Center for By-Products Utilization

Transcription

1 Center for By-Products Utilization DEMONSTRATION OF MANUFACTURING TECHNOLOGY FOR CONCRETE AND CLSM UTILIZING WOOD ASH FROM WISCONSIN By Tarun R. Naik, Rudolph N. Kraus, and Rafat Siddique Report No. CBU REP-485 November 2002 Report for Year 1 activities submitted to the Wisconsin Department of Natural Resources, Madison, WI, for Project # Department of Civil Engineering and Mechanics College of Engineering and Applied Science THE UNIVERSITY OF WISCONSIN - MILWAUKEE

2 YEAR - 1 TECHNICAL REPORT Project Title: DEMONSTRATION OF MANUFACTURING TECHNOLOGY FOR CONCRETE AND CLSM UTILIZING WOOD ASH FROM WISCONSIN Principal Investigator: Tarun R. Naik UWM Center for By-Products Utilization University of Wisconsin-Milwaukee Other Project Personnel: Rudolph N. Kraus and Rafat Siddique UWM Center for By-Products Utilization University of Wisconsin-Milwaukee ABSTRACT Wisconsin industry generates approximately one million dry tons (or approx. 1.8 million cubic yards) of wood ash per year. Disposal of wood ash in landfills costs Wisconsin industry significant direct cost plus unknown future liabilities due to environmental concerns related to such materials in landfills. This project will establish the initial manufacturing technology for use of wood ash generated by the forest products industry in concrete (structural-grade concrete) and flowable slurry (Controlled Low Strength Materials, CLSM) through an initial laboratory evaluation followed by prototype manufacturing and full-scale manufacturing. A technology transfer seminar, which also included a demonstration of the placement of concrete and CLSM mixtures containing wood ash, was conducted to transfer the knowledge developed about the use of wood ash in construction material to the engineering community; including industrial and government

3 agencies, as well as the concrete construction industry. This report presents the work carried out during the first year of this project. The project work was started with the laboratory manufacturing of CLSM and concrete mixtures at the facilities of the UWM Center for By-Products Utilization, University of Wisconsin-Milwaukee. Three different CLSM mixtures (SL-1, SL-2, and SL-3) were first proportioned in the laboratory. The CLSM mixtures manufactured in the laboratory contained wood ash and cement from 2130 to 995 lb/yd 3 and 81 to 116 lb/yd 3 respectively. Tests were performed for density; bleed water, settlement, and compressive strength. Four different concrete mixtures (ML1-A, ML2-A, ML4-A, and ML4-B) were also manufactured in the laboratory. Mixture ML1-A did not contain wood ash, whereas other mixtures contained between 36 and 87 lb/yd 3 of wood ash. All four mixtures had a Class C fly ash content between 50 and 165 lb/yd 3 to simulate the usual types of concrete manufactured by ready-mixed concrete plants in Wisconsin. Additionally, based upon past R&D work conducted at UWM Center for By- Products Utilization, this range of Class C fly ash was used to take advantage of available alkalies in wood ash to activate coal ash. Based on the results of lab manufacturing of CLSM and concrete mixtures, prototype manufacturing was conduced at a ready-mixed concrete plant (Midway Concrete Co.) in Rothschild, WI. Three series of CLSM mixtures (SL-1, SL-2, and SL-3) and four series of concrete mixtures (R-1, R-2, R-3, and R-4) were manufactured. Tests were performed for bleed water, density, settlement, and compressive strength for CLSM mixtures. Compressive strength was evaluated at the ages of 7, 14, 28, 91, and 182 days. Test -ii-

4 results at the 28-day age show that CLSM achieved compressive strengths between 90 and 190 psi. The concrete mixtures were tested for fresh concrete properties and specimens were made for compressive strength, splitting tensile strength, flexural strength, drying shrinkage, and freezing and thawing. Tests for strength properties were performed at the ages of 7, 14, 28, and 91 days. The concrete mixtures attained 28-day compressive strengths between 4315 and 5065 psi and an increase in strength was observed at 91-day. Similar trends were also observed for splitting tensile strength and flexural strength. Full-scale manufacturing of CLSM and concrete mixtures was also conducted at the readymixed plant in Rothschild, WI. Three series of CLSM mixtures (S-1, S-2, and S-3) were manufactured. For each series, between five and seven batches of CLSM were manufactured. The volume of each batch of CLSM was approximately nine cubic yards. Tests were performed for density, settlement, and bleed water. Specimens were cast for compressive strength and water permeability. The compressive strength of the CLSM mixtures ranged from 40 to 120 psi at the age of 28 days, 100 to 205 psi at 91days, 135 to 830 psi at 182 days, and 150 to 2090 psi at 365 days. Water permeability tests were performed at 63, 90, and 227 days. Permeability values were between 6.8 x 10-5 and 3.3 x 10-5 cm/sec at 63 days; between 2.1 x 10-5 and 3.9 x 10-5 cm/sec at 90 days; and between 11 x 10-5 and 28 x 10-5 cm/sec at 227 days of testing. -iii-

5 Four series of concrete mixtures (C-1, C-2, C-3, and C-4) were manufactured. Each series consisted of three to four batches of approximately nine cubic yards each. Tests were performed for fresh concrete properties. Specimens were prepared for testing of compressive strength, splitting tensile strength, flexural strength, drying shrinkage, and freezing and thawing resistance. Compressive strengths between 3625 and 5410 psi were achieved at the age of 28 days. There was a continuous increase in the compressive strength at later ages of 91, 182, and 365 days. Similar results were also observed for splitting tensile strength and flexural strength. Tests were also performed for drying shrinkage and freezing and thawing. The concrete mixtures were tested for pulse velocity, relative dynamic modulus, and percent length change up to 300 freezing and thawing cycles. Test results after 300 cycles of freezing and thawing indicat that inclusion of wood ash in the concrete mixtures does not affect freezing and thawing resistance of the concrete mixtures. There was no significant change on the drying shrinkage of concrete specimens made with or without wood ash. Significant efforts were made during the first year of the project to transfer the technology for the use of wood ash in concrete and CLSM to the engineering community; including industrial, government agencies, concrete construction industries, and others industries. A technology transfer seminar was conducted on September 27, 2001 in Rothschild, WI. The seminar consisted of a half day of presentations followed by a construction demonstration of the placement of concrete containing wood ash for a pavement slab and flowable slurry containing wood ash for the pavement base course. -iv-

6 Although not directly supported by the funds of this project, additional presentations were made in Wisconsin and elsewhere on the use of wood ash furthering the technology transfer. Rudolph N. Kraus, Assistant Director, UWM Center for By-Products Utilization, made a presentation on Wood Ash: A New Pozzolanic Material - Its Uses in Concrete and Concrete Products, Roller-Compacted Concrete Pavements, Blended Cements, and Flowable Slurry on March 18, 2002 at the UWM-CBU Workshop on the Use of Fly Ash and other Coal- Combustion Products in Concrete and Construction Materials. Tarun R. Naik, Director, UWM Center for By-Products Utilization made a presentation on Wood Ash: A New Source of Pozzolanic Material at another UWM-CBU seminar on Recent Advances in Cementitious Materials held (May 17-18, 2002) in Milwaukee. Tarun R. Naik has also made several presentations on the use of wood ash as a construction material: High-Volume Fly Ash Concrete in Structures and Pavements Seminar, ACI Maharastra Chapter, Mumbai, India, July, 2001; Residual Wood Ash Conference Residual-to-Revenue, Richmond, BC, Canada, November 2001; Weyerhaeuser Co., Seattle, WA, November 2001, ACI Fall 2002 Convention, Phoenix, AZ, October 2002, CANMET/ACI Lyon, France, and Barcelona, November 2002, and at other places. Additional technical papers have been published or submitted for publication from activities of this project. A paper titled Durability of Concrete Incorporating Wood Fly Ash has been accepted for presentation and publication at the Sixth CANMET/ACI International Conference on Durability of Concrete, Thessaloniki, Greece, June Another paper titled Properties of Controlled Low-Strength Material made with Wood Fly Ash has been submitted for presentation and publication at the ASTM Symposium on Innovations in -v-

7 Controlled Low-Strength Material (Flowable Slurry), Denver, Colorado, June A paper titled Greener Concrete Using Recycled Materials was published by the ACI Concrete International, July 2002, which contained important information from the Rothschild construction project. Another paper has been preliminarily accepted for publication by the ASCE Geotechnical and Geoenvironmental Engineering Division titled Permeability of Flowable Slurry Materials Containing Wood Ash. -vi-

8 TABLE OF CONTENTS Section Page 1.0 INTRODUCTION AND BACKGROUND LITERATURE REVIEW Properties of Wood Ash Beneficial Uses of Wood Ash Land Application Pollution Control Construction Materials OBJECTIVES RESEARCH DESIGN EXPERIMENTAL PROCEDURES Materials Wood Ash Fine Aggregate Coarse Aggregate Class C Fly Ash Cement Elemental Analysis Mineralogical Analysis Manufacturing of CLSM and Concrete Mixtures and Testing...21 of specimens Laboratory Mixtures CLSM laboratory mixtures Concrete laboratory mixtures Prototype Manufacturing CLSM prototype mixtures Concrete prototype mixtures Full-Scale Manufacturing CLSM full-scale mixtures Concrete full-scale mixtures vii-

9 TABLE OF CONTENTS (Continued) Section Page 6.0 RESULTS AND DISCUSSION Laboratory and Prototype Manufacturing (Selection and Refinement of Mixtures and Testing)) Materials Elemental Analysis Mineralogical Analysis Lab Manufacturing Results Laboratory CLSM mixture results Mixture proportions and fresh properties Compressive strength Laboratory concrete mixture results Mixture proportions and fresh properties Compressive strength Prototype Manufacturing Results Prototype CLSM mixture results Mixture proportions and fresh properties Compressive strength Prototype concrete mixture results Mixture proportions and fresh properties Compressive strength Splitting tensile strength Flexural strength Compressive strength from portions of beams broken in flexure Resistance to freezing and thawing Drying Shrinkage Full-Scale Manufacturing/Production Results Full-scale CLSM mixture results Mixture proportions and fresh properties Compressive strength Water permeability viii-

10 TABLE OF CONTENTS (Continued) Section Page Full-scale concrete mixture results Mixture proportions and fresh properties Compressive strength Splitting tensile strength Flexural strength Compressive strength from portions of beams broken in flexure Resistance to freezing and thawing Drying Shrinkage Technology Transfer and Field Demonstration CONCLUSIONS FUTURE PLAN LIST OF REFERENCES APPENDIX ix-

11 Table No./Title LIST OF TABLES Page Table 1 - Physical Properties of Fine and Coarse Aggregates for Laboratory Mixtures Table 2 - Gradation of Fine and Coarse Aggregates for Laboratory Mixtures Table 3 - Analysis for Oxides, SO3, and Loss on Ignition for Cement for Laboratory Mixtures Table 4 - Physical Properties of Cement for Laboratory Mixtures Table 5 - Physical Properties of Wood Ash for Laboratory Mixtures Table 6 - Analysis for Oxides, SO3, and Loss on Ignition for Wood Ash for Laboratory Mixtures Table 7 - Physical Properties of Class C Fly Ash for Laboratory Mixtures Table 8 - Analysis for Oxides, SO3, and Loss on Ignition for Class C Fly Ash for Laboratory Mixtures Table 9 - Elemental Analysis of Cement and Wood Ash for Laboratory Mixtures Table 10 - Mineralogy of Wood Ash for Laboratory Mixtures Table 11 - Mineralogy of Cement and Class C Fly Ash for Laboratory Mixtures Table 12 - Mixture Proportions and Fresh Properties of CLSM Mixtures from Laboratory Manufacturing Table 13 - Bleed water of CLSM Mixtures from Laboratory Manufacturing Table 14- Settlement of CLSM Mixtures from Laboratory Manufacturing Table 15- Compressive Strength for CLSM Mixtures from Laboratory Manufacturing Table 16 - Mixture Proportions and Fresh Concrete Properties for Air-Entrained Concrete from Laboratory Manufacturing Table 17 - Compressive Strength of Air-Entrained Concrete Mixtures from Laboratory Manufacturing Table 18 - Mixture Proportions and Fresh Properties for CLSM Mixtures from...72 Prototype Manufacturing Table 19 - Bleed water for CLSM Mixtures from Prototype Manufacturing Table 20 - Settlement for CLSM Mixtures from Prototype Manufacturing...74 Table 21 - Compressive Strength for CLSM Mixtures from Prototype Manufacturing Table 22 - Mixture Proportions for Air-Entrained Concrete from Prototype Manufacturing x-

12 Table 23 - Compressive Strength for Air-Entrained Concrete Mixtures from Prototype Manufacturing Table 24 - Splitting Tensile Strength for Concrete Mixtures from Prototype Manufacturing Table 25- Flexural Strength of Concrete Mixtures for Prototype Manufacturing Table 26- Compressive Strength for Concrete Mixtures Using Portions of Beam Broken in Flexure from Prototype Manufacturing Table 27 - Mixture Proportions and Fresh Properties for CLSM Mixtures...81 from Full-Scale Manufacturing, Series S-1 Table 28 - Mixture Proportions and Fresh Properties of CLSM Mixtures...82 from Full-Scale Manufacturing, Series S-2 Table 29 - Mixture Proportions and Fresh Properties of CLSM Mixtures...83 from Full-Scale Manufacturing, Series S-3 Table 30 - Bleed water from CLSM Mixtures from Full-Scale Manufacturing...84 Table 31 - Settlement for CLSM Mixtures from Full-Scale Manufacturing...85 Table 32 - Compressive Strength for CLSM Mixtures from Full-Scale Manufacturing, Series S-1 Table 33 - Compressive Strength for CLSM Mixtures from Full-Scale Manufacturing, Series S-2 Table 34 - Compressive Strength for CLSM Mixtures from Full-Scale Manufacturing, Series S-3 Table 35 - Permeability of CLSM Mixtures from Full-Scale Manufacturing, Series S Table 36 - Permeability of CLSM Mixtures from Full-Scale Manufacturing, Series S Table 37 - Mixture Proportions and Fresh Properties for Air-Entrained Concrete from Full-Scale Manufacturing, Series C-1 Table 38 - Mixture Proportions and Fresh Concrete Properties of Air-Entrained Concrete Full-Scale Manufacturing, Series C-2 Table 39 - Mixture Proportions and Fresh Concrete Properties of Air-Entrained Concrete from Full-Scale Manufacturing, Series C-3 Table 40 - Mixture Proportions and Fresh Concrete Properties of Air-Entrained Concrete from Full-Scale Manufacturing, Series C-4 Table 41 - Compressive Strength for Concrete Mixtures from Full-Scale Manufacturing, Series C-1 Table 42 - Compressive Strength of Air-Entrained Concrete Mixtures from Full-Scale Manufacturing, Series C-2 -xi-

13 Table 43 - Compressive Strength for Concrete Mixtures from Full-Scale Manufacturing, Series C-3 Table 44 - Compressive Strength for Concrete Mixtures from Full-Scale Manufacturing, Series C-4 Table 45 - Splitting Tensile Strength for Concrete Mixtures from Full-Scale Manufacturing Table 46 - Flexural Strength for Concrete Mixtures from Full-Scale Manufacturing Table 47 - Compressive Strength for Concrete Mixtures Using Portions of Beams Broken in Flexure from Full-Scale Manufacturing xii-

14 LIST OF FIGURES Figure No./Title Page Fig 1- Pulse Velocity versus Freezing and Thawing Cycles for Prototype Manufacturing Fig 2- Relative Dynamic Modulus versus Freezing and Thawing Cycles for Prototype Manufacturing Fig 3- Percent Length Change versus Freezing and Thawing Cycles for Prototype Manufacturing Fig 4- Drying Shrinkage of Concrete Mixtures from Prototype Manufacturing Fig 5- Pulse Velocity versus Freezing and Thawing Cycles for Full-Scale Manufacturing Fig 6- Relative Dynamic Modulus versus Freezing and Thawing Cycles for Full-Scale Manufacturing Fig.7- Percent Length Change versus Freezing and Thawing Cycles for Full-Scale Manufacturing Fig.8 - Drying Shrinkage of Concrete Mixtures for Full-Scale Manufacturing xiii-

15 1.0 INTRODUCTION AND BACKGROUND Wisconsin industries (pulp and paper mills, saw mills, wood products industries such as doors and windows, and other forest products industries) generate approximately one million dry tons (or approx. 1.8 million cubic yards) of wood ash per year. NCASI has estimated that of the total wood ash produced in the U.S., only about 28% is being utilized [1]. Disposal of wood ash in landfills costs Wisconsin industry significant direct cost plus unknown future liabilities due to environmental concerns related to such materials in landfills. This project will establish initial manufacturing technology for the use of wood ash generated by the forest products industry in concrete and flowable slurry (Controlled Low Strength Materials, CLSM), through an initial laboratory evaluation followed by prototype manufacturing and full-scale manufacturing. A technology transfer seminar was conducted, which demonstrated the placement of concrete and CLSM mixtures containing wood ash for a materials handling area in Rothschild, WI, at the Weyerhaeuser Company plant. CLSM is a very fluid cementitious material that flows like a liquid and supports like a solid, without compacting. It is self-compacting and self-leveling. It hardens in a defined and predictable manner. ACI 229R defines CLSM flowable slurry as "cementitious material that is in a flowable state at placement and has specified compressive strengths of 1200 psi or less at the age of 28 days." A number of names including flowable fill, unshrinkable fill, manufactured dirt, controlled density fill, flowable mortar, etc., are being used to describe this material. CLSM is used primarily for non-structural -1-

16 applications. Its consistency is similar to that of pancake batter. CLSM can be placed quickly with minimum labor. It can harden within a few hours of placement. For excavatable slurry, compressive strength should be in the range of 50 to 100 psi at the 28-day age. In cases where higher strengths are required, and/or future excavation is not expected, CLSM mixtures can be proportioned with higher amounts of cementitious materials. For use as a permanent fill material, CLSM mixtures can be proportioned to attain strengths of up to 1200 psi at the age of 28 days. Developing different strength levels for CLSM with wood ash could allow for greater flexibility for potential uses of CLSM such as backfill around underground electric transmission cables, water distribution lines, gas lines, and other similar trench excavations, road sub-base, foundation base materials. This project once completed will suggest practical solutions to disposal problems associated with wood ash for the forest products industry in Wisconsin through the development of this technology for commercial production of concrete and CLSM containing wood ash. -2-

17 2.0 LITERATURE REVIEW Typical wood burned for fuel at pulp and paper mills and wood products industries may consist of saw dust, wood chips, bark, saw mill scraps, hard chips rejected from pulping, excess screenings such as sheaves and primary residuals without mixed secondary residuals. Physical and chemical properties of wood ash are important in determining their beneficial uses. These properties are influenced by species of tree, tree growing regions and conditions, method and manner of combustion including temperature, other fuel used with wood fuel, and method of wood ash collection [1, 2, 3]. Further quality variation in the wood ash properties occur when wood is co-fired with other supplementary fuels such as coal, coke, gas, and the relative quantity of wood verses such other fuels [1]. The following sections deal with the information collected on properties and options for constructive uses for wood ash. 2.1 Properties of Wood Ash Etiegni and Campbell [2] studied the effects of combustion temperature on yield and chemical properties of wood ash. For this investigation, lodgepole pine saw dust collected from a sawmill was combusted in an electric furnace at different temperatures for 6 to 9 hours or until the ash weight became constant. The results showed that wood ash yield decreased by 45% when combustion temperature were increased from about 550 to 1100 C (1000 to 2000 F). The average particle size of the wood ash was found to be 230 ìm. The concentration of potassium, sodium, zinc, and carbonate decreased while concentrations of other metal ions remained constant or increased with increasing -3-

18 temperature. The ph of wood ash was found to vary between 9 and Etiegni, et al. [2,3] obtained X-ray diffraction data to determine the presence of various compounds in dry and wet ash which was then dried for 24 hours. The major oxides detected in the wood ash were lime (CaO), calcite (CaCO 3 ), portlandite (Ca (OH) 2) and calcium silicate (Ca 2 SiO 4 ). The authors reported that swelling of wood ash occurred due to the possible hydration of silicates and lime present in the ash. Campbell [4] presented data on major and trace elements in wood ash. The major elements were calcium (7-33%), potassium (3-4%), magnesium (1-2%), phosphorus ( %), manganese ( %), and sodium ( %). The trace elements were zinc, boron, copper, molybdenum, and others at parts per million levels. Carbon content in wood ash was found to vary between 4 and 34% by mass. Mishra, et al. [5] investigated elemental and molecular composition of mineral matters in ash from five types of wood and two types of barks as a function of temperature. The mass loss occurred in the range of 23 to 48% when the combustion temperature was increased from 500 to 1300 o C (930 to 2370 o F). This was attributed to decreased elemental mass concentrations of K, S, B, Na, and Cu resulting from increased temperature. Steenari and Lindqvist [6] characterized fly ashes derived from co-combustion of wood chips and fossil fuels, and compared their properties to those obtained from combustion of wood ash alone. In their work, wood fly ash samples were obtained by the co-firing of wood chips with coal, oil, and peat in utility boilers in Sweden. The fly ashes derived from the cocombustion of wood with coal or peat exhibited lower concentrations of calcium, potassium, -4-

19 and chlorine, and higher concentrations of aluminum ion and sulfur relative to pure wood ash. The ph of leachates obtained from the co-combustion ashes were lower compared to pure wood ash. The concentrations of trace metals in these ashes were similar to those observed in pure wood ashes. Steenari [7] presented possible chemical reactions involved in the hydration of wood ash concrete. Equation 1 describes the reaction involving CaO and H 2 0. CaO + H 2 O = Ca (OH) 2 (1) This reaction is rapid and exothermic, and leads to the formation of inter-particle bond. The next reaction occurs due to exposure to moisture and air as given by Equation 2. Ca (OH) 2+ H 2 O+ CO 2 (gas) = Ca (OH) 2 (aqueous)+ H 2 CO 3 (aqueous) = CaCO 3 +2H 2 O (2) Due to very low (or none) solubility of CaCO 3 compared to CaO and Ca (OH) 2, the above hydration process produces a more stabilized reaction product. After the carbonation reaction (Equation 2), the third reaction leads to the formation of an ettringite as described by Equation 3. Ca 3 Al 2 O 6 + 3CaSO H 2 O = Ca 6 Al 2 (SO 4 ) 3(OH) 1226H2O (3) In the above equation, tricalcium aluminate is used as an example. However, other soluble components can be substituted for these compounds in the ettringite formation reaction described by Equation (3). This ettringite is stable at ph levels greater than 10.5 [7]. This chemical product contributes to the strength development of the hydrated wood ash material and restricts the release of calcium, aluminum, and sulfate. Naik [8] determined physical and chemical properties of wood ashes derived from different mills. Scanning Electron Microscopy (SEM) was used to determine shape of wood ash -5-

20 particles. The SEM micrographs showed wood ashes as a heterogeneous mixture of particles of varying sizes, which were generally angular in shape. The wood fly ash consisted of cellular particles, which were unburned, or partially burned wood or bark particles. The average moisture content values for the wood ash studied were about 13% for fly ash and 22% for bottom ash. All wood ash samples were first oven-dried at 99 0 C (210 o F) and then tested for gradation in accordance with ASTM C 136 using standard sieve sizes. average amount of fly ash passing sieve #200 (75 ìm) was 50% (ASTM C 117). The The average amount of fly ash retained on sieve No. 325 (45 µm) was about 31% for wood fly ash (ASTM C 430). Test results for unit weight or bulk density (ASTM C 29) exhibited average density values of 490 kg/m 3 (30.6 lb/ft 3 ) for fly ash and 827 kg/m 3 (51.6 lb/ft 3 ) for bottom ash. Specific gravity (ASTM C 188) tests showed an average specific gravity value of 2.48 for wood fly ash. Specific gravity (ASTM C 128) tests for bottom ash showed an average specific gravity value of The average saturated surface dry (SSD) moisture content (ASTM C 128) values were 10.3% for fly ash and 7.5% for bottom ash. The average cement activity index ASTM C 311/ C 109 at the age of 28 days for fly ash was about 66% of the control. exhibited a value of 116%. The average water requirement (ASTM C 311) for fly ash Autoclave expansion tests for fly ash exhibited a low average expansion value of 0.2 percent. 2.2 Beneficial Uses of Wood Ash Approximately 70% of the wood ash generated in the U.S.A. is landfilled; an additional 20% is applied on land as a soil supplement [2-14]. The remaining 10% has been used for miscellaneous applications [1-4] including construction materials, metal recovery, and -6-

21 pollution control. Landfilling is becoming very restrictive due to shrinking landfill space and strict environmental regulations. The use of wood ash as a soil supplement is becoming more limited due to the presence of heavy metals and high alkalinity, as well as reduced availability of land for application. Due to these reasons, many attempts are being made to develop high-volume use technologies for wood ash, especially for use in construction materials [8,12] Land application Based on the properties of wood ash, it can be used as a source of nutrients for plant growth, and as a liming material and neutralizing agent for acidic soil. Etiegni [3] reported the use of wood ash as an agricultural soil supplement and liming material. For that investigation, two types of plants (winter wheat and poplar) were grown in a greenhouse on six different Idaho soils amended with varying amounts of wood ash. The results indicated a substantial increase in the wheat biomass and in the diameter and height of the poplar at ash concentrations of up to 2% (16 tons/acre). Based on the results obtained, the author indicated that wood ash could be used as a low-grade fertilizer containing potassium and as a liming agent. Meyers and Kopecky [9] evaluated the effects of land spreading of wood ash on the yield and elemental composition of forage crops and soil nutrient levels using both greenhouse and field investigations. The use of wood ash resulted in a higher yield compared to those obtained with limed and fertilized control treatments. No adverse effects were noted at wood ash application rates of up to 20 tons/acre. -7-

22 Nguyen and Pascal [10] measured tree growth responses using two sources of wood ash as a forest soil amendment. Four different application rates (0, 2, 4, and 8% by mass) were used in their investigation. The tree growth responses were measured using greenhouse and microcosm approaches. The addition of wood ash affected all the measured growth responses (height, diameter, and total leaf area) within the tested range. However, 2% (i.e., 16 tons/acre) application rate was found to be optimum. Bramryd and Frashman [11] reported a decrease in acidity and aluminum concentration when wood ash was applied to the soil having 35-year old pine trees in Sweden. Except Cu, no significant increase in heavy metal concentrations was found due to the addition of wood ash. However, the concentration of extractable Mn increased. Naylor and Schmidt [14] evaluated wood as a fertilizer and liming material. In their study, wood ash was mixed with two acidic soils at rates of 0, 0.4, 1.8 and 2.4 tons/acre to assess changes in extractable nutrients and soil ph. Generally, concentrations of extractable P, K, and Ca increased with increasing ash application rate. The same trend was also noticed for soil ph. The neutralizing capability of the ash was found to be half of that achieved by using agricultural limestone Pollution Control Wood ash has been used as a replacement of lime or cement kiln dust in the solidification of hazardous wastes [1]. It has also been used for odor as well as ph control of hazardous and -8-

23 non-hazardous wastes. Wood ash has been added to compost as a color and odor control. Wood ash has been found to capture several water borne contaminants [1] Construction materials Very limited work has been done to find applications of wood ash as a construction material, particularly in cement-based materials. Due to high carbon content in wood ash, its use is limited to low- and medium-strength concrete materials. In Europe, wood ash has also been used as a feedstock in the manufacture of portland cement [2]. Based on the measured physical, chemical, morphological properties, Naik [8] reported that wood ash has a substantial potential for use as a pozzolanic mineral admixture and an activator in cement-based materials. He further indicated that wood ash has significant potential for use in numerous other materials including Controlled Low Strength Materials (CLSM), low- and medium-strength concrete, masonry products, roller-compacted concrete pavements (RCCP), materials for road base, and blended cements. Naik [12] investigated the use of wood ash as a major ingredient in the manufacture of CLSM meeting ACI 229 requirements. All CLSM mixtures consisted of wood fly ash, water, and cement. A total of 31 CLSM mixtures were proportioned using three sources of wood fly ash to obtain a range of compressive strengths from 50 psi to 150 psi at the age of 28 days. Each CLSM mixture was tested for its fresh/rheological and hardened properties. Fresh CLSM properties included unit weight, amount of bleedwater, settlement, and setting and hardening characteristics. Hardened CLSM properties included compressive strength, -9-

24 density, and permeability. Several CLSM mixtures containing high volumes of wood fly ash were found to be appropriate for backfill of excavations, and/or for making low- to medium-strength concrete [8, 12]. Mukherji, et al. [13] performed experiments to explore the use of wood ash in the ceramic industry. They reported that wood ash derived from the Neem (Margosa) tree could be used as a substitute for CaCO 3 in the manufacture of glaze. A series of color stains was also manufactured using the "Neem" wood ash and other ingredients. These stains were calcined at C ( F). The glazes and colors developed using this wood ash were tested and evaluated for the desired properties for these materials [13]. The authors concluded that the glazes and colors developed in their investigation are suitable for use in both green and baked ware. -10-

25 3.0 OBJECTIVES Wood ash is generated by saw mills, pulp mills, and the wood products industry, by burning a combination of wood products, such as bark, twigs, knots, chips, etc. with other fuels such as coal, coke, oil, and natural gas to generate electricity and/or steam required for their manufacturing processes. The aim of this project is to develop manufacturing and performance requirements for structural-grade concrete and CLSM (flowable slurry) containing wood ash from Wisconsin industry for construction applications. In order to demonstrate the use of wood ash in concrete and CLSM, the project is planned over a two-year period (June 1, 2001 to October 31, 2003). The project activities include refinement of laboratory mixture proportions through prototype-scale manufacturing at the facilities of a ready-mixed concrete producer, and establishing final mixtures for full-scale manufacture of concrete and CLSM. Also, a construction demonstration is scheduled. Implementation of the technology developed from this project should increase utilization of wood ash materials, reducing the pressure on Wisconsin landfills; and develop a market for products containing wood ash, which do not exist currently. This will benefit industry, the environment, and the citizens of Wisconsin. -11-

26 4.0 RESEARCH DESIGN This project consists of the following eight tasks: Task 1: Selection of Materials and Mixtures; Task 2: Mixture Proportions Refinement; Task 3: Prototype Manufacturing; Task 4: Evaluation of Mixtures; Task 5: Full-scale Manufacturing; Task 6: Technology Transfer and Construction Demonstration Plan; Task 7: Wood Ash Concrete and CLSM Demonstration; Task 8: Reports. A summary of the progress of each of these tasks is given below. Details of the results of each task are described in later sections of this report. Task 1: Selection of Materials and Mixtures Materials used for this project included sand, coarse aggregate, ASTM Type I cement, ASTM C 618 Type C fly ash, and wood ash. In the first year of the project, wood ash from the Weyerhaeuser Company at Rothschild,WI, was chosen. All components of the CLSM and concrete (wood ash, cement, and aggregate) were tested for their chemical and physical properties using ASTM or other applicable test methods. These properties were used in determining mixture proportions of both CLSM and concrete developed in this project. Task 2: Mixture Proportions Refinement Based on previous work conducted and reported by UWM-CBU using different ash materials [17], two sources of wood ash were selected. Wood ash from the Weyerhaeuser Company, Rothschild, WI, was selected for the first year of the work. Three series of CLSM mixture proportions, and four series of concrete mixture proportions were developed in the laboratory. Cement content in CLSM mixtures varied from 81 to 116 lb/yd 3 and wood ash content varied between 995 and 2130 lb/yd 3. For concrete mixtures, wood ash content varied -12-

27 between 36 and 87 lb/yd 3 and Class C fly ash content between 50 and 165 lb/yd 3. CLSM mixtures were tested for unit weight, temperature, air content, settlement, bleed water, and compressive strength. Concrete mixtures were tested for fresh concrete properties and compressive strength. Task 3: Prototype Manufacturing Based on the mixture proportions developed at UWM-CBU, prototype-scale manufacturing was carried out at a ready-mixed concrete plant (Midway Concrete Co.) near Rothschild, WI. Each batch of CLSM or concrete was between one and two cubic yards. Three CLSM and four concrete mixtures were manufactured for the prototype series. Wood ash was not stored at the facilities of Midway Concrete Co. It was transported directly from the Weyerhaeuser Company plant and either dumped into a hopper used to batch the CLSM materials for the mixtures, or manually weighed for concrete mixtures. Task 4: Evaluation of Mixtures CLSM prototype mixtures containing wood ash were tested for various properties. The CLSM was monitored for its rheological and hardened CLSM characteristics of bleed water, settlement, compressive strength, and permeability. Concrete prototype mixtures containing wood ash were tested for rheological, physical, and mechanical properties. Fresh concrete properties such as air content, workability, unit weight, and temperature were measured. Test specimens were made for evaluating -13-

28 compressive strength, splitting tensile strength, flexural strength, drying shrinkage, and freezing and thawing. Test results from the laboratory and prototype manufacturing were evaluated for physical and chemical properties. Based on the evaluation, CLSM and concrete mixtures were selected for full-scale manufacturing and a construction demonstration. Task 5: Full-Scale Manufacturing Full-scale manufacturing was carried out at the Midway Concrete Co., a ready-mixed concrete plant in Rothschild, WI. Three series of CLSM mixture proportions were made. For each series, between five and seven batches of CLSM were manufactured. The volume of each batch of CLSM was approximately nine cubic yards. The CLSM was monitored for its rheological and hardened CLSM characteristics such as bleed water, settlement, compressive strength, and water permeability. Four series of concrete mixtures were also made. Each series consisted of three to four batches of approximately nine cubic yards of concrete. Fresh concrete properties such as air content, workability, unit weight, and temperature were measured. Test specimens were made for evaluating compressive strength, splitting tensile strength, flexural strength, shrinkage, and freezing-thawing resistance. -14-

29 Task 6: Technology Transfer and Construction Demonstration A technology transfer seminar was conducted in Rothschild, WI, on September 27, The title of the seminar was Workshop and Construction Demonstration for Use of Wood Ash in Concrete and Flowable Slurry. A total of 26 people attended the seminar. The Speakers for this seminar were Tarun R. Naik of UWM-CBU, Bruce W. Ramme of We Energies, and Michael Miller of the Wisconsin DNR. They presented information on the use of flowable slurry and concrete incorporating wood ash and fly ash, as well as on environmental issues and regulations. The technology transfer seminar consisted of a halfday of presentations followed by a demonstration of the use and placement of wood ash in flowable slurry and in concrete. A section of pavement in a log-handling yard located in the Weyerhaeuser Rothschild mill was used for the demonstration. Additional technology transfer activities have also been performed. Results of the project have been presented at various venues as well as at other UWM-CBU sponsored workshops. Although not supported by the funds of this project, additional presentations were made in Wisconsin on the use of wood ash to further the technology transfer activities. Rudolph N. Kraus, Assistant Director, UWM Center for By-Products Utilization, made a presentation entitled Wood Ash: A New Pozzolanic Material: Its Uses in Concrete and Concrete Products, Roller-Compacted Concrete Pavements, Blended Cements, and Flowable Slurry on March 18, 2002 at the UWM-CBU Workshop on the Use of Fly Ash and other Coal- Combustion Products in Concrete and Construction Materials. Prof. Tarun R. Naik, Director, UWM Center for By-Products Utilization made a presentation entitled Wood Ash: -15-

30 A New Source of Pozzolanic Material at the UWM-CBU seminar on Recent Advances in Cementitious Materials held (May 17-18, 2002) in Milwaukee. Two technical papers have also been developed from the report of this project. A paper entitled Durability of Concrete Incorporating Wood Fly Ash has been accepted for presentation and publication at the Sixth CANMET/ACI International Conference on Durability of Concrete, Thessaloniki, Greece, June Another paper entitled Properties of Controlled Low-Strength Material made with Wood Fly Ash has been submitted for presentation and publication at the ASTM Symposium on Innovations in Controlled Low- Strength Material (Flowable Slurry), Denver, Colorado, June Similar workshops and seminars may be planned in the next year. Task 7: Wood Ash Concrete and CLSM Demonstration A demonstration of a section of structural slab using air-entrained concrete and a demonstration of CLSM used for a section of pavement base was conducted. The structural slab and base course were used for a section of log yard at the facilities of the Weyerhaeuser Company, Rothschild, WI. Mixtures from the full-scale CLSM and concrete manufacturing were used for the demonstration. Each concrete mixture was used to cast a section of the pavement area of about 800 to 1200 ft 2. The thickness of the concrete slab was specified at eight inches. Minimum concrete compressive strength was specified to be 4000 psi at the age of 28 days. The area used for the construction of the three series of CLSM pavement base was about 800 to 1200 ft 2. The thickness of the CLSM base was varied between 9 and 24 inches depending on the depth excavated. Air-entrained concrete and CLSM containing -16-

31 wood ash was manufactured at the facilities of Midway Concrete Co., Rothschild, WI. For the construction demonstration, wood ash was not stored at the facilities of Midway Concrete Co. Ash was transported directly from the Weyerhaeuser Company plant and either dumped into a hopper used to batch the CLSM materials for the mixtures, or manually weighed for concrete mixtures. -17-

32 5.0 EXPERIMENTAL PROCEDURES 5.1 Materials Materials used in this project consisted of cement, fine and coarse aggregates (concrete sand and crushed stone), one source of wood ash, and one source of Class C fly ash. Materials were characterized for their chemical and physical properties in accordance with the applicable ASTM standards Wood ash Wood ash from one source was used during the first year of this project. Properties of the wood ash were determined in accordance with ASTM C 618 requirements for chemical and physical properties. Chemical properties included oxides, basic chemical elements, and mineralogy. Physical property tests included fineness (ASTM C 430), strength activity index with cement (ASTM C 109), water requirement (ASTM C 109), autoclave expansion (ASTM C 151), and specific gravity (ASTM C 188) Fine aggregate One source of clean concrete sand was utilized in this investigation for all CLSM mixtures and concrete mixtures. Physical properties of the sand were determined in accordance with ASTM C 33 requirements: unit weight (ASTM C 29), specific gravity and absorption (ASTM C 128), fineness (ASTM C 136), material finer than #200 sieve (ASTM C 117), and organic impurities (ASTM C 40). -18-

33 5.1.3 Coarse aggregate One source of coarse aggregate was utilized in this investigation for the concrete mixtures. The maximum size of the coarse aggregate was 3/4". Physical properties of the coarse aggregate were also determined in accordance with ASTM C 33 requirements: unit weight (ASTM C 29), specific gravity and absorption (ASTM C 128), fineness (ASTM C 136), material finer than #200 sieve (ASTM C 117), and organic impurities (ASTM C 40) Class C fly ash One source of Class C fly ash (We Energies, Pleasant Prairie Power Plant, Pleasant Prairie, WI) meeting the specifications of ASTM C 618 was used for the concrete mixtures. Fly ash was characterized for chemical properties (ASTM C 618) including oxides, basic chemical elements and mineralogy; and physical properties: fineness (ASTM C 430), strength activity index with cement (ASTM C 109), water requirement (ASTM C 109), autoclave expansion (ASTM C 151), and specific gravity (ASTM C 188)) Cement Type I portand cement was used. Its physical and chemical properties were determined in accordance with applicable ASTM test methods. Cement was tested per ASTM C 150 requirements for air content (ASTM C 185), fineness (ASTM C 204), autoclave expansion (ASTM C 151), compressive strength (ASTM C 109), time of setting (ASTM C 191), and specific gravity (ASTM C 188). -19-

34 5.2 Elemental Analysis Wood ash, Class C fly ash, and cement were analyzed using Instrumental Neutron Activation Analysis. The neutron activation analysis method exposes the sample to neurons, which results in an activation of many elements. This activation consists of radiation of various elements. For the ash and cement utilized in this project, gamma-ray emissions were detected. Many different elements may be detected simultaneously based on the gammaray energies and half-lives. 5.3 Mineralogical Analysis Two grams of each sample were ground in a power driven mortar and pestle unit for 55 minutes with ethyl alcohol. The alcohol was then evaporated for mineralogical analysis of the sample. The diffraction mount used was a specially made back loading holder, in which the sample was poured against a matte surface disk and secured in place with a second smaller disk mounted into the holder through an "O" ring seal. The matte surface disk was then removed. The samples were weighed while loading so that each mount contained the same amount of the sample powder. The sample was mounted on a diffractometer (a Nicolet I2 automated unit). The parameters used for producing the scan (diffraction pattern) were optimized for quantitative analysis of the minerals. The file, which was produced during the scan, was graphically converted on a computer screen and plotted. The plot was searched for crystalline phases present using an automated Hanawalt search, by looking through a list of expected phases for the sample using first and second strongest lines and by using computer overlays of the plot using standard phases from the JCPDS file to test -20-

35 each phase. The overlay plot was generated from the unknown test sample and a standard sample. The presence or absence of the phase was verified using the standard. After the phases were tabulated, the diffraction file was converted to run on the "SQ" program, which uses the phases assigned, calculates a match between the observed pattern and a pattern generated from the assigned phases. Various parameters were adjusted to obtain this match. The scale factors assigned to each phase were converted into weight percents of each phase. A second pattern was run in which ZnO was added in the amount of 50%. In the test samples containing amorphous material, the percentage of ZnO measured by "SQ" was higher than 50%. The magnitude of this change was used to calculate the amount of amorphous material in the sample. 5.4 Manufacturing of CLSM and Concrete Mixtures and Testing of Specimens Laboratory mixtures CLSM laboratory mixtures Three CLSM mixtures were proportioned and manufactured in the laboratory of the UWM Center for By-Products Utilization. Laboratory mixture procedures were followed as outlined in ACI 229R for mixing CLSM in a ready-mixed concrete truck mixer. First, 70 to 80 percent of the water required was added to the mixer. Subsequently, half of the fine aggregate and/or ash was added to the mixer and mixed for one minute. Then, all of the cement and half of the remaining ash was added to the mixer and again mixed for one minute. Then, the rest of the ash was added. Finally, with continued mixing, the remaining -21-

36 aggregate and remaining water was added. After all materials were added, the mixture was mixed for a minimum of three more minutes. CLSM mixtures had a wood ash content between 995 and 2130 lb/yd 3, whereas cement content varied between 81 and 116 lb/yd 3. The first two CLSM mixtures consisted of wood ash, ASTM Type I cement, and water. The third mixture contained wood ash, ASTM Type I cement, sand, and water. The sand content in the third mixture was 1570 lb/yd 3. CLSM mixtures had a flow between 12 and 13.5 inches and a unit weight between 108 and 115 lb/ft 3. Fresh CLSM properties such as air content (ASTM D 6023), flow (ASTM D 6103), unit weight (ASTM D 6023), temperature (ASTM C 1064), and setting (ASTM D 6024) were measured. Air temperature was also measured and recorded. CLSM test specimens were prepared from each mixture for compressive strength (ASTM D 4832) and water permeability (ASTM D 5084). The compressive strength of CLSM was measured at the ages of 1, 2 and 3 days. The amount of bleedwater and level of the solids (settlement) of CLSM mixtures was measured in a 6x12-inch cylinder. All test specimens were cast in accordance with ASTM D Concrete laboratory mixtures Air-entrained concrete mixtures were batched in the laboratory of the UWM Center for Byproducts Utilization. Four series of mixtures were proportioned. All laboratory concrete mixtures were mixed in a rotating drum concrete mixer in accordance with ASTM C

37 Coarse aggregate was added first to the mixer and then mixed for a few revolutions. Fine aggregate and cement were then added to the mixer. These ingredients were mixed dry for two minutes. Thereafter, water was added and all ingredients in the mixer were mixed for three minutes, followed by a 3-minute rest and then mixed for an additional 2-minute. The air-entraining admixture was introduced into the mixture with the water. The first mixture (Control) was proportioned without wood ash, and the remaining three mixtures contained wood ash. All four concrete mixtures contained Class C fly ash. Wood ash and Class C fly ash were used as a partial replacement of cement in the concrete mixtures. Concrete laboratory mixtures contained 0, 7.5, 17.5, and 17.5% wood ash by weight of cementitious materials. The slump of all concrete mixtures was maintained between 3 and 4-1/2 inches. The fresh concrete density varied between and 146 lb/ft 3. Fresh concrete properties including slump (ASTM C 143), air content (ASTM C 138), unit weight (ASTM C 138), and concrete temperature (ASTM C 1064) were measured for each mixture. Ambient air temperature was also measured and recorded. For each concrete mixture, concrete specimens were cast in accordance with ASTM C 192. Concrete specimens were cast for compressive strength (ASTM C 39), and were tested at 3, 14, and 28 days. Specimens were cured for one day in their molds at 75 ± 5 o F, then demolded and placed in a standard moist-curing room (100% R.H. and 73 ± 3 o F) until the time of test. -23-