The alkali-activation of fly ash and slag individually as single precursors each have specific challenges. Alkali-activated fly ash usually requires curing at elevated temperatures to develop strength which is a potential barrier to widespread use in the concrete industry [17].

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 ...

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.

The change in the relative mass of concrete was minimal at 10% fly ash content and 4% alkali equivalent. The fly ash in the concrete was fully activated as a result of the combined action of the alkali activator and the remaining alkali in the modified municipal sludge, which encouraged concrete hydration and structural compactness.

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].

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 …

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 ...

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

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 …

The fly ash had a much higher alkali content (4.27% Na 2 O eq). Though, due to their low solubility, alkalis in fly ash were not expected to significantly contribute to the ASR reactions and the associated expansion [10, 35]. Aggregates were composed of either inert pea gravel with a maximum size of 10 mm, reactive sand with a fineness modulus ...

Fly ash has a higher SiO 2 content whereas PC contains more CaO. Typically, Class F fly ash has less than 15% CaO content and Class C fly ash has greater than 20% CaO. More than 70% of Class F fly ash consists of …

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 …

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 ...

In the present paper, the mechanism of activation of a fly ash (no other solid material was used) with highly alkaline solutions is described. These solutions, made with …

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 …

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.

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 ...

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, …

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. …

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 ...

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, …

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 …

Overall the results show a general decrease in initial strength and increase in final strength as the fly ash content increases, though considerable variability is found within the results. This would suggest that the GGBS is the primary contributor to the initial strength with the fly ash contributing to the strength gain with time.

On the other hand, the UCS of the soils stabilised with alkali-activated fly ash increased considerably with the increase in fly ash content at 7 and 28 days of curing. In general, the UCS of the soils stabilised with alkali-activated fly ash almost doubled, from 15% to 25% fly ash content, at 28 days of curing.

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 …

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 …

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.

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.

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 ...

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