Center for By-Products Utilization

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1 Center for By-Products Utilization MPU ASH AS A POTENTIAL SOURCE FOR CONSTRUCTION MATERIALS By Tarun R. Naik and Rudolph N. Kraus Report No. CBU Rep-438 July 2001 Submitted to Raymond F. Sturzl, Manitowoc Public Utilities - Manitowoc, WI Department of Civil Engineering and Mechanics College of Engineering and Applied Science THE UNIVERSITY OF WISCONSIN - MILWAUKEE

2 MPU Ash as a Potential Source for Construction Materials A Report Submitted to Raymond F. Sturzl Manitowoc Public Utilities Manitowoc, WI July 2001 REP-438

3 MPU Ash as a Potential Source for Construction Materials by Tarun R. Naik, Ph.D., P.E. and Rudolph N. Kraus UWM 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) ii

4 Executive Summary TITLE: MPU Ash as a Potential Source for Construction Materials SOURCE: UWM-CBU Report No. CBU , REP-421, 2001 BACKGROUND/PURPOSE: To conduct physical, chemical, mineralogical, and microstructural tests for determining properties of three sources of typical Manitowoc Public Utilities (MPU) ashes (Combined MPU #5 and #7 Bottom Ash, MPU #8 Bottom Ash, and MPU #8 Fly Ash) to evaluate their potential options for beneficial reuse. The three sources were also selected for evaluation per WI-DNR Chapter NR 538 requirements. The three ash sources were selected based upon their diverse character (such as color, texture, type of collection system/process, etc.) in consultation with Mr. Raymond F. Sturzl, Manitowoc Public Utilities. These three ash sources were specifically identified for characterization before their possible use in a new type of concrete called DPC (Defined-Performance Concrete). OBJECTIVE: The primary objective of this project was to recommend alternatives to the normal practice of landfilling by evaluating potential reuse/recycle applications for these materials, especially in cementbased, durable, construction materials. CONCLUSIONS: MPU s ashes have considerable potential for many applications. However, the performance of these ashes needs to be established for individual applications. Evaluation of the MPU ashes conducted per the requirements of WI-DNR Chapter NR 538 indicates that the combined MPU #5 and #7 bottom ash materials meets the requirements of a NR 538 Category 2 material, while the MPU #8 fly ash and MPU #8 bottom ash meets Category 4 requirements. The following are some of the high-volume applications that would require further evaluation before their use in actual construction projects. These applications could consume all of the ashes currently being produced by Manitowoc Public Utilities. Flowable Materials have up to 1200 psi compressive strength, have flowing-mud type of consistency and fluidity, contain very little portland cement and a lot of water, and consist mostly of ash or similar materials. It is believed that concrete Bricks, Blocks, and Paving Stones could also be made with the ashes evaluated. Additionally the MPU #8 fly ash should be useful for replacement of clay in clay bricks manufacturing. The test data collected also indicate that the MPU ashes can be used as a partial replacement of aggregates and/or cement in Structuralgrade Concrete. It is also concluded that there is a potential for high-value use of the MPU #8 fly ash in manufacturing Blended Cements. Soil stabilization or site remediation is another significant potential use of the MPU ashes tested. Paving applications, such as Roller Compacted Concrete for parking lots and access roadways, would also be a high-value use of MPU ashes tested. Based upon the this initial testing performed for the project, these applications have the potential to be a significant source of revenue for MPU. A further evaluation is very strongly recommended. Probability of success is very high. RECOMMENDATIONS: Further evaluation is recommended, starting with lab-scale production and testing of ash use in the above mentioned applications. Cost/benefit analysis and marketing studies should be undertaken; and a long-term evaluation program for these products should be started. This includes the development of ash specifications for high-potential, high-value, applications such as DPC (Defined- Performance Concrete). iii

5 Table of Contents Item Page Executive Summary... ii List of Tables...v List of Figures... vii Section 1: Introduction...1 Section 2: Tests of MPU Coal Combustion Products...3 EXPERIMENTAL PROGRAM...3 PHYSICAL PROPERTIES...3 As-Received Moisture Content...3 Particle Size Analysis...4 Unit Weight...6 Specific Gravity...7 SSD Absorption...7 ASTM C 618 TESTS...8 Physical Properties per ASTM C Cement Activity Index...8 Water Requirement...10 Lime Activity Index...10 Autoclave Expansion...11 Evaluation with Activators...12 Chemical Properties per ASTM C CHEMICAL COMPOSITION...15 ELEMENTAL ANALYSIS...15 SCANNING ELECTRON MICROSCOPY (SEM)...16 Section 3: Constructive Use Options for MPU Ashes...18 INTRODUCTION...18 USES OF MPU FLY ASHES...18 Section 4: Suggestions for Further Evaluations...20 FLOWABLE MATERIALS...20 BRICKS, BLOCKS, AND PAVING STONES...21 STRUCTURAL-GRADE CONCRETE...21 BLENDED CEMENT...21 ROLLER-COMPACTED CONCRETE PAVEMENT...22 SOIL AMENDMENT WITH OR WITHOUT DREDGED MATERIALS...22 iv

6 Table of Contents (Continued) Item Page Section 5: References...63 APPENDIX 1: WI-DNR NR 538 Analysis...64 WISCONSIN DNR CHAPTER NR 538 STANDARDS...65 LEACHATE CHARACTERISTICS OF MPU COAL ASHES...65 ELEMENTAL CHARACTERISTICS OF MPU COAL ASH...66 DNR NR 538 SPECIFIED USE OPTIONS...67 APPENDIX 2: Modified ASTM C 422 for Particle Size Analysis...78 v

7 List of Tables Item Page Table 1 - Background Information on the MPU Ash...24 Table 2 - As-Received MPU Ash Moisture Content...26 Table 3 - Sieve Analysis of MPU Ash...28 Table 4 - Material Finer Than No. 200 Sieve by Washing...29 Table 5 - Materials Retained on No. 325 Sieve...30 Table 6 - Unit Weight and Voids Table 7 - Specific Gravity...36 Table 8 - Specific Gravity...37 Table 9 - Absorption...38 Table 10 - Physical Tests Requirements of Coal Fly Ash per ASTM C Table 11 - Mortar Cube Compressive Strength...41 Table 12 - Strength Activity Index with Cement...41 Table 13 - Water Requirement...42 Table 14 - Pozzolanic Activity Index with Lime Table 15 - Autoclave Expansion or Contraction...42 Table 16 - Mortar Cube Compressive Strength with Activators Table 17 - Strength Activity Index with Cement with Activators..45 Table 18 - Chemical Analysis...47 Table 19 - Mineralogy of MPU Ash...49 Table 20 - Elemental Analysis...51 Table 21 - Potential Uses of the MPU Ashes...55 vi

8 List of Tables (Continued) Item Page Table 22 - Beneficial Use Methods for By-Products Based Upon Characterization Category, per NR Table 23 - Leachate Analysis Data for MPU Ashes Table 24 - Leachate Standards per DNR NR Table 25 - NR 538 Categories for MPU Ashes per Lechate Analysis Table 26 - NR 538 Elemental Analysis for MPU Ashes...72 Table 27 - Elemental Analysis per DNR NR Table 28 - NR 538 Categories for MPU Ashes per Elemental Analysis vii

9 List of Figures Item Page Fig. 1: Particle Size Distribution of MPU #5 - #7 Bottom Ash...31 Fig. 2: Particle Size Distribution of MPU #8 Bottom Ash...32 Fig. 3: Particle Size Distribution of MPU #8 Fly Ash...33 Figure 4 7: SEM Photomicrographs of MPU #5 Bottom Ash...59 Figure 8 11: SEM Photomicrographs of MPU #7 Bottom Ash...60 Figure 12 15: SEM Photomicrographs of MPU #8 Bottom Ash...61 Figure 16-19: SEM Photomicrographs of MPU #8 Fly Ash 62 viii

10 Section 1 Introduction The scope of this project was to determine physical, chemical, mineralogical, and microscopical (i.e., morphological) properties of the Manitowoc Public Utilities (MPU) coal combustion products from daily operations. The main objective of this project is to recommend alternatives to the normal practice of landfilling by recommending potential reuse/recycling applications for these materials. Four different types of coal combustion products were collected for this project: MPU #5 bottom ash, MPU # 7 bottom ash, MPU #8 bottom ash, and MPU #8 fly ash. MPU #5 bottom ash and MPU #7 bottom ash are stored in a combined form at MPU. Therefore, to minimize cost of testing and using these materials, these two materials were blended in the approximate proportions that they are available in storage (1/3 MPU #5 bottom ash, 2/3 MPU #7 bottom ash by weight per MPU) before being tested. Background information on the source of the ash materials was obtained from Manitowoc Public Utilities describing the type of boilers, coal sources, etc. (Table 1). It has been established by previous projects at the UWM Center for By-Products Utilization (UWM- CBU) that properties of coal combustion products (i.e. different types of ashes) vary from boiler to boiler depending upon the type and source of fuel, how the ash is collected, design and operation of the boiler, etc. Therefore, it is important to determine physical, chemical, and morphological properties of the ash for determining their appropriate use options. Before beginning any quantitative testing, the general physical appearance of the MPU materials were evaluated. The MPU #5 bottom ash consisted of white, brown, and beige particles, was dry, and in appearance varied in size from fine sand to approximately 3/8-inch size pieces. The ash 1

11 pieces were lightweight and easily broken apart. The MPU #7 bottom ash was typically brown in color, dry, appeared to be a typical coal bottom ash type of material with gradation varying from a sand-like material with larger pieces up to approximately one-inch. MPU #8 bottom ash was a mixture of small white and light brown pieces, dry, and generally had a gradation similar to a sand. Some larger brown to black particles up to 1/4-inch were also present. The MPU #8 fly ash was a very fine, dry, dark-gray ash. In order to evaluate the potential of the MPU ashes for various cement-based uses such as for aggregate or as a substitute for cement, typical ASTM tests were conducted. ASTM provides standard specifications for both aggregate for use in cement-based products (ASTM C 33) as well as for coal fly ash use in concrete (ASTM C 618). To judge the suitability of the MPU ash resource for potential use as a mineral admixture in cement-based materials, tests were performed as described in the following sections and compared to the requirements specified in ASTM C 33 and C

12 Section 2 Tests of MPU Coal Combustion Products EXPERIMENTAL PROGRAM A test program was designed to measure physical, chemical, mineralogical, and microscopical properties of the ashes from MPU boilers. Four different coal combustion products were received from MPU. Three sources of bottom ash, MPU #5 bottom ash, MPU #7 bottom ash, and MPU #8 bottom ash; and one source of fly ash MPU #8 fly ash, were selected for evaluation. Prior to testing, the MPU #5 bottom ash and MPU #7 bottom ash were blended in accordance with the direction of MPU, one part MPU #5 bottom ash and two parts MPU #7 bottom ash, by weight. In order to measure various properties of these ash products, the following experiments were carried out. PHYSICAL PROPERTIES As-Received Moisture Content As-received moisture content (MC) of the MPU ashes were determined in accordance with the ASTM Test Designation C 311. Table 2 provides the test data. The results show that all three materials, MPU #5 - #7 bottom ash, MPU #8 bottom ash, and MPU #8 fly ash had low moisture contents (0.1%, 0.1%, and 0.4%, respectively). Although all three ash materials would meet ASTM C 618 requirements for moisture content (3% max.), it is important to maintain consistent, low moisture contents when using these materials in future applications since there are some significant negative attributes associated with moisture in any ash: (1) Moisture/water content leads to cost of shipping water along with the ash to the potential user of the ash. This, of course, increases the cost to the user in obtaining the ash for beneficial reuse. 3

13 (2) If the moisture content is not within control, then the variation leads to quality control problems for the user. (3) The water content is a critical parameter for manufacturing cement-based products. Therefore, if the user is planning to use the ash in cement-based materials, then the water content must be controlled in a narrow range to control the quality of such products. (4) Wetting the ash with or soaking it in water destroys potential cementitious ability of the ash. (5) A typical manufacturer of cement-based materials is equipped very well to handle dry or relatively dry materials. Therefore, wet or variable moisture content ash would make it harder for MPU to market these ashes for reuse/recycle purposes to such manufacturers. Particle Size Analysis Ash samples were first oven-dried at 210 F ± 10 F and then were tested for gradation using standard sieve sizes (1" through #100), as reported in Table 3, in accordance with ASTM Test Designation C 136. Ash samples were also tested in accordance with ASTM test designation C 117 to determine the amount of material finer than No. 200 sieve by washing as reported in Table 4. One ash sample, MPU #8 fly ash, was not evaluated using ASTM C 136 and C 117 due to the fact that this source of the ash was too fine to conduct such tests. The MPU #8 fly ash sample was tested for materials passing No. 325 sieve by washing under pressure in accordance with ASTM Test Designation C 430. Bottom ash samples were too coarse for the ASTM C 430 test. Results are reported in Table 5. The particle size distribution of the MPU #8 fly ash sample was analyzed in accordance with ASTM C 422 (hydrometer analysis) since this material has a significant percentage of fine particles (passing #100 sieve). The complete size distribution of all of the ashes are shown in Fig. 1 to Fig. 3. Particle size analysis data in Table 3 show that the MPU #5 - #7 bottom ash generally is a coarse 4

14 material with approximately 60% of the material between 3/8" and #16 sieve (1.18 mm). Approximately 20% of the MPU #5 - #7 bottom ash sample consisted of particles larger than 3/8" and 20% of the particles were finer than No. 16 (1.18 mm) sieve. Furthermore, this material had less than 2% of the total materials passing No. 200 sieve when washed with water (Table 4). The particle size distribution of the MPU #8 bottom ash more closely resembled the particle size distribution of a sand rather than a coarse aggregate (Table 3). The particle size distribution of the MPU #8 bottom ash also shows that the material has more fine particles present than a typical concrete sand (84% of the materials passing a #30 sieve). The MPU #8 bottom ash also had approximately 6% passing the No. 200 sieve upon washing, Table 4. ASTM C 33 specifies that for a manufactured sand, free of clay or shale, a maximum of 5% passing of No 200 sieve is allowed for aggregate used in concrete subjected to abrasion, and a maximum of 7% for all other concrete. The test data indicates (Table 4) that the two sources of bottom ash may be acceptable for partial replacement of aggregate in readymixed concrete and/or as both coarse and fine aggregates replacements in dry-cast concrete products such as bricks, blocks, and paving stones because of its generally coarse gradation. Furthermore, the MPU #5 - #7 bottom ash and MPU #8 bottom ash materials are not fine enough; i.e., too coarse, to be used for cement replacement in concrete. These coarser materials (MPU #5 - #7 bottom ash and MPU #8 fly ash) may be more suitable for use in a backfill material such as in controlled lowstrength materials CLSM. Figs. 1 and 2 show gradation of MPU bottom ashes. Table 5 data show that the MPU #8 fly ash did not have a considerable amount of material retained on the No. 325 sieve (22.5%). ASTM C 618 for coal fly ash classifies a value of maximum 34% retained on the No. 325 sieve as satisfactory for use in concrete. Based upon this criterion for pulverized coal fly ash, the MPU #8 fly ash meets this requirement of ASTM C 618. These results 5

15 indicate that, based upon the fineness of the material, the MPU #8 fly ash is quite suitable as a cement replacement in concrete and also for CLSM-type of flowable slurry products. Test data for particle size analysis in accordance with the modified ASTM C 422 are presented in Fig. 3. Appendix 2 provides the details of this modified ASTM test. This figure shows that the gradation of the MPU #8 fly ash (Fig. 3) is reasonably uniform. Unit Weight Unit weight (i.e., bulk density) of the ash was determined in accordance with the ASTM Test Designation C 29. Table 6 provides the test results. Bulk density of the MPU #5 - #7 bottom ash and MPU #8 bottom ash was 37, and 96 lb/ft³, respectively. The fine ash material (MPU #8 fly ash) had a density value of approximately 50 lb/ft³. This is consistent for the gradation of the bottom ash, which showed a significant amount of coarser fractions of the ash materials. These data indicate that the MPU #8 bottom ash material may be suitable for replacing regular, normal-weight, sand and the MPU #5 - #7 bottom ash may be used for coarse aggregates in making semi-lightweight or lightweight concrete and/or CLSM. Such lightweight construction materials are well suited for insulating fill for roofs and walls, as well as sound and/or ground vibration barriers. Typical manufactured light-weight coarse aggregates costs about $45 per ton. Determining the bulk density value is also necessary for calculations for establishing and modifying cement-based construction materials mixture proportioning. Percentage of voids in Table 6 indicate amount of free space available for packing of other materials in making cement-based materials. The higher the percent voids, the higher the amount of other materials necessary for making cement-based materials. 6

16 Specific Gravity Specific gravity tests for the fine ash material (MPU #8 fly ash) were conducted in accordance with the ASTM Test Designation C 188, Table 7. Results show that the specific gravity for the MPU #8 fly ash is This is a similar order of magnitude as a typical coal fly ash, though this ash has a slightly higher specific gravity value than typical Class F coal fly ash (specific gravity approximately 2.50), and a typical Class C fly ash (specific gravity approximately 2.60). Specific gravity of typical Wisconsin sand is about 2.7. Specific gravity value is necessary for determining relative substitution rate for fly ash versus amount of cement or sand replaced in a mixture; and, also for calculations for establishing and modifying cement-based construction materials mixture proportions. Specific gravity tests for the MPU #5 - #7 bottom ash and MPU #8 bottom ash were carried out in accordance with ASTM Test Designation C 128. Test results are shown in Table 8. The MPU #5 - #7 bottom ash had an average apparent specific gravity of This is considerably lower than the specific gravity for typical aggregates used in concrete, which is around Therefore, this source of ash should be useful as semi-lightweight and/or lightweight aggregates. Specific gravity of MPU #8 bottom ash, 2.64, is consistent with that of a typical natural aggregate for making conrete. SSD Absorption For the coarser ashes (MPU #5 - #7 bottom ash and MPU #8 bottom ash) saturated surface dry (SSD) moisture absorption tests in accordance with the ASTM Test Designation C 128 were conducted. Results are shown in Table 9. These ash materials, had SSD absorption values that were considerably higher than that for typical natural sand or coarse aggregate used in concrete, which is typically less than 2%. The SSD absorption value is an indication of the porosity of the 7

17 aggregates. Typical lightweight aggregates used in concrete generally have very high absorption values and must be pre-soaked in order to manufacture consistent quality workable concrete. SSD moisture absorption value is also required for calculations for establishing and modifying cementbased construction materials mixture proportioning. Higher absorption materials may lead to better curing of the cement-based materials after they are cast; and, therefore, better quality for such materials. ASTM C 618 TESTS Physical Properties per ASTM C 618 ASTM C 618 provides standard specifications for coal fly ash and natural pozzolans for use in concrete. Therefore, to judge the suitability of the MPU ash resource for potential use as a mineral admixture in cement-based materials, physical tests were performed as described below in accordance with the ASTM Test Designation C 618. Table 10 shows physical properties requirements for coal fly ash and natural pozzolans per ASTM Test C 618. The following physical properties of the MPU ash were determined: (1) Cement Activity Index; (2) Water Requirement; (3) Activity Index with Lime; and, (4) Autoclave Expansion. Cement Activity Index Cement activity index tests for fine ash materials (MPU #8 fly ash) were performed in accordance with the ASTM Test Designation C 311/C 109. Two-inch mortar cubes were made in a prescribed manner using a mixture of cement, sand, and water, without any ash (Control Mixture). Compressive strength tests were conducted at the age of 3, 7, 14, and 28 days. Actual strength test results, in psi, are reported in Table 11 for the test specimens made from the Control Mixture. 8

18 Additional test mixtures were prepared using 80% cement and 20% MPU #8 fly ash, by weight (instead of cement only without MPU ash as in the Control Mixture). Results are reported in Table 11 similar to the Control Mixture. Comparison of the MPU ash mixture cube compressive strengths, with the Control Mixture, is reported in Table 12. These results are designated as Strength Activity Index with Cement. In this comparison, the Control Mixture was assigned a value of 100, at each age, and all other cube compressive strength values were scaled from this reference datum. The cube compressive strength test results, Table 11, for the MPU #8 fly ash mixtures were lower than that for the Control Mixture without fly ash. The Activity Index with Cement data, Table 12, for this ash was 60% to 71% (higher than 75% required by ASTM C 618 at either the 7 or 28-day age) for the compressive strength, compared with the Control Mixture without the MPU ash. However, the actual test data, Table 11, show that sufficient compressive strength can be achieved with the MPU #8 fly ash even though these ash mixtures did not perform as well as the no ash Control Mixture. Based upon the cube compressive strength data, overall, it can be concluded that the MPU #8 fly ash is suitable for making CLSM (which by the ACI Committee 229 Definition has up to 1,200 psi compressive strength at the 28-day age), including making typical structural-grade (up to 5,000 psi compressive strength) concrete for base course and/or sub-base course for pavement of highways, roadways, and airfields; driveways; parking lots; highway pavements and bridges; parking garages; and other similar construction applications. This ash source can also be considered quite satisfactory for housing construction where typically a compressive strength of 3,000 psi concrete, at the age of 28 days, is used. The MPU #8 fly ash resource can also be used for in-house concrete construction needs of MPU. 9

19 In summary, ASTM C 618 classifies a value at 7-day or 28-day age of 75 or above for the Activity Index with Cement for coal fly ash as passing. Based upon this criterion only, the MPU #8 fly ash does not pass either the 7 or 28-day requirement. Water Requirement Water requirement tests for the MPU #8 fly ash was performed in accordance with the ASTM Test Designation C 311. This test determines the relative amount of water that may be required for mixture proportioning of cement-based construction materials. It is well established that the lower the water required for a desired value of workability for the cement-based material, the higher the overall quality of the product. Test data for water requirement for the MPU #8 fly ash is reported in Table 13. The results show that the average value for water requirement for the MPU #8 fly ash was lower than the maximum value specified in ASTM C 618. ASTM C 618 specifies a maximum value of 105 or 115, depending upon the type of ash, as an acceptable value for water requirement. For coal fly ash the acceptable value is 105, while that for natural pozzolan (volcanic ash) it is 115. It is concluded that the MPU #8 fly ash should perform satisfactorily in cement-based construction materials. For the same workability as a concrete having no fly ash, a mixture containing MPU #8 fly ash would require approximately the same or less amount of water. Lime Activity Index Lime activity index tests for the MPU #8 fly ash were performed in accordance with ASTM test requirements. Although not currently part of the ASTM test procedures or requirements for coal fly ash and natural pozzolans, the test was performed to obtain additional information on the MPU ashes. The activity index with lime provides an indication of the potential long-term reactivity of the 10

20 ash in a cementitious mixture. Based upon the 1992 ASTM standard, test procedure C 311/C 109 was followed for the testing the MPU #8 fly ash. Two-inch mortar cubes were made in a prescribed manner using a mixture of lime, sand, water, and MPU #8 fly ash. Cubes were cured for 24 hours at room temperature (73 F) and then for six days at 131 F. Compressive strength tests were conducted at the age of 7 days. Actual strength test results, in psi, are reported in Table 14 for these test specimens. Compressive strength test results for the MPU #8 fly ash was 465 psi at the age of 7 days (Table 14). The 1992 ASTM C 618 specified a minimum requirement of 800 psi for a typical coal ash. Although the MPU #8 fly ash compressive strength is somewhat lower than the required minimum value for coal ash, the ash did show pozzolanic activity. Autoclave Expansion Autoclave expansion tests for the MPU #8 fly ash was performed in accordance with the ASTM Test Designation C 311/C 151. Test specimens in the shape of 1"x1"x11" bars were cast using cement paste containing this MPU ash. The test specimens were then subjected to a high-temperature steam bath at approximately 295 psi pressure in a boiler (a pressure cooker meeting the requirements of the ASTM). The test results, given in Table 15, show that the expansion was negligible. The range of expansion values recorded (-0.05%) for the MPU #8 fly ash samples tested were well below the acceptable maximum limit of expansion/contraction of 0.8%, as specified by ASTM C 618 for coal fly ash. Therefore, the MPU #8 fly ash tested is acceptable in terms of long-term soundness/durability from the viewpoint of undesirable autoclave expansion. 11

21 Evaluation with Activators The MPU #8 fly ash was evaluated with chemical activators to determine if the strength development characteristics of the ash in cementitious materials could be improved. Three different special activators were used for this evaluation: Activator #1, #2, and #3. Two different cement replacement rates (20% and 40%) were used to determine if improved compressive strength could be achieved using more ash. Table 16 shows the actual strength test results at the age of 7 and 28 days. For comparison, the compressive strength results are also shown in Table 16 for the standard 20% cement replacement rate without activators. The Strength Activity Index with Cement of the MPU #8 fly ash mortar cubes, with and without chemical activators, is reported in Table 17. The Activity Index with Cement for the MPU #8 fly ash without activators was approximately 60% at the 7-day age, and about 72% at the 28-day age. A minimum of 75% is specified by ASTM C 618 for coal ash at either the 7-day or 28-day age. Without activators, MPU #8 fly ash does not meet this ASTM requirement. However, the Activity Index results for the ashes with activators indicate that at the 20% replacement level, all three activators increased the compressive strength of the mortar cubes. In the case of Activator #2, even at the 40% replacement level the strength increased compared to the 20% fly ash level without any activators at the 7-day age. Activator #1 at a 20% cement replacement increases the compressive strength noticeably at the age of 7 days (approximately 73% vs. 60% without activators). Activator #2 at a 20% cement replacement increases the compressive strength significantly at the age of 7 days (approximately 85% vs. 60% without activators). Activator #3 at a 20% cement replacement also increased the compressive strength at the age of 7 days (approximately 67% vs. 60% without activators). At the age of 28 days, the compressive strength of the mixtures using activators were slightly lower than the mixture without activators at 12

22 the 20% replacement level. Use of activators generally show that strength of concrete can be improved due to activators. CHEMICAL PROPERTIES PER ASTM C 618 Chemical analysis tests were conducted to determine oxides present in the three sources of the MPU ash. X-ray fluorescence (XRF) technique was used to detect the presence of silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), iron oxide (Fe 2 O 3 ), calcium oxide (CaO), magnesium oxide (MgO), titanium oxide (TiO 2 ), potassium oxide (K 2 O), and sodium oxide (Na 2 O). In this method, ignited samples were fused in a 4:1 ratio with lithium carbonate-lithium tetraborate flux and cast into pellets in platinum molds. The XRF technique for measuring sulfate (SO 3 ) involves grinding the ash sample and manufacturing a compressed pellet with boric acid. A double dilution method using a 4:1 and a 10:1 ratio with boric acid was used to correct for matrix effects. These buttons were used to measure x-ray fluorescence intensities for the desired element, in accordance with standard practice for cementitious materials, by using an automated Philips PW1410 x-ray spectrometer. The percentages of each element were derived from the measured intensities through a standardized computer program based on a procedure outlined for low-dilution fusion. This is a standard practice for detecting oxides in cementitious compounds, including coal fly ash. Tests are reported in Table 18. Loss on ignition (LOI), moisture content, and available alkali (Na 2 O equivalent) for the pre-dried MPU ashes were also determined. These test results are also reported in Table 18. According to the oxide analysis data, the MPU #5-#7 bottom ash, MPU #8 bottom ash, and MPU #8 fly ash do not meet Class C or F coal fly ash requirements due to one or more of the following: high LOI, low combined silicon dioxide, aluminum oxide, and iron oxide, and high sulfate contents. The 13

23 calcium oxide content for the MPU #8 bottom ash and MPU fly ash is judged to be very good because the calcium oxide values are above 10 percent. The MPU #8 fly ash contained over 47% of calcium oxide. Therefore this fly ash may have uses in blended cement applications. Furthermore, the magnesium oxide values are judged to be quite low for all MPU ash samples to minimize the soundness/durability related problems created due to a high-mgo value, which is generally accepted to be greater than five percent. In general, all oxides present, except the combined silicon dioxide, aluminum oxide, and iron oxide; LOI; and the sulfate content; were within limits specified in the ASTM C 618 for coal fly ash. Loss on ignition (LOI) for the MPU #8 fly ash (approximately 14%) is higher than that permitted (maximum 6%) by ASTM C 618 for coal fly ash. Under certain circumstances, up to 12% maximum LOI is permitted by ASTM C 618. Recent research at the UWM Center for By-Products Utilization show that high-loi coal ash can be effectively used for CLSM as well as no-fines concrete and roller compacted concrete pavements. Currents practice in Wisconsin and elsewhere also show that high-loi coal fly ash should generally perform satisfactorily for CLSM. High-LOI ashes affect the use of air-entering agent used in concrete to make the concrete resistant to a freezing and thawing environment. In general, therefore, the MPU ashes may be used for CLSM and concrete, no-fines concrete, roller compacted concrete pavements, dry-cast concrete products, etc. These types of construction materials do not require the use of air-entraining agent for freezing and thawing resistance of concrete. 14

24 CHEMICAL COMPOSITION The mineral analysis, (i.e., chemical composition) for the MPU ashes were conducted by using the X-ray diffraction (XRD) method. The results are shown in Table 19. A typical coal fly ash contains approximately 80% glass (amorphous) phase. Since the glass contents of fly ash contributes to its potential pozzolanic reactivity, a higher amount of glass phase is preferred when a fly ash is used as cementitious materials. The MPU #5 - #7 bottom ash contained the highest amounts of glass phase (54%). The MPU #8 fly ash had glass phase content of only 29% while no glass phases were detected in the MPU #8 Bottom ash. The MPU #8 bottom ash also had an anhydrite form of CaSO 4 content of 72%, which in previous studies by UWM-CBU has had expansive characteristics when used in cement-based materials and also liberated a significant quantity of heat of reaction when combined with water. The high anhydrite CaSO 4 content of the MPU #8 bottom ash could lead to its use by industries typically using anhydrite CaSO 4 in their manufacturing processes. Anhydrite CaSO 4 is used as a source of sulfates in the manufacture of sulfuric acid and is also used in the manufacturing of paper, where it is used as a filler material. The MPU #8 fly ash also had a high amount of anhydrite CaSO 4, 46%, and also a relatively high free lime content, 17%, similar to MPU #8 bottom ash. Both free lime and anhydrite CaSO 4, when combined with water, liberates a noticeable amount of heat. The presence of anhydrite CaSO 4 and lime should be taken into account when using these two materials (MPU #8 bottom ash and MPU #8 fly ash) in a cement-based product. ELEMENTAL ANALYSIS All MPU ash samples were analyzed for total chemical make-up by the Instrumental Neutron Activation Analysis (INAA). Knowledge of total elemental concentration is necessary because it 15

25 provides an insight into the possibility of leaching potential characteristics of the material tested. Leaching of trace metals is known to be highly dependent upon the temperature of the combustion in the boiler and how these trace elements are converted to chemical compounds. A high concentration of undesirable elements does not necessarily mean that these undesirable elements will leach. Tests for leachate characteristics of construction materials, such as TCLP, must be performed in order to conduct the environmental assessment of the materials proposed to be used and the product (e.g., cement-based materials) to be made from it. The results for the elemental analysis performed are reported in Table 20. SCANNING ELECTRON MICROSCOPY (SEM) A scanning electron microscope available at the University of Wisconsin-Milwaukee was employed for this part of the investigation. SEM pictures (photomicrographs) for the four MPU ashes were obtained, Figures 4 through 19. These SEM pictures are an important part of understanding the character and morphology of the particles of the product being evaluated for considering their constructive use options. For example, studying the morphology allows judgment to be made regarding the physical and/or mechanical bond that might be possible for the ash in creating new construction materials. Also, it allows an opportunity to study the contours of the particles and how they may help in mixing and manufacturing these new types of materials. The particle morphology also helps in understanding the level of completeness of combustion and microstructure of burned, partially burned, or unburned particles. This evaluation of level of combustion, and particle size and distribution, also help in judging the water demand that may be placed upon when making cementbased materials from such ashes. 16

26 The MPU #5 bottom ash (Figs. 4-7) consists of large particles which have a glass-like structure. The particles have small voids (approximately 5 μm) distributed over the surface. The MPU #7 bottom ash (Figs. 8-11) also consists of large particles; however, they have two different types of features: some particles have numerous voids, while other particles have a smooth glass-like appearance. Although bottom ash material with the porous structure would be lightweight, these types of materials when used as concrete aggregates, may not be very durable when subjected to abrasion. The MPU #8 bottom ash is considerable finer than the MPU #5 or #7 bottom ashes. The size of the MPU #8 bottom ash particles closely resemble a fine sand (Fig. 12). At magnifications of 100x up to 1000x (Figs ), the surface of the particles show a significant amount of cracking indicating that either an expansion took place while the particles were rapidly cooled, or the surface of the particles were more rapidly breakable, soft, and/or friable than the rest of the structure. The interior of the particles when viewed through the cracks at 1000x (Fig. 15) show a fine angular structure in contrast to the smooth surface of the particles. SEM micrographs of the MPU #8 fly ash are shown in Figs The MPU #8 fly ash is a fine material with irregularly shaped particles. These type of fly ash particles differ from that of typical pulverized coal combustion fly ash that are generally spherical in shape. The irregularly shaped particles would not be beneficial for reducing water demand when used in making concrete. 17

27 Section 3 Constructive Use Options for MPU Ashes INTRODUCTION A number of uses of coal combustion products (CCP) in construction materials already exist [1]. However, these applications depend upon physical, chemical, mineralogical, and surface properties of such products. The same is true for the MPU ashes. The following sections deal with potential uses of the MPU ashes analyzed in this investigation. USES OF MPU ASHES The size distribution of the MPU #8 fly ash is similar to that of conventional coal ash products. In general, however, MPU #8 fly ash is not as fine as typical coal fly ash. Furthermore, the MPU #8 fly ash is irregular in shape versus spherical shape for coal fly ash. This means that when MPU #8 fly ash is added in mortar or concrete, workability of fresh mortar or concrete may not be helped as much as that typical with the use of coal fly ash. In fact, some porous particles of unburned or partially burned or coal (charcoal) may absorb the water added in mortar or concrete and further reduce the workability of the mixture. Some of the MPU ashes have high-loi (i.e., unburned or partially burned organics). This investigation revealed that the MPU ash samples generally did not conform to all parts of the ASTM C 618 Class F or C requirements for coal fly ash for applications in cement-based composites. ASTM C 618 also gives standard specifications for natural pozzolans, e.g., a volcanic ash. The MPU #8 fly ash is expected to be suitable for use in typical structural-grade (up to 5,000 18

28 psi) concrete. The MPU ashes are also very suitable for CLSM and grouting applications. The MPU #5 - #7 bottom ash materials have a low specific gravity and may be useful as a lightweight aggregate in concrete. For more useful applications, with or without beneficiating MPU ashes, further study would be needed to develop optimum use options. A list of potential uses of the MPU ashes are presented in Table

29 Section 4 Suggestions for Further Evaluations As indicated in Section 3, the MPU ashes have considerable potential for many applications. However, the performance of these MPU ashes needs to be proven for individual applications. The following are some of the potential high-volume applications that would require further proof for various uses. It is anticipated that these applications can consume most of the ash products produced by MPU. FLOWABLE MATERIALS Large amounts of MPU ashes can be utilized in manufacture of flowable fill (a.k.a. manufactured soil) material. This is defined by ACI Committee 229 as Controlled Low-Strength Material (CLSM). The compressive strength of CLSM can be very little (10 psi) up to 1200 psi, at the age of 28 days. This material can be used for foundations, bridge abutments, buildings, retaining walls, utility trenches, etc. as backfill; as embankment, grouts, abandoned tunnel and mine filling for stabilization of such cavities, etc. See Table 21 for more details. CLSM can be manufactured with large amounts of MPU ash, low amount of cement and/or lime, and high water-to-cementitious materials ratio to produce the flowable fill. A previous study by UWM-CBU evaluated a combination of MPU #8 fly ash and bottom ash in CLSM. The other coarser bottom ash such as MPU #5-#7 bottom ash may also be used in CLSM fill applications. An evaluation study is strongly recommended in order to produce CLSM for various applications with 20

30 this material for approval by local environmental agencies, such as the Wisconsin Department of Natural Resources. BRICKS, BLOCKS, AND PAVING STONES The MPU ashes have potential for applications in numerous masonry products such as bricks, blocks, and paving stones. However, in order to meet the ASTM requirements for strength and durability, testing and evaluation work is necessary. The results of such testing would be used in developing specifications for the MPU ash in the manufacture of masonry products. Lab and/or proto-type manufacturing-scale evaluation is strongly recommended. Probability of success is very high. STRUCTURAL-GRADE CONCRETE The MPU ashes can be used as a partial replacement of sand (MPU #8 bottom ash), coarse aggregate (MPU #5 - #7 bottom ash), and/or cement (MPU #8 fly ash) in concrete. This is a very broad conclusion from the work conducted as a part of this test evaluation. Test results show that these ashes did not meet all ASTM C 618 coal ash requirements for concrete products applications. In order to determine the effects of optimum inclusion of these ashes on concrete strength and durability properties, a lab study is very strongly recommended. Probability of success is very high. BLENDED CEMENT The highest market value use of the MPU ashes is in the production of blended cements. Blended cement material is typically composed of portland cement, coal fly ash, and/or other cementitious or pozzolonic materials, and chemicals. Probability of success is very high. 21

31 ROLLER-COMPACTED CONCRETE PAVEMENT The MPU ashes can be used for Roller-Compacted Concrete Pavement (RCCP) in all types of Wisconsin weather. RCCP using MPU ashes would be a very important application. RCCP popularity is increasing in Wisconsin. Lab evaluation is very strongly recommended for future applications. Probability of success is very high. SOIL AMENDMENT WITH OR WITHOUT DREDGED MATERIALS Wisconsin dredges a significant tonnage of dredged materials from the Great Lakes and the Mississippi River to keep the navigation channels open. The MPU ashes would be an excellent additive to dredged materials to make manufactured topsoil for use in tree farms, sod farms, potting soil, new growth woods/plantations, etc. These ashes may act as a desiccant, deodorizer, and chemical activators for dredged materials. The resulting manufactured topsoil can be used as a fertilizer, and to decrease subsurface porosity and improve infiltration characteristics of soils. Further lab study is very strongly recommended. Probability of success is very high. 22

32 MANITOWOC PUBLIC UTILITIES ASH BACKGROUND INFORMATION MPU #5 Boiler, MPU #7 Boiler, MPU #8 Boiler 23

33 Table 1 - Background Information on the MPU Ash Source MPU Boiler #5 & Boiler #7 MPU Boiler #8 Make of Boiler Wickes Foster-Wheeler Type of Boiler Stoker CFBA - Circulating Fluidized Bed Age of Boiler 40 years 12 years Type of Fuel 95% Bituminous Coal (PA), 5% Paper Pallets 20% Bituminous Coal (PA), 75% Petroleum Coke, 5% Paper Pallets Maximum Size of Fuel 1/2" (coal), 1/8" dia. x 1" long wood 1/2" (coal), ~1/8" dia. wood pellets Amount of Fuel Used Per Year 80,000 tons (coal), 5,000 tons (wood) 35,000 tons Burning Temperature, Deg.F 2,650 1,600 Type of Energy Steam Steam Amount of Energy 170,000 #/hr 200,000 #/hr Wet or Dry Ash Collection Dry Dry Amount of Bottom Ash 15,000 tons 15,000 tons Amount of Fly Ash 5,000 tons 4,000 tons 24

34 MANITOWOC PUBLIC UTILITIES ASH CHARACTERIZATION Combined MPU #5 & #7 Bottom Ash, MPU #8 Bottom Ash, and MPU #8 Fly Ash. 25

35 Table 2 - As-Received MPU Ash Moisture Content Moisture Content, % Ash Source MPU # 5 - #7 Bottom Ash MPU #8 Bottom Ash MPU #8 Fly Ash Actual* Average * Moisture content, as-received, % = (as-received sample wt. - dry sample wt.) * 100 dry sample weight 26

36 MANITOWOC PUBLIC UTILITIES ASH PARTICLE SIZE ANALYSIS 27

37 Table 3 - Sieve Analysis of MPU Ash (As-Received Samples) (Tests conducted per ASTM C 136) MPU #5 - #7 Bottom Ash Sieve Size % Passing* ASTM C 33 % Passing for No. 6 Coarse Aggregate ASTM C 33 % Passing for Sand 1-1/2" (38.1 mm) to 100 1" (25.4 mm) /4" (19.05 mm) to /2" (12.7 mm) /8" (9.5 mm) to #4 (4.75 mm) to 5 95 to 100 #8 (2.36 mm) to 100 #16 (1.18 mm) to 85 #30 (600 μm**) to 60 #50 (300 μm**) to 30 #100 (150 μm**) to 10 MPU #8 Bottom Ash Sieve Size % Passing* ASTM C 33 % Passing for sand 3/8" (9.5 mm) #4 (4.75 mm) to 100 #8 (2.36 mm) to 100 #16 (1.18 mm) to 85 #30 (600 μm**) to 60 #50 (300 μm**) to 30 #100 (150 μm**) to 10 * Values reported for % passing are the average of two tests. ** 1.0 μm = 10-6 m = mm 28

38 Table 4 - Material Finer Than No. 200 Sieve by Washing (As-Received Samples) (Tests conducted per ASTM C 117) Material Finer than No. 200 Sieve (%) Ash Source MPU #5 - #7 Bottom Ash MPU #8 Bottom Ash MPU #8 Fly Ash Actual N/A* N/A* Average N/A* * This test (ASTM C 117) is not applicable, material is very fine. 29

39 Table 5 - Materials Retained on No. 325 Sieve (Tests conducted per ASTM C 311/C 430) % Retained on No. 325 Sieve (As-Received Sample) Ash Source MPU #5 - #7 Bottom Ash MPU #8 Bottom Ash MPU #8 Fly Ash Actual NA* NA* NA* NA* Average NA* NA* 22.5 * NA = This test (ASTM C 311/C 430) is not applicable, material is very coarse. 30

40 Percent Passing ASTM C 136 Sieve Analysis Particle Diameter, mm Fig. 1: Particle Size Distribution of MPU #5-#7 Bottom Ash GEN

41 Percent Passing ASTM C 136 Sieve Analysis Particle Diameter, mm Fig. 2: Particle Size Distribution of MPU #8 Bottom Ash GEN

42 Percent Finer ASTM D 422 Hydrometer Analysis, see Appendix Particle Diameter, (mm) Fig. 3: Particle Size Distribution of MPU #8 Fly Ash GEN

43 MANITOWOC PUBLIC UTILITIES ASH UNIT WEIGHT, VOIDS, SPECIFIC GRAVITY, AND SSD MOISTURE CONTENT 34

44 Table 6 - Unit Weight and Voids (Tests conducted on as-received samples per modified ASTM C 29, utilizing 0.10 ft 3 measure) Unit Weight (lbs/ft 3 ) Voids (%) Ash Source Actual Average Actual Average MPU #5 - #7 Bottom Ash MPU #8 Bottom Ash MPU #8 Fly Ash

45 Table 7 - Specific Gravity (Tests Conducted per ASTM C 311/C 188) Specific Gravity Ash Source MPU #5 - #7 Bottom Ash MPU #8 Bottom Ash MPU #8 Fly Ash Actual N/A* N/A* N/A* N/A* Average N/A* N/A* 2.68 *This test (ASTM C 311/ C 188) is not applicable due to the sample gradation being too coarse. 36

46 Table 8 - Specific Gravity (Tests Conducted per ASTM C 128) Bulk Specific Gravity Bulk Specific Gravity (SSD Basis) Apparent Specific Gravity Ash Source Actual Average Actual Average Actual Average MPU #5 - #7 Bottom Ash* MPU #8 Bottom Ash MPU #8 Fly Ash** NA NA NA NA NA NA NA NA NA *Sample was first sieved over No. 8 sieve. Test was conducted on the ash that passed through this No. 8 sieve since the procedure of ASTM C 128 is for specific gravity for fine aggregates. **This test (ASTM C 128) is not applicable because this fly ash sample is too fine. 37

47 Table 9 - Absorption (Tests Conducted per ASTM C 128) SSD Absorption, % Ash Source MPU #5 - #7 Bottom Ash* MPU #8 Bottom Ash MPU #8 Fly Ash Actual NA** NA** Average NA** *Samples were first sieved over No. 8 sieve. Tests were conducted on the ash that passed through this No. 8 sieve since the procedure of ASTM C 128 is for fine aggregates. ** This test (ASTM C 128) is not applicable for very fine materials such as MPU #8 fly ash. 38

48 MANITOWOC PUBLIC UTILITIES ASH ASTM C 618 PHYSICAL PROPERTIES 39

49 Table 10 - Physical Test Requirements of Coal Fly Ash per ASTM C 618 TEST ASTM C 618 SPECIFICATIONS CLASS N CLASS C CLASS F Retained on No.325 sieve, (%) 34 max 34 max 34 max Strength Activity Index with Cement at 7 or 28 days, (% of Control) 75 min 75 min 75 min Water Requirement (% of Control) 115 max 105 max 105 max Autoclave Expansion, (%) ±0.8 ±0.8 ±0.8 Moisture Content, (%) 3.0 max 3.0 max 3.0 max Loss on Ignition, (%)* 10.0 max 6.0 max 6.0 max Specific Gravity Variation from Mean, (%) Fineness Specific Gravity 5 max 5 max 5 max 5 max 5 max 5 max *Under certain circumstances, up to 12% max. LOI may be allowed. 40