The Coal Combustion Products program at Ohio State has been working for more than 20 years now to advance the beneficial use of coal combustion residues in applications that are environmentally protective, commercially competitive, and technically sound. The program has been supported for more than two decades by a coalition of state and federal agencies, utilities, trade organization, and other stakeholders from across the nation. In the last decade, the program has focused on the use of coal combustion residues to reclaim and bring to productive use abandoned mined lands which would not reclaimed if it were not for the availability of coal combustion by-products. This presentation will bring forth speakers from Ohio State, ODNR – Division of Mineral Resources Management, AEP, and Ohio Mineland Partnership to focus on how collaborative field research can advance the science as well as make a significant impact on the environmental benefits of reclamation using coal combustion residues along with tree reclamation to sequester CO2 – unlike current grassland methods of reclamation. Panelists will include: Dr. Tarunjit Singh Butalia, research associate professor, Ohio State; Lanny Erdos, chief, Division of Mineral Resources Management, ODNR; Pedro Amaya, head of civil engineering, American Electric Power; and Bob First, president, Ohio Mineland Partnership.

Several industry, government agencies and university programs have conducted extensive studies on the characterization and beneficial uses of coal combustion by-product materials and much of this information is available. This chapter focuses primarily on flue gas desulfurization (FGD) by-products. In the past, FGD by-products were treated primarily as a waste and landfilled. However, landfill sites are becoming scarce and disposal costs are constantly increasing. Provided the environmental impacts are minimal and socially acceptable, land application uses can provide economic benefit to both the producer and the end user of the FGD. The chapter highlights some of the general issues related to beneficial land application uses of FGD by-products. It provides specific examples or case studies where FGD by-products were used in agriculture, for engineered uses and in the coal mining industry. The chapter provides information on things learned to optimize the benefits of the FGD by-products while maintaining the quality of the environment.

By-products produced from dry flue gas desulfurization (DFGD) have been used in many engineering applications. Structural fill and/or mine reclamation applications utilize more than 74 and 22% of the annual DFGD production in Europe and the United States, respectively. In China, although there are reports showing the applications of DFGD materials in the production of bricks, precast concrete, highway construction, and agricultural applications, large-scale, high-volume uses have developed slowly. One of the major roadblocks to high-volume utilization is lack of knowledge regarding the associated utilization issues. In order to better understand the environmental response of Chinese DFGD materials, this study compared the leaching characteristics of three typical DFGD materials produced from different flue gas sources (i.e., coal-fired boiler, iron and steel sintering plant, and circulating fluidized bed (CFB) boiler). The goal of this study is to characterize the release of inorganic constituents of concern (COCs) under the leaching conditions (i.e., pH dependence, percolation column, and diffusion-controlled conditions) representing different potential application scenarios. Except for Se, the maximum concentrations of all selected COCs (Hg, B, Mo, As, Ba, Cd, Cr, Pb, Sb, Co, and Tl) under all tested leaching conditions were lower than the toxicity levels. The high release of Se observed under acidic conditions in the pH-dependent leaching tests might be adversely promoted by nitric acid induced oxidation of sparingly soluble selenite minerals to soluble selenate counterparts. Rapid initial releases of Mo, Se, B, and Tl were found during the early stages of the percolation column leaching tests. B, Mo and Se were found to be the most readily leachable COCs under the scenarios when the leaching is equilibrium-controlled. Under a diffusion-controlled leaching environment, Cr and Tl showed the highest cumulative mass release among the COCs. (C) 2017 Elsevier Ltd. All rights reserved.

Flue-gas desulfurization (FGD) materials are solids generated when the SO2 in exhaust gases from coal-fired power plants is removed before the gases are released to the atmosphere. Over 60 million tons of FGD materials are generated annually in the United States, about half of which is used beneficially. Mine reclamation accounts for about half of beneficially used FGD, and the FGD gypsum used in the production of wallboard utilizes the next largest volume of FGD. Cement manufacture, construction of structural fills, and agricultural applications each utilizes significant volumes of FGD products. The current utilization of FGD material, which is about 50%, is expected to increase incrementally over the next decade, with the greatest volumes being in wallboard manufacture and the greatest gains in percentage use being in agricultural applications.

Two full-scale coal mine reclamation projects using coal combustion residues (CCRs) were recently carried out at highwall pit complexes near the Conesville and Cardinal coal-fired power plants owned by American Electric Power. The environment impacts of the reclamation projects were examined by regularly monitoring the leaching characteristics of the backfilling CCRs and the water quality of the uppermost aquifers underlying the sites. With over five years of field monitoring, it shows that the water quality at both demonstration sites had changed since the reclamation began. By analyzing the change of the hydrogeochemical properties, it was concluded that the water quality impact observed at the Conesville Five Points site was unlikely due to the seepage of FGD material leachates. Reclamation activities, such as logging, grading, and dewatering changed the hydrogeological conditions and resulted in the observed water quality changes. The same hydrogeological effect on water quality was also found at the Cardinal Star Ridge site during the early stage of the reclamation (approximately the first 22 months). Subsequent measurements showed the water quality to be strongly influenced by the water in the reclaimed highwall pit. Despite the changes to the water quality, the impacts are insignificant and temporary. None of the constitutes showed concentration levels higher than the regulatory leaching limits set by the Ohio Department of Natural Resources' Division of Mineral Resources Management for utilizing CCRs in mined land reclamation. Compared to the local aquifers, the concentrations of eleven selected constituents remained at comparable levels throughout the study period. There are four constituents (i.e., As, Be, Sb, and Tl) that exceeded their respective MCLs after the reclamation began. These detections were found shortly (i.e., within 2 years) after the reclamation began and decreased to the levels either lower than the respective detection limits or similar to the background levels.

A proper load transfer model describing the pile and surrounding soil interaction is important for accurately predicting the behavior of piles. In this paper, a new load transfer hyperbolic model for the pile-soil interface is developed based on soil-structure interface tests reported in the literature, which consider the characteristics of increasing initial shear stiffness, the development of shear strength at the pile-soil interface, the loading, step by step loading, unloading, and reverse loading shearing behavior of the pile-soil interface with consolidation. The proposed model was validated by the close agreement between the computed results and published case histories. Further studies based on the proposed model considering negative skin friction on single piles under pile head load and/or surcharge were subsequently conducted. It was found that the pile-soil interface undergoes complicated shearing, and the depth of the neutral plane (NP) and the skin friction along the pile shaft vary during consolidation. The magnitude of the pile head load and pile installation time has a significant impact on the depth of the NP and the dragload. Pile capacity was shown to decrease with consolidation.

Water quality in the uppermost aquifer system underlying a surface coal mine is analyzed to determine the impact of reclamation using flue gas desulfurization (FGD) gypsum. Water samples collected monthly from nine monitoring wells surrounding the reclamation area and two nearby surface water bodies are analyzed for over 27 water quality constituents. Based on results from 18 months of “pre-reclamation” monitoring, the background water quality was determined to assess both temporal and spatial variations. The background data is then analyzed to explore the similarity of hydrochemical properties among the monitoring wells and surface waters using hierarchical cluster analysis (HCA). The Ward’s method used in HCA groups water samples into three major groups, which have distinctive predominant cations and anions. The observed similarity is likely correlated to the geological layers where the groundwater samples are collected from, as well as the direction of groundwater flow. Four important components, which explain over 80% of the variability observed in the water quality data, are extracted from the monitored water quality constituents using principal components analysis (PCA). Principal Component 1 (PC1) corresponds to major ions (e.g., SO4 , Cl, K, Ca, and Na) and the resulting comprehensive parameters (i.e., electrical conductivity and TDS). PC2, PC3, and PC4 are correlated with Si, alkalinity, and B, respectively. Currently, over 170,000 tons of FGD gypsum and sulfite-rich material have been used for the on-going reclamation activity. The impact on water quality is assessed using data collected from over 12 months of “during-reclamation” monitoring with a statistical trend analysis method. 2013 World of Coal Ash (WOCA) Conference April 22-25, 2013 in Lexington, KY http://www.flyash.info/

Dry process is a major technology for flue gas desulfurization (FGD) other than wet process. It has advantages of lower capital cost and power usage, less land use, no waste water treatment and of application to the regions with limited water resources. In recent years, dry FGD process has been developed into a multi-pollutants ( SO3, HCl, HF and Hg) control technology. In addition, it becomes competitive for use in a largescale power plant burning a high sulfur coal, due to the emerging more efficient dry FGD technologies such as circulating fluidized-bed flue gas desulfurization (CFB-FGD) and NID processes. However, the utilization of Dry FGD by-product has been developed slowly. In contrast to FGD gypsum, the major sulfur-containing component in dry FGD by-product generated from the desulfurization system is calcium sulfite hemihydrate (CaSO3·1/2 H2O). Compositions and properties of by-products are often site-specific and can be affected strongly by coal types, flue gas compositions, unit operating conditions and other factors. In this paper, characteristics and utilization of dry FGD by-products from different sources in China and US will be compared. The recent development in by-product utilization, especially in China, will be discussed. In addition, an international cooperation program between research and industrial organizations in US and China to advance by-product utilization will be illustrated.

Since the passage of modern day US coal mining laws over 35 years ago, remining has played an important role in watershed restoration. However this restoration activity has not been well documented, including the impacts of CCP reclamation when used in combination with remining. Studying the impact remining has had on a watershed basis is important and can serve as valuable background information for regulators involved in the permitting activity as well as the general public. During remining operations, acid-forming materials are removed with the extraction of coal, pollution abatement best management practices (BMPs) are implemented under applicable regulatory requirements, and the abandoned mined land is reclaimed. During remining, many of the problems associated with abandoned mined lands, such as dangerous highwalls, can be corrected without the use of public funds. Furthermore the implementation of appropriate BMPs during remining can be effective at improving the water quality of pre-existing discharges. The use of CCPs, particularly fly ash and FGD materials, in the reclamation of the remined lands offers the opportunity to alleviate problems associated with pre-law legacy mines. Using Geographic Information Systems (ArcGIS) to digitally model the trajectory of remining operations in the Duck Creek Watershed, we present an overview of the impact of remining and reclamation (including the use of CCPs) at the watershed level. In this study, we have chosen the Duck Creek Watershed for which historical data from 1970s is available. This watershed study provides valuable information to current regulators of active mine operations who examine remining applications submitted by coal mining industry. The BMPs utilized by these coal remining operations are described along with the impacts on the watershed. World of Coal Ash (WOCA) Conference May 9-12, 2011, in Denver, CO, USA http://www.flyash.info/

Geocomposite leachate collection systems are increasingly being considered as a replacement for conventional graded sand filters in coal combustion products (CCP) landfills. The geocomposites liners are attractive because they are not as thick as the graded sand filters still largely in use. To be a satisfactory substitute for filters constructed of natural materials, the geocomposite must not restrict the flow of leachate to the collection system while, at the same time, prevent the migration of the material to be retained through the filter and into the leachate collection system. An experimental program designed to test the suitability of a specific geocomposite system in a CCP landfill was performed. In a modified triaxial chamber, the hydraulic conductivity of the geocomposite was measured alone and with four different materials. The effluent was collected at several times during the test and the amount of particulate material in the water as a function of the volume of liquid passing through the CCP was determined. Three of these materials were CCPs commonly placed in utility landfills: fly ash, stabilized FGD (calcium sulfite), and FGD gypsum. The fourth material was uniformly graded sand used as a control. The permeability measured for geocomposite was greater than the value recorded for any of the retained materials; indicating system permeability would not be controlled by the hydraulic conductivity of the geocomposite although system (material plus geocomposite) permeability was lower than the value measured for the material alone. In three of the four materials tested the amount of particulate matter in the leachate decreased to very low steady-state levels. The amount of fly ash in the leachate increased throughout the test to the point where testing had to be terminated when drainage lines from the triaxial chamber became clogged with fly ash. In general, the experimental program conducted on landfilled CCPs demonstrated the suitability of geocomposites as filters in a leachate collection system. The results of tests conducted on the fly ash/geocomposite system showed that additional testing is World of Coal Ash (WOCA) Conference May 9-12, 2011, in Denver, CO, USA http://www.flyash.info/

The release of mercury from concrete containing fly ashes from various generator boilers and powdered activated carbon sorbent used to capture mercury was measured in laboratory experiments. Release of gaseous mercury from these concretes was less than 0.31% of the total quantity of mercury present. The observed gaseous emissions of mercury during the curing process demonstrated a dependency on the organic carbon content of the fly ash, with mercury release decreasing with increasing carbon content. Further, lower gaseous emissions of mercury were observed for concretes incorporating ash containing activated carbon sorbent than would be expected based on the observed association with organic carbon, suggesting that the powdered activated carbon more tightly binds the mercury as compared to unburned carbon in the ash. Following the initial 28-day curing interval, mercury release diminished with time. In separate leaching experiments, average mercury concentrations leached from fly ash concretes were less than 4.1 ng/L after 18 h and 7 days, demonstrating that less than 0.02% of the mercury was released during leaching.

This study demonstrates the use of Class F fly ash in combination with lime or lime kiln dust in the full depth reclamation (FDR) of asphalt pavements. FDR, in the context of this paper, is a process of pulverizing a predetermined amount of flexible pavement that is structurally deficient, blending it with chemical additives and water, and compacting it in place to construct a new stabilized base course. Test sections of two structurally deficient asphalt pavements were reclaimed using Class F fly ash in combination with lime and lime kiln dust. In addition, control sections were constructed using cement, cement and emulsion, lime kiln dust and emulsion, and mill and fill. The service performance and structural behavior of the FDR pavement test sections were monitored to determine how the fly ash sections compared to other more traditional pavement rehabilitation techniques. Service performance and structural behavior were determined with the use of sensors embedded in the road and Falling Weight Deflectometer (FWD) tests. Monitoring results of the FWD tests conducted up to 2 years after reclamation show that the cement, fly ash+LKD, and fly ash+lime sections exhibited two year resilient modulus values comparable to open graded cement stabilized aggregates (more than 750 ksi). The cement treatment resulted in a significant increase in resilient modulus within 3 weeks of construction and beyond this curing time, the stiffness increase was slow. On the other hand, the LKD+fly ash and lime+fly ash test sections indicated slower shorter-term increase in stiffness but at the end of 24 months of performance, the LKD+fly ash and lime+fly ash sections had performed similar to the cement test section. Additional longer-term testing data will be available from ongoing pavement performance and environmental condition data collection at the two pavement sites.

Although the utilization of fly ash has increased over the last several decades, more than 60 percent of the fly ash produced each year in the United States continues to be disposed in ash ponds and landfills. Many disposal facilities are now or will soon be filled to their design capacity. As a result, there is an increasing interest in reclaiming existing fly ash pond areas. One possible use is as foundation for new disposal facilities, parking lots or even buildings. Before these facilities could be constructed on former fly ash ponds, the response of the fly ash to imposed loads must be determined. In the current study, constant rate of strain (CRS) consolidation tests as per ASTM D4186 were performed on medium-scale resedimented Class F fly ash samples. The compressibility behavior of the fly ash tested was found to be similar to published results for inorganic sandy silt and poorly graded sand. The value of secondary compression coefficient was found to be small.

� Abstract—This study demonstrates the use of Class F fly ash in combination with lime or lime kiln dust in the full depth reclamation (FDR) of asphalt pavements. FDR, in the context of this paper, is a process of pulverizing a predetermined amount of flexible pavement that is structurally deficient, blending it with chemical additives and water, and compacting it in place to construct a new stabilized base course. Test sections of two structurally deficient asphalt pavements were reclaimed using Class F fly ash in combination with lime and lime kiln dust. In addition, control sections were constructed using cement, cement and emulsion, lime kiln dust and emulsion, and mill and fill. The service performance and structural behavior of the FDR pavement test sections were monitored to determine how the fly ash sections compared to other more traditional pavement rehabilitation techniques. Service performance and structural behavior were determined with the use of sensors embedded in the road and Falling Weight Deflectometer (FWD) tests. Monitoring results of the FWD tests conducted up to 2 years after reclamation show that the cement, fly ash+LKD, and fly ash+lime sections exhibited two year resilient modulus values comparable to open graded cement stabilized aggregates (more than 750 ksi). The cement treatment resulted in a significant increase in resilient modulus within 3 weeks of construction and beyond this curing time, the stiffness increase was slow. On the other hand, the fly ash+LKD and fly ash+lime test sections indicated slower shorter-term increase in stiffness. The fly ash+LKD and fly ash+lime section average resilient modulus values at two years after construction were in excess of 800 ksi. Additional longer-term testing data will be available from ongoing pavement performance and environmental condition data collection at the two pavement sites.

Liquefaction resistance and post-liquefaction shear strength of impounded Class F fly ash are investigated using laboratory experiments. The study was aimed to evaluate liquefaction potential of a 45ha impoundment proposed as a base for a utility monofill. The evaluation included cyclic triaxial tests performed on reconstituted fly ash specimens with various densities at different confining stresses and cyclic stress ratios representative of the impounded material and the seismic environment. The results are presented in the form of design charts. Post-liquefaction strengths were measured by reconsolidating the specimens at the initial effective confining stress and performing consolidated undrained triaxial tests. The measured cyclic strength was compared with the seismically induced stresses in the profile using a one-dimensional wave propagation method. The cyclic loadings imposed on the ash by the design earthquakes were found to be lower than the measured cyclic strength of the material. The post liquefaction shear strengths showed some scatter; however, they were typically higher than the initial shear strengths before exposure of the material to cyclic load.

In this study, the release of metals and metalloids from full-scale portland cement concrete pavements containing coal combustion products (CCPs) was evaluated by laboratory leaching tests and accelerated loading of full-scale pavement sections under well-controlled conditions. An equivalent of 20 years of highway traffic loading was simulated at the OSU/OU Accelerated Pavement Load Facility (APLF). Three types of portland cement concrete driving surface layers were tested, including a control section [i.e., ordinary portland cement (PC) concrete] containing no fly ash and two sections in which fly ash was substituted for a fraction of the cement; i.e., 30% fly ash (FA30) and 50% fly ash (FA50). In general, the concentrations of minor and trace elements were higher in the toxicity characteristic leaching procedure (TCLP) leachates than in the leachates obtained from synthetic precipitation leaching procedure and ASTM leaching procedures. Importantly, none of the leachate concentrations exceeded the TCLP limits or primary drinking water standards. Surface runoff monitoring results showed the highest release rates of inorganic elements from the FA50 concrete pavement, whereas there were little differences in release rates between PC and FA30 concretes. The release of elements generally decreased with increasing pavement loading. Except for Cr, elements were released as particulates (>0.45 mu m) rather than dissolved constituents. The incorporation of fly ash in the PC cement concrete pavements examined in this study resulted in little or no deleterious environmental impact from the leaching of inorganic elements over the lifetime of the pavement system.

Gaseous mercury released from aerated concrete during both presteam curing at 25 degrees C and steam curing at 80 degrees C was measured in controlled laboratory experiments. Mercury release originated from two major components in the concrete mixture: (1) class F coal fly ash and (2) a mixture of the fly ash and powdered activated carbon onto which elemental mercury was adsorbed. Mercury emitted during each curing cycle was collected on iodated carbon traps in a purge-and-trap arrangement and subsequently measured by cold-vapor atomic fluorescence spectrometry. Through 3 h of presteam curing, the release of mercury from the freshly prepared mixture was less than 0.03 ng/kg of concrete. Releases of total mercury over the 21 h steam curing process ranged from 0.4 to 5.8 ng of mercury/kg of concrete and depended upon mercury concentrations in the concrete. The steam-cured concrete had a higher mercury release rate (ng kg(-1) h(-1)) compared to air-cured concrete containing fly ash, but the shorter curing interval resulted in less total release of mercury from the steam-cured concrete. The mercury flux from exposed concrete surfaces to mercury-free air ranged from 0.77 to 11.1 ng m(-2) h(-1), which was similar to mercury fluxes for natural soils to ambient air of 4.2 ng m(-2) h(-1) reported by others. Less than 0.022% of the total quantity of mercury present from all mercury sources in the concrete was released during the curing process, and therefore, nearly all of the mercury was retained in the concrete.