Utilization Of Bottom Ash Research Articles

The Effect of Bottom Ash on Fresh Characteristic, Compressive Strength and Water Absorption of Self-Compacting Concrete

Bottom ash is a solid residue produced through combustion process in a coal-fired power plant. It has been catogarized as a waste and usually disposed in the utility disposed site. With higher demand on the power energy, more coal-power plant are constructed and abundance of bottom ash are produced. Recently, the utilization of bottom ash in the construction industry has gained the interest of researches. Since it has similiar particle size distribution as normal sand, many attempt has been made in studying it potential use in mortar and concrete. In complementary to that, this paper presents the effect of bottom ash on fresh and hardened properties of self-compacting concrete (SCC). Bottom ash is used as fine aggregate replacing sand with replacement ratio range from 0% to 30% by volume. The effects of bottom ash on the SCC were investigated by comparing the test result of SCC mixed bottom ash with control specimens (0% of bottom ash). The test result on fresh properties of the concrete mixture revealed that, as the replacement level of bottom ash increased, the slump flow, L-box passing ratio and segregation resistance ratio (SR) decreased. Nevertheless, the slump flow time (T500) result increased with the increased of bottom ash content. The results show that the porosity and the irregular shape of the bottom ash particle has great influence on workability and viscosity of the fresh concete. The compressive strength and water absorption test are carried out on the sample at curing time of 7 and 28days. In terms of strength, the use of bottom ash in the production of SCC has increased the compressive strength of the concrete up to 15% replacement level. The increase in strength show the presence of the pozzolanic reactivity in a concrete with bottom ash particle. The water absorption rate was observed to be lower with a sample which having 10% and 15% replacement level.

Utilization of Bottom Ash for Sintered Artificial Aggregate

At present high temperature fly ashes are already quite widely used as a secondary raw material in building materials. Fly ashes are usually able to fully replace classical materials. FBC ashes also gradually finding their place for example in production of autoclaved aerated concrete, in binders or solidification of hazardous waste. However, the coarser types of energy by-products are relatively difficult to use. Therefore, this part of the work focused on the study of usability of bottom ashes for artificial sintered aggregates. The article will focus on results of laboratory firing in muffle furnace, dedicated to testing of maximum bottom ash content in the mixture with the fly ash and special type of clay.

Occurrence and Significance of Secondary Iron-rich Products in Landfilled MSWI Bottom Ash

Incineration is one of the most effective techniques for the treatment of both municipal and hazardous wastes. Via this technique, the majority of toxic substances are expected to be stabilized in the durable matrix of the end-ofprocess bottom ash products. These products consist of a variety of glassy/crystalline components including primary Fe-rich phases that may undergo alterations when exposed to natural environment. In the present research, the impact of natural weathering on the behavior of primary Fe-rich phases, their alteration, and the formation of the relevant secondary products in the weathered bottom ash samples of a (mono) landfill site was systematically investigated. Samples of various ages (1-20 yrs) were collected from four locations of the landfill in 2009. Optical microscopy, SEM-EDX, XRD and XRF examinations were applied in order to document the footprints of weathering processes. Using these techniques, we understood that several secondary (newly-formed) products (amorphous or crystalline) have been developed, including goethite (α-FeOOH), lepidocrocite (γ-FeOOH), hematite (Fe2O3), magnetite (Fe3O4), iron oxide (FeO), and Fe-rich Ca-Si and Ca-Al-Si gel phases. They occurred under variable environmental conditions as the weathering products of the primary iron-rich phases. The strong affinity of these secondary phases with heavy metals of environmental significance such as Zn, Cu, Pb, and Ni was also identified. This suggests that the development of secondary Fe-rich products can partially contribute to the reduction of heavy metals release to the surrounding environments. However such phenomena may have inhibitory effect on the utilization of bottom ash as recycled aggregates.

Tanjung Bin Coal Bottom Ash: From Waste to Concrete Material

Coal Bottom Ash (CBA) is a by-product from the generation of electricity using pulverized coal; Tanjung Bin power plant in Malaysia is a coal-based power plant that generates tonnes of bottom ash daily without known economic value that ends up in the ash pond. Due to the problems associated with the disposal ash pond in terms of cost and environmental impact, attention has now been focused on how best to utilize this waste. This paper present the recent development achieved on the utilization of bottom ash from Tanjung Bin power plant Malaysia in concrete development; physical and chemical properties, workability and fresh concrete properties as well as the strength development of Tanjung Bin bottom ash.

Utilization of bottom ash as a low-cost sorbent for the removal and recovery of a toxic halogen containing dye eosin yellow

Removal and recovery of a hazardous halogen-containing dye Eosin Yellow were investigated using Bottom Ash as adsorbent. During the studies various essential factors influencing the adsorption, like sieve size of adsorbent, adsorbate concentration, amount of adsorbent, pH of the solution, contact time, and temperature have been monitored. Attempts have also been made to verify Langmuir, Freundlich, Tempkin, and D-R adsorption isotherm models. The feasibility of the ongoing adsorption has been ascertained on the basis of Langmuir adsorption isotherm. The free energy, entropy, and enthalpy of the ongoing adsorption process have been evaluated as about 26 kJ mol−1, 22 kJ mol−1, and 20 kJ mol−1, respectively. Contact time studies reveal that the ongoing adsorption equilibrate within 3 h of contact. It is found that the adsorption of Eosin Yellow over Bottom Ash follows a pseudo-second-order kinetics. At all the temperatures rate constant of the process was calculated around 5 × 10−8 sec g mol−1. During bulk removal through column operation about 97% percentage saturation of the dye is obtained. Desorption studies exhibit that the percentage recovery of Eosin Yellow dye on eluenting NaOH solution through exhausted column is about 90%.

Efecto de la adición de mezclas de ceniza volante y ceniza de fondo procedentes del carbón en la resistencia mecánica y porosidad de cementos Portland

New additions to the cement are needed to achieve a more sustainable and durable construction material. Within this context, bottom ashes can be used as a main constituent of Portland cements when it is mixed in an optimized proportion with fly ashes. The mechanical characteristics of standarized mortars made of mixes of pulverized coal combustion bottom and fly ashes are studied. The mortars were made of ordinary Portland cement (CEM I 42.5 N) and mixes of bottom ashes with fly ashes in similar proportions to those of CEM II/A-V, CEM II/B-V and CEM IV/A (V). Summing up, it can be said that the utilization of bottom ashes mixed with fly ashes in replacement levels from 0% to 100% do not affect significantively on the mechanical caracteristics of the mortars considered in the present study which had an addition maximum content of 35%.

Use of power plant bottom ash as fine and coarse aggregates in high-strength concrete

In this study, experiments have been carried out to evaluate the utilization of bottom ash (by-product of power plant) as fine and coarse aggregates in high-strength concrete with compressive strength of 60–80 MPa. Firstly, the chemical and physical characteristics of bottom ash particles, such as chemical compositions, specific gravity and SEM images, were investigated. Further experiments were conducted by replacing fine and coarse bottom ash with normal sand and gravel varying in percentages (25%, 50%, 75%, and 100%). The effect of fine and coarse bottom ash on the flow characteristics and density of concrete mixture was investigated in the aspect of particle shapes and paste absorption of bottom ash. Mechanical properties, such as compressive strengths and modulus of elasticity and flexural strength of high-strength concrete with bottom ash were evaluated. It was found that the slump flow of fresh concrete was slightly decreased from 530 mm to 420 mm when coarse bottom ash was replaced 100% of normal coarse aggregates, while fine bottom ash did not affect the slump flow. Moreover, it also showed that both of fine and coarse bottom ash aggregates had more influence on the flexural strength than compressive strength.

Reuse potential of low-calcium bottom ash as aggregate through pelletization

Coal combustion residues which include fly ash, bottom ash and boiler slag is one of the major pollutants as these residues require large land area for their disposal. Among these residues, utilization of bottom ash in the construction industry is very low. This paper explains the use of bottom ash through pelletization. Raw bottom ash could not be pelletized as such due to its coarseness. Though pulverized bottom ash could be pelletized, the pelletization efficiency was low, and the aggregates were too weak to withstand the handling stresses. To improve the pelletization efficiency, different clay and cementitious binders were used with bottom ash. The influence of different factors and their interaction effects were studied on the duration of pelletization process and the pelletization efficiency through fractional factorial design. Addition of binders facilitated conversion of low-calcium bottom ash into aggregates. To achieve maximum pelletization efficiency, the binder content and moisture requirements vary with type of binder. Addition of Ca(OH) 2 improved the (i) pelletization efficiency, (ii) reduced the duration of pelletization process from an average of 14–7 min, and (iii) reduced the binder dosage for a given pelletization efficiency. For aggregate with clay binders and cementitious binder, Ca(OH) 2 and binder dosage have significant effect in reducing the duration of pelletization process.

Life cycle assessment of disposal of residues from municipal solid waste incineration: Recycling of bottom ash in road construction or landfilling in Denmark evaluated in the ROAD-RES model

Two disposal methods for MSWI bottom ash were assessed in a new life cycle assessment (LCA) model for road construction and disposal of residues. The two scenarios evaluated in the model were: (i) landfilling of bottom ash in a coastal landfill in Denmark and (ii) recycling of bottom ash as subbase layer in an asphalted secondary road. The LCA included resource and energy consumption, and emissions associated with upgrading of bottom ash, transport, landfilling processes, incorporation of bottom ash in road, substitution of natural gravel as road construction material and leaching of heavy metals and salts from bottom ash in road as well as in landfill. Environmental impacts associated with emissions to air, fresh surface water, marine surface water, groundwater and soil were aggregated into 12 environmental impact categories: Global Warming, Photochemical Ozone Formation, Nutrient Enrichment, Acidification, Stratospheric Ozone Depletion, Human Toxicity via air/water/soil, Ecotoxicity in water/soil, and a new impact category, Stored Ecotoxicity to water/soil that accounts for the presence of heavy metals and very persistent organic compounds that in the long-term might leach. Leaching of heavy metals and salts from bottom ash was estimated from a series of laboratory leaching tests. For both scenarios, Ecotoxicity water was, when evaluated for the first 100 yr, the most important among the twelve impact categories involved in the assessment. Human Toxicity soil was also important, especially for the Road scenario. When the long-term leaching of heavy metals from bottom ash was evaluated, based on the total content of heavy metals in bottom ash, all impact categories became negligible compared to the potential Stored Ecotoxicity, which was two orders of magnitudes greater than Ecotoxicity water. Copper was the constituent that gave the strongest contributions to the ecotoxicities. The most important resources consumed were clay as liner in landfill and the groundwater resource which was potentially spoiled due to leaching of salts from bottom ash in road. The difference in environmental impacts between landfilling and utilization of bottom ash in road was marginal when these alternatives were assessed in a life cycle perspective.

Retention of Metals Leached From Municipal Solid Waste Incineration (MSWI) Bottom Ashes in Soils

Utilization of bottom ash in road construction may lead to a release of contaminants that can affect the soil of the swales constructed along these roads. Column tests were performed to evaluate the retention behavior of Cu, Cr, Zn, and Pb, originating from municipal solid waste incineration (MSWI) bottom ash leachate, in two substrates: peat and mould (a cultural soil). A chemical sequential extraction method was used to predict the risk associated with the release of the retained elements with modifications of environmental conditions. Apart from the dissolution of organic matter (OM), ash leachate properties hindered the metal transport from peat. Mould was efficient only in removing Zn, making it a less favorable substrate for the leachate control along the roads. Readily soluble forms made up a minor fraction of the retained metals in peat, reducing the risk of metal release due to ion exchange and pH drop. Changes in redox potential might be the main cause of Zn desorption from peat as the Fe-Mn oxides were the main scavengers for this metal. Oxidation of OM would be the primary reason of Cu and Cr release, while for Pb both fractions (Fe-Mn oxides and OM) might equally contribute to the metal discharge.

Feasible Experimental Study on the Utilization of a 300MW CFB Boiler Desulfurizating Bottom Ash for Construction Applications

Circulating fluidized bed (CFB) boiler has entered electric power industry field because of burning a wide range of fuels, while still achieving strict air emissions requirements. This study focuses on a 300MW CFB boiler, which will be one of the largest CFB boiler in the world. In a CFB boiler, fuels were burned with the addition of limestone to capture SO2 in a solid form. Therefore, the volume of ashes, both bottom ash and fly ash, discharged from a CFB boiler is much higher than the ashes discharged from a pulverized coal-fired (PC) boiler at the same capacity of the boiler. CFB boiler ash cannot be used as a cement replacement in concrete due to its unacceptably high sulfur content. The disposal in landfills has been the most common means of handling ash in circulating fluidized bed boiler power plants. However, for a 300MW CFB boiler power plant, there will be 600,000tons of ash discharged per year and will result in great volumes and disposal cost of ash byproduct. It was very necessary to solve the utilization of CFB ash and to decrease the disposal cost of CFB ash. The feasible experimental study results on the utilization of the bottom ashes of a 300MW CFB boiler in Baima power plant in China were reported in this paper. The bottom ashes used for test came from the discharged bottom ashes in a 100MW CFB boiler in which the anthracite and limestone designed for the 300MW CFB project was burned. The results of this study showed that the bottom ash could be used for cementitious material, road concrete, and road base material. The masonry cements, road concrete with 30MPa compressive strength and 4.0MPa flexural strength, and the road base material used for base courses of the expressway, the main road and the minor lane were all prepared with milled CFB bottom ashes in the lab. The better methods of utilization of the bottom ashes were discussed in this paper.

Utilization of bottom ash from the incineration of separated wastes as a cement substitute

Waste incineration is still an essential technology in the concept of integrated waste management. Most of the combustion residues are incinerator bottom ash. It has been discovered that incinerator bottom ash from the incineration of separated waste in the primary chamber of the modular two-stage incinerator mainly consists of metal oxides, especially SiO2 and CaO, in proportions that are quite similar to those in cement and so the feasibility of its application as a substitute for cement in concrete was investigated. It was found that after 28 days, the flexural and compressive strengths of the binder using bottom ash were practically comparable with those of a pure cement mixture. The results show that it is reasonable to use a binder containing incinerator bottom ash for applications in which an early-stage lower strength of concrete element is acceptable.

Time Dependent Strength and Stiffness of PCC Bottom Ash-Bentonite Mixtures

Utilization of bottom ash from burning of pulverized coal in construction-related applications has received some attention within the last decade. Its use in geotechnical engineering applications is still very limited, however. Within the last few years several studies have been completed to evaluate strength, stiffness, and durability properties of pulverized coal combustion (PCC) bottom ash mixed with various admixtures. Studies have shown that the physical properties of bottom ash obtained from burning of pulverized coal are similar to that of natural sand with particle sizes ranging from fine gravel to fine sand and low percentages of silt and clay sized particles. However, unlike sand, chemical composition of bottom ash results in change of strength and stiffness characteristics of the bottom ash-admixture mixtures with time. In this study, change in strength and stiffness characteristics of Illinois PCC bottom ash and bentonite mixtures with time are evaluated. A series of unconfined compression tests on bottom ash-bentonite mixtures at various curing ages was performed in the laboratory. Results presented show that strength and stiffness of bottom ash-bentonite mixtures changed significantly with time.

Utilisation of bottom ash in road construction: a lysimeter study.

The incineration of municipal solid waste (MSW) results in the annual production of 2.7 million tons of bottom ash in France. Utilisation of bottom ash in road construction is encouraged in France but strictly regulated. Because the incinerator residues contain enriched concentrations of metals and salts, particular attention must be focused on the potential environmental problems. In the present study, a laboratory tool (lysimeter) has been developed to reproduce the conditions of bottom ash utilisation and to study their environmental impact via the percolates collected at the bottom of the lysimeter. Four lysimeter experiments were conducted in order to study reproducibility, as well as the influence of water flow rate and pressure on the composition of the percolates. The lysimeter experiments have been then compared with the utilisation of bottom ash under real conditions (two experimental road sections). The comparison of results of lysimeter test and those measured after performing the French standard leach test (AFNOR NF X31-210) shows a recovery of 89% for the chlorides and between 30 and 35% for the sulfates. This indicates that almost all chlorides have been dissolved, contrary to the sulfates, which are less soluble.

Utilisation of bottom ash in road construction: evaluation of the environmental impact

France incinerates about 40% of its municipal solid waste (MSW), producing 2.7 million tons of bottom ash annually. Utilisation of bottom ash (BA) is encouraged in France but strictly regulated. Only bottom ash meeting specific criteria and produced in accordance with a quality assurance plan can be used in roadbeds and embankments. In order to evaluate the environmental impact of BA used in road construction under real conditions, two road sections were built: one containing a sub-layer of BA and the other, constructed using only natural gravel to serve as a reference. Water percolating through each roadbed was collected and sampled periodically over three years. Analysis of the samples shows minimal leaching of pollutants from BA. The results are encouraging and indicate that BA utilisation can be safe and can have an environmental impact no greater than that of natural materials.

Effect of moisture content of highly porous bottom ash on properties of concrete mixture and hardened concrete

Research for advantageous utilisation of bottom ash presently formed at thermal power stations by using pulverised coal combustion is being conducted at The Research Institute of The College of Judea and Samaria (Ariel, Israel). It proves the effectiveness of comprehensive use of highly porous bottom ash as aggregate and fly ash as additive for production of lightweight concrete. Proportions, properties and conditions of producing normal weight concrete-comprised fly ash were considered by a number of experiments. However, the problem of using highly porous aggregates with fly ash as an additive is inadequately studied and elucidated in technical publications. One of the main features of these concrete mixtures is a high content of water, resulting in two conditions: (a) absorption of water by highly porous bottom ash particles; and (b) bonding the water to the fine fly ash particles. The goal of this research was to study the proportions and properties of the considered concretes. The research was concentrated on evaluating the effect of moisture content of the bottom ash on the lightweight concrete strength and the concrete mixture proportions. The actual problem depends on using water to sluice off the bottom ash from the furnaces and hydraulic transport at present power stations.

Effect of moisture content of highly porous bottom ash on properties of concrete mixture and hardened concrete

Research for advantageous utilisation of bottom ash presently formed at thermal power stations by using pulverised coal combustion is being conducted at The Research Institute of The College of Judea and Samaria (Ariel, Israel). It proves the effectiveness of comprehensive use of highly porous bottom ash as aggregate and fly ash as additive for production of lightweight concrete. Proportions, properties and conditions of producing normal weight concrete-comprised fly ash were considered by a number of experiments. However, the problem of using highly porous aggregates with fly ash as an additive is inadequately studied and elucidated in technical publications. One of the main features of these concrete mixtures is a high content of water, resulting in two conditions: (a) absorption of water by highly porous bottom ash particles; and (b) bonding the water to the fine fly ash particles. The goal of this research was to study the proportions and properties of the considered concretes. The research was concentrated on evaluating the effect of moisture content of the bottom ash on the lightweight concrete strength and the concrete mixture proportions. The actual problem depends on using water to sluice off the bottom ash from the furnaces and hydraulic transport at present power stations.

The usability of bottom ash as an engineering material when amended with different matrices

This study aims at investigating the utilization of bottom ash obtained from four different power stations as a construction fill and landfill bottom liner. For the matrix material, commercial powdered bentonite, construction lime and natural clay were used. Compaction tests (Standard Proctor and vibratory hammer) were carried out on the different ratios of bottom ash and matrix material. The optimum water content ranged from 40 to 45% yielding a dry density mostly ca 1 Mg m −3. Uniaxial compressive strength of mixtures ranges from 0.1 to 0.5 kgf cm −2 which showed a 3–20-fold increase when tested on 28-day cured specimens. Triaxial compression tests yield varying rates of shear strength which also showed as high as an 11-fold increase for cured specimens. The hydraulic conductivity of those mixtures was mostly ca 10 −4 cm s −1, which is not considered to be low enough for landfill lining. Leaching tests using deionized water were also performed to investigate the possible effect of leachate produced from the mixtures on the environment. In conclusion a light density and environmentally friendly mixture is determined and proposed as construction filler.

An approach for estimation of contaminant release during utilization and disposal of municipal waste combustion residues

The use of appropriate leaching tests and leaching models can help to predict how constituents in municipal waste combustion residues will leach during either utilization or disposal scenarios. This paper presents a general approach for estimating constituent release from MWC residues under a variety of management scenarios through use of fundamental leaching, site specific design and regional climatic parameters. Leaching behavior is categorized as being controlled by either (i) constituent availability or solubility for percolation-dominated scenarios with loose granular residues, or, (ii) controlled by diffusion for flow around scenarios with compacted granular residues or monolithic products containing residues. Three broad scenarios involving either disposal or utilization are used to illustrate the approach. The scenarios are applied to bottom ash, combined ash and APC residue. In two specific cases pertinent to bottom ash utilization, field data are used to verify the approach. Field data are also used to verify the approach for disposal of combined ash. These methodologies hold promise for serving as a basis for evaluating and comparing potential environmental impacts from different management scenarios for combustion residues and for other waste materials.