Properties Of Coal Bottom Ash Research Articles

Properties and microstructure development of alkali- activated coal bottom ash and titanium- extraction tailing slag binder

In this study, ground coal bottom ash (CBA) and titanium-extraction tailing slag (TS) were used as source materials to prepare alkali- activated materials (AAMs). The effects of grinding time on the properties of CBA and TS were investigated, and it was found that the optimum reactivity of CBA and TS appeared at specific surface areas of 700 ∼ 800 m2/kg. The influence of alkali content and modulus of water glass, water–solid mass (w/b) ratios and TS content on the fresh and hardening properties of AAMs were investigated. Furthermore, the reaction process of the binder was conducted by using XRD, FT-IR, SEM and hydration heat. Results showed that increasing the alkali content, reducing modulus of water glass, and adding TS into system could promote the reaction of AAM. A binder with more desirable properties was prepared at alkali content of 12%, water glass modulus of 1.2, w/b ratio of 0.45 and TS content of 20%. Its compressive strength at 7 d and 28 d was 20.8 MPa and 25.9 MPa, respectively. Microstructure analysis showed that the reaction products of binder contained AFm, N-A-S-H gel, C-S-H gel and C-A-S-H gel. This research tried to provide a fundamental basis for preparing clinker-free cement concrete from local industrial wastes to achieve sustainable development.

Effects of Roller Compacted Concrete Incorporating Coal Bottom Ash as a Fine Aggregate Replacement

Coal bottom ash (CBA) is a by-product generated in the coal furnaces of thermal power plants. It has adverse effects on the environment and requires additional landfill storage. However, the physical appearance of CBA is similar to that of sand, with particle sizes ranging from fine to coarse aggregates. Hence, many previous studies have focused on its application instead of sand for conventional concrete and structural fill materials considering natural sand depletion. Roller compacted concrete (RCC) is a zero-slump concrete with better compressive strength than conventional concrete because of the aggregate interlock achieved due to the compactness. It uses a low cement content but requires a large amount of sand. However, the applicability of CBA to RCC is limited. The properties of CBA may vary depending on the location. Therefore, this study aims to evaluate the effect of CBA as a sand replacement in RCC in terms of strength and long-term performance by conducting an empirical experiment under given conditions. Initially, a comprehensive literature review of various concrete strengths using CBA as sand replacement is provided. Thereafter, details related to the experiments on the strength and durability of the given CBA are presented. The results show that the RCC strength improves when CBA increases owing to the good gradation and low percentage of calcium oxide. Furthermore, the samples displayed acceptable freeze–thaw resistance values, but the scaling resistance values were small, owing to the high-water absorption. Therefore, CBA can be used in RCC as sand for improved structural performance, while additional research should be conducted to improve its long-term performance.

Sustainable Energy Recovery From the Malaysian Coal Bottom Ash and the Effects of Fineness in Improving Concrete Properties

The particle size (µm) of coal bottom ash displayed significant effects on the concrete engineering properties. This research aims to assess the improvement of engineering properties of concrete containing CBA (fineness: 75 and 100 µm) known as Mix 75 and Mix 100, and to optimize the percentage of coal bottom ash as supplementary cement materials in concrete. The physicochemical properties of coal bottom ash were analyzed using X-ray fluorescence, X-ray diffraction, particle size distribution (PSD), and a scanning electron microscope. The strength of concrete was determined based on workability and compressive and splitting tensile strengths. The concrete strength improvement was optimized by response surface methodology. The results of the study showed that coal bottom ash was rich in silicates based on the highest peak at 45°. The scanning electron microscope images showed that coal bottom ash has few cenospheres and components of irregular-shaped char particles. The splitting tensile strengths in 28 curing days gradually decreased with an increase in coal bottom ash. The optimal percentage of coal bottom ash in Mix 75 is equivalent to 6% within 45.4 curing days producing 40 MPa of compressive strength. Meanwhile, the optimal percentage of CBA in Mix 100 is equivalent to 12% within 56 curing days producing 50 MPa of compressive strength. The future works needed to extend the experimental observations are the economic analysis and effect of the greenhouse reduction on the usage of CBA in building infrastructure.

Selected Strength Properties of Coal Bottom Ash (CBA) Concrete Containing Fly Ash under Different Curing and Drying Conditions.

This study aims to evaluate the effect of curing and drying conditions on the strength properties of concrete containing coal bottom ash (CBA) and fly ash as substitutes for fine aggregates and cement, respectively. The strength properties of the concrete including CBA and fly ash were evaluated under two different curing and drying conditions: saturated surface-dry (SSD) conditions and oven-dried conditions at curing ages of 28 and 91 days. The natural fine aggregates of the mixtures were replaced by CBA fine aggregates at 25%, 50%, 75%, and 100% by volume. In addition, the cement in the mixtures was partly replaced with fly ash at 20% and 40%. The experimental program included the measurement of the unit weight, compressive strength, splitting tensile strength, flexural strength, and ultrasonic pulse velocity of the concrete. The test results showed that the compressive strength, splitting tensile strength, and flexural strength decreased as the CBA content increased under both SSD and oven-dried conditions. The curing and drying conditions of the concrete with CBA and fly ash considerably influenced the reduction in the compressive, splitting, and flexural tensile strengths of the concrete. Additionally, the experimental results showed that fly ash insignificantly contributed to the reduction in the strength properties under both SSD and oven-dried conditions. Finally, the relationships between ultrasonic pulse velocity and the splitting tensile strength, flexural tensile strength, and compressive strength were investigated.

Strength Properties of High-Strength Concrete Containing Coal Bottom Ash as a Replacement of Aggregates

Most previous studies on the strength properties of coal bottom ash (CBA) concrete have focused on concrete with a normal compressive strength, and thus, studies on the strength properties of high-strength concrete (HSC) containing CBA are limited. Therefore, the effects of replacing fine aggregates with CBA and variations in the curing age on the strength properties of HSC with a compressive strength of greater than 60 MPa were investigated in this study. The different CBA contents included 25, 50, 75, and 100%, and the different curing ages were 28 and 56 days. The mechanical properties of the HSC with CBA incorporated as fine aggregates were examined. The experimental results revealed that CBA could be partially or totally substituted for fine aggregates during HSC production. The test results also showed that the compressive, splitting tensile, and flexural strengths of the HSC containing CBA fine aggregates slightly decreased as the CBA content increased. Moreover, useful relationships between the compressive strength, splitting tensile strength, and flexural strength were suggested, and the predictions reasonably agreed with the measurements. Compared to those of the control specimen, the pulse velocities of the HSC specimens at various CBA contents decreased by less than 3%. In addition, equations for predicting the strength values of CBA concrete by using the ultrasonic pulse velocity were suggested.

Effects of Microwave Energy on Fast Compressive Strength Development of Coal Bottom Ash-Based Geopolymers

Microwave energy has been shown to be effective for geopolymer synthesis due to its fast and penetrative heating characteristics; however, the changes in the physicochemical properties of the geopolymer, resulting from the microwave irradiation, have not been fully elucidated. Therefore, this study is aimed at investigating the effect of the microwaving on the properties of coal bottom ash(CBA) geopolymers. We prepared geopolymer samples by casting a mixture of ground CBA and 14 M NaOH solution against cubic molds with a hand press machine, followed by pre-curing in a dry oven at 75 °C for 24 h and microwaving under various powers and durations. The compressive strength strongly depended on the moisture content, i.e., the strength increased from 21 to 65 MPa or higher as the moisture content decreased to critical values, after which the strength began to decrease. The results showed that microwave energy stimulated an additional geopolymerization by evaporating the redundant free water. This led to the strength gain, although the over-irradiation generated a high internal stress and poor structural integrity, which resulted in the strength loss. Therefore, the appropriate application of microwave energy is a promising option for synthesizing high-strength geopolymers in a cost- and time-effective manner.

Characterization of Coal Bottom Ash &its Potential to be used as Catalyst in Biomass Gasification

Abstract A potential renewable and sustainable green energy source is biomass gasification. The role of catalyst is significant in biomass gasification technology to overcome associated problems like tar reduction and to make it economically viable. Several catalysts like dolomite, alkaline metal, nickel, etc. have been incorporated which plays an essential role in higher product yield and tar reduction but holds problems like inactivity, regeneration, and cost. In this study, physio-chemical properties of coal bottom ash have been studied for its application as a catalyst in biomass steam gasification. The characterization of coal bottom ash comprises of surface morphology analysis, existing elements, pore size, and volume, as well as surface area and bulk density, were reported. The results showed that elements like Si, Fe, Al, Ca and Mg were present in coal bottom ash which have been previously used as a catalyst in biomass gasification. The pore diameter of coal bottom ash is 4 nm, the specific pore volume is 0.01474 cm3/g, specific surface area of 17.64 m2/g which lies it in mesoporous classification. Also, it is observed that CaO mineral exists in coal bottom ash support in reducing the CO2 gas while improving syngas yield. The presence of SiO2 shows that it can use as bed material while Fe2O3 improves the tar reduction in the product gas whereas CaO assists to capture CO2 in the process whereas, alumina resist sintering of metal catalyst. Coal bottom ash is economically viable due to abundance and low cost. Based on its composition (presence of Ca, Mg and other alkali metal) as analyzed .it can be used as an alkaline metal catalyst.

Evaluation of the properties of coal bottom ash, as regards the possibilities of using it in biological land reclamation

The use of waste in land reclamation projects or road works is a generally applied method of waste recycling since coal bottom ash can be used in plant substrate. This paper presents the results of research on the physical and chemical properties and the toxicity of waste originating from power stations, in the form of coal bottom ash collected from pulverisedfuel and fluidised-bed boilers. To evaluate the eco-toxicological properties of waste, a series of plant growing tests were conducted, with the use of selected plant species, as well as germination tests in water extracts of waste. The latter were intended to determine whether coal bottom ash displayed cytostatic activity, while, in the case of pot experiments, the purpose was to determine the germination rates and growths of both above-ground and underground parts of plants. The test results indicated that the influence of the tested coal bottom ash on the plant development and growth depended on physical and chemical properties of that waste. The reactions of plants were also changing depending on the proportion of waste in soil.

Coal Bottom Ash as Sustainable Material in Concrete � A Review

Objective: This paper reviews the literature available on coal bottom ash (CBA) and its applications in building industry. Methods: The current trends on the reuse of CBA have been reviewed and the various properties of CBA are presented and discussed. Different percentage of CBA replacement in concrete was used. Findings: CBA were found thermally stable within the temperature range considered. Workability of fresh concrete containing CBA show a lower value due to the higher amount of replacement which required huge amount of water which effect the workability. Compressive strength of the concrete shows that it’s reached optimum strength beyond 28 days and no leachate of toxic elements in CBA was present. Application/Improvements: The review of the literature showed that the CBA was successfully recycle and applied for replacement as fine aggregate as well as coarse aggregate. It is concluded that the recycling of CBA as cement replacement material and also processing of CBA to develop nano-material are the future of CBA research. Keywords: Coal Bottom Ash, Compressive Strength, Power Plant, Sustainable Material, Workability

A Comprehensive Review on the Properties of Coal Bottom Ash in Concrete as Sound Absorption Material

The government is currently implementing policies to increase the usage of coal as fuel for electricity generation. At the same time, the dependency on gas will be reduced. In addition, coal power plants in Malaysia produce large amounts of industrial waste such as bottom ash which is collected in impoundment ponds (ash pond). However, millions of tons of coal ash (bottom ash) waste are collected in ponds near power plant stations. Since bottom ash has been classified as hazardous material that threatens the health and safety of human life, an innovative and sustainable solution has been introduced to reuse or recycle industrial waste such as coal bottom ash in concrete mixtures to create a greener and more sustainable world. Bottom ash has the potential to be used as concrete material to replace fine aggregates, coarse aggregates or both. Hence, this paper provides an overview of previous research which used bottom ash as fine aggregate replacement in conventional concrete. The workability, compressive strength, flexural strength, and sound absorption of bottom ash in concrete are reviewed.

Physical and Chemical Properties of Coal Bottom Ash (CBA) from Tanjung Bin Power Plant

The objective of this study is to determine the physical and chemical characteristics of Coal Bottom Ash (CBA) obtained from Tanjung Bin Power Plant Station and compare them with the characteristics of natural river sand (as a replacement of fine aggregates). Bottom ash is the by-product of coal combustion during the electricity generating process. However, excess bottom ash production due to the high production of electricity in Malaysia has caused several environmental problems. Therefore, several tests have been conducted in order to determine the physical and chemical properties of bottom ash such as specific gravity, density, particle size distribution, Scanning Electron Microscopic (SEM) and X- Ray Fluorescence (XRF) in the attempt to produce sustainable material from waste. The results indicated that the natural fine aggregate and coal bottom ash have very different physical and chemical properties. Bottom ash was classified as Class C ash. The porous structure, angular and rough texture of bottom ash affected its specific gravity and particle density. From the tests, it was found that bottom ash is recommended to be used in concrete as a replacement for fine aggregates.