Effect Of Fly Ash Addition Research Articles

Influence of Reclaimed Asphalt Pavement Aggregates on Strength and Durability Properties of Concrete Mixes in Rigid Pavements

The use of Reclaimed Asphalt Pavement (RAP) aggregates in rigid pavements instead of conventional aggregates in Himalayan regions solves the problem associated with shrinking natural resources and dumping of wastes. This study studied the effect of partial replacement of conventional coarse aggregates by RAP in Dry Lean Concrete (DLC) mixes suitable for rigid pavements. A total of 114 specimens (cubical and cylindrical) were cast and tested for mechanical and durability properties as per ASTM and IS code guidelines, partially replaced with CRAP by 25%, 50%, and 75% by weight. The simultaneous effect of fly ash addition by partial replacement of cement by it was also studied. The study concludes that 25% partial replacement by CRAP with 10% fly ash as partial replacement of cement led to the achievement of the strength benchmark as mandated by IRC SP 44 (2014). It was also observed that durability properties such as resistance to acid attack, sulphate attack and carbonation also improved in DLC mixes, including CRAP and fly ash, when compared to control mixes.

Influence of Reclaimed Asphalt Pavement Aggregates on Strength and Durability Properties of Concrete Mixes in Rigid Pavements

The use of Reclaimed Asphalt Pavement (RAP) aggregates in rigid pavements instead of conventional aggregates in Himalayan regions solves the problem associated with shrinking natural resources and dumping of wastes. This study studied the effect of partial replacement of conventional coarse aggregates by RAP in Dry Lean Concrete (DLC) mixes suitable for rigid pavements. A total of 114 specimens (cubical and cylindrical) were cast and tested for mechanical and durability properties as per ASTM and IS code guidelines, partially replaced with CRAP by 25%, 50%, and 75% by weight. The simultaneous effect of fly ash addition by partial replacement of cement by it was also studied. The study concludes that 25% partial replacement by CRAP with 10% fly ash as partial replacement of cement led to the achievement of the strength benchmark as mandated by IRC SP 44 (2014). It was also observed that durability properties such as resistance to acid attack, sulphate attack and carbonation also improved in DLC mixes, including CRAP and fly ash, when compared to control mixes.

Effect of fly ash addition on the mechanical properties of pervious concrete

Due to the unique permeable characteristics, the use of pervious concrete finds applications in various construction projects. The perviousness of the concrete can be achieved through exclusion of fine aggregates from its matrix. The study investigates the possibility of developing a sustainable pervious concrete through the utilization of fly ash as a partial replacement for cement. The overall objective of the current study is to promote sustainability in the development of a pervious concrete by partial replacement of cement by fly ash without compromising the strength. In total, different trails were prepared by replacing the cement with fly ash up to 40% in levels of 10%. Two sizes of coarse aggregates such as 12.5 mm and 20 mm were added to identify their significance. The experimental findings revealed that the mechanical properties of pervious concrete were improved with 20% of fly ash. After 28 days of curing, addition of higher proportion of fly-ash resulted in the decrease of compressive strength. Another important observation is the downfall of the porosity (i.e., high permeability) due to the increasing dosage of fly-ash.

Analysis of Durability of Watertight Concretes Modified with the Addition of Fly Ash.

The growing demand for watertight concrete structures is conducive to the development of research in this area, but their results are rarely published. In order to partially fill this gap, the authors of the publication present the results of research into the effect of fly ash addition on the watertightness of concrete. Prior to the tests, a recipe for a concrete mix with the addition of a sealing admixture modified with fly ash was developed. The following properties were analyzed: consistency of the concrete mix, air content in the concrete mix, compressive strength of concrete, depth of penetration of water under pressure, and frost resistance of concrete for F150 level. The work meets the expectations of the construction industry with respect to the production of concrete structures resistant not only to the penetration of water into concrete but also resistant to aggressive substances dissolved in water that accelerate the destruction of concrete and corrosion of reinforcement bars. Based on the test results, it was found that the addition of fly ash to the concrete mix enhances the positive impact of the applied sealing admixture, increasing the tightness of the concrete. It reduces the depth of penetration of water under pressure and therefore increases the frost resistance of concrete.

Workability Assessment of Pumpable Structural-Grade Heavy-Weight Concrete Using Novel Coaxial Cylinder Method

The mixture proportioning of heavy-weight concrete (HWC), as seen from the literature, is primarily based on a trial-and-error approach; even so, data from the literature indicate that obtaining high-slump mixtures for high density levels (more than 3.1 g/cm3) is difficult. Because heavy-density aggregates are prone to segregation at high slump, a low water to cement ratio is generally used for HWCs, and full-scale pumping trials are needed for checking pumping placement. For structural-grade HWCs used in nuclear facilities and specific infrastructure such as tunnel cross-rail floating slabs, rheological properties are needed to quantify the workability for pumping placement. Because use of rheological assessment methods using sophisticated rheometers cannot be realized easily onsite, a novel coaxial cylinder method is proposed in this study for determining the yield stress of HWCs delivering 3,800 to 3,900 kg/m3 density. The device proposed in this study is portable and can be used also onsite. Four structural-grade hematite aggregate HWCs, with design strengths varying from 40 to 70 MPa, were designed with ordinary portland cement. To understand the effect of fly ash addition on rheological behavior, one of the structural-grade HWC with three different levels (15%, 25%, and 35%) of fly ash was investigated. For referring the initial workability and workability retention properties of HWCs used in jobsite pumping, the conventional slump test values of the mixture were compared with yield stress measurements. Experimental investigations suggested that the method proposed in this study are able to adequately capture the workability characteristics required for pumpable mixtures. Further, it was seen that 35% partial replacement of fly ash resulted in 100% reduction in yield stress of HWC mixtures. Fly ash replacement (15% to 35%) did not significantly alter the hardened concrete density (3,800 kg/m3); however, attainment of the specified compressive strength depended on the replacement level of fly ash and extended curing period.

Mechanical properties, pore characteristics and microstructure of modified magnesium slag cemented coal-based solid waste backfill materials: Affected by fly ash addition and curing temperature

The high-temperature, deep-well environment can affect the mechanical properties and long-term stability of modified magnesium slag cemented coal-based solid waste backfill material (MMS-CBM). The purpose of this study was to investigate the effects of fly ash addition (0 %, 10 %, 20 %, 30 % and 40 %) and curing temperature (20 °C, 30 °C and 40 °C) on the mechanical properties, pore characteristics and microstructure of MMS-CBM. Based on this, relevant laboratory tests (uniaxial compressive strength test, pore structure test and microstructure test) were conducted to characterize the influence mechanism of fly ash addition and curing temperature on the performance of MMS-CBM. The results show that the physical properties (uniaxial compressive strength, pore characteristics and microstructure) of MMS-CBM are significantly affected by fly ash addition and curing temperature. With the increase of fly ash addition, the number of active particles and hydration products involved in the hydration reaction gradually increased, and the physical properties of MMS-CBM were gradually optimized. With the increase of curing temperature, the hydration reaction rate and hydration reaction degree of MMS-CBM gradually deepened, which accelerated the volcanic ash reaction of fly ash particles, which had a promoting effect on the early intensity of MMS-CBM. However, the subsequent strength of MMS-CBM will be affected by thermal damage, resulting in deterioration of physical properties and seriously affecting the long-term stability of MMS-CBM. In addition, the porosity and fractal dimension of MMS-CBM are linearly related to the uniaxial compressive strength, indicating that the pore characteristics can reflect the mechanical properties of MMS-CBM. This study provides a theoretical reference value for the application of MMS-CBM in high-temperature deep wells.

Influence of Fly Ash on the Fluidity of Blast Furnace Slag for the Preparation of Slag Wool

Using fly ash as the modifier, blast furnace slag was modified to prepare slag wool, fulfilling the goal of using one type of waste to make use of another type of waste, and it is of great significance for the comprehensive utilization of industrial bulk solid wastes and resource recycling. In the process of forming fiber from blast furnace slag, fluidity is the key factor affecting the smooth formation of fiber from slag. To explore the changes in the fluidity of modified blast furnace slag, the temperature-dependent viscosity of modified blast furnace slag with different amounts of fly ash added was measured, and the effects of fly ash addition on the viscosity, fluidity, and activation energy of particle migration, and slag structure of modified blast furnace slag were investigated. The results indicated that with the increase in the amount of fly ash added, in the high-temperature region (>1324 °C), the viscosity of modified blast furnace slag increases gradually, the fluidity decreases gradually (i.e., the fluidity becomes worse), and the suitable fiber-forming temperature range gradually widens. When the fly ash addition increases from 5% to 25%, the trend of the activation energy of slag particle migration is as follows: increase, decrease, increase significantly, decrease. When the addition of fly ash is less than 20%, the SiO2 content and slag temperature jointly affect the breakage and reorganization of oxygen bridge bonding in the silicon-oxygen tetrahedron in the slag structure. When the addition of fly ash increases to 25%, the slag temperature dominates the breakage of oxygen bridge bonding in the silicon-oxygen tetrahedron in the slag structure. When using fly ash as the modifier to prepare slag wool, from the perspective of slag fluidity and process operability, the optimum addition amount of fly ash is 15%.

Ultrasonic pulse velocity and electrical resistance of low-fines self-consolidating concrete for pavements

This study presents laboratory results of compressive strength (CS), ultrasonic pulse velocity (UPV), and surface electrical resistivity (ER) of low-fines self-consolidating concrete (LF-SCC) mixes with fly ash (FA) replacing ordinary Portland cement. The effect of FA addition on these properties at curing periods of 28, 56, and 90 day is discussed. From the results it is observed that addition of FA up to 20% is found to enhance the attributes of LF-SCC mixes in terms of CS, UPV and ER. The range of 28 days strength is 37.74 – 51.60 MPa. From the results of UPV all LF-SCC are found to be ‘Good’ concrete grades. The results of ER at all the curing periods show that all the six LF-SCCs are rated as ‘very low’ in terms of penetration of chloride ions as ER results are found to be in the range of 37–254 kΩ-cm.

Influence of Utilization of Fly Ash as Sand Replacement Agent in Sustainable Flexible Pavement

The current investigation work has investigated the utilization of Fly Ash (FA) in soil improvement and to assess the impacts of addition of various rates of FA on the sample of unsaturated soil. Effect of fly ash addition has been investigated on moisture content, degree of compaction and densities of unsaturated soil by directing different experiments. In the primary phase samples have been prepared with included FA in the percentages of 12%, 17%, 22%, and 27% respectively. Moisture content and densities experiments have been conducted without addition of FA for reference value. Each experiment was carried out with the mixtures having their optimal moisture content (OMC) and their maximum dry density (MDD). With the increase in percentage of water the degree of compaction, Dry density as well as bulk density has been increased up to a certain limit beyond this shows reverse result. Decrease in dry density was higher as compared to bulk density of the sample while increase in moisture content has been observed with the addition of FA in the sample. Addition of fly ash up to a certain limit shows good agreement for utilization as sand replacement or additives in civil application for sustainable applications.

Investigating the Effect of Fly Ash Addition on the Metallurgical and Mechanical Behavior of Al-Si-Mg-Cu Alloy for Engine Cylinder Head Application.

The authors researched the physical, metallurgical, and mechanical characteristics of A354 alloy (Al-Si-Mg-Cu) reinforced with 5, 10, and 15 wt% of fly ash metal matrix composites. A baseline alloy and three composites were fabricated by a liquid metallurgy route and poured into a permanent mold to obtain cast rods of dimension Φ32 mm × 156 mm. The metallurgical characterization of the developed alloy and metal matrix composites was conducted using energy-dispersive spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray diffraction. All the developed composites showed a pore-free nature, but only A354 alloy reinforced with 5 wt% of fly ash (AF5) possessed a homogeneous distribution and perfect bonding of the fly ash with the A354 matrix. Therefore, transmission electron microscopy (TEM) analysis was performed on the sample AF5. All developed alloys and metal matrix composites were subjected to hardness and mechanical property tests. It was observed that the AF5 sample had 170 ± 5.6 HV and tensile strength of 216 ± 2.3 MPa, 18.8% and 24.8% higher than the A354 matrix, but the ductility (6.5 ± 0.43%) was reduced by 23% from the baseline alloy. Finally, the fractography analysis was conducted on all the samples using FESEM to analyze the fracture mode. The fabricated 5 wt% fly ash-based metal matrix composite showed better mechanical performance than other samples. Hence, sample AF5 is suggested for manufacturing components in automotive and structural parts.

Development of building materials based on a high content of fly ash and polycondensation products from Chinese heat and power plants

Abstract The addition of fly ash from thermal power plants (TPP) and chemical additives, such as polycondensation products of acetone and formaldehyde, is an effective and economical method for increasing the strength and durability of building materials, in particular concrete. Fly ash added to the concrete and mortars at 10%–15% does not reduce their technical properties, while polycondensation products of acetone and formaldehyde plasticize and accelerate the hardening process of concrete. The study aims to substantiate the possibility of obtaining concrete on dense aggregates with a high content of fly ash through the use of polycondensation products of acetone and formaldehyde as additives, which are highly soluble in water and polyfunctional. The strength indicators were determined using standard methods. The study has shown quantitative changes in the properties of the fly ash-concrete mixture, improvement of its physical and technical characteristics, and durability of the fly ash concrete with the addition of polycondensation products of acetone and formaldehyde. In the present study, the authors determine the effect of fly ash addition on the properties of a concrete mixture, as well as the maximum possible content of fly ash that can be added to concrete to maximize certain properties required of the mixture; additionally, the same action is conducted with the addition of polycondensation products of acetone and formaldehyde concomitant with the addition of fly ash.

Formulation and optimization of a phosphogypsum – fly ash – lime composite for road construction: A statistical mixture design approach

This paper investigates the valorization of phosphogypsum and fly ash by-products as a road construction material through lime stabilization. To this end, an extreme vertices design was adopted to model the compaction characteristics, mechanical performance at different curing periods and durability upon wetting/drying (W/D) cycles of the mixture. Statistical analysis of the obtained regression models showed that the measured responses decrease with phosphogypsum addition while fly ash and lime cause them to increase. The increasing effect of fly ash addition was especially noticeable on compressive strengths at early ages (7–28 days), whereas at longer curing periods (90–360 days), these were mainly governed by its interaction with lime following the activation of the pozzolanic reaction where phosphogypsum acted as a catalyst to improve fly ash reactivity. However, a negative impact of excess lime beyond a threshold has been noted. The compressive strength at 28 days combined with weight loss upon W/D cycles were used as optimization responses to detect regions of interest, within the design space, where requirements are met for a subbase utilization.

Stabilization/solidification of hazardous lead glass by geopolymers

Stabilization/solidification (S/S) of lead in hazardous waste cathode ray tube (CRT) glass by using geopolymers is a promising disposal method for further construction use. In this study, the effects of fly ash addition and waste CRT glass aggregate on the properties of slag-based geopolymers were investigated. Results show that the addition of 50 wt% fly ash into the geopolymer containing 50 wt% waste CRT glass can mitigate the alkali-silica expansion by 61%, slightly decrease the compressive strength by 1.5 MPa and promote the generation of mullite. On the other hand, the PbO released from waste CRT glass can retard the hydration process, but without changing the crystalline phase composition and the aluminosilicate structure of geopolymers. Therefore, the S/S of waste CRT glass by geopolymers mainly depends on the physical encapsulation effect. Furthermore, fly ash addition can degrade the S/S performance of geopolymers due to the increase of the total porosity representing the channel number. Finally, based on the requirements of volume stability, compressive strength, and leaching concentration of Pb, a mix proportion of 50 wt% fly ash and 50 wt% slag can be proposed for recycling waste CRT glass in a non-hazardous way. Overall, this study is an innovative attempt to reveal the feasibility of utilizing waste CRT glass in geopolymers as fine aggregate.

Effects of fly ash addition on the rheological characteristics of red MUD slurry: An approach to the sustainable mining waste management

The aim of this paper is to study the addition of fly ash in red mud slurry in the view of environmental sustainability, as a contribution to waste disposal methods. Three mixtures with red mud concentrations ranging from 400 g/L to 800 g/L and fly ash addition (maximum of 30% per mass of solid in the slurry) were studied. Textural and morphological aspects were analysed by Scanning Electron Microscope (SEM). Additionally, the chemical composition (major oxides analysis) was performed by ICP-OES. To evaluate the rheological behaviour, measurements using a MCR102 Rheometer were carried out. The addition of fly ash follows a similar rheological behaviour to that shown by the red mud slurry. After dewatering, red mud slurry with fly ash shows a stable framework formed by the interaction of red mud with the silica and silica-aluminium compounds that could be used as raw material, according to international standards.

Effect of fly ash addition on slurry dewatering by electro-osmosis combined with mechanical pressure

In this study, fly ash was used as an additive to increase the dewatering efficiency of an excavated soil slurry treated by electro-osmosis combined with mechanical pressure and thus effectively obtain a low-moisture treated slurry with wider applicability; the properties of the treated slurry were also studied. The results showed that, at a fly ash dosage of 5%, the drainage volume was 350 mL, which presented significantly better dewaterability properties than the unconditioned slurry, the water content of the anode and cathode layer after treated was 20.5% and 19.1%, the compressibility coefficient was 0.170 MPa−1 and 0.152 MPa−1, and the shear strength was 81.2 kPa and 85.1 kPa, respectively. And we also studied the physical properties of the treated slurry at different locations, the physical properties were also affected by the fly ash dosage. It was concluded that fly ash used in adequate concentrations can reduce the slurry water content, and fly ash also can improve the mechanical properties of excavated soil slurry after the mechanical dewatering combined with electro-osmosis.

Retraction Note to: Microstructure and mechanical behavior of A356/SiC/Fly-ash hybrid composites produced by electromagnetic stir casting

Electromagnetic stir casting is one of the simplest ways of producing defect free aluminum matrix composites. This work focuses on the fabrication of aluminum matrix composites reinforced with various weight percentages of SiC particulates and Fly-ash by modified electromagnetic stir casting route. The distribution of SiC and Fly-ash particles in the matrix was improved by providing externally argon gas into the melt during electromagnetic stirring. Five samples of hybrid composite with different combination of Fly-ash and SiC (25 μm) were prepared by electromagnetic stir casting method. Mechanical properties (tensile strength, hardness, toughness and fatigue strength) and microstructure of all five samples were analyzed. Microstructure presents that the reinforcements (SiC particulates and Fly-ash) are uniformly distributed in the matrix (A356). The results reveal that sample of A356/15 %SiC/5 % Fly-ash shows best result among all the selected samples. Density, porosity, specific strength and thermal expansion were also calculated to see the effect of Fly-ash addition.

Strength development and microstructural investigation of lead-zinc mill tailings based paste backfill with fly ash as alternative binder

The increasing popularity of paste backfilling demands alternative binder optimisation and bulk waste disposal. This study investigates the efficacy of fly ash (FA) as partial replacement of ordinary portland cement (OPC) for paste backfill application in underground mines. The effect of FA addition on uniaxial compressive strength (UCS) and cohesion of paste backfill are demonstrated. The strength development was correlated with microstructural evolution using scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS). The study revealed that the rate of strength development in paste backfill slowed down when OPC was substituted by FA. However, the targeted 28 days' UCS of 1.1 MPa for the backfilling stope of lead-zinc mine was achieved with binder dosages of 8 wt% OPC, 7 wt% OPC, 6 wt% OPC, 7 wt% OPC +1 wt% FA and 6 wt% OPC +2 wt% FA. Thus, FA is a suitable binder substitute and up to 25% of OPC (8 wt%) can be replaced with FA. Analysis of microstructural evolution in paste backfill revealed that calcium silicate hydrate (C–S–H) did not develop in OPC-FA binder based paste backfill at its early days’ of curing and gypsum was found only in samples with OPC as sole binder. The multiple linear regression analysis on interaction effects of OPC, curing time, FA replacement percentage for 8 wt% and 5 wt% binder groups indicated that the UCS development is more sensitive towards FA replacement. The obtained results would help in better understanding and design of paste backfill for lead-zinc underground mines.

Electrochemical responses and chloride ingress in reinforced Belite-Ye’elimite-Ferrite (BYF) cement matrix exposed to exogenous salt sources

Reinforced Belite-Ye’elimite-Ferrite (BYF) mortars cured for different times and exposed for 90 and 182 days to a chloride-rich solution (full immersion and dry/wet cycles) were compared to Portland equivalents in terms of porosity, corrosion, chloride ingress and sorptivity. The effect of fly ash addition was also considered. BYF- and Portland-embedded rebars remained passivated through 182-day testing. The apparent chloride diffusion coefficients were about 10−12 m² s-1, except for 28-day-cured BYF mortars containing fly ash, which exhibited higher values. The results contribute to a better assessment of durability issues concerning BYF matrices, indicating they can be a reliable alternative to Portland.

1-18 フライアッシュ添加のコークス品質への影響

1-18 フライアッシュ添加のコークス品質への影響

Effects of flyash addition on the dry sliding tribological behavior of aluminum composites

Flyash is an industrial waste obtained from thermal power plants. The mixing of flyash particles in the air may cause damage to the environment. In this paper, attempts have been made to utilize the waste flyash particle to fabricate an aluminium composite. Three aluminium composites with fly-ash (5 wt%–10 wt%) were fabricated using a stir casting with vortex technique. Wear and friction behavior of the aluminium flyash composites was evaluated using a linear reciprocating tribometer at 0.38 Mpa pressure and 10 Hz frequency against a mild steel counter surface. It is established that flyash contents enhanced the wear and friction behavior of the aluminium metal composite. The aluminium-flyash composite with 10 wt% flyash particles yields the lowest amount of wear, friction coefficient value and maximum hardness among the fabricated materials. The scanning electron microscope (SEM) images also indicated the lower microcutting and wear wedges on the 10 wt% flyash composite.