sands. They are composed of mixtures of sand with a small amount of a binder, ranging from 0.5 to 2.0% (8). The core should have the characteristics of strength, permeability, surface smoothness, and collapsibility. Two major groups of binder used are: inorganic and organic binders. Examples for inorganic binders are cement and sodium silicate. Organic type binders are classified as oil binders and synthetic binders. Approximately 1 to 4% of synthetic binders are used in the core sand mixture, whereas, normally inorganic binder such as cement is used in the range of 8 to 12% of the mixture. The by-products from the cores, known as core butts, are removed by the stakeout process (9). Ferrous foundries molten metal is composed of iron and steel, and its composition is controlled by adding or removing carbon and certain alloying elements. Non-ferrous foundries molten materials are primarily made up of aluminum, brass, bronze, or copper. The melting operations produce by-products which may include some discarded metals, metal particles trapped in molds, and metallic dust from room cleaning. -8

20 Cleaning operation is performed to remove sand and other metal protrusions that are formed during casting processes. The cleaning room by-product materials can include grinding materials, steel shots, etc. which are normally discarded. The grinding materials consist of silica, silicon carbide, alumina, and small amounts of binders (9). Steel shots are small steel pellets that are shot at castings to remove excess sand Properties of Foundry Sand Traeger (10), investigated properties of discarded foundry sand with an intention to use it in a highway embankment construction. The results showed that foundry by-products would provide appropriate material for highway uses. American Foundrymen's Society (11) conducted a study to evaluate grain size distribution, AFS grain fineness number, ph, moisture content, density, LOI, grain shape, and surface areas of used foundry sands. The results showed significant variability in these parameters which resulted because of type of equipment used, the size and shape of the casting made, amount of core material per casting, type of additives, and number of times sand was recycled. Greer et al. (12) studied the properties of composite samples secured from three different foundries. The foundry wastes as poorly graded sand-silt mixtures which were pervious to semi-pervious, and possessed good shear strength, low compressibility, and based on the experimental results, classified good workability -9

21 during road construction. The foundry can be analyzed for elemental concentrations, oxides, and presence of compounds by several techniques (13,14). American Foundrymen's Society (11) determined chemical oxides of a foundry sample by using x-ray fluorescence technique (Table 2.2). The Neutron Activation analysis is most commonly used in determination of elemental concentration of materials (13). TABLE 2.2: Chemical Oxide Analysis of Foundry Waste Sand (11) Analyses % SiO Al 2 O Fe 2 O CaO 0.1 MgO 0.3 SO Na 2 O 0.2 K 2 O 0.3 TiO P 2 O Mn 2 O SrO 0.0 LOI 5.2 TOTAL Fly Ash Fly Ash is derived as a by-product of the coal combustion process in coal-fired -10

22 power plants. It is composed of largely spherical particles varying in diameter in the range of µm. The fly ash is captured by either mechanical, electrostatic precipitators, or other particulate collectors from the flue gases prior to discharge into the atmosphere (15). The physical properties of fly ash such as fineness, specific gravity, and pozzolanic index are of special interest. The fineness is known to influence the rate of chemical reaction, and flowability of the material. The reactivity increases with a decrease in size of fly ash (16). The specific gravity of fly ash normally depends mainly on the iron oxide and carbon content and varies between 2 to 2.8 The value of specific gravity is needed in mixture of concrete. The pozzolanic activity index of fly ash is a measure of the relative strength development of the fly ash mixture during high temperature reactions in presence of lime or cement. The pozzolanic index is defined as the ratio of the average strength of the fly ash mortar to that of the reference mortar. The presence of type and relative amounts of mineral matter in coal determines the chemical composition of fly ash (15). The oxides such as SiO 2, Al 2 O 3, and Fe 2 O 3 in the pozzolans in form of amorphous (non-crystalline) structures can participate in pozzolanic reactions at ordinary temperature. In this reaction, the above oxides react with Ca(OH) 2 released from hydration of calcium silicates present in portland cement to form compounds having cementitious properties. Fly ash generated from coal materials contains reactive siliceous or aluminouns materials which are capable of reacting with lime in the presence of moisture to form stable calcium silicate hydrates possessing cementitious properties (15). ASTM categorizes fly ash in two major -11

23 classes: Class F and Class C. The Class F fly ash generally contain less than 10% calcium oxide (CaO), whereas Class C fly ash typically contains 15 to 35% calcium oxide (CaO). The chemical and physical requirements of fly ash according to ASTM C618 are given in Tables 2.3 and

24 TABLE 2.3: ASTM C 618 Chemical Requirements for Fly Ash (17) Class Class C F Silicon Dioxide (SiO 2 ) plus Aluminum Oxide (Al 2 O 3 ) plus Iron Oxide (Fe 2 O 3 ), min., % Sulfur Trioxide (SO 3 ), max., % Available Alkalies, as Na 2 O, max., % Moisture Content, max., % Loss on Ignition, max., % TABLE 2.4: ASTM C 618 Physical Requirements for Fly Ash (17) Class Class C F Fineness, Amount Retained on No. 325 Sieve, max., % Pozzolanic Activity Index: with Portland Cement, at 28 Days, min., % of control with Lime, at 7 days min., psi Water Requirement, max., % of control Soundness, Autoclave Expansion or Contraction, max., % Increase of Drying Shrinkage of Mortar Bars at 28 days, max., % Reactivity with Cement Alkalies, Mortar Expansion at 14 days, max., % Specific Gravity, max. Variation from Average, % Percent Retained on No. 325 Sieve, max. Variation, Percentage Points from Average FLOWABLE SLURRY MATERIALS Flowable slurry material has been studied by a number of researchers (18-30). -13

25 Fuston et al. (27) produced flowable slurry materials consisting of fly ash, cement (4 to 5 percent by weight), and water. The results show compressive strength of the materials varying from 50 to 100 psi at 28 days and dry density ranged from 70 to 85 lb/ft 3. The permeability of the materials was about 5 x 10-6 cm/s, which places them between soil backfill materials, (i.e., 10-1 to 10-3 for sand and 10-7 and lower for clay materials). Larson (28) manufactured CLSM for strength levels in the range of psi at 28 days and density ranging between lb/ft 3. These mixtures were batched, mixed, transported and placed using ready-mixed concrete plants and transit mixers. The materials developed were used by the Iowa DOT for numerous applications including protection of ground water from contamination, protection of river banks, culverts, drainage ditches, seawall, bridges, etc. Buss (29) proportioned a flowable slurry material consisting of 212 lb Type 1 Portland Cement, 505 lb Type F Fly Ash, 2232 lb sand, and 438 lb water. The study compared performance of various backfilling materials in replacement of nine culverts as shown in Table 2.5. Of the materials tested, the flowable mortar was the lowest cost material system with a low settlement. TABLE 2.5: Comparison of Backfill Methods (29) Type of Backfill Settlement (in.) Cost ($) On-Site Soil 1.5 1,790-14

26 Granular 0 1,880 Flowable Mortar Naik et al. (30) established flowable fly ash slurry mixtures with high class F fly ash content and low cement for compressive strength in the range of psi at 28 days. The authors indicated that higher strength slurries can be produced by adding more cement, and/or aggregates such as bottom ash or sand, and/or less mixing water. The slurry material was utilized to fill abandoned steam service tunnels, sidewalk cavity, abandoned steam utility facility, abandoned sewers, etc. 2.4 LEACHATE STUDIES Leachate Test Methods Four different leachate methods: EP-Toxicity method, TCLP method, American Foundrymen's Society (AFS) method, and ASTM method are used to characterize waste materials. A comparison of these methods is presented in Table 2.6. The Extraction Procedure (EP) toxicity technique employs an acidic (ph = 5 ± 0.2) leaching medium and a liquid to solid ratio of 20 : 1, to determine toxicity of a solid waste. The leachate from this test is analyzed for arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver. If these parameters exceed 100 times the drinking water criteria then the waste is categorized as an EP hazardous waste (12). -15

27 The TCLP test is carried out to evaluate mobility of both inorganic and organic contaminants in liquid, solid, and multiphase waste system. In this test, the leaching medium TABLE 2.6: Comparison of Laboratory Leaching Tests (12) Item EP-Toxicity TCLP AFS ASTM Leaching Medium Deionized Water, 0.5 N ph 4.93 ± 0.05 Deionize d Water Deionized Water Acetic Acid Added to adjust ph to 5.0 ± 0.2 Acetate Buffer Liquid to Solid Ratio 20 to 1 20 to 1 5 to 1 20 to 1 Contact Time Method of Mixing 24 hours 18 hours 24 hours 48 hours 72 hours Continuous Rotation at 30 RPM Filtering Once 0.45 micron Number of Elutions Continuous Rotation at 30 RPM Once 0.7 micron glass Invert 15 time in 24 hours Once 0.45 micron 18 hours Continuou s Rotation at 29 RPM Once 0.45 micron to be used depends on the alkalinity of the solid phase of the waste. A sample of the waste is extracted with an appropriate buffered acetic acid solution for 18 ± 2 hours. Then the extract obtained from the TCLP is tested to see whether or not it exceeds the thresholds established by the Environmental Protection Agency. -16

28 The AFS test employs deionized water as a leaching medium. This method provides an indication of the release of certain chemical parameters over a period of time (11). The ASTM test method employs only one elution which is agitated for 18-hour period the sample is then allowed to settle for 5 minutes after which a vacuum or pressure filter is used to filter the liquid through a 45 µm filter. The resulting filtrate is analyzed for concentration of certain constituents Leachate Test Results on Foundry Sand Ham et al. (31) evaluated leaching characteristics of used foundry sand. The results revealed that: (1) Leaching potential was greatly influenced by the process temperature, the greatest matter release was observed with the sand not subjected to process temperature, and, (2) Constituents of the leachates depended upon type of sand which reflected the differences in resins and binders present in the waste material. Ham et al. (32) compared the leachate quality in foundry landfills with samples taken from above the zone of saturation with the leachate data derived from the laboratory testing. Their results indicated that leachates from the unsaturated zone had relatively low concentrations with respect to drinking water standards for all contaminants except iron, manganese, and fluoride, and leach test conducted on auger waste samples were more accurate in predicting field leachate compositions than leach -17

29 test on raw composite waste. Based on leachate tests, Traeger (10) reported that foundry wastes would not be classified as hazardous in accordance with the RCRA criteria Leachate Characteristics of Fly Ash Triano and Frantz (33) evaluated the leachate characteristics of concrete made with municipal solid waste (MSW) fly ashes from both refuse-derived fuel (RDF) and mass burn plants. They used EP-Toxicity test method to determine the amount of leachable heavy metals in these concretes. The result of the investigation is presented in Table 2.7. The results showed very small amount of heavy metal leached from the concrete in spite of high concentration of leachable heavy metals. Edil et al. (34) studied the interaction of inorganic leachate with compacted western coal pozzolanic fly ash liners to meet the normal requirement for permeability. They further studied the effects of long-term permeation of inorganic leachates solutions on such liner materials. The results revealed that calcium and sulfur concentrations were lower when permeability was lower. However, no variation was observed in sodium, chloride, boron, cadmium, and ph data. In general, Zinc concentrations were found to be higher at lower permeabilities. They concluded that in order to have a low permeable fly ash liner material for low level of leachates, type and -18

30 percentage of fly ash, compaction effort and moisture content should be controlled. -19

31 TABLE 2.7 : EPTOX Results for Concrete Samples (33) Leachate Metal Concentrations (ppb) Samples Silver Barium Cadmium Chromium Lead Control 4 1, R7-7.5% Below detectio n limit R8-7.5% R9-7.5% R9-15% Below detectio n limit Below detectio n limit Below detectio n limit 615 Below detection limit Below detection limit 1, M-7.5% Below detection limit 101 Below detection limit M-15% C-7.5% Below detectio n limit Below detectio n limit 705 Below detection limit 39 Below detection limit C-15% Below detection limit Detection Limit Toxicity Limit 5, ,00 0 1,000 5,000 5,000 Note: Values for arsenic, mercury, and selenium are not shown because previous analyses showed negligible amounts of these metals. -20

32 SECTION 3 EXPERIMENTAL PROGRAM 3.1 GENERAL In this work, two fly ash slurry mixtures without foundry sand were selected as reference mixtures for the present study. Two types of foundry sand (clean and used) were used as a replacement of fly ash in manufacture of flowable slurry. All the constituent materials of the flowable slurry were tested for their physical, chemical, and leachate properties in accordance with applicable ASTM test methods. The clean sand was obtained from Badger Mining Corporation and the used foundry sand was obtained from Maynard Steel Casting Company. For comparison purposes, some properties of regular concrete sand were also studied. The flowable slurry mixtures were produced by partially replacing fly ash with foundry sand in the reference slurry mixtures. The four replacement levels ( 30%, 50%, 70%, and 85%) were used for each foundry material. 3.2 PROPERTIES OF FOUNDRY SAND Physical properties of both the clean and used foundry sand were determined -21

33 using appropriate ASTM standards. The parameters such as Moisture Content (ASTM C566), Unit Weight and Volume of Voids (ASTM C29), Specific Gravity and Absorption (ASTM C128), Sieve Analysis and Fineness Modulus (ASTM C136), Material finer than #200 (75µm) sieve (ASTM C117), Clay Lumps and Friable Particles (ASTM C142), Organic Impurities for Fine Aggregates (ASTM C40), the effect of Organic Impurities on Strength of Mortar (ASTM C87), and Soundness of Aggregates by Sodium Sulphate (ASTM C88) were evaluated. The moisture content of as received sand was measured in accordance with ASTM C566. The samples were visually inspected at various intervals to examine if the binders melted or not. After 24 hours, the sands were pressed with fingers to see if the binder melted. The results showed that the binders remained in a crispy, unmelted state. The unit weight was determined by the dry rodded method in accordance with ASTM C29 using oven dried sample of sand. The bulk specific gravity (dry basis) was determined in accordance with ASTM C128. Sieve analysis was performed according to ASTM C136. The fineness modulus was computed from the cumulative percentage retained on the set of standard sieves in accordance with ASTM C136. ASTM C117 was followed to determine materials finer than 75µm. In order to determine clay lumps and friable particles, ASTM C142 had to be modified for its use for foundry sands. According to ASTM C142, the sample -22

34 selected should be retained on No. 16 (1.18 mm) sieve and final wet sieving is to be done on 850µm (No. 20) sieve. Since the foundry sands tested were smaller than regular concrete sand, the above specification could not be directly applied as less than 3 percent of the sample was retained on No. 16 sieve. As a result, No. 100 (150 µm) sieve was selected instead of the No. 16 (1.18 mm) sieve which could retain 90 percent of the particles. Wet sieving was performed using No. 140 (106 µm) sieve. The test (ASTM C87) for effect of organic impurities in fine aggregate on the strength of mortar was performed on samples which failed to meet ASTM C40 requirement. The strength comparison of unwashed and washed sand cubes were carried out at the age of 7 days. A modified ASTM C88 was used to measure soundness of the foundry sands. In accordance with ASTM C88 test standards, the test sample shall be such that it contains 100 grams of all materials retained on No. 4 (4.75 mm), No. 8 (2.36 mm), No. 16 (1.18 mm), No. 30 (600 µm), and No. 50 (300 µm) sieves, and respectively passing through sieves 3/8 in (9.5 mm), No. 4 (4.75 mm), No. 8 (2.36 mm), No. 16 (1.18 mm) and No. 30 (600 µm). Since, foundry sand was finer than No. 30 sieve, only about 0.2 to 2.1 percent of the sands was retained on No. 4 (4.75 mm) sieve, and up to No. 30 (600 µm) sieve. Therefore, the ASTM technique was modified to evaluate the soundness of the foundry sands for this investigation. The sample used was 100 grams passing through No. 30 (600 µm) sieve and retained on No. 50 (300 µm) sieve. -23

35 Foundry sand samples were analyzed using Instrumental Neutron Activation Analysis at Nuclear Reactor Laboratories, at the University of Wisconsin-Madison (35). 3.3 PROPERTIES OF FLY ASH Two low-calcium fly ashes (ASTM Class F) were obtained from two different sources, one from Oak Creek and the other from Port Washington Power Plants of Wisconsin Electric Power Company. determined according to ASTM C618. Physical properties of the fly ashes were Elemental analysis of the fly ashes was performed using the Instrumental Neutron Activation analysis. 3.4 PROPERTIES OF CEMENT A Type I cement obtained from LaFarge Corporation was used in this study. Its properties, both physical and chemical, were determined in accordance with applicable ASTM test methods as required by ASTM C150. The physical properties of the cement such as air content (ASTM C185), fineness, blain air permeability (ASTM C204), soundness (ASTM C151), specific gravity (ASTM C188), compressive strength of cube (ASTM C109), and initial setting time (ASTM C191) were determined. 3.5 MIXTURE PROPORTIONS FOR FLOWABLE SLURRY MATERIALS -24

36 3.5.1 General In this work, two reference flowable fly ash slurry mixtures were proportioned; one with Oak Creek fly ash and the other with Port Washington fly ash. The first reference mixture with the Oak Creek fly ash was proportioned to obtain a flow of 16±1 in. and the second reference mixture was proportioned to obtain a slump of 11±2 in. For each reference, other mixtures were proportioned to contain foundry sand as a replacement of fly ash. These mixtures were proportioned to have a compressive strengths in the range of psi. Details of these mixtures are given in the following sections. The mixtures meeting approximately (strength of at least 40 psi) the above requirements were classified as primary mixtures and the remaining mixtures were classified as secondary mixtures Oak Creek Fly Ash Mixtures A total of 17 different Oak Creek Class F fly ash mixtures were manufactured at the Center for By-Products Utilization Concrete Laboratory. Nine of them were primary mixtures. Of these one was control mixture without foundry sand and the other eight had different replacements of the fly ash (30, 50, 70, and 85%) with the two sources of foundry sand (Badger clean sand and Maynard used sand). The replacement of the fly ash by the foundry sand were on a weight basis. The mixture proportions are presented in Tables 3.1(a), 3.1(b), 3.1(c), and 3.1(d). All the mixtures were -25

37 proportioned to attain the 28-day compressive strength in the range of psi and the flow/spread of 16±1 in. by varying the amount of water in the mixtures. The flow/spread was determined in accordance with the ACI 229 method using a 3" dia. x 6" long cylinder. The mixtures were designated as S1 through S9, with appropriate sub-designation as "P" for primary and "S" for secondary mixes. -26

38 TABLE 3.1(a): Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures Containing no Foundry Sand* Mix No. S1 Foundry Sand, % 0 Batch Designation OCPP-1(S ) OCPP-2(S ) OCPP-3(S ) OCPP-4(S ) OCPP-5(S) S1-1(P ) S1-2(P ) Cement, lb/yd Fly Ash, lb/yd Foundry Sand, lb/yd 3 Water, lb/yd Water to Cementitious Materials Ratio Flow/Spread, in.** 29 15¾ 15¼ 15¾ 16½ 16¼ 16¼ Air Content, % Air Temperature, F Slurry Temperature, F Slurry Density, lb/ft Test Specimens f c, l, p f c, l, p f c f c f c f c f c, l, p Number of Specimens 30, 4, 3 31, 4, , 4, 3 Date 4/16/93 4/19/93 5/6/93 5/25/93 6/8/93 6/8/93 6/8/93 * B = Badger clean sand; M = Maynard used sand; S = secondary mixtures; P = primary mixtures; f c = compressive strength specimens; l = length change specimens; and, p = permeability specimens. ** Initial diameter was 3 in. The reported "Flow/Spread" indicates final diameter of the flowable slurry. -27

39 TABLE 3.1(b): Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures with Foundry Sand* Mix No. S2 S3 Foundry Sand, (%) 30(B) 50(B) Batch Designation S2-1(S) S2-2(S S2-3(P S2-4(P) S3-1(S) S3-2(S S3-3(P) S3-4(P) ) ) ) Cement, lb/yd Fly Ash, lb/yd Foundry Sand, lb/yd Water, lb/yd Water to Cementitious Materials Ratio Flow/Spread, in.** 25¼ 26½ 16 15¾ 12¾ 12¾ 16 15¾ Air Content, % Air Temperature, F Slurry Temperature, F Slurry Density, lb/ft Test Specimens f c f c, l, p f c f c, l, p f c f c, l, p f c f c, l, p Number of Specimens 22 8, 6, , 6, , 4, , 4, 3 Date 6/8/93 6/8/93 6/11/9 3 6/15/93 6/14/93 6/15/9 3 6/25/93 6/25/93 * B = Badger clean sand; M = Maynard used sand; S = secondary mixtures; P = primary mixtures; f c = compressive strength specimens; l = length change specimens; and, p = permeability specimens. ** Initial diameter was 3 in. The reported "Flow/Spread" indicates final diameter of the flowable slurry. -28

40 TABLE 3.1(c): Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures with Foundry Sand* Mix No. S4 S5 S6 Foundry Sand, (%) 70(B) 85(B) 30(M) Batch Designation S4-1(S) S4-2(P) S4-3(P) S5-1(P) S5-2(P) S6-1(P S6-2(P) ) Cement, lb/yd Fly Ash, lb/yd Foundry Sand, lb/yd Water, lb/yd Water to Cementitious Materials Ratio Flow/Spread, in.** ¾ 16¼ Air Content, % Air Temperature, F Slurry Temperature, F Slurry Density, lb/ft Test Specimens f c f c, l, p f c f c f c, l, p f c f c, l, p Number of Specimens 15 12, 4, , 4, , 3, 3 Date 6/14/93 6/22/93 6/29/93 6/25/93 7/2/93 6/15/9 3 6/25/93 * B = Badger clean sand; M = Maynard used sand; S = secondary mixtures; P = primary mixtures; f c = compressive strength specimens; l = length change specimens; and, p = permeability specimens. ** Initial diameter was 3 in. The reported "Flow/Spread" indicates final diameter of the flowable slurry. -29

41 TABLE 3.1(d): Mixture Proportions and Fresh Slurry Properties for the Oak Creek Fly Ash Mixtures with Foundry Sand* Mix No. S7 S8 S9 Foundry Sand, (%) 50(M) 70(M) 85(M) Batch Designation S7-1(P S7-2(P S8-1(P S8-2(P S9-1(P) S9-2(P) ) ) ) ) Cement, lb/yd Fly Ash, lb/yd Foundry Sand, lb/yd Water, lb/yd Water to Cementitious Materials Ratio Flow/Spread, in.** ¾ 16½ 16¼ Air Content, % Air Temperature, F Slurry Temperature, F Slurry Density, lb/ft Test Specimens f c f c, l, p f c f c, l, p f c f c, l, p Number of Specimens 15 14, 3, , 3, , 4, 3 Date 6/29/9 3 7/2/93 6/29/9 3 7/2/93 7/2/93 7/9/93 * B = Badger clean sand; M = Maynard used sand; S = secondary mixtures; P = primary mixtures; f c = compressive strength specimens; l = length change specimens; and, p = permeability specimens. ** Initial diameter was 3 in. The reported "Flow/Spread" indicates final diameter of the flowable slurry. -30

42 3.5.3 Port Washington Fly Ash Mixtures A total of 15 different Port Washington Class F fly ash mixtures were produced at the Center for By-Products Utilization Laboratory. Out of 15 mixtures, 9 mixtures were classifiedas primary mixtures. One of them was the control mixture without foundry sand. The other eight mixtures contained foundry sands (Badger clean sand and Maynard used sand) as a replacement of fly ash. The replacement of the fly ash by foundry sand was made at 30, 50, 70, and 85% levels on a weight basis. The mixture proportions are presented in Tables 3.2(a), 3.2(b), and 3.2(c). The mixtures were proportioned to have the 28-day compressive strength in the psi. and the flow/spread of the mixtures of 11±2 in. by varying the amount of water in the mixtures. The flow/spread was determined in accordance with the ACI 229 method. The mixtures were designated as P1 through P9, including the sub-designations "P" for the primary mixtures and "S" for the secondary mixtures. 3.6 MANUFACTURING TECHNIQUE FOR FLOWABLE SLURRY MIXTURES Ingredients of the fly ash slurry mixtures were mixed at the Center for By-Products Utilization concrete laboratory using a 9 cu.ft. capacity power driven revolving paddle mixer. At the present time standard mixing procedure for slurry is not available. As a result, the mixing procedure, as described below, was developed at the Center for By-Products Utilization. For the control mixtures without foundry sand, the inside of the mixer was initially sprayed with water, and then the mixer drum was -31

43 drained of any excess water. All the cement and half of the mixing water were added in the mixer and mixed for three minutes. Then, half of the -32

44 TABLE 3.2(a): Mixture Proportions and Fresh Slurry Properties for the Port Washington Fly Ash Mixtures Containing no Foundry Sand* Mix No. P1 Foundry Sand, (%) 0 Batch Designation P1-1(S) P1-2(S P1-3(S P1-4(S P1-5(S P1-6(S P1-7(P) P1-8(P) ) ) ) ) ) Cement, lb/yd Fly Ash, lb/yd Foundry Sand, lb/yd 3 Water, lb/yd Water to Cementitious Ratio Flow/Spread, in.** 10¼ ½ 10 10½ 11½ 11¾ Air Content, % Air Temperature, F Slurry Temperature, F Slurry Density, lb/ft Test Specimens f c f c f c f c f c f c f c f c, l, p Number of Specimens , 4, 3 Date 9/3/93 9/3/93 9/4/93 9/4/93 9/18/93 9/18/9 3 9/30/93 9/30/93 * B = Badger clean sand; M = Maynard used sand; S = secondary mixtures; P = primary mixtures; f c = compressive strength specimens; l = length change specimens; and, p = permeability specimens. ** Initial diameter was 3 in. The reported "Flow/Spread" indicates final diameter of the flowable slurry. -33