Evaluation of GVRD Municipal Incinerator Ash as a Supplementary Cementing Material in Concrete

Transcription

1 Evaluation of GVRD Municipal Incinerator Ash as a Supplementary Cementing Material in Concrete AMEC Report No. VA06294 Submitted to: EcoSmart Concrete Project World Trade Centre Canada Place Vancouver, British Columbia V6C 3E1 Attn. Maggie Wojtarowicz, E.I.T. Project Engineer Prepared by: Raymond T. Hemmings, Ph.D., CChem. Hemmings & Associates, LLC Bruce J. Cornelius, P.Eng. AMEC Earth & Environmental a Division of AMEC Americas Limited March 15, 2004

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3 TABLE OF CONTENTS Page REPORT SUMMARY INTRODUCTION Background Scope of Study REVIEW OF EXISTING INFORMATION Public Literature Search Consultant Data Comments on Existing Information Review MATERIALS CHARACTERIZATION Sample Procurement Incinerator Ash Other Raw Materials EVALUATION OF SCM POTENTIAL OF INCINERATOR ASH Methodology Pozzolanic Reactivity Standardized Testing Mix Proportioning Trials Chemical and Mineralogical Features ENVIRONMENTAL STABILIZATION OF INCINERATOR ASH Leachability of Cement Stabilized MIA Mortars Stability of Cement Stabilized MIA Mortars FORENSIC EXAMINATION OF AGED CONCRETE Preliminary Inspection Petrographic Examination Chemical and Mineralogical Features Microstructural Features Leachability of Aged Concrete Summary of Forensic Findings DISCUSSION Material Properties of Incinerator Ash Pozzolanic Reactivity Potential of Burnaby MIA Mechanistic Considerations Environmental Stabilization of Burnaby MIA Potential Use of MIA in Cement and Concrete CONCLUSIONS AND RECOMMENDATIONS Conclusions Recommendations LIMITATIONS AND CLOSURE...36 Tables...37 Figures...45 Appendices...59 AMEC Report No. VA

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5 REPORT SUMMARY This report describes a study for the EcoSmart Concrete Project (EcoSmart) to determine if untreated fly ash produced by the Greater Vancouver Regional District (GVRD) Municipal Incinerator in Burnaby (referred to as MIA) is a technically feasible supplementary cementing material (SCM) suitable for use in Portland cement concrete and other cement-based materials. From an environmental perspective, international efforts have demonstrated that SCMs are particularly advantageous as a means of reducing greenhouse gas (GHG) emissions associated with the production of cementbased materials. The evaluation of MIA is part of EcoSmart s broader program to identify the availability and applicability of SCMs suited to this purpose to maximize the environmental benefits of cement replacement. A co-benefit of the study is that it could provide a solution to a continuing local environmental problem relating to the management and disposal of the MIA. The Burnaby MIA is currently regulated as a special waste that is subject to costly chemical processing before being sent for disposal at the Cache Creek landfill. Thus, in addition to potential applications to mitigate GHG emissions through cement replacement in concrete, beneficial use of the Burnaby MIA will also have other environmental as well as financial incentives. The scope of the study has included: a summary and collective evaluation of the existing public information on MIA; materials characterization of the MIA to establish the critical chemical, physical and mineralogical properties; laboratory evaluation of the MIA as a potential pozzolanic SCM in concrete; forensic analysis of aged concrete containing MIA; and evaluation of the effectiveness of cement to environmentally stabilize and sequester toxics and heavy metals present in MIA. Based on the findings of the study, a number of technical and institutional barriers have been identified that will significantly impact the potential use of the Burnaby MIA in cement and concrete: Compositionally, the MIA is largely comprised of calcium and alkali metal chloride and hydroxide salts and is not a pozzolan / SCM in the conventional sense. The potential of the MIA as an SCM is restricted by the current requirements of ASTM and CSA cement and concrete standards that are specific to existing SCMs (such as coal fly ash, blast furnace slag, and silica fume). ASTM C-618 expressly prohibits the use of municipal incinerator fly ash in concrete. The MIA exhibits very high water demand and poor strength activity when tested as a conventional SCM. From a strength perspective, mix proportioning trials indicated that acceptable mixes could be prepared at 10% cement replacement levels, particularly in the presence of high volumes of coal fly ash. Although it is not a pozzolan, the MIA is chemically active in a cement system and the reaction mechanisms have been discussed. At cement replacement levels typical of pozzolans in concrete (10 20%), the high levels of chlorides in the MIA cause acceleration of set and significant heat generation in large batches. The MIA contains ammonium salts that release ammonia when mixed with cement in the plastic state. This ammonia has the potential to be a health and safety issue, particularly in a pre-cast concrete plant environment. Exactly the same issue has AMEC Report No. VA

6 caused significant problems with the use and marketing of coal fly ash from electrical power plants retrofitted with SCR NOx control technologies. The very high levels of chloride effectively prohibit any use of the MIA in reinforced concrete due to the induced corrosion of embedded reinforcing steel. Special handling equipment will also be needed to produce concrete due to the aggressiveness of MIA towards steel when moist. Durability testing indicates that MIA should not be used in concrete exposed to aggressive environments, such as sulphate-rich groundwaters, sewage, soils, etc. The high alkali content of the MIA is especially problematic if potentially reactive aggregates are used in concrete. Environmental regulations may restrict the movement, handling, storage and end use of MIA as a consequence of the presence of heavy metals such as lead and cadmium. There is a public perception of MIA as a hazardous waste. In view of these technical performance and institutional issues, potential use of the Burnaby MIA in the cement and concrete industry will be limited and confined to noncritical, non-reinforced applications such as landscaping blocks, artificial reefs, etc. It is unlikely, however, that this could consume more than a small fraction of the total production of MIA from the GVRD incinerator. While the use of MIA as an SCM is not considered feasible, from an environmental perspective the study has confirmed that cement stabilization is an effective means for sequestering the toxics and heavy metals from the MIA. This could possibly provide a lower cost waste management option for the Burnaby MIA. Accelerated testing shows that the cement-stabilized MIA does have a potential stability problem under aggressive exposure conditions, especially in a sulphate environment, that requires further investigation. The following recommendations are made to EcoSmart with respect to continued evaluation of management options for the Burnaby incinerator ash: Conduct a technical-economic assessment of cement-stabilization for management of the Burnaby MIA compared to current chemical treatment and landfill practices. This assessment should include investigation of a wider range of mix designs focused on cement contents and strengths to identify the lower limit of performance consistent with effective metals sequestering and physical stability. Conduct a chemical and microstructural investigation to better understand the reaction mechanisms involved with MIA in the cement system, particularly as it relates to the issues of long-term chemical and physical stability. Develop a comprehensive database of the chemical, physical and mineralogical properties of the Burnaby MIA over an extended period of time to better characterize the extent of variability in the material. Identify potential willing partners to become potential users of MIA in large volume concrete applications, such as low end, unreinforced concrete. There would appear to be some limited potential for use in non-critical, non-structural concrete. 6 AMEC Report No. VA06294

7 1.0 INTRODUCTION 1.1 Background and Terms of Reference The purpose of this study is to assist the EcoSmart Concrete Project (EcoSmart) in establishing whether untreated fly ash produced by the Greater Vancouver Regional District (GVRD) Municipal Incinerator in Burnaby (hereafter referred to as MIA) is a technically feasible supplementary cementing material (SCM) suitable for use in Portland cement concrete and other cement-based materials. From an environmental perspective, considerable international effort, including project work by EcoSmart, has demonstrated that SCMs are particularly advantageous as a means of reducing greenhouse gas (GHG) emissions associated with the production of Portland cementbased materials. The evaluation of municipal incinerator ash is part of EcoSmart s broader program to identify the availability and applicability of SCMs suited to this purpose to maximize the environmental benefits of cement replacement. Additionally, EcoSmart hopes to provide a solution to a continuing local environmental problem relating to the management and disposal of the MIA. The Burnaby MIA is currently regulated as a special waste that, as a consequence, is subject to costly chemical processing before being sent for disposal at the Cache Creek landfill. Thus, in addition to potential applications to mitigate GHG emissions through cement replacement in concrete, beneficial use of the Burnaby MIA will also have other environmental as well as financial incentives, including, but not limited to: Avoided disposal providing a reduction in environmental impact and an extension to the service life of the landfill; Avoided transportation leading to reductions in costs and the associated GHG signature; Avoided need for chemical processing thereby reducing the operating costs for the GVRD incinerator and further reducing the transportation-associated GHG. In developing beneficial uses for industrial by-products, it is always desirable to look for opportunities that are properly matched both in scale and chemical/physical requirements with the by-product. One such large-scale potential application that appears to be well-suited to the quantity and characteristics of the MIA is the production of pre-cast concrete units, such as lock blocks and other non-structural landscaping and related applications. In particular, applications that use sufficient quantities of cementitious binder materials to achieve significant compressive strengths also provide the chemical activity and environment needed to effectively immobilize (or sequester) heavy metals present in the Burnaby MIA. In addition to the use of MIA by itself as an admixture in Portland cement concrete, the potential also exists for beneficial synergies of MIA with other commonly used SCMs (e.g., coal fly ash, natural pozzolans, and finely divided metallurgical slags) that can be incorporated with the MIA in ternary blended cement systems. AMEC Report No. VA

8 1.2 Scope of Study The principal objectives of the study by AMEC described in this report may be summarized as follows: To review the publicly available existing information on MIA to identify potential beneficial uses and/or barriers from both technical as well as institutional perspectives. To evaluate the pozzolanic reactivity potential of the Burnaby MIA, and to explore the optimum mixture proportions of MIA to use in concrete, as a percentage of the total cementing material(s). To determine the ability of Portland cement concrete and related cement-based materials to stabilize and sequester toxics and heavy metals present in MIA. To recommend a course of action to EcoSmart with respect to the potential of beneficially utilizing the Burnaby MIA in concrete and cement-based materials. The report has been organized into the following sections addressing the objectives of the study: Section 2 provides a summary and collective evaluation of the existing public information; Section 3 summarizes the materials characterization of the Burnaby MIA to establish the critical chemical, physical and mineralogical properties; Section 4 summarizes the laboratory evaluation of the Burnaby MIA as a potential pozzolanic supplementary cementing material in Portland cement concrete, both alone and in ternary blends with other SCMs; Section 5 provides an evaluation of the effectiveness of cement for environmental stabilization of MIA; and Section 6 summarizes the findings of a forensic analysis of aged concrete containing MIA. The findings of the study are discussed in Section 7. Conclusions and recommendations for the study are collected in Section 8. Appendices to the report provide details of the database information search. 2.0 REVIEW OF EXISTING INFORMATION In the early stages of the project AMEC conducted a critical review of the publicly available literature on MIA with particular reference to information relating to uses of the material in cement and concrete systems. The goal of this review was to identify potential beneficial uses and/or barriers from both technical as well as institutional perspectives. This also included a review of existing information available from the GVRD and local consultants on previous evaluation trials of MIA in concrete and other cement-based materials. The highlights of this review are summarized as follows. 2.1 Public Literature Search A computerized search of the Chemical Abstracts and Compendex commercial bibliographic databases returned 191 open file publications and patents related to concept of municipal incinerator ash and incorporating the terms cement and/or concrete. This total was reviewed and sorted to remove entries that were not relevant to MIA use in concrete, reducing the total to 154 (77 papers and 77 patents). These 8 AMEC Report No. VA06294

9 bibliographic references are collected in Appendix A for the patents and Appendix B for publications. Of this set, a total of twelve patents (12, 23, 40, 46, 49, 50, 55, 56, 64, 68, 72, 77) and fifteen papers (90, 91, 94-98, 103, 104, 110, 118, 127,136, 136, 151) deal with melting of MIA by various techniques, generally with a view of producing either a stable aggregate material for use as base material / concrete aggregate, or as a method of reducing the heavy metal leachability of the MIA prior to disposal. This set of references all require secondary thermal processing of the MIA, which of course will consume energy and thus impart a greenhouse gas (GHG) penalty to the municipal solid waste (MSW) incinerator employing these techniques. As such, they are not considered germane to the goals of the current project. Soil cements are referenced four times. Two published patents (69, 73) refer to the use of MIA in combination with fine aggregate and Portland cement to achieve the relatively low strengths of ~2 MPa (300 psi) needed to produce a stable soil cement meeting the EPA leachate toxicity tests for classification as non-hazardous. Two papers (99,100) deal with the use of MSW bottom ash formulations and their soil cement mechanical properties. When the publications discuss the use of MIA as an aggregate material, they most often refer to bottom ash component of the MSW incinerator waste stream. There are nine patents (5, 8, 10, 15-18, 65, 76) and eleven papers (88, 89, 107, 116, 117, 140, 145, 146, 148, 150, 153) dealing with granulated MIA compositions. These references either use the raw MSW bottom ash as produced or make use of cementing agents to produce a granular material from the fine MIA materials. These uses follow the trend of adding a stabilizing agent to reduce toxic leachates, followed by a low value end-use as a fill material. Nine references, including three patents (41, 42, 51) and six papers (84-87, 101, 147) address methods of pre-treating the MIA, primarily to reduce the leachability of toxic metals and in some cases to reduce the alkali chloride contents. The methods for removing selected compounds from the MIA include simple washing of the MIA to remove the soluble alkali chlorides, HCl treatment to remove heavy metals as their chlorides, and some use of an unidentified new additive. These methods are usually followed by some form of physical stabilization/solidification of the treated MIA, usually with hydraulic cement, but in one case by pressure extrusion in conjunction with waste plastics. The treated MIA materials are reported to be acceptable for use in Portland cement concrete, but no details are given about either the fate of the treatment residues or the nature of the new additive used for the treatment. Seven patents (44, 45, 48, 52, 53, 70, 75) and three papers (122, 124, 129) address specifically the use of Portland cement formulations to reduce MIA leachabilty prior to disposal. These references include studies of the leachability of metals and organic compounds. A survey of ashes for metals and radioactive species (124) indicated that radioactivity was not significant in MIA materials. This set of references indicates that the toxic leachate problems associated with municipal solid waste MIA are well known, and that sequestering of toxic metals with Portland cement is a widely applicable solution. AMEC Report No. VA

10 There are nine references to Eco-Cement (1, 3, 31, 79, 82, 138, 139, 142, 144), a product that uses MIA as a raw material to produce a hydraulic cement product. These products generally use the MIA as a calcium and chlorine source for the formation of calcium chloroaluminates. The finished Eco-Cement product is often referred to as a low chloride product suitable for use in reinforced concrete. Given the very high chloride content of the Burnaby MIA, it is considered unlikely that its use as a raw material for Eco-Cement, or use in reinforced concrete, are viable. Sixteen patent references are for processes in which MIA is fired prior to use. Eight of these patents (22, 25, 27-30, 32, 33) specifically reference the presence of calcium chloroaluminates (represented by cement chemist s shorthand as C 11 A 7 CaCl 2 ) in combination with conventional Portland cement phases as part of the fired final product. The remaining four patents are for two sintered products (43, 54) and two fired (57, 58) products, which specify aggregate type end-uses. Two of the remaining patents (14, 58) specify low chloride values (0.1% Cl or less), which effectively precludes use of any raw MIA materials. Three patents, that are related to those mentioned above, directly use MIA as clinker (19-21). In these cases, the use of the term clinker necessarily implies that the MIA requires further processing (at least comminution) prior to use. Again, calcium chloroaluminates are identified as active ingredients. These applications are also not directly relevant to the use of MIA as a supplementary cementing material in normal Portland cement concrete. Incinerator ash use in concrete is the topic in seventeen references (4, 9, 24, 26, 35, 36, 38, 39, 60, 61, 63, 71, 78, 114, 119, 127, 143) where Portland cement is the main binder phase and MIA is either a complementary cementitious material or a recycled material. In five cases (7,13,81-83), low chloride contents (<1% Cl) for the MIA are again specifically mentioned, suggesting that significant pre-treatment of the incinerator ash must be occurring. In two cases (66, 154), the set-accelerating nature of MIA is mentioned as a useable feature. These concrete applications are generally targeting the potential environmental benefits of energy savings, resource conservation and greenhouse gas reduction. Several miscellaneous applications relevant to potential cement and concrete applications for MIA were also noted. One reference discusses the use MIA with high alumina cement (2), where the available alumina can readily react with the soluble chlorides present in the MIA. Two references discuss the use of sulphur as the cementing agent (thermoplastic), with one apparently mixing elemental sulphur with fired MIA compositions (11), and the second molten sulphur for hazardous material stabilization (67). MIA is mentioned as a potential chloride source in Sorel cement (magnesium oxy-chloride cement) in two references (105, 149). A single reference uses melted waste plastic to stabilize the MIA by physical encapsulation (47). Characterization and leaching studies account for eleven references (102, 106, 111, 112, 120, 121, 123, 128, 131, 135, 141), all of which are published papers. The work generally deals with the extent of leaching of heavy metals from MIA under a variety of environmental exposure conditions, from aged landfill sites to various water sources. 10 AMEC Report No. VA06294

11 Five references (78, 93, 113, 122, 129) cite studies where formulations of MIA with Portland cement are evaluated for their ability to reduce the leachability of the heavy metals present in the MIA. In all cases, the leachability of metals (specifically lead and cadmium, which are the major source of contamination in most sources of MIA) was greatly reduced by solidification/stabilization with Portland cement. Recent work by Goh et al (78) examined an ash source with similar chemical properties to the Burnaby MIA, and is perhaps most relevant to the present study. While these authors provide details of physical, elemental and calculated oxide compositions of the MIA, there was evidently no attempt made to properly identify the mineralogical species present or the reaction mechanisms involved. It was found that the use of up to 10% MIA in cement mortars resulted in good performance, but problems were found with set times at all addition levels (5% to 20%). As is the case for all MIA studies where Portland cement was used, the heavy metals in the MIA were effectively prevented from leaching when incorporated in a cementitious matrix. A noteworthy feature, however, is that the cement mortars required up to 120 days curing time before the leachates conformed to the U.S. EPA limits. 2.2 Consultant Data Information was also made available to the present study which included earlier work conducted by consultants during the period between 1988 and This body of work is summarized as follows: Characterization of Incinerator Bottom Ash (AGRA Earth & Environmental Limited VA04220, 8 April 1998). Bottom ash was treated to remove metals and the treated product examined for possible use as either fine sand or kiln feed material. This work is not relevant to the current study of the incinerator fly ash. Burnaby Incinerator Fly Ash Bench Scale Testing (Hardy BBT Limited, VA01869, Aug ). This work involved testing of high MIA content slurry mixes, with set retardation by added sugar. The results indicate the potential for set acceleration of MIA with Portland cement. Pilot Plant Study Solidification of Burnaby Incinerator Ash (Hardy BBT Limited, VA A500, May 1991). This work concluded that Portland cement is an effective treatment for MIA to reduce leachable lead. Solidification of Burnaby Incinerator Ash Phases 1 and 2 (Hardy BBT Limited, VA and VA , March-August 1990). This combined study provided the data required to proceed with the Pilot plant study above, with a recommended dosage of 30% cement used to stabilize the MIA against lead leaching. Investigation into Solidification of Burnaby Incinerator Fly Ash (Hardy Associates (1978) Ltd., VA-01242, Jan-July 1989). This work examined the characteristics of the Burnaby MIA and considered several treatment options, including cementation and the Chemfix process. AMEC Report No. VA

12 The studies summarized above indicate that the Burnaby MIA at the time of the testing programs was adequately stabilized with respect to lead leaching by use of Portland cement. The use of sugar to moderate set times indicates the potential for the MIA to accelerate Portland cement hydration. 2.3 Comments on Existing Information Review Several of the cited references examined MIA from multiple locations, so it is not surprising that many conclude that the material can be highly variable from source to source. This is readily explained when considering the wide range of variables associated with the operation of an MSW incinerator, which include: MSW sources, which will vary depending on the local conditions, collection practices, and local recycling efforts; Operating temperatures in the incinerator, which can be sensitive to fuel; Pollution abatement protocols, which can remove some components from the ash stream and add others (i.e., sorbents for HCl control, ammonia for NOx control); Collection and storage systems (wet or dry). This inherent variability demands that each source of MIA be carefully examined prior to any large-scale efforts directed to beneficial use and/or alternate disposal. Factors such as heavy metals loading and chloride content can have major effects on both the selection of appropriate end-uses and selection of ancillary equipment for ash handling. There is a great deal of information available about the leachability of heavy metals from MIA, this being primarily focused on the elements lead and cadmium which are a common problem for most MSW incinerators. This leachability information is used to define the MIA as either hazardous or non-hazardous, and tends to be the final arbiter applied to any ash management protocol. In most cases, the suitability of a given solidification/stabilization treatment is decided by its ability to considerably reduce or eliminate leaching of lead and cadmium. While the leaching behavior of MIA is well documented, as is the elemental make-up of the materials, it is apparent and quite surprising that there is very little detailed information reported on the mineralogical constituents and speciation of the ash. While this may not of great significance when the material is subjected to subsequent high temperature processing, it is extremely important when the MIA is subjected to chemical reactions as with cementitious materials. The mineralogical species present in the ash must be characterized and understood in order to explain and control their behaviour in cementitious systems. These data can also be used to predict whether the solidified MIA formulations will be stable in the long-term under specific exposure conditions. The overall findings from the review of the existing public information relating to MIA in cement and concrete systems are summarized as follows: There is considerable difference in the characteristics of MIA produced by different MSW incinerators, the consequence of which is that information developed from one source is not necessarily transferable to a new source. Therefore, each source 12 AMEC Report No. VA06294

13 should be characterized independently and time-based variability at a single source is also very likely. Surprisingly, there is no information available on the fundamental chemical and mineralogical speciation in MIA that allows direct a priori comparison with conventional supplementary cementing materials. There is a considerable body of published information that identifies Portland cement as an effective reagent for stabilization/solidification of MIA to immobilize the heavy metals present against leaching. There is, however, very little scientific and engineering information relating to the development and acceptance of beneficial uses for MIA in the cement and concrete industry. There would appear to be some potential for use in non-critical, nonstructural concrete applications such as landscaping blocks and artificial reefs. Potential technical barriers that may impact the beneficial use of MIA in cement and concrete include: (a) The high levels of chloride present in MIA have a significant and negative effect on cement hydration that impacts set time and strength development of concrete; (b) Although not specifically mentioned in the literature, the same high levels of chloride also present a considerable barrier for use in reinforced concrete because of the potential for induced corrosion of embedded steel; and (c) Also not noted in the literature is the fact that NOx control technologies at many MSW incinerators (GVRD-Burnaby included) lead to the formation of ammonium salts that will be collected with the MIA. These salts will lead to the release of ammonia during concrete production that could be a significant occupational health problem. Exactly the same issue has caused significant problems with the use and marketing of coal fly ash from electrical power plants retrofitted with SCR NOx control technologies. Potential institutional barriers that could impact the beneficial use of MIA in cement and concrete include: (a) Environmental regulations that may restrict the movement, handling, storage and end use of MIA as a consequence of the presence of heavy metals such as lead and cadmium; (b) Occupational health regulations that may be applicable as a consequence of the release of ammonia when MIA is used in concrete, especially precast concrete or masonry units manufactured indoors; (c) Standards and specifications specific to existing supplementary cementing materials (such as coal fly ash, blast furnace slag, and silica fume) that do not currently allow the incorporation of MSW ash in concrete; and (d) The public perception of MIA as a hazardous waste. AMEC Report No. VA

14 3.0 MATERIALS CHARACTERIZATION In a study of this kind, it is very important to have a detailed understanding of the chemical, physical, and mineralogical properties of all the raw materials to be used. These data provide baseline information that is valuable for the refinement of cementitious mix designs to investigate the potential pozzolanic reactivity of the Burnaby MIA. Other raw materials, including Portland cement, coal fly ash and ground granulated blast furnace slag, were also characterized for basic chemical and physical properties to confirm that they were representative of their sources. 3.1 Sample Procurement Untreated MIA was collected over a period of six consecutive days of production from the GVRD incinerator, with a view to determining its compositional variability and to obtain a representative composite sample. A total of twelve 5-gal pails, two from each of the six days, was collected over this time period. Representative samples of Portland cement (CSA Type 10), coal fly ash, and granulated metallurgical slag were obtained from commercial sources. 3.2 Incinerator Ash Samples of the fresh Burnaby MIA were received in AMEC s Hamilton laboratory on July 23, The as-received MIA was a free-flowing fine particulate with a light gray colour and a characteristic bitter/metallic odor. Some larger flecks of black carbon-rich material were dispersed throughout. The as-received MIA material was highly aerated with a correspondingly low bulk density (loose 0.41 g/cm 3, vibrated 0.52 g/cm 3 ) and a very high specific surface area of ~12,500 cm 2 /g as determined by the ASTM C-204 air permeability (Blaine) method. The specific gravity was Approximately 24.5% of the material was retained on a 45 µm (325#) screen, a fineness comparable with many coal fly ashes. The moisture content determined by the mass loss at 110 C was 2.6%. The bulk elemental composition of the six Burnaby MIA samples as determined by ICPS analysis is summarized in Table 1. Also shown is the average and standard deviation represented by the data set. It is common practice in cement chemistry and geochemistry to represent elemental analyses in terms of the element oxides (Table 2), since bonds to oxygen are the most common in these silicates and aluminosilicates. This approach, however, is not entirely adequate for representation of the Burnaby MIA data because of the very high chloride content arising from flue gas scrubbing of HCl by lime. To address this issue, the data in Table 2 were recast in terms of both oxides and chlorides (Table 3) based on reasonable assumptions on chloride speciation. Chemically, the composition of the Burnaby MIA mostly reflects the species calcium (~36% CaO), chloride (~20% Cl) and bound water (~43% H 2 0) associated with lime sorbent clean up of the flue gas at the incinerator. Of particular note is the very low content of the elements silicon (SiO 2 ), aluminum (Al 2 O 3 ) and iron (Fe 2 O 3 ) that are major components in conventional concrete pozzolans. Typical values for the sum of these oxides (SiO 2 +Al 2 O 3 +Fe 2 O 3 ) is >70% for Class F fly ash, >80% for Class N natural pozzolans, and 45 50% for iron ore blast furnace slags (see Section 3.3). The comparable oxide sum value for the Burnaby MIA is 6% at best, an exceedingly low 14 AMEC Report No. VA06294

15 value. The very high loss on ignition (LOI) values reported in the analyses (Tables 1-3) reflect the presence of chemically bound water (hydroxides and hydrates), and to a lesser extent carbon dioxide (carbonates), in the compounds in the MIA Notable among the minor and trace elements in the MIA are the comparatively high levels of lead (~4400 ppm Pb), titanium (4200 ppm Ti), zinc (~19000 ppm Zn) and antimony (~1300 ppm Sb). The high level of phosphorus (3000 ppm P) is attributed to the use of phosphoric acid at the incinerator for enhancement of trace metal capture. Trace metal leachability in the Burnaby MIA is discussed in Section 5. A split sample of the Burnaby MIA was also analyzed for total nitrogen content by the Kjeldahl method, with a result of 0.02%, or 200 ppm, as N. This amount of nitrogen is equivalent to 240 ppm as ammonia, most likely present in the MIA as ammonium chloride, NH 4 Cl or ammonium sulphate, (NH 4 ) 2 SO 4. This component is a consequence of the use of ammonia at the Burnaby incinerator for control of NOx emissions. Inspection of the chemical data indicate that the Burnaby MIA samples are reasonably consistent in their properties over the course of six days and are representative of the source. This is shown graphically in Figure 1. Composite samples of these six materials were prepared and used for all subsequent laboratory testing. From a cementitious reactivity perspective, of particular importance is the mineralogical composition of the MIA. A typical X-ray powder diffraction pattern for the Burnaby MIA together with assignments of the component mineral phases is given in Figure 2. The main crystalline components of the MIA are calcium hydroxide (Ca(OH) 2 ), calcium chloride (CaCl 2 ), sodium chloride (NaCl), anhydrite (anhydrous calcium sulphate, CaSO 4 ), calcite (CaCO 3 ), and minor amounts of quartz (SiO 2 ). Based on the chemical analysis and mineralogical data, the proportions of the various components in the Burnaby MIA can be estimated, as is shown Table 4. As can be seen, most of these components are calcium species associated with flue gas scrubbing at the incinerator as a result of reactions between lime with hydrogen chloride and, to a lesser extent, sulphur oxides. There is very little evidence for conventional silicate or aluminosilicate pozzolan components. As discussed in Section 7, the high levels of chloride in the Burnaby MIA are very significant in cement and concrete systems both for their effect on set times as well as the potential for increased corrosion of embedded reinforcing steel. Equally significant for use in concrete is the presence of ammonium species in the MIA. Some typical scanning electron microscope (SEM) images showing the general morphology and fine particle size of the Burnaby MIA are collected in Figure 6. The fluffy, cauliform appearance is consistent with the very high surface area determined for the material and is typical of products from a hydrated lime sorbent system. 3.3 Other Raw Materials Representative samples of cementitious binders and pozzolans were obtained for the study from the following commercial sources in August 2003: CSA Type 10 Portland cement (OPC) from Lafarge, British Columbia; Class F subbituminous coal fly ash (PFA) AMEC Report No. VA

16 from the Sundance GS, Alberta; and ground granulated blast furnace slag (BFS) from GranCem in Ontario. Note that to help avoid confusion with the municipal incinerator fly ash, the study has adopted the shorthand of PFA for the coal fly ash. The PFA terminology, standing for pulverized fuel ash, is used extensively in Britain. The chemical compositions of the three cementitious binders are compared in Table 5. These data are represented conventionally as the element oxides, which is appropriate for these siliceous materials. X-ray powder diffraction patterns and mineralogical phase assignments for the materials are shown in Figures 3 5. In marked contrast with the composition data for the Burnaby MIA (Section 3.2), it can be seen that the sum of the major oxides (SiO 2 +Al 2 O 3 +Fe 2 O 3 ) is substantial for both supplementary cementing materials: PFA 83.4%, BFS 48.2%. The reactive components in these SCMs are calcium aluminosilicate glasses that comprise ~75% of the PFA and >95% of the BFS. The accessory minerals, quartz, mullite and hematite, in the PFA are unreactive in cement systems. SEM images showing the typical spherical morphology of the PFA and those showing the angular, blocky nature of the ground granulated BFS are shown in Figure 7 and 8, respectively. All three reference cementitious materials are considered to be representative of their sources. 4.0 EVALUATION OF SCM POTENTIAL OF INCINERATOR ASH The overall goal of this aspect of the study was to evaluate the pozzolanic reactivity potential of the Burnaby MIA, and in particular to determine whether the material is able to function as a supplementary cementing material (SCM) in concrete in the same way as the well-established SCMs, namely coal fly ash, blast furnace slag, silica fume and metakaolin. While there are some phenomenological accounts of using MIA in concrete, the authors are not aware of any study in which MIA has been examined systematically in terms of its basic materials chemistry properties in a cement system. 4.1 Methodology Although the function of SCMs in concrete is strongly driven by chemical reactions of the silicates and aluminosilicates with alkalis and lime from the hydrating Portland cement (see Section 7), it is conventional to evaluate them by physical means, typically by measuring and comparing strength development in mortars in which various proportions of the cement are replaced with the SCM. There are a number of standardized methods for conducting this test, the most common being ASTM C-618/C-311 that is used in this study in which 20% by weight of the cement is replaced with the pozzolan under evaluation. The pozzolanic activity, or strength activity index, of the MIA as determined by this test method requires mixing the cementitious mortar to a constant flow value, which is determined by that of the control OPC mortar at a fixed water to cement (w/c) ratio of The Burnaby MIA was also evaluated at 10% cement replacement, a level that is lower than specified in ASTM-C-618/C-311 but more in keeping with high surface area SCMs such as silica fume and metakaolin. A further series of ternary binder mixes (designated as OPC-MIA-PFA and OPC-MIA-BFS) was prepared with the MIA in combination with the two most widely used SCMs: namely, Class F subbituminous coal fly ash (PFA) and 16 AMEC Report No. VA06294

17 ground granulated blast furnace slag (BFS). These latter materials were selected for their potential to mitigate any potentially deleterious physical effects or chemical reactions with the MIA in cement mortars as well as providing some workability advantages to the mixes in the plastic state. As noted earlier, the chemical and physical properties of the MIA can be expected to have at least two immediate effects on the cement mortars: (a) the very high measured surface area can be expected to increase water requirement; and (b) the high chloride content will impact cement hydration and likely decrease set times. PFA generally results in lower water requirement in mortars due to the plasticizing and floc breaking effects of its spherical particles, so it was employed in some mixes with the MIA in an effort to partially offset the high water demand of the MIA. Both the PFA and BFS also tend towards slower set times and strength development (often resulting in higher longterm strengths), which could be advantageous in moderating the expected set acceleration from the MIA. The testing of long-term physical stability of cement mortar mixes incorporating the MIA is discussed in Section Pozzolanic Reactivity Standardized Testing According to requirements of ASTM C-618: Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete, a 28- day strength of at least 75% of the OPC control mortar is required to meet the Class N (natural pozzolan) or Class F (coal fly ash) requirements. The strength activity indices for the MIA and the commercial SCMs, PFA and BFS, were determined by ASTM C-311: Standard Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland-Cement Concrete. Table 6 provides the mix proportions and compressive strength results for these tests, which include the following three binder series: (a) a control mix with 100% Type 10 OPC; (b) three binary combinations 80:20 OPC-MIA, 80:20 OPC-PFA and 80:20 OPC- BFS; and (c) two ternary combinations 80:10:10 OPC-MIA-PFA and 80:10:10 OPC-MIA- BFS. The strength activity index data for this series of mixes is compared in Figure 9. As noted, by this protocol the test mortars are prepared with the same flow value as the control OPC mortar. For the 80:20 OPC-MIA mortar, an additional 11% water was required to achieve standard flow, which partially explains the low strength results. In the ternary mortar mix 80:10:10 OPC-MIA-PFA, the use of a lower amount of MIA and the plasticizing effect of the PFA effectively negates the water demand problem, but, surprisingly, results in even lower strength. The 80:20 OPC-PFA mortar achieves a strength activity index of 97%, which easily meets the ASTM C day strength requirement of 75% for Class F fly ash. By comparison, the 80:20 OPC-MIA mortar is marginal and just meets the minimum 28-day strength requirement of 75% of control (although as will be discussed in Section 7, it does not comply with a majority of the other requirements of ASTM C-618). AMEC Report No. VA

18 When the MIA is blended 50:50 with PFA, the resultant ternary 80:10:10 OPC-MIA-PFA mortar performs somewhat worse (68%) than the 80:20 OPC-MIA mortar, despite the advantage of a lower w/c ratio. Conversely, when MIA is blended 50:50 with BFS, the resultant ternary 80:10:10 OPC-MIA-BFS exceeds the performance of the 80:20 OPC- BFS mortar (117% verses 105%). These data suggest that the MIA is affecting the pozzolanic reactions of the other SCMs. 4.3 Mix Proportioning Trials Table 7 provides the mix proportions and strength development results for a series of binary 80:20 OPC-SCM mortars prepared at a constant w/c ratio of 0.485; and Table 8 provides the strength development results to date for a second series of binary 90:10 OPC-SCM mortars with lower SCM contents, all prepared at a constant w/c ratio of Under these conditions, the 80:20 OPC-MIA mortar achieved a strength that was 84% of the control mortar after 28 days, of curing, but with the penalty of a very stiff and almost unworkable mixture (flow of only 28%, compared to 126% and 99% for the PFA and BFS mortars, respectively). When the MIA content was reduced to 10% (90:10 OPC-MIA) and a lower w/c ratio of 0.45 was used (comparable to that expected in typical 32 MPa concrete) the OPC-MIA mix actually exceeded the OPC control mortar at 28 days, with little effect on flow. The strength development data for these series of mixes are compared graphically in Figure 10A. Table 9 provides results for two preliminary high-volume fly ash (HVFA) mixes incorporating the Burnaby MIA. A ternary mix design 60:10:30 OPC-MIA-PFA incorporating 10% MIA was selected and prepared at w/c ratios of and to correspond to the control mixes from Tables 7 and 8. The strength development data to 28 days are compared in Figure 10B. It can be seen that the HVFA mix at w/c = has reached a satisfactory strength of 50 MPa at 28 days, representing about 90% of the control OPC mix at the same w/c. The strength of the HVFA mix at w/c = is slightly lower at 45 MPa, representing 95% of the control, and still quite impressive. The data indicate that the Burnaby MIA significantly increases the water demand of mortars and, as a consequence, significantly decreases the compressive strength at 20% Portland cement replacement. The strength activity index results show 20% MIA replacement of Portland cement results in 28-day strengths that are 75% of the OPC control. This is partly attributable to the higher water content required for the mixes prepared at constant flow, where the MIA mortar requires a w/c ratio of 0.54 to achieve the same flow as the OPC mortar at a w/c ratio of The increased water demand in these mixes is consistent with the high specific surface area of the Burnaby MIA (~12,500 cm 2 /g, compared to values of 3,500 5,000 cm 2 /g for Portland cement and slag) as well as the chemical composition. Also of note is a very strong ammonia odour evolved during the preparation of mortar mixes containing MIA, this being a consequence of the alkaline (high ph) environment of the hydrating Portland cement reacting with ammonium salts (most probably ammonium chloride, NH 4 Cl) in the MIA. This could present a potential health and safety issue to be 18 AMEC Report No. VA06294

19 considered and addressed during the preparation of large amounts of MIA concrete, especially if the mixes are prepared indoors. Another potential issue related to MIA use is the observation of corrosion of steel mold surfaces when preparing mortar bar samples. Normally, the bleed water from cement mortars does not affect the bar molds. In the case of the MIA mortars, however, areas where the bleed water collected on the steel surface showed marked corrosion as early as 24 hours after casting. This could impact all aspects of concrete production with MIA, from dry powder handling equipment to ready-mix trucks and pumps. The set time (Vicat needles, ASTM C-191) for a 90:10 OPC-MIA cement paste containing 10% by mass of the Burnaby MIA was determined. The control 100% OPC paste had a normal initial set time of 80 minutes, and a final set time of 195 minutes. The paste containing the 10% MIA, had an initial set time within 15 minutes, and a final set time of 50 minutes. In addition to the accelerated set, considerable heat generation was also noted with the 90:10 OPC-MIA cement paste. Although such rapid set was not observed during preparation of mortar cubes (likely due to the moderating effect of the sand on the temperature and the 5 minute interval between adding water to the mortar and the completion of the cubes) this issue will need to be addressed for workability and finishability of concrete. 4.4 Chemical and Mineralogical Features A series of binary OPC-MIA test mortars was prepared to examine the mineralogical and microstructural composition of the hydrated cementitious binder. The mortars selected included the binary combinations 90:10 OPC-MIA and 80:20 OPC-MIA, as well as two ternary combinations 80:10:10 OPC-MIA-PFA and OPC-MIA-BFS. Samples for analysis were recovered from the hardened mortar samples by gently crushing the samples and then carefully grinding the material in such a way as to minimize degradation of the silica sand aggregate. The resulting powder was separated on a 150 µm screen (the silica sand used to prepare the mortars is nominally 96% coarser than 150 µm) to recover a cement paste fraction containing a minimum amount of residual crushed silica sand. The mineralogical compositions of the paste concentrates recovered in this way from the test mortars are shown in Figures 11 and 12. The quartz present in the X-ray diffraction patterns is the result of some silica sand being recovered along with the cementitious phases. The mineralogical data confirm the presence of calcium hydroxide (Ca(OH) 2 ) and the calcium sulphoaluminate, ettringite (Ca 6 Al 2 (SO 4 ) 3 (OH) 12.26H 2 O) in all of the mortar samples, together with some unhydrated Portland cement. These compounds are all normally associated with Portland cement hydration. There is no direct evidence in any of the mortar samples for the sodium, potassium and calcium chlorides identified in the raw MIA (see Section 3). This is not unexpected because these alkali chlorides are all highly soluble and reactive in a cement system such that they would not remain as distinct compounds after mixing with water. The most notable cement hydration product seen in the MIA mortars, which is absent from the control 100% OPC mortars, is Friedel s salt (Ca 2 Al(OH) 6 Cl.2H 2 O) also known as hydrocalumite. This calcium chloroaluminate compound forms as a result of chemical AMEC Report No. VA

20 reaction of the chloride salts in the MIA with available aluminum species released from the Portland cement (or SCMs). This chloride-based reaction is different from the normal reaction path taken by aluminum species in cement systems, where sulphate is the dominant reactant and calcium sulphoaluminate, or ettringite, is the usual primary product. Interestingly, the available data are consistent with the formation of the calcium chloroaluminate being enhanced by the presence of PFA or BFS in the cement. This is most likely attributable to the additional available aluminum in these SCMs. A possible explanation of this observation follows. In plain Portland cement mortars the gypsum interground with the cement normally reacts quickly with tricalcium aluminate (C 3 A) to form ettringite, thereby moderating the early hydration of the C 3 A to control flash setting. When MIA is included in the mix, the ettringite-forming reaction effectively starves the system of aluminum and limits the formation of calcium chloroaluminate (Figure 11). In a sense, the sulphoaluminate- and chloroaluminate-forming reactions can be considered to be competing with each other for the available aluminum from the cement. The lower content of calcium hydroxide lines in the 80:20 OPC-MIA system compared with the 90:10 system indicates that lime is consumed by the formation of the chloroaluminate analogous with the formation of sulphoaluminate. With the ternary 80:10:10 OPC-MIA-PFA and OPC-MIA-BFS mortars, an additional reservoir of reactive aluminum is available in the form of alkali-soluble aluminate species released from the glassy aluminosilicate phases in the SCMs (PFA and BFS). This available aluminum can react with the soluble chlorides from the MIA to continue forming calcium chloroaluminate (Figure 12). This complexation of soluble chloride facilitated by the SCMs is an example of how these valuable cement additives can help to mitigate the presence of harmful cations in concrete. 5.0 ENVIRONMENTAL STABILIZATION OF INCINERATOR ASH In addition to evaluating the potential of the Burnaby MIA as a supplementary cementing material (see Section 4), another goal of the project was to assess the ability of Portland cement concrete and related cement-based materials to stabilize and sequester toxics and heavy metals present in the MIA. This latter type of information is a key to establishing the potential environmental benefits of incorporating the Burnaby MIA in concrete and other cement-based materials both as a beneficial use as well as a technically sound stabilization/solidification alternative for management of the material. As noted earlier, the Burnaby MIA is currently regulated in British Columbia as a special waste that requires costly chemical treatment before being sent for disposal at the Cache Creek landfill. EcoSmart hopes that cement and concrete technology may provide a solution to this continuing local environmental problem relating to the management and disposal of the MIA. Any replacement of Portland cement in concrete by the Burnaby MIA would both help reduce regional GHG emissions as well as providing other environmental and financial benefits, such as: (a) avoided disposal, providing a reduction in environmental impact and an extension to the service life of the landfill; (b) avoided transportation, leading to reductions in costs and the associated GHG signature; and (c) avoided need for chemical processing, thus reducing the 20 AMEC Report No. VA06294

21 operating costs for the GVRD incinerator and further reducing the transportationassociated GHG. The efficacy of cement stabilization of the Burnaby MIA as a means of immobilizing (sequestering) the heavy metals and other toxics was evaluated by preparing Portland cement mortars containing the material which were then subjected to standardized metals leachability (TCLP) testing to provide a simulation of potentially aggressive environmental exposures. Equally important to the efficacy of this approach is the integrity and long-term physical stability (often referred to as durability in concrete technology) of the cement-stabilized MIA, particularly in terms of its resistance to common aggressive chemical environments such as sulphate-containing groundwaters or soils to which concrete can be exposed, as well as internal chemical attack resulting from reactivity of the aggregates in the concrete (alkali-silica reactivity). It is well established that incorporation of SCMs is very beneficial to reducing deterioration of concrete by these two mechanisms, to the extent that these properties are incorporated into the ASTM standards and specifications for SCMs. These tests were therefore included in the present study to provide a convenient means for evaluating both the function of the Burnaby MIA as a potential SCM as well as its role in affecting the efficacy of cement stabilization. 5.1 Leachability of Cement Stabilized MIA Mortars A composite sample of the raw, unstabilized Burnaby MIA was first tested for baseline leachability of the Schedule 4 regulated metals (arsenic, barium, boron, cadmium, chromium, lead, mercury, selenium, silver and uranium) and total PCBs by the Ontario Regulation 558-TCLP protocol (Table 10). As expected from its relatively high lead levels (~4400 ppm Pb), the as-received MIA exceeds the Schedule 4 leachate criteria for lead (measured 33.1 mg/l vs. limit of 5 mg/l). All other regulated metals as well as total PCBs show leachability levels that are well below the Schedule 4 criteria. Selected Portland cement mortars containing two different levels of the Burnaby MIA (10% and 20%) were then prepared according to the protocols described in Section 4 for the evaluation of strength development. These mortars were allowed to cure at ambient temperature (21 23 C) and100% relative humidity for 90 days before leach testing according to the Ontario Regulation 558-TCLP Leachate procedure (Table 11). Since the raw Burnaby MIA did not exhibit any detectable PCBs during the baseline TCLP testing, the MIA mortars were not tested for the leaching of PCBs. From the data collected in Table 11, it can be seen that none of the laboratory prepared MIA mortars (80:20 OPC-MIA, 80:10:10 OPC-MIA-PFA, and 80:10:10 OPC-MIA-BFS) showed any leaching of lead above the detection limit of 0.05 mg/l in the TCLP test. Given the percentage of MIA in the mortars (4.72% for 20% OPC replacement, 2.36% for 10% OPC replacement) there would be the potential to produce lead leachate values of 1.56 and 0.78 mg/l if there were no chemical sequestering of lead taking place in the mortars. These results demonstrate that the cementitious matrix has rendered the lead in the Burnaby MIA unavailable for leaching under TCLP conditions. AMEC Report No. VA

22 5.2 Stability of Cement Stabilized MIA Mortars The retention of physical integrity of the MIA mortars was evaluated by two standardized tests that are routinely used in concrete SCM testing: ASTM C-1012 for sulphate resistance; and ASTM C-441 for alkali-silica reactivity. The sulphate resistance and alkali-silica reactivity testing is complete to 16 weeks age, and is scheduled to continue for at least 6 months total duration (Figures 13 and 14). It can be seen that the incorporation of the Burnaby MIA in the mortars markedly increases the amount of sulphate-induced expansion at a 10% cement replacement level relative to the 100% OPC control sample (Figure 13). Surprisingly, the use of a ternary blend with PFA (80:10:10 OPC-MIA-PFA) shows only a very minor improvement in sulphate durability. Similarly in the ASTM C-441 series of tests for alkali-silica reactivity, the data indicate that the MIA mortars at 10% cement replacement, with or without PFA or BFS, all result in significantly increased expansion of the test mortars relative to the 100% OPC control. Given the durability results to date, it is clear that the MIA is not acting at all like typical supplementary cementing materials that generally improve the durability of concrete. Rather it appears that the Burnaby MIA is accelerating the deterioration under the conditions used for the test methods. This is discussed further in Section FORENSIC EXAMINATION OF AGED CONCRETE During the early stages of the project, AMEC became aware of a 10-year old concrete median barrier that was found at the GVRD Incinerator site and was believed to contain the Burnaby MIA, albeit with an undocumented mix design. Although the history of this concrete is not known, EcoSmart agreed that it was still a potentially valuable sample that with appropriate forensic examination could provide useful information on the effects of long-term aging on concrete containing the MIA. Examination of this aged concrete included assessment of compressive strength, depth of carbonation, permeability, leachability (TCLP), microstructure and phase composition. The goal was to establish the general condition of the concrete and to determine whether there have been any long-term effects, positive or negative, associated with the presence of MIA. 6.1 Preliminary Inspection A single concrete core sample 278 mm long and 96 mm in diameter containing an unknown quantity of MIA was submitted for examination. The core appeared to have a polymer coating on the exposed surface, suggesting that the concrete in service was protected from the environment. The sample was cut into sections for unconfined compressive strength, rapid chloride permeability and microstructural/petrographic testing. Physical testing showed that the concrete core was quite strong, with an unconfined compressive strength of 55.8 MPa (8,090 psi). The rapid chloride permeability of the 22 AMEC Report No. VA06294

23 concrete was also good, with a value of 883 coulombs when tested by ASTM C Visual inspection of sections of embedded steel showed no indication of corrosion. At the outset, these data indicated that the concrete was of good quality. 6.2 Petrographic Examination Whole Concrete: The core piece examined measured 96 mm in diameter by 89 mm in length. The external surface of the core was covered with a pale green coloured membrane that was well bonded to the concrete core. No indication of debonding of the membrane from the concrete was noted, nor was there any indication of voiding between the membrane and the concrete substrate. Phenolphthalein testing indicated less than 1 mm of carbonation below the membrane layer. Entrapped voids accounted for approximately 1% by volume of the concrete, resulting in a very solid appearance to the concrete. Coarse Aggregate: The concrete core contains a rounded gravel coarse aggregate with a maximum particle size of 15 mm. The principal rock lithologies include a combination various silicates of intrusive, metamorphic and sedimentary origins, which in total accounts for approximately 20% of the concrete by volume. The rock lithologies and their proportions includes the following: Granite 23% Altered Volcanic 4.5% Volcanic (Andesite) 22% Greywacke 4.5% Arkose 14% Sandstone 4.5% Ryholite 14% Gabbro 4.5% Argillite 9% Typically, the particles are rounded in shape and evenly graded, with no evidence of a preferred orientation for the particles. Segregation is present between 55 and 80 mm from the external surface of the core such that no coarse aggregate are present in this zone. Overall, the coarse aggregate is well bonded to the cement paste; however, some cracking along this interface is evident. All of the particles show good field performance with no evidence of alkali-aggregate reactivity (AAR). Fine Aggregate: The fine aggregate accounts for approximately 40 45% of the concrete by volume. Compositionally, the fine aggregate includes a combination of rock fragments (65%) and grains of quartz and/or feldspar (35%). The rock fragments include lithologies in approximately similar proportions to that found in the coarse aggregate. Both the rock fragments and the mineral grains vary in shape from rounded to angular, with the former being primarily rounded. This aggregate is evenly graded and evenly distributed throughout, except for an increased proportion of sand at depth were there is a lack of coarse aggregate (i.e. between 55 and 80 mm from the top surface). No evidence of a preferred orientation is present in the fine aggregate. Overall, it is well bonded to the cement paste, except for minor cracking along the paste-fine aggregate interface. This aggregate has shown good field performance with no evidence of alkali-aggregate reactivity (AAR). AMEC Report No. VA

24 Cement Paste: Accounting for approximately 30% by volume of the concrete, the cement paste is a mottled grey colour with a sub translucent appearance on broken surfaces. No evidence of bleeding is noted in the cement paste and no evidence of retempering is evident. The cement paste in general is well bonded to the aggregates and is strong as indicated by the compressive strength results (> 50 MPa) obtained on a companion section from this core. As mentioned earlier, phenolphthalein testing of a fresh surface of the core indicates approximately 1 mm of carbonation. This is confirmed through thin section analysis, which indicates that pervasive carbonation of the paste is limited to the first millimeter beneath the membrane surface. No other indication of carbonation of the paste is noticed below this level, even along micro-cracks that intersect much of the cement paste. Un-hydrated particles of MIA are evident in the paste along with Portland cement. These ash particles occur in a variety of forms ranging from irregular shaped masses to elongated black carbon fillers to various coloured spheres. Approximately 3% by volume of the concrete is made up of remnant grains of the MIA. In contrast, the remnant Portland cement grains account for approximately 15% by volume of the concrete. Calcium hydroxide in the cement paste occurs as anhedral clots randomly scattered through the paste, narrow, partial rims along aggregate interfaces and as very finegrained masses. The calcium hydroxide accounts for approximately 3% by volume of the concrete. This proportion of calcium hydroxide is above average for a concrete with this compressive strength and this proportion of cement paste. Voids: This concrete has a good air-entrainment system with approximately 9% voids by volume of concrete. These voids are well dispersed throughout the concrete, with no evidence of clustering or concentration along coarse aggregate interfaces. As mentioned earlier, there is a very low proportion of entrapped voids, and it is estimated that this void system would have a spacing factor between 0.10 and 0.15 mm, and a specific surface value above 35 mm -1. In general, the interior appearance of the voids is dull, however, in the upper 5 to10 mm of the core, secondary mineralization of the voids is common. This mineralization is principally in the smaller sized voids and occurs as a lining, partial filling and complete filling of the voids. The mineralization appears to be a combination of ettringite and/ or calcium hydroxide. No evidence of carbonation of the cement paste along the periphery of these voids was noted. Cracks: Micro-cracking is frequent in amount throughout the cement paste and throughout the entire length of the core. Typically these cracks appear in a random to branching pattern through the cement paste and to a limited extent along the aggregate interfaces. These cracks range in width from to mm, with the former being the most common. These cracks do not appear to be filled with any secondary mineralization and are not related to any embedded items. Embedded Items: A 5 mm steel reinforcing screen is found at a depth of 8 mm from the exterior surface. This screen is clean, with no indication of corrosion and it appears well 24 AMEC Report No. VA06294

25 bonded to the cement paste with only one small void (3 mm) present at one part along its length. No indication of carbonation was noted along the length of the screen when tested with phenolphthalein. 6.3 Chemical and Mineralogical Features Figure 15 shows the XRD pattern of a paste concentrate prepared from the site concrete by the same technique as described in Section 4.4. The XRD pattern shows the expected contributions from the aggregate species (quartz, anorthite, muscovite, tremolite) in the concrete, consistent with the rock lithologies identified above. In addition, calcium hydroxide (Ca(OH) 2 ), and the calcium sulphoaluminate, ettringite (Ca 6 Al 2 (SO 4 ) 3 (OH) 12.26H 2 O) are also clearly identified in the concrete, both of which are normal components of Portland cement hydration. There are no diffraction lines associated with the alkali chloride species (NaCl, KCl, CaCl 2 ) identified in the raw Burnaby MIA. As the chloride species in the MIA are readily soluble and reactive this is not unexpected. Also, it should be noted that calcium hydroxide is a product of the hydration of Portland cement, so the presence of MIA in the concrete cannot be definitively deduced from observation of this phase alone. However, more significantly, the aged concrete sample does appear to contain Friedel s salt, Ca 2 Al(OH) 6 Cl.2H 2 O, a calcium monochloroaluminate hydrate phase which is often associated with cement hydration in the presence of soluble chlorides. Based on the mortar results reported in Section 4.4, the observation of this compound in the aged concrete provides strong evidence that MIA was in fact present in the mix. The total chloride content of the paste concentrate was determined to be 1.08% Cl by mass. Given the mass fraction of the concrete represented by the paste concentrate, this suggests a minimum total chloride content for the concrete of 0.4% Cl. The MIA content of the cementitious phase of the concrete is estimated to be about 10%. This is based on assumptions for the cement content of the concrete and the expected chloride content of the MIA used at the time of its manufacture, and is consistent with the estimates made above. The chloride content of the aged concrete is cause for concern from the perspective of its impact on corrosion of embedded steel. The normal threshold for steel corrosion in concrete is 0.025% Cl, a factor of 16 less than that determined for the MIA concrete. The 0.025% Cl value is normally corrected to account for the chloride content of the aggregate material (it is assumed that chloride in aggregate is unavailable in concrete). However, it is unlikely that the chloride content of the MIA can be reasonably treated in the same manner as that from the aggregate. Also, although the calcium chloroaluminate is stable, it is not currently clear if all or even a significant fraction of the chloride inherent in the MIA is sequestered in this form. This presents the distinct possibility that chloride is readily available to promote corrosion when MIA is used in reinforced concrete. The apparent anomaly that the aged concrete does not exhibit corrosion of the embedded steel is attributed to the exposure history of the material that evidently prevented moisture from penetrating into the matrix. Moisture in this case is the essential missing component for the corrosion mechanism. AMEC Report No. VA

26 6.4 Microstructural Features Figures 16 and 17 show scanning electron microscope images with corresponding energy dispersive X-ray analysis (EDXA) elemental maps for polished surfaces prepared from the aged MIA concrete sample. Of particular note is the uniform distribution of both sulphur and chlorine throughout the cement paste. This indicates that both the Friedel s salt (containing chloride) and ettringite (containing sulphur) are distributed uniformly within the cement paste, and do not appear to be concentrated either in voids or microcracks, as they typically are when involved in secondary destructive mineralization processes. However, given the combined strength, low permeability, and low carbonation of the concrete, together with the apparent application of an external coating material, it is entirely possible that the aged concrete has not been exposed to significant moisture in service, and that any potential mobilization of species associated with MIA has been greatly reduced, or even halted. 6.5 Leachability of Aged Concrete The results of the leachability testing of the aged concrete sample according to the Ontario Regulation 558-TCLP Leachate procedure are given in Table 11 in comparison with the data obtained for the MIA mortars. It can be seen that none of the regulated metals in the aged concrete exceed the Schedule 4 criteria, confirming that the cement system is effective in immobilizing (sequestering) the toxic species over the long term. 6.6 Summary of Forensic Findings This aspect of the study has confirmed that the aged concrete submitted for forensic examination does in fact contain MIA. Based on the available data and assumptions made in the analysis outlined above, the MIA content is estimated at about 10% of the cement content. The aged concrete is of surprisingly good quality, with very high strength, low permeability, very little carbonation, and no indication of secondary mineralizations as an indicator of deleterious internal chemical reactions. With such a concrete, it is considered unlikely that any deleterious reactions that could potentially occur have had the right combination of conditions particularly exposure to moisture to manifest themselves. Due to the highly speculative nature of the results obtained in this section, the reader should exercise caution in applying the results elsewhere. 26 AMEC Report No. VA06294

27 7.0 DISCUSSION The experimental findings described in Sections 3 6 of the report are now discussed in terms of the overall objectives of the study. 7.1 Material Properties of Incinerator Ash This study has provided new insights into the properties of the fly ash produced by the GVRD incinerator. The Burnaby MIA is a complex mixture of components that are mostly by-products from the flue gas clean up process using lime sorbent. The MIA is comprised largely of hydrated calcium chloride (35%) and calcium hydroxide (29%), together with sodium and potassium chlorides (11.3%), calcium sulphate (4.2%) and calcium carbonate (5%). Minor components make up a further 9% of the material. This leaves only about 6% of the MIA at best that can be attributed to the silicate or aluminosilicate components characteristic of conventional pozzolans. Species of this type could originate from clays used as mineral fillers for paper, cardboard and plastics as well as soil, ceramic and vitreous detritus in the garbage. However, because the operating temperature (~1000 C) of the GVRD incinerator is lower than their fusion temperature, these materials will be not be melted during combustion, as is the case with PFA or slag. This potential pozzolan fraction in the MIA is not only relatively insignificant in volume, it is also likely to be highly variable. This is the first indicator that the Burnaby MIA is not a pozzolan in the conventional sense. The study has also shown that the Burnaby MIA contains ammonium salts (~240 ppm as NH 3 ) that are a by-product of the NOx emission control technology used at the incinerator. These species are of significance and may present a health and safety problem if the MIA is used in a cement and concrete system, particularly in a confined space (see Section 7.3). 7.2 Pozzolanic Reactivity Potential of Burnaby MIA One of the principal goals of this study was to evaluate the pozzolanic reactivity potential of the Burnaby Municipal Incinerator fly ash, and to evaluate a range of mixture proportions of the MIA which could potentially be useable in concrete. Performance in Cementitious Systems: Under ASTM C-618/C-311 test conditions, the Burnaby MIA performs poorly and just meets the minimum level of strength requirement for either Class N or Class F material. As noted in Section 4, when used at 20% OPC replacement the MIA results in a significant increase in water demand. The MIA is penalized in this test due to its high surface area. The problem of water demand is manageable to some degree when the replacement level of the MIA is reduced to 10%; and it is also aided by the use of ternary blends with equal proportions of MIA with PFA or BFS. Similarly, mixtures with high PFA volumes (HVFA mix designs) show promise. However, there are other considerations with regard to MIA as a potential SCM, which include its effect on set times and the liberation of ammonia during the batching process. Standards and Specifications: It is useful at this point to examine how the standards and specifications define both Pozzolan and fly ash physically, chemically and by performance: AMEC Report No. VA

28 ASTM C defines a pozzolan as: A siliceous or siliceous and aluminous material which in itself possesses little or no cementitious value, but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementious properties. This definition, which until recently was incorporated in ASTM C-618, clearly does not encompass a material of the composition established for the Burnaby MIA. In ASTM C fly ash is defined as: The finely divided residue that results from the combustion of ground or powdered coal and that is transported by flue gasses from the combustion zone to the particle removal system. NOTE 2 of this same specification includes the statement: This definition of fly ash does not include, among other things, the residue resulting from: (1) the burning of municipal garbage or any other refuse with coal; (2) the injection of lime directly into the boiler for sulfur removal; or (3) the burning of industrial or municipal garbage in incinerators commonly known as incinerator ash. The ASTM C-618 definition therefore clearly excludes the use of the term Fly Ash in reference to MIA as a constituent in concrete. Similarly, the ASTM C-125 definition of a Pozzolan does not apply to either the raw chemical and mineralogical composition of the MIA or to the observed reactivity of the material in cementitious systems (see Section 4.4). The performance of the Burnaby MIA tested in this study as a potential SCM by the procedures defined in ASTM C-618 is summarized as follows in comparison with the requirements for Class N (natural pozzolans) and Class F (coal fly ash) pozzolans: ASTM C Requirements Spec Class N Spec Class F Actual MIA Comment Chemical Requirements: SiO 2+Al 2O 3+Fe 2O 3, min % <6 Fail Sulfur trioxide (SO 3), max % Pass Moisture content, max % Marginal Loss on ignition, max % Fail Physical Requirements: Fineness, +45 µm, max % Pass Strength activity index, 28d, min % of control Marginal Water requirement, max % of control Marginal Soundness, autoclave, max % TBD Uniformity 5 5 ND Unknown Optional Requirements: Increase in drying shrinkage Effectiveness in controlling alkali-silica reaction Fail Effectiveness contributing to sulfate resistance * Fail *data to 4 months only 28 AMEC Report No. VA06294

29 Clearly, the Burnaby MIA does not meet the majority of the requirements for consideration as an SCM for use in concrete under this widely used specification. However, this does not mean that the MIA is not chemically active in these systems, as will be discussed in the following section. 7.3 Mechanistic Considerations As discussed in Section 7.2, a central focus of the study has been to evaluate the potential utility of the Burnaby MIA as a supplementary cementing material. The materials characterization data certainly indicate there may be a problem with this proposition, this being supported phenomenologically by the physical testing of cement mortars with MIA which is not consistent with the material functioning as an active pozzolan in the cement hydration process. At the same time, however, the effects MIA has on set time, strength development and the release of ammonia all indicate that it is chemically active in the cement system, albeit not in the form of a pozzolan. The possible mechanistic reasons for this behaviour are now briefly examined. The Pozzolan Reaction: The main reactive components in conventional SCMs coal fly ash, blast furnace slag, silica fume, metakaolin are the amorphous (glassy) silicates that contain varying amounts of aluminum and iron (alumino-silicates and ferrosilicates). These amorphous silicates can be considered as disordered threedimensional Si O Si networks with aluminum and iron substituting for approximately one-third of the silicon atoms. In the strongly alkaline pore fluid produced by hydrating Portland cement (ph >13), the silicate networks will be depolymerized by bond breaking at Si O Si and Si O Al linkages: Si O Si + M + OH - Si OH + Si O - M + Si O Al + M + OH - Si OH + {Al(OH) 4 } - M + (M = Na or K) These processes may be considered as a combination of hydrolysis and alkali sorption or ion-exchange. As the reaction proceeds, the surface of the silicate becomes increasingly hydrolyzed, while retaining its physical form. Eventually, the outer silicate units will have depolymerized sufficiently for them to enter solution as soluble silicates and aluminates, at which point they react with other ions in solution in the pore fluids to form insoluble hydration products. The supplementary cementing action is achieved by reaction of silica in solution with calcium to form calcium silicate hydrate (C S H), through the silico-pozzolanic reaction: S O Si + OH - S OH + Si O - [SiO(OH) 3 ] - + Ca(OH) 2 C S H This C S H formed in this reaction is similar to that largely responsible for the binding and strength development of Portland cement concrete and typically develops as a poorly crystalline to amorphous material. Given the composition of the MIA with its very low SiO 2 +Al 2 O 3 +Fe 2 O 3, this classical pozzolanic reaction that is characteristic of all supplementary cementing materials cannot be occurring to any significant extent. AMEC Report No. VA

30 Chemical Reactions Involving MIA: If the MIA is not undergoing pozzolanic reactions, the immediate question, then, is what reactions are occurring with the material in the cement system? There is no doubt that the calcium and alkali metal salts comprising the MIA are all soluble and very reactive in cementitious systems. The main effect, evident very soon after mixing, is the marked heat evolution and reduction of initial and final set time which can be directly attributed to the very large concentration of soluble chloride ions flooding the system from the MIA. This effect of chloride ions is a well recognized effect in concrete technology and calcium chloride has long been known to accelerate both the setting and hardening of Portland cement concrete. A typical dosage rate for calcium chloride in concrete is about 2% based on the cement content of the mix. Since the calcium and alkali metal chlorides represent about 46% of the MIA (Table 4), in a typical 80:20 OPC-MIA mortar this equates to an equivalent chloride dosage of about 9.2% almost a five-fold excess compared to the usual dosage. Some of this accelerating effect in the MIA system may be attributable to the interference with the set-controlling reaction of gypsum with C 3 A to form ettringite, 6Ca [Al(OH) 4 ] - + 4OH - + 3SO H 2 O by formation of the calcium chloroaluminate, Friedel s salt: [Ca 3 Al(OH) 6 12H 2 O] 2 (SO 4 ) 3 2H 2 O 2Ca 2+ + [Al(OH) 4 ] - + 2OH - + Cl - + 2H 2 O Ca 2 Al(OH) 6 Cl.2H 2 O But the likely dominant cause is the increased rate of hydration of the alite (C 3 S) in the Portland cement: C 3 S + n H 2 O C S H + x Ca(OH) 2 With the massive overdose of chloride ions in the MIA mortars, it is likely that both processes are occurring. As discussed in Section 4, the chloroaluminate may also be formed in longer-term reactions when SCMs like PFA and BFS are present to provide a source of reactive aluminum. In any event, these reactions likely leave substantial concentrations of uncomplexed chloride ion in the pore fluid system. Another consequence of the presence of such high levels of chlorides is that while very early strength may increase, long-term strength is often reduced, and some properties related to the microstructure of the paste, such as resistance to sulphate attack, are also adversely affected. Release of Ammonia: As noted in Section 4, the OPC-MIA mortars all produce a very strong odour of ammonia upon mixing. Ammonia is produced by hydrolysis of ammonium salts (mostly chloride) present in the MIA under the highly alkaline conditions (ph >13) present in the pore fluids when cement hydrates: NH 4 Cl + OH - NH 3 + Cl - + H 2 O (NH 4 ) 2 SO 4 + 2OH - 2NH 3 + SO H 2 O 30 AMEC Report No. VA06294

31 The total nitrogen content of 200 ppm determined for the raw Burnaby MIA, corresponds to a total potential ammonia release of 240 ppm. Assuming that MIA replaces 10% of OPC in a 300 kg cement per cubic meter concrete mix, the potential release of ammonia is estimated to be 7.92 grams. This would be enough ammonia to bring 130 m 3 of air (a volume approximately 16 x32 x8 ) to the OSHA exposure limit of 50 ppm, or 215 m 3 (a volume approximately 30 x30 x8 ) to the 30-ppm level that humans can generally detect. As noted earlier, this release of ammonia from the Burnaby MIA in contact with cement is exactly the same issue that has caused significant problems throughout the United States with the utilization and marketing of coal fly ash contaminated with ammonium salts produced by electrical power plants retrofitted with SCR NOx emission control technologies. Stability: The two standardized durability tests conducted in this study on MIAcontaining mortars are strong indicators of potential instability in the binder system. Excessive expansion, far in excess of the 100% OPC control mortar, was apparent in both the accelerated alkali-silica and sulphate exposure tests. On the one hand, the tests confirm that the Burnaby MIA does not have the pozzolanic properties that provide stability to the paste system, as is typically found with established SCMs. But on the other hand, they are symptomatic of chemical instability. Further work will be required to properly identify the mechanisms involved, but it may be speculated that the instability is exacerbated by the excessively high chloride and alkali metal ion concentrations in the binders that may contribute to chloroaluminate and sulphoaluminate expansion under the test conditions. It is well established that high alkali contents in the cement paste are a major factor contributing to alkali-silica reactivity in concrete. This instability is evidently not manifested in the aged concrete from the Burnaby site, which leads us to believe that the concrete was not subjected to the exposure conditions which promote the loss of integrity. The presence of a polymer coating, in conjunction with the high strength, low permeability and low degree of carbonation of this concrete, all mean that there was very little opportunity for water to penetrate the concrete. Corrosion: There are two issues related to corrosion. First, the high chloride content of the Burnaby MIA could cause corrosion problems with steel equipment typically used for storage and concrete handling, mixing and placing. Second, in common with commercial chloride-based chemical accelerators, the MIA would not be specified for use in reinforced concrete because of the potential problem with chloride induced corrosion of reinforcing steel. Use in utility grade, non-reinforced concrete is possible provided the caveats discussed above are not considered a problem. 7.4 Environmental Stabilization of Burnaby MIA Another goal of the project was to evaluate the ability of Portland cement concrete and related cement-based materials to stabilize and sequester toxics and heavy metals present in MIA. This presents an alternative and economically very attractive MIA management option if technically feasible. The effectiveness of cement stabilization has been examined in this study on a range of mix designs incorporating the Burnaby MIA, as well as the sample of aged concrete containing the MIA from the GVRD site. AMEC Report No. VA

32 Leachability: The leachability test is the gold standard of all environmental stabilization processes. As detailed in Section 5, standardized leach testing confirms that the raw Burnaby MIA releases significant amounts of lead (33.1 mg/l Pb) a value that is approximately six-times the Ontario Regulation 558 schedule 4 TCLP limit (Table 10). There is some release of barium, boron, and arsenic as well, but at levels well below the Schedule 4 limits and approaching the detection limits. In contrast, when the Burnaby MIA is incorporated in a cementitious mortar, the lead and all the other heavy metals are very effectively immobilized, with no detectable concentrations present in the leachate in the TCLP test. As an indicator of the excellent attenuation efficiency, if all the lead present in the MIA were to leach out, we would expect between mg/l Pb in the leachate. The same comments apply to the aged MIA concrete which shows lead in the TCLP leachate close to the detection limit and less than 2% of the regulated limit of 5 mg/l Pb. These results demonstrate that the incorporation of the Burnaby MIA into a cementitious matrix results in effective sequestering and environmental stabilization of the heavy metals present in the raw materials. Cement Stabilization Mechanism: The heavy metals present in the MIA will be initially mobilized in the presence of water during mixing of the concrete or mortar. However, they will enter into a highly alkaline medium that will precipitate the metals as insoluble hydroxides or similar phases that become encapsulated or complexed by the developing cement matrix. The net effect is that the trace metals associated with the MIA will be chemically and physically immobilized as the MIA reacts in the concrete. Low permeability in the cementitious system is a further advantage by significantly reducing the flux of water reaching the metals that further reduces their opportunity to leach into the environment. A further significant factor is that, on a total mass basis, the metal concentrations in the MIA will be diluted by a factor of approximately twenty depending on the mix design of the concrete. This predicted low leachability of the metals is confirmed by the TCLP data (Section 5), suggesting there is a very low probability that the MIA will leach hazardous components when it is present in concrete in service. Long-Term Stability of Cement-Stabilized MIA: The accelerated durability testing discussed in Section 7.3 shows that the cement stabilized Burnaby MIA does have a potential stability problem under aggressive exposure conditions, especially in a sulphate environment, that requires further investigation. Other Environmental Factors: Wash water used for cleaning out ready mix trucks and other equipment used for handling MIA-containing concrete could become contaminated with lead and other heavy metals present in the MIA. This would require assessment on a case-by-case basis and may require the development of control measures for the management and disposal of the wash water and sludge at the plant or site. If cement stabilization is used as a treatment method, there would be an increased volume of material destined for disposal that could have a potential impact on transportationrelated GHG emissions. 32 AMEC Report No. VA06294

33 7.5 Potential Use of MIA in Cement and Concrete As noted above, the use of the Burnaby MIA at cement replacement levels greater than 10-15% are not feasible due to the combined effects of increased water demand and acceleration of initial and final set times. The use of PFA in combination with MIA partially offsets the problem of water demand, but the strength results are poor relative to the control and comparable slag mixes. Mixes using high volumes of coal fly ash, however, may prove viable provided a low-cost source of PFA is available. Use of the MIA at a 10% cement replacement level does not result in such severe water demand, and produces more acceptable strength results at lower w/c ratios. The sulphate resistance of concrete made with MIA may, however, be compromised, suggesting that it should not be used when the concrete may be exposed to aggressive environments. Similarly, the Burnaby MIA does not perform well with reactive aggregates in the ASTM C-441 alkali-silica reactivity test, indicating that it should not be used with suspect or marginal quality aggregates without testing the proposed mix design. Our findings suggest that use of the Burnaby MIA at a 10% OPC replacement level in a typical kg/ m 3 mix design concrete may be feasible, assuming of course that all the caveats identified in this report are properly addressed, in particular that the material is not used in reinforced concrete. Given this scenario it is possible to estimate the potential production rate of concrete if all the MIA is consumed. Given that the GVRD incinerator produces approximately 20 tonnes per day of MSW fly ash, then approximately 666 m 3 of concrete are required to consume one day s production. If the incinerator operated continuously, this represents some 243,000 m 3 of concrete per year. Clearly, this level of production requires relatively large volume products. Given the constraints, some potential uses for the Burnaby MIA and the technical / commercial barriers which must be overcome, are summarized as follows Highway median barriers using the above assumptions about concrete mix design, approximately 2,500 linear feet of standard median barriers would be needed to consume one day s MIA production. Potential problems with corrosion of embedded reinforcing steel must be addressed. Landscaping lock blocks this application could consume significant quantities of material. There is also the potential to increase the MIA content of the blocks, depending on the performance specification of the particular application. Although not a beneficial use per-se, consideration should be given to cement-based stabilization of the Burnaby MIA as a management alternative to treatment prior to disposal. AMEC Report No. VA

34 8.0 CONCLUSIONS AND RECOMMENDATIONS 8.1 Conclusions The following conclusions have been drawn from this study: 1. Existing literature pertaining to MIA in relation to cement and concrete technology is dominated by cement-based solidification and/or stabilization as a means of reducing metals leachability. Surprisingly, there is an information gap in the public literature concerning the fundamental chemical and mineralogical speciation in MIA that does not allow direct a priori comparison with conventional supplementary cementing materials. There is very little scientific and engineering information relating to the development and acceptance of beneficial uses for MIA in the cement and concrete industry. 2. Compositionally, the study has demonstrated that the Burnaby MIA is largely comprised of calcium and alkali metal salts and hydroxides and is not a pozzolan / supplementary cementing material in the conventional sense. 3. Technical performance factors that will impact the potential use of the Burnaby MIA in cement and concrete: (a) The MIA exhibits very high water demand and poor strength activity when tested as a conventional SCM. From a strength perspective, mix proportioning trials indicated that acceptable mixes could be prepared at 10% cement replacement levels, particularly in the presence of high volumes of fly ash. (b) Although it is not as a pozzolan, the MIA is chemically active in a cement system and the reaction mechanisms have been discussed. At cement replacement levels typically used for pozzolans in concrete (10 20%), the high levels of chlorides in the MIA cause acceleration of set and significant heat generation in large batches. (c) The MIA contains ammonium salts that will release ammonia when mixed with cement in the plastic state. This ammonia has the potential to be a health and safety issue, particularly in a pre-cast concrete plant environment. Exactly the same issue has caused significant problems with the use and marketing of coal fly ash from electrical power plants retrofitted with SCR NOx control technologies. (d) The very high levels of chloride effectively prohibit any use of the MIA in reinforced concrete due to the induced corrosion of embedded reinforcing steel items in concrete. Special handling equipment will also be needed to produce concrete due to its aggressiveness of MIA towards steel when moist. (e) Durability testing indicates that MIA should not be used in concrete exposed to aggressive environments, such as sulphate-rich groundwaters, sewage, soils, etc. The high alkali content of the Burnaby MIA is especially problematic if potentially reactive aggregates are used in concrete so much so that conventional SCMs such as PFA or BFS are unable to mitigate the problem. 34 AMEC Report No. VA06294

35 4. Institutional barriers have been identified which will impact the potential uses of the Burnaby MIA: (a) The potential of the Burnaby MIA as an SCM is restricted by the current requirements of ASTM and CSA cement and concrete standards that are specific to existing supplementary cementing materials (such as coal fly ash, blast furnace slag, and silica fume). ASTM C-618 expressly prohibits the use of municipal incinerator fly ash in concrete. (b) Environmental regulations that may restrict the movement, handling, storage and end use of MIA as a consequence of the presence of heavy metals such as lead and cadmium. (c) Occupational health regulations that may be applicable as a consequence of the release of ammonia when MIA is used in concrete, especially precast concrete or masonry units manufactured indoors. (d) The public perception of MIA as a hazardous waste. 5. Potential Uses: In view of these technical performance and institutional issues, potential use of the Burnaby MIA in the cement and concrete industry will be limited and confined to non-critical, non-reinforced applications such as landscaping blocks, artificial reefs, etc. It is unlikely, however, that this could consume more than a small fraction of the total production of MIA from the GVRD incinerator. 6. Environmental stabilization potential: While the use of MIA as an SCM is not considered feasible, from an environmental perspective the study has confirmed that cement stabilization is an effective means for sequestering the toxics and heavy metals from the MIA. This could provide a lower cost waste management option for the Burnaby MIA. Accelerated testing shows that the cement-stabilized MIA does have a potential stability problem under aggressive exposure conditions, especially in a sulphate environment, that requires further investigation. 8.2 Recommendations The following recommendations are made with respect to continued evaluation of management options for the Burnaby incinerator ash: 1. Conduct a technical-economic assessment of cement-stabilization for management of the Burnaby MIA compared to current chemical treatment practices. This assessment should include investigation of a wider range of mix designs focused on cement contents and strengths to identify the lower limit of performance consistent with effective metals sequestering and physical stability. 2. Conduct a chemical and microstructural investigation to better understand the reaction mechanisms involved with MIA in the cement system, particularly as it relates to the issues of long-term chemical and physical stability. AMEC Report No. VA

36 3. Develop a comprehensive database of the chemical, physical and mineralogical properties of the Burnaby MIA over an extended period of time to better characterize the extent of variability in the material. 4. Identify potential willing partners to become potential users of MIA in large volume concrete applications, such as low end, unreinforced concrete. There would appear to be some limited potential for use in non-critical, non-structural concrete. 9.0 LIMITATIONS AND CLOSURE This report is based on review of the documents and test results noted in this report and AMEC's general knowledge and experience in concrete technology. It has been prepared in accordance with generally accepted materials engineering practices. Although AMEC has taken measures to ensure the accuracy and validity of the results and conclusions presented, it accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this report. No other warranty, expressed or implied, is made. AMEC thanks you for the opportunity to be of service. We trust that this report meets with EcoSmart s immediate requirements. Please contact our office should you have any questions. Yours truly, AMEC Earth & Environmental a Division of AMEC Americas Limited Reviewed by Bruce J. Cornelius, P.Eng. Senior Materials Engineer D.R. Morgan, Ph.D., P.Eng. Chief Materials Engineer Raymond T. Hemmings, Ph.D., CChem. President and Principal Hemmings & Associates, LLC 36 AMEC Report No. VA06294

37 Tables AMEC Report No. VA

38 Table 1. Chemical Composition of Burnaby MIA Samples by Element (ppm) Element MIA-1 MIA-2 MIA-3 MIA-4 MIA-5 MIA-6 Average SD Ag Al As Ba C Ca Cd Cl Co Cr Cu Fe K Mg Mn Mo Na Ni P Pb S Sb Si Sn Sr Ti V Y Zn LOI* * Loss on ignition 38 AMEC Report No. VA06294

39 Table 2. Major Chemical Components of Burnaby MIA Samples Expressed as Element Oxides (mass %) Element Oxide MIA-1 MIA-2 MIA-3 MIA-4 MIA-5 MIA-6 Average SD SiO Al 2O Fe 2O CaO MgO Na 2O K 2O TiO P 2O MnO Zn C S LOI* * Loss on ignition (including chemically bound H 2O and CO 2) Table 3. Major Chemical Components of Burnaby MIA Samples Recast as Chlorides and Oxides (mass %) Element Oxide/ Chloride MIA-1 MIA-2 MIA-3 MIA-4 MIA-5 MIA-6 Average SD SiO Al 2O Fe 2O CaO CaCl MgO NaCl KCl TiO P 2O MnO Zn C SO LOI* * Loss on ignition (including chemically bound H 2O and CO 2) AMEC Report No. VA

40 Table 4. Estimated Compound Distribution in Burnaby MIA Major % Notes Calcium hydroxide, Ca(OH) 2 29 Sorbent related Calcium chloride, CaCl 2.6H 2O 35 Sorbent related Sodium chloride, NaCl 7.5 Sorbent related? Calcite, CaCO 3 5 Sorbent related Potassium chloride, KCl 3.8 Sorbent related? Anhydrite, CaSO Sorbent related Quartz, SiO 2 3 Possible sand in sorbent? Zinc, Zn 1.6 Lead, Pb 0.5 Minor and trace elements 2 Free carbon 1.2 Unburned combustible organics Ammonium chloride, NH 4Cl <1 NH 3 injection for NOx control Unaccounted for 6.2 Possible clay/shale (SiO 2+Al 2O 3+Fe 2O 3) Table 5. Chemical and Mineralogical Composition (Mass %) of Binders Element Oxide OPC PFA BFS SiO Al 2O Fe 2O CaO MgO Na 2O K 2O TiO MnO P 2O SO S C LOI SiO 2+Al 2O 3+Fe 2O Total Alkali (as Na 2O) (a) Mineral Components: C 3S 66.0 (b) amorph >75 (c) amorph >95 (d) C 2S 8.7 Qz minor Mw trace C 3A 6.1 Mu minor C 4AF 10.8 Hm trace (a) Sum (Na 2O K 2O) (b) Calculated (Bogue) composition, C = CaO; S = SiO 2; A = Al 2O 3; F = Fe 2O 3 (c) Amorph = Ca-aluminosilicate glass; Qz = quartz, SiO 2; Mu = mullite, Al 6Si 2O 13; Hm = hematite, Fe 2O 3 (d) Amorph = Ca-aluminosilicate glass; Mw = merwiniteca 3Mg(SiO 4) 2 40 AMEC Report No. VA06294

41 Table 6. Strength Activity Index of Binary and Ternary MIA Mortars (28 Days, ASTM C-618) BINARY TERNARY Parameter Control OPC-MIA OPC-PFA OPC-BFS OPC-MIA-PFA OPC-MIA-BFS Cement (%) Incinerator Ash (%) PFA (%) GGBF Slag (%) w/c Ratio Flow (%) Water requirement, % day (MPa) day (% Control) Table 7. Compressive Strength Development of Binary and Ternary MIA Mortars (w/c Ratio 0.485) BINARY TERNARY Parameter Control OPC-MIA OPC-PFA OPC-BFS OPC-MIA-PFA OPC-MIA-BFS Cement (%) Incinerator Ash (%) PFA (%) GGBF Slag (%) Flow (%) day (MPa) day (MPa) day (MPa) day (% control) day (% control) day (% Control) AMEC Report No. VA

42 Table 8. Compressive Strength Development of Binary and Ternary MIA Mortars (w/c Ratio 0.45) Parameter Control OPC-MIA OPC-MIA-PFA OPC-MIA-BFS Cement (%) Incinerator Ash (%) PFA (%) GGBF Slag (%) Flow (%) day (MPa) day (MPa) day (MPa) day (% control) day (% control) day (% Control) Table 9. Compressive Strength Development of Ternary 60:10:30 OPC-MIA-PFA High Volume Fly Ash Mortars Parameter OPC-MIA-PFA w/c = 0.45 OPC-MIA-PFA w/c = Cement (%) Incinerator Ash (%) PFA (%) w/c Ratio Flow (%) day (MPa) day (MPa) day (MPa) day (% control*) day (% control*) day (% control*) * Using Control at w/c ratio 0.45 and 0.485, respectively. 42 AMEC Report No. VA06294

43 Table 10. TCLP Results (mg/l) for Composite Burnaby MIA* Parameters Units Reg. Limit* MDL Raw MIA Arsenic (mg/l) Barium (mg/l) Boron (mg/l) Cadmium (mg/l) Chromium (mg/l) Lead (mg/l) Mercury (mg/l) < Selenium (mg/l) Silver (mg/l) <0.05 Uranium (mg/l) <0.07 Total PCBs (mg/l) <0.002 * Schedule 4 Leachate Criteria, Ontario Regulation TCLP Leachate, PCBs and Metals Table 11. TCLP Results (mg/l) for Selected Mortar Samples Incorporating MIA (Ontario Regulation 558 TCLP Leachate, Metals) Parameters (mg/l) Sch. 4 Leachate Criteria MDL Raw MIA 80:20 OPC-MIA 80:10:10 OPC-MIA- PFA 80:10:10 OPC-MIA- BFS Aged Concrete Arsenic Barium Boron <0.01 Cadmium <0.005 <0.005 <0.005 <0.005 Chromium <0.01 Lead <0.05 <0.05 < Mercury < < < < < Selenium <0.001 <0.001 <0.001 <0.001 Silver <0.05 <0.05 <0.05 <0.05 <0.05 Uranium < AMEC Report No. VA

44 44 AMEC Report No. VA06294

45 Figures AMEC Report No. VA

46 CaO Chloride LOI Major Component Mass Percent MIA Sample Mass Percent Minor Component SiO2 Na2O K2O Al2O3 Zn Carbon Sulphur MIA Sample Concentration (ppm) Trace Component Lead Antimony Copper Tin Strontium Barium Cadmium Arsenic MIA Sample Figure 1. Uniformity of concentrations of major, minor and trace constituents in six Burnaby MIA samples. 46 AMEC Report No. VA06294

47 CClH = CaCl 2 Ca(OH) 2 *H 2 O CCl = CaCl 2 *6H 2 O NaCl = Sodium Chloride Cc = Calcite Qz - Quartz Ah = Anhydrite CClH MIA NaCl CClH Intensity NaCl CClH Cc Ah Qz CClH CCl CCl Ah Qz Cc CCl CCl CCl CClH Ah CClH CCl Qz Cc CClH CCl NaCl CClH NaCl CClH Ah CClH CClH CClH NaCl Qz Degrees 2θ Figure 2. Typical XRD powder pattern (CuK α ) for MIA showing constituents phases. Lafarge Type 10 Cement C3S = Tricalcium Silicate C2S = Dicalcium Silicate C3A = Tricalcium Aluminate C4AF = Calcium Aluminate Ferrite Gy = Gypsum C 3S C 2S C C 3 S 3S C 2S Intensity 300 C 2S C 2 S C 3S C 3S Gy C 4AF C 3S Gy C 3S C 3A C 3A C 4 AF C 3 S C 3S C 2S Gy Gy C 3A C 4AF C 3S C C 3S 4 AF C 3 S C 3A C 3S Degrees 2θ Figure 3. XRD pattern (CuK α ) for Lafarge CSA Type 10 Portland cement. AMEC Report No. VA

48 400 Qz = Quartz Mu = Mullite Lm = CaO Qz Sundance 300 Intensity 200 Mu Qz Mu 100 Mu Glass LmMu Mu Qz Lm Mu Qz Qz Mu Mu Qz Qz Lm Qz Mu Qz Qz Qz Degrees 2θ Figure 4. XRD pattern (CuK α ) for Sundance GS coal fly ash. 150 GranCem 100 Intensity 50 Glass Degrees 2θ Figure 5. XRD pattern (CuK α ) for GranCem blast furnace slag. 48 AMEC Report No. VA06294

49 Figure 6. Scanning electron microscope (SEM) images of Burnaby incinerator ash showing cauliform morphology. AMEC Report No. VA

50 Figure 7. Scanning electron microscope (SEM) images of coal fly ash showing typical spherical morphology. 50 AMEC Report No. VA06294

51 Figure 8. Scanning electron microscope (SEM) images of ground granulated blast furnace slag. AMEC Report No. VA

52 120 Strength Activity Index (20% Cement Replacement) Compressive Strength (% Control) ASTM C618 Limit 0 Control MIA PFA BFS MIA-PFA MIA-BFS Figure 9. Strength activity indices at 28 days according to ASTM C OPC-MIA-PFA HVFA Mortars 3 Days 7 Days 28 Days Compressive Strength (MPa) w/c = w/c = Figure 10B. Strength development of ternary 60:10:30 OPC-MIA-PFA mortars at w/c ratio and AMEC Report No. VA06294

53 70 Strength Development at 10% OPC Replacement (w/c = 0.45) 60 Compressive Strength (MPa) Days 7 Days 28 Days 0 OPC Control MIA MIA+PFA MIA+BFS 50 Strength Development at 20% OPC Replacement (w/c = 0.485) Compressive Strength (MPa) Days 7 Days 28 Days 0 OPC Control MIA PFA BFS MIA+PFA MIA+BFS Figure 10A. Strength development of binary and ternary MIA mortars at 10% OPC replacement (upper) and 20% OPC replacement (lower). AMEC Report No. VA

54 CH = Calcium Hydroxide Fs = Friedel's Salt Cc = Calcite Qz - Quartz Aft = Ettringite PC = Portland Cement CH Qz Qz PC PC CH Fs Fs AFt Fs :20 PC-MIA AFt Intensity CH 200 Qz PC PC 100 AFt Fs Fs Fs 90:10 PC-MIA AFt Degrees 2θ Figure 11. XRD patterns (CuK α ) for binary 90:10 and 80:20 OPC-MIA paste concentrates CH = Calcium Hydroxide Fs = Friedel's Salt Cc = Calcite Qz - Quartz Aft = Ettringite PC = Portland Cement Fs CH Qz PC PC CH AFt Intensity :10:10 PC-MIA-BFS AFt Qz Fs PC Fs 150 AFt Fs Qz Fs Fs PC AFt 80:10:10 PC-MIA-PFA Degrees 2θ Figure 12. XRD patterns (CuK α ) for ternary 80:10:10 OPC-MIA-PFA and 80:10:10 OPC-MIA-BFS paste concentrates. 54 AMEC Report No. VA06294

55 Control 90:10 PC-MIA 80:10:10 PC-MIA-PFA ASTM C1012 Expansion (%) Time (weeks) Figure 13. Sulphate resistance expansion data to 16 weeks of exposure (ASTM C-1012). ASTM C Control 90:10 PC-MIA 80:10:10 Vol% PC-MIA-PFA 80:10:10 Mass% PC-MIA-FA 80:10:10 PC-MIA-BFS 0.40 Expansion (%) Time (weeks) Figure 14. ASR resistance expansion data to 16 weeks (ASTM C-441) AMEC Report No. VA

56 CH Qz An Aged Concrete CH CH = Calcium Hydroxide Fs = Friedel's Salt Cc = Calcite Qz - Quartz Aft = Ettringite Tm = Tremolite Clc = Clinoclore Mv = Muscovite An = Anorthite Intensity 200 Qz Clc AFt Fs Mv Tm Clc An AFt Clc An Mv Mv An Fs An Clc Mv Tm Tm Mv Cc CH An An An AFt Qz An Qz Qz Qz Fs Qz CH Qz CH CH Qz Qz Qz Qz Degrees 2θ Figure 15. XRD pattern (CuK α ) for paste concrete recovered from aged concrete believed to contain Burnaby MIA. 56 AMEC Report No. VA06294

57 Figure 16. SEM image (top) of polished surface of aged concrete sample, with elemental maps for calcium, silicon, chlorine and sulphur. AMEC Report No. VA

58 Figure 17. SEM image (top) of polished surface of aged concrete sample at higher magnification, with elemental maps for calcium, silicon, chlorine and sulphur. 58 AMEC Report No. VA06294