Strength Properties of Alkali-Activated Fly Ash

Fly ash is a by-product of coal-fired power plants and a rich source of aluminosilicate. This paper reports the compaction and strength properties of fly ash activated …

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Room temperature alkali activation of fly ash: The effect …

The Italian fly ash (kindly supplied by General Admixtures Spa, Ponzano Veneto, Treviso, Italy) ... Geopolymers were prepared with constant fly ash content (FA ... alkali activation of fly ash at room temperature represents a valid approach in developing market ready products. Developing comprehensive knowledge of geopolymer precursors is a ...

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Alkali Content of Fly Ash

Sodium and potassium are the common alkalis present in fly ash. Excessive amounts of fly ash alkalis can cause efflorescence problems in concrete products and raise concern about the effectiveness of the fly ash to mitigate alkali-silica reaction (ASR). The available alkali test, which is commonly used to measure fly ash alkali, takes approximately 35 days for …

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Alkalis Content

Expressed in different forms throughout the literature, alkali content, in general, refers to the quantity of elemental alkali metals (i.e., Na +, ... Bakharev [54] studied the effect of alkali cation type (sodium and potassium) on the thermal performance of fly ash geopolymers. It was reported that potassium based geopolymers performed better ...

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Alkali-activated fly ashes : A cement for the future

The first aspect to be emphasized in the general process of alkali activation is related to the variability of the kinetics and the governing mechanisms used to describe the mentioned process. ... the material obtained when the fly ash is activated with solutions of alkali hydroxide mixed with sodium silicate or potassium silicate (solutions 3 ...

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The effect of fly ash additive on the resistance of concrete to alkali

When fly ash content is increased to 45%, UPV increases up to 4145 m/s or 1.17% more. The highest UPV of 4151 m/s was recorded in specimens containing 55% of fly ash, and this value is 1.32% higher compared to UPV in control specimens. When fly ash content is increased to 65%, UPV drops down to 4147 m/s.

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ASTM C618 Fly Ash Specification: Comparison with Other

However, the quantity of fly ash needed for alkali-silica reaction prevention depends on various concrete mixture parameters, including aggregate source and OPC alkali content, as well as fly ash properties. Therefore, alkali-silica reaction control is specified under ASTM C1778-20 rather than under ASTM C618.

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Study on the Properties of High Fly Ash Content Alkali-Activated Fly

In order to efficiently utilize industrial solid waste while minimizing the preparation cost of engineering materials and the technical difficulty of construction, this paper prepared a high fly ash content alkali-activated fly ash slag composite system at normal temperatures and conducted an in-depth investigation on it. A systematic study was conducted on the workability, …

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Influence of Different Parameters on the Performance of Alkali

Figure 5 a shows the effect of different fly ash content on the compressive strength of the material. As the fly ash content increases from 60% to 90%, the compressive strength at each age gradually decreases. When the content of fly ash is 60%, the compressive strength is the maximum value.

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Workability, rheology, and geopolymerization of fly ash …

The Class F fly ash used in this experiment was obtained from the Huaneng Power Plant in Qingdao, Shandong Province, China. It has a specific surface area of 517 m 2 /kg and an apparent density of 2.12 g/cm 3. Its chemical composition is listed in Table 2. The total Si oxide and Al oxide content of the fly ash is 82.45 %.

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Characteristics and applications of fly ash as a sustainable

The main purpose of this work is to provide a comprehensive review of fly ash as a construction material. To achieve this goal, this literature review uses the following five steps: (1) Selecting review topics as follows: characterization, compositional understanding, activation approaches, nanotechnology applications, durability and sustainability evaluations of fly ash or …

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Melting and Dissolving Fly Ash by NaOH for the Removal …

The Fe 2 O 3 content of the prepared molecular sieve drops to 0.25% after the alkali treatment from 2.87% by merely acid leaching of fly ash, while the content of CaO drops to 0.066% from 1.18%. The chemical formula of the P molecular sieve prepared is confirmed as Na 6 Al 6 Si 10 O 32 ·12H 2 O through ICP examination.

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Fly ash properties, characterization, and applications: A review

Zeolite synthesis by an alkali hydrothermal reaction is performed on three main steps, dissolution, condensation, and crystallization ... Additionally, due to the high content of CaO (≥10%), Class C fly ash can raise pH and accordingly has been applied at absurdly high rates. On the other hand, Class F ashes contain mostly low CaO content ...

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Quantitative XRD study of amorphous phase in alkali activated …

The unreacted glassy content of fly ash and the amorphous reaction product content in alkali activated fly ash obtained after direct decomposition of the X-ray pattern with age shown in Fig. 8. The contents are determined as the proportion of the area under the intensity profile obtained from the PV fits to area under the total intensity profile.

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Influence of the Fly Ash Content on the Fresh and Hardened …

Figure 1 shows the variation in initial and final setting times of alkali-activated slag/fly ash mixtures with variation in fly ash content and chemical admixture. The setting time of the BFS sample was an initial time of 9.8 h and a final time of 11.8 h, while those of the other samples were delayed: 10 h and 13.7 h for 85% BFS and 19 h ...

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Metakaolin and fly ash alkali-activated mortars compared with

Alkali-activated cements (AAC) are a novel class of cement-like materials obtained by the polymerization reaction of a solid aluminosilicate with an aqueous solution of alkali hydroxide, silicate, carbonate, or sulfate [2].Aluminosilicate precursors are generally industrial by-products, such as slags or fly ashes, or natural rocks, such as kaolin, which forms metakaolin …

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Alkaline Activation of Fly Ash: An Overview

Activation of fly ash enhance several properties of fly ash such as improvement in strength, shrinkage characteristics, acid and fire resistance, cold weather resistance, great workability …

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(PDF) Effect of Various Alkaline Activator Solutions on Compressive

solution/fly ash and fine/coarse aggregate ratio in preparing the first series of specimens were 0.5 and 1, respectivel y. Table 4 represents mix designs of the specimens for the first

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Composition and microstructure of alkali activated fly ash …

Additionally, in the bibliography many references about zeolite synthesis by alkali hydrothermal reaction of coal fly ashes can be found [14], [15], [16], [17].In these works it has been already explained that the type of zeolite formed at the end of the process will mainly depend on the experimental conditions (nature and concentration of the activator, curing temperature and …

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Textural Alterations in Coal Fly Ash due to Alkali Activation

AbstractOver the years, coal fly ash has been used as a backfill material in embankments, mines, roads and around pipelines. Recently, there has been a growing interest in its alkali activation for synthesis of both geopolymers and highly porous minerals ...

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Study on Characterization and Properties of Alkali …

Fly ash: Fly ash is one of the residues generated in the combustion of coal. Fly ash is generally captured from the chimneys of power generation facilities. These ash particles consist of silica, …

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Chapter 3

Fly ash reacts with available alkali in the concrete, which makes them less available to react with certain silica minerals contained in the aggregates. ... The higher the carbon content in the fly ash, the more difficult it is to control the air content. Further, if the carbon content varies, air content must be closely monitored and admixture ...

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The importance of the network-modifying element content in fly ash …

In general, the size distribution is highly influential on the degree of alkali activation of fly ash because a large portion of alkali activation occurs at the surface of fly ash particles facing solution [10], [11].

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Influence of calcium oxide and sodium silicate on the setting

To investigate the effects of CaO and Na 2 O·nSiO 2 compound activators on the setting, hardening, and shrinkage properties of alkali-activated fly ash slag (AAFS) mortars, we examined the hydration characteristics and mechanical properties of CaO/Na 2 O·nSiO 2 activated slag/FA. This was accomplished by testing the setting time, hydration ...

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Factors affecting the drying shrinkage of alkali-activated …

faster reaction in alkali media than y ash. For S75/F25, the initial and nal setting times were 14 and 34 min, respectively, whereas for S50/F50, as the slag content was decreased and the y ash content was increased the initial and final setting times were 37 and 95 min, respec - tively. For S25/F75, the initial and nal setting times were 43

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(PDF) Effects of Fly Ash on the properties of Alkali

Results showed that decrease in fly ash content irrespective of % of alkali activators and alkali modulus (Ms), the compressive strength was increasing and setting time was getting shorter. The ...

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A numerical study on chloride transport in alkali-activated fly ash …

In general, the resistance to chloride penetration is considered to be an important parameter for evaluating the durability of reinforced concrete. ... [30] found that adding fly ash into alkali-activated slag system would change the amount of hydration products of C-A-S-H and N-A-S-H. A dense C-A-S-H gel helped to enhance the durability of ...

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Resource utilization of municipal solid waste incineration fly ash

Fly ash (FA), MSWIFA, sodium hydroxide, and sodium silicate alkali were mixed to make alkali-activated cementitious materials. The compressive strength of pure MSWIFA alkali-activated cementitious material was 10 MPa, the flexural strength was 1 MPa, and the strength of alkali-activated cementitious material increased as the MSWIFA contented ...

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Alkaline Activation of Fly Ash: An Overview

The alkali activation of fly ash has become an important area of research because it is possible to use these materials to synthesize inexpensive and ecologically ... Fly ashes having high content of toxins/ heavy metals may be used deposited under expert advice. The environment

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Mechanistic study on the utilisation and mineral formation of

Fly ash, a significant byproduct of municipal solid waste incineration, garners attention for its harmless treatment and resource utilisation. Existing research has demonstrated the viability of incorporating fly ash into the sintering process and explored its influence on the sintering bonding phase.

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[PDF] Alkali content of fly ash

Sodium and potassium are the common alkalis present in fly ash. Excessive amounts of fly ash alkalis can cause efflorescence problems in concrete products and raise …

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Class C fly ash-based alkali activated cement as a potential

Fly ash is a by-product of the coal combustion process and is basically a waste material. Fly ash is mainly composed of alumina and silica, which, when combined with an alkaline solution, undergoes a geopolymerization process. These converts fly ash into a binder, mainly an aluminosilicate gel, which, when mixed with water, behaves as a cement.

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Fresh mechanical and durability properties of alkali …

116 Innovative Infrastructure Solutions (2022) 7:116 1 3 Page 2 of 14 reaction mechanism of AAC can be classied (on the basis of their composition) into high calcium contents and low

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Strength Properties of Alkali-Activated Fly Ash

In general, an increase in stabilizer content increases the MDD value whereas the OMC decreases. The maximum UCS value of the stabilized specimens is found to be 3.5 MPa. …

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Thermodynamic modeling of alkali-activated fly ash paste

Alkali-activated fly ash (AAFA) is a sustainable, cement-free binder that forms through the reaction of fly ash with alkaline activator(s). Properly mixed and cured, AAFA can surpass Portland cement in various engineering aspects, including achieving higher mechanical strength [1, 2], exhibiting greater chemical resistance [3, 4], demonstrating lower shrinkage [5] …

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Effect of Activator and Mineral Admixtures on the …

The high autogenous shrinkage of alkali-activated fly ash/slag (AASF) poses a significant concern for the widespread application of AASF in structural engineering. The present study compares the efficacy of activator and mineral admixtures in mitigating the autogenous shrinkage of AASF, and discusses the underlying mechanism. The results show that the use of …

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Aggregates Obtained by Alkali Activation of Fly Ash: The …

On the other hand, alkali-activated fly ash synthesized by an alkali activator comprising a higher content of silicon, and consequently a higher Si/Al ratio (Si/Al > 1.6), will enable the incorporation of a substantial amount of dissolved aluminum into the aluminosilicate oligomers which are consumed upon alkali activation and the formation of ...

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What Is Fly Ash and How Is It Used in Concrete?

Since fly ash contains aluminous and siliceous components, it may form cement when mixed with water if the calcium content of the fly ash is high enough. Similarly, mixing fly ash with lime and water can create a substance similar to Portland cement. ... high-durability concrete that is resistant to sulphates and alkali-aggregate reactions ...

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A Ten-Year Study on Alkali Content of Coal Fly Ash

Some national standard specifies that the alkali content in Portland cement, calculated by Na2 O + 0.658 K2 O, should not exceed 0.60%. Therefore, the coal fly ash alkali content in blended …

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