Effect Of Fly Ash Content Research Articles

Degradation Behavior of CFB Fly Ash Filled Unsaturated Polyester Composites under Acidic Environment

In this study, the degradation behavior of circulating fluidized bed (CFB) fly ash reinforced unsaturated polyester composites at different loadings of 0%, 10%, 20%, 30%, and 40% CFB fly ash were observed at different temperatures of 30°C, 50°C, and 80°C under acidic environment. The mass uptakes of the samples were recorded at specified time intervals to determine the effects of fly ash content and temperature. Scanning electron microscopy was used to show if there were changes in the microstructure of the samples. Moreover, the glass transition temperature found from the differential scanning calorimetry showed that the types of diffusion behavior that may take place were the Fickian and non-Fickian (Case II). However, the empirical diffusion model used illustrated that only the Fickian diffusion had occurred.

Effect of Fly Ash Content on Mechanical Properties of Cement-Fly Ash Stabilized Crushed Stones

To improve the impact of fly ash on the properties of cement-fly ash stabilized crushed stone, and promote it popularize and apply better. This paper investigated the effect of fly ash content on unconfined compressive strength, cleavage strength and resilient modulus of cement-fly ash stabilized crushed stones, and those relationships between mechanical parameters. The results showed that with increasing of the fly ash content, the unconfined compressive strength and cleavage strength increased at first, then decreased, the resilient modulus decreased, and The brittleness index increased. We can conclude that the optimal fly ash content is between 10% and 15%, and increment of fly ash content can improve its crack-resistance.

Chloride ion transport in fly ash mortar under action of fatigue loading

In order to study the chloride ion transport performance in fly ash addition mortar, a new method, in which the fatigue loading and chloride diffusion are undertaken simultaneously, was developed. This method realizes coupling the fatigue damage process and the process of chloride transporting of fly ash mortar. The transport performance of chloride in fly ash mortar specimens was studied under different stress levels. Moreover, the effect of fly ash content on transport performance of chloride ion in mortar was investigated. AE (Acoustic Emission) and SEM were used to acquire the damage distribution of mortar specimens under action of fatigue load. The results show that the diffusion coefficient of chloride in mortar specimens increases with stress level of fatigue loading. The addition of fly ash can mitigate the penetration of chloride ion. The results of microcrack 3D location acquired by AE, accompanied with crack characterizing from SEM, indicate that the damage degree of mortar specimen increases with stress level of fatigue loading. Furthermore, higher damage degree of mortar leads to more the chloride ion content in the sample.

Effects of Fly Ash Content on the Strength Property of Cement Concrete Pavement

Using ordinary material, calculating through the external addition method and then adjusting through experimental tests, the mixing proportion of cement mortar is determined. The testing results show that: when the water cement ratio is 0.50, the fly ash content is too large and the strength of cement mortar will sharply decrease with the increase of its content. Therefore, the fly ash content in engineering cannot exceed 30% of the gelled material.

The effect of fly ash content and types of aggregates on the properties of pre-fabricated concrete interlocking blocks (PCIBs)

We studied the influence of fly ash content and replacement of crushed sand stone aggregate with concrete wastes and marble wastes in pre-fabricated concrete interlocking blocks (PCIBs). We have compared properties of PCIBs with fly ash produced with three different replacement ratios of aggregate. Compressive strength, tensile splitting strength, density, apparent porosity, water absorption by weight, abrasion resistance, alkali-silica reaction and freeze–thaw resistance of PCIBs were determined. When comparing the PCIBs with crushed sand stone, the replacement of crushed sand stone with concrete waste and marble waste results in lower physical and mechanical properties. By contrast, replacement of cement with fly ash (from 10% to 20%) has a significant effect in increasing important properties of PCIBs.

Synthesis and characterization of fly ash modified mine tailings-based geopolymers

Each year, the mining industry generates a significant amount of mine tailings. Storage of these tailings occupies large areas of land and leads to high monetary, environmental and ecological costs. In this research, a feasibility study is performed on geopolymerization of mine tailings so that they can be recycled and utilized as construction material. Considering the extremely high silicon to aluminum (Si/Al) ratio for the mine tailings, class F fly ash is used to adjust the Si/Al ratio. Sodium hydroxide (NaOH) solution is used as the alkaline reaction agent. The research consists of unconfined compression tests to evaluate the mechanical properties, scanning electron microscopy (SEM) imaging to investigate the microstructure, and the X-ray diffraction (XRD) analysis to study the phase compositions. The effects of fly ash content (which affects the Si/Al ratio), alkalinity (NaOH concentration), and curing time on the geopolymerization of mine tailings are studied in a systematic way. The results show that the Si/Al ratio and the alkalinity have profound effects on the mechanical and micro-structural properties of the mine tailings-based geopolymers. The curing time affects the mechanical and micro-structural properties of the mine tailings-based geopolymers mainly during the first 7 days. Based on the research, it can be concluded that mine tailings are a viable and promising construction material if the geopolymerization technology is utilized.

Effect of Fly Ash Content on Properties of Fly Ash-Coal Gangue Foam Concrete

The effect of the fly ash content on the properties of the fly ash-coal gangue foam concrete was studied in this paper. Results revealed that: With the increase of the fly ash content, the dry density, the compressive strength and the shrinkage of the fly ash-coal gangue foam concrete decrease; the density of the fly ash - coal gangue foam concrete was influenced greatly by the ratio of water to total dry material. The pore structure and microstructure of the foam concrete was analyzed by scanning electron microscopy, and the results show that most of the pores are fine, closed, and even distributed.

유동층(流動層) 연소기(撚燒器)로 부터 발생(發生)된 석탄(石炭) 비산(飛散)재를 이용(利用)한 인공경량골재(人工輕量骨材) 제조(製造)

유동층 연소 방식의 화력발전소에서 발생된 석탄 비산재를 점토와 혼합하여 8 mm 크기의 구형 성형체를 제조한 후, <TEX>$1050^{\circ}C{\sim}1250^{\circ}C$</TEX>에서 10분 직화 소성하여 인공골재를 제조하고, 골재의 발포특성에 미치는 비산재의 영향을 분석하였다. 비산재가 50 wt% 미만으로 첨가원 시편은 발포되면서 black-coring 현상을 나타내었다. 비산재가 50 wt% 이상 포함되면, 소성온도와 함께 골재의 부피비중이 높아지면서 시편 전체가 검은색으로 변하였다. 이는 미연탄소 함량의 증가로 인해 과도한 환원분위기가 형성되고 따라서 가스가 급속히 방출됨과 동시에 대부분의 산화철이 환원되기 때문이다. 소성온도가 같을 경우 비산재 함유량이 높을수록 골재의 부피비중은 낮아지는 경향을 보였다. 비산재 첨가량이 10 wt%인 경우를 제외한 모든 시편들은 소성 온도를 높이면 홉수율이 감소하였는데 이는 고온일수록 액상이 많이 형성되었기 때문이다. 본 연구에서 제조된 유통층 연소기 석탄 비산재에 점토가 10~90 wt% 첨가된 시편들은 부피비중이 0,9~1.8, 흡수율이 8~60%로 다양한 특성을 나타내어 중량 내지 경량골재로 사용이 가능할 것으로 생각된다. The spherical artificial aggregates (AAs) with a diameter of 8 mm, which contains fly ashes discharged from the fluidized bed combustion in a thermal power plant and clay were manufactured by direct sintering method at <TEX>$1050{\sim}1250^{\circ}C$</TEX> for 10 minutes. The effect of fly ash contents on the bloating phenomenon in the AAs was analyzed. The AAs containing fly ash of the amount under 50 wt% showed the black-coring and bloating phenomena. The AAs containing fly ash of the amount over 5Owt%, however, the specific gravity was increased and the color of specimens fully changed to black. These color change phenomena were caused from the formation of FeO by the reduction reaction of almost <TEX>$Fe_2O_3$</TEX> component by the excessive reducing atmosphere formed simultaneously with the rapid emission of the gases generated from the high contents of unburned carbon of with increasing the added fly ash amount. Specific gravity was decreased as fly ash contents increased in the case of sintering at the same temperature condition. Water absorption of all specimens except of the specimens containing 10 wt% fly ashes decreased with increasing sintering temperature. These were because a liquid phase was formed as the increasing the sintering temperature. In the case of the specimens manufactured in this study containing fly ashes discharged from the fluidized bed combustor in a the thermal power plant and 10~90 wt% of clay, the specific gravity was 0.9~1.8 and the water absorptivity was 8~60%, therefore it is considered that those results can be applied to the light or heavy aggregates.

The effects of intumescent flame retardant including ammonium polyphosphate/pentaerythritol and fly ash fillers on the physicomechanical properties of rigid polyurethane foams

AbstractIn this study, rigid polyurethane foams that contain up to 5.0 wt % fly ash (FA) being a by‐product of thermal power stations and being cheap source were successfully produced using a polyurethane injection machine. The effects of FA content on the thermal conductivity, compressive strength, and flammability were investigated. The morphology of the cell was observed under a special microscope. The incorporation of FA in rigid polyurethane foams may dramatically decrease production costs and reduce environmental pollution. In addition, the effects of intumescent flame retardant composed of ammonium polyphosphate and pentaerythritol were examined in pure rigid polyurethane foams and FA‐rigid polyurethane foams. It was found that 5.0 and 7.5 wt % intumescent flame retardant loadings enhanced the thermal stability and improved the flammability resistance of the foams. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of Fly Ash Content on Mechanical Properties of Cement-Fly Ash Stabilized Crushed Stones

This paper investigates the effect of fly ash content on unconfined compressive strength, cleavage strength and resilient modulus of cement-fly ash stabilized crushed stones. The relationships between mechanical parameters were also studied. The results show that with fly ash content increasing, the unconfined compressive strength and cleavage strength were increasing firstly but decreased then, and the resilient modulus were decreasing. The brittleness index was increased by the increment of fly ash content. It can be concluded that the optimal fly ash content in cement-fly ash stabilized crushed stones is between 10% and 15%, and increment of fly ash content can improve its crack-resistance.

Effect of flyash content, particle size of flyash, and type of silane coupling agents on the properties of recycled poly(ethylene terephthalate)/flyash composites

AbstractRecent time's polymer waste disposal is a challenging task as the quantity of polymer waste is increasing day by day. Here particulate composites have been developed from recycled poly(ethylene terephthalate) filled with flyash. Flyash of different particle sizes have been used, and effect of particle size and flyash content on the mechanical properties of composites has been analyzed. Tensile and flexural properties of the composites are found to increase with increase in filler content up to 15% and after that decreases due to the agglomeration of flyash particles. SEM studies also showed good dispersion at lower loadings. The use of silane coupling agents was found to increase the flyash/WPET interaction there by increase in mechanical properties is observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of Fly Ash Content on Friction and Dry Sliding Wear Behavior of Glass Fiber Reinforced Polymer Composites - A Taguchi Approach

The tribological behavior of glass fiber reinforced vinylester composites filled with fly ash particulates were studied using a pin-on-disc wear apparatus under dry sliding conditions. The influence of friction and wear parameters like (pv) factor, sliding distance and percentage of filler content, on the friction and sliding wear rate were investigated. A plan of experiments, based on the Taguchi technique, was performed to acquire data in a controlled way. An orthogonal array and analysis of variance (ANOVA) were applied to investigate the influence of process parameters on the coefficient of friction and sliding wear behaviour of these composites. The Taguchi design of experiment approach eliminates the need for repeated experiments and thus saves time, material and cost. Taguchi approach identifies not only the significant control factors but also their interactions influencing the coefficient of friction and specific wear rate predominantly. The results showed that the inclusion of fly ash as filler materials in glass vinylester composites decreases the coefficient of friction and increases the wear resistance of the glass vinylester composites significantly.

Effect of Fly Ash Content and Aggregate Gradation on the Durability of Concrete Pavements

In the regions where temperature fluctuations are large ranging from below freezing in winter to high temperatures in summer, concrete highway pavements fail because of poor durability rather than lack of strength. The effect of fly ash replacement of Portland cement and the use of dense aggregate gradation on the durability of concrete mixtures is studied in this research. Eight concrete mixtures were cast, four of them using the aggregates as per current specifications and the other four mixtures using dense graded aggregates. For each of these two gradations, different fly ash replacement amounts of 30, 35, 40, and 45% for Portland cement were used. All mixtures were designed for 6% air content, and 25–38 mm (1 to 1 1∕2 in.) slump for the freshly mixed concrete. The study shows that the increase of fly ash content from 30 to 45% increased the durability of concrete mixtures without the loss of compressive and flexural strengths. The concrete mixtures containing dense graded aggregates, and higher perce...

Volume Change Behavior of Fly Ash-Stabilized Clays

This paper presents, by way of comparison, the effect of fly ash on the volume change of two different types of clay, one a highly plastic expansive clay and the other a nonexpansive clay, also of high plasticity. Expansive clays swell on absorbing water and shrink on drying. Nonexpansive clays undergo large compression at high water contents. The effect of fly ash content on free swell index, swell potential, and swelling pressure of expansive clays was studied. Compression index and secondary consolidation characteristics of both expansive and nonexpansive clays were also determined. Swell potential and swelling pressure, when determined at constant dry unit weight of the sample (mixture), decreased by nearly 50% and, when determined at constant weight of clay, increased by nearly 60% at 20% fly ash content. Compression index and coefficient of secondary consolidation of both the clays decreased by 40% at 20% fly ash content.

Impact properties of geopolymer based extrudates incorporated with fly ash and PVA short fiber

A PVA short fiber reinforced fly ash-geopolymer composites manufactured by extrusion technique (SFRGC) is developed in this study. The effects of fly ash content and fiber volume fraction on the rheological and impact behaviors of SFRGC are systemically investigated. Freeze–thaw cycles and sulfuric acid attack tests are also employed to study the durability of SFRGC. The experimental results show that for normally curing SFRGC, the addition of PVA fiber increases greatly the ductility of SFRGC, especially in the case of high volume fraction of fiber, resulting in the change of impact failure mode from brittle pattern to ductile one. As a result, a great increase in the impact toughness is seen in SFRGC with high fiber content. Comparatively the addition of fly ash exhibits obvious influence on the rhelogical and impact behaviors. The spherical shape of fly ash can greatly improve the extrudability of fresh SFRGC pastes. SFRGC without or with low percentage of fly ash possesses very high impact strength and stiffness. However, when too much fly ash is incorporated, the impact resistance of SFRGC is reduced rapidly. For SFRGC undergone freeze–thaw cycles and 1 month of sulfuric acid solution attack, only 5% or less of loss in impact strength is observed. The corresponding microstructure and failure mechanism are also explored by Laser particle size analysis (LSA), X-ray diffraction analysis (XRD), Scanning Electron Microscope (SEM), and Mercury intrusion porosimetry (MIP) techniques.

Impact behavior and microstructural characteristics of PVA fiber reinforced fly ash-geopolymer boards prepared by extrusion technique

A short PVA fiber reinforced fly ash-geopolymer boards (SFRFGBs) manufactured by extrusion technique is developed in this study. The effects of fly ash content and fiber volume fraction on the impact behavior of SFRFGBs are also investigated. In order to better understand the impact behaviors of SFRFGBs with different content of fly ash and fiber, Laser particle size analysis (LSA), X-ray diffraction analysis (XRD), Scanning Electron Microscope (SEM), Mercury intrusion porosimetry (MIP) are employed to explore the microstructure and failure mechanism. The experimental results show the addition of PVA fiber changes the impact failure mode from a brittle pattern to ductile pattern, resulting in a great increase in impact toughness for SFRFGBs with high volume fraction of fiber. SFRFGBs without or with low percentage of fly ash possess very high impact strength and stiffness. However, when too much fly ash was incorporated, the impact resistance of SFRFGBs is reduced obviously. This can be explained by the fact that low percentage of fly ash addition significantly improved the extrudability of fresh Geopolymer composites, resulting in a formation of very dense and compacted matrix with high-quality finish. When too much fly ash is added, the Geopolymer product is greatly reduced, resulting in a formation of very poor matrix.

Effect of Fly Ash Content on Impact, Compression, and Water Absorption Properties of Epoxy Toughened with Epoxy Phenol Cashew Nut Shell Liquid–Fly Ash Composites

Fly ash, a waste product generated in a thermal power plant in huge quantities has been posing problems of disposal. The purpose of this study is to make a meaningful utilization of fly ash as the filler in pure epoxy resin matrix and 20% epoxy phenol cashew nut shell liquid (EPCNSL)toughened epoxy matrix. The properties under consideration are impact, compression, and water absorption. Composites are made with varying proportions of fly ash in epoxy resin and 20% EPCNSL-toughened epoxy resin. The compression properties are measured on a computerized universal testing machine according to ASTM procedure. The impact strength is determined using an izod impact tester for unnotched specimens. The toughened matrix filled with fly ash composites shows improved compression modulus over pure epoxy–fly ash composites. The toughened matrix composites show better water absorption property over pure epoxy–fly ash composites.

Effect of Fly Ash Content on Zeolite Synthesis from Coal Fly Ash Prepared by Hydrothermal Treatment.

原料フライアッシュの成分組成が水熱法によって生成されるゼオライトの結晶形態に与える影響について検討した．その結果，シリカ含有率が低く溶出速度の遅いフライアッシュを原料に用いると，フィリップサイトとヒドロキシソーダライトが生成することがわかった．また，反応液中のシリケートイオン濃度をアルミン酸イオン濃度よりも常に高い状態に保ちながら水熱処理を行うことで，選択的にフィリップサイトを合成できることが明らかとなった．さらに，フライアッシュから反応液中にシリケートイオン，アルミン酸イオンが溶出し，中間生成物を経てフィリップサイトの結晶が生成するという反応機構モデルを提案した．本モデルにより反応液中のイオン挙動並びにフィリップサイト生成量の経時変化をある程度定量的に説明でき，中間生成物の生成速度，結晶化反応の反応速度，臨界濃度は，原料とするフライアッシュの性状によらず一定であることが示唆された．

The effect of high content of fly ash on the properties of glass fiber reinforced cementitious composites

The objective of this paper was to study glass fiber reinforced cementitious composites (GFRCC) with Portland cement, a high content of fly ash as matrix. The effect of fly ash content, the initial curing time, and accelerated ageing on the flexural strength of GFRCC was investigated. The suitability of the accelerated ageing method was queried by analyzing the results from SEM observation, XRD analysis, and deflection testing.

Evaluation of Type C Fly Ash in Cold In-Place Recycling

The Kansas Department of Transportation has developed an innovative method of rehabilitating low-volume pavements using cold in-place recycling (CIR) and Type C fly ash. Previous field test sections have indicated that fly ash improves constructability and moisture sensitivity. However, the same field test sections have exhibited increased cracking with increased fly ash content and a drop in pavement modulus with time. A laboratory study was undertaken to evaluate the effect of fly ash content on CIR. Reclaimed asphalt pavement (RAP) was mixed with 3, 7, 11, and 15 percent Type C fly ash and the fatigue life, durability, freeze-thaw resistance, and thermal cracking potential of laboratory-compacted samples were evaluated. RAP mixed with asphalt emulsion and asphalt emulsion with hydrated lime were evaluated as well. The results indicated that 7 to 11 percent Type C fly ash provided optimal laboratory freeze-thaw and moisture sensitivity performance. Increasing the fly ash content resulted in a brittle fatigue behavior as well as an increased thermal fracture temperature. AASHTO T283 is recommended for selecting the optimum fly ash content.