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Optimization of Proportions of Alkali-Activated …

To enhance the application of alkali-activated materials in mine filling, cemented tailings backfill was prepared using slag, fly ash, sodium silicate, and NaOH as primary constituents. The effects of the raw material type and …

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Effects of Fly Ash Inclusion and Alkali Activation on Physical

The UCS of the soil increased with the addition of alkali activators, fly ash content, and the curing time. The highest UCS result was found with 25% fly ash content, M+ of 16% and SM of 1.25 at 28 days of curing which can improve the …

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In-depth investigation on macro-properties and micro-mechanism …

Mechanical properties, microstructure, and chloride content of alkali-activated fly ash paste made with sea water. Materials, 13 (6) (2020), 10.3390/ma13061467. Google Scholar [25] H. Taghvayi, K. Behfarnia, M. Khalili. The effect of alkali concentration and sodium silicate modulus on the properties of alkali-activated slag concrete.

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Long Term Efficacy of Fly Ash in Mitigating Alkali-Silica

Dacite concretes with fly ash exhibit negligible expansion regardless of the effective cement alkali content (from 0.6% up to 1% Na 2 O eq) which indicates that fly ash can mitigate ASR even when the cement alkali content is higher than 0.6% Na 2 O eq. This suggests that reactive aggregates can be used and that the cement alkali limit can be ...

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Using Class C Fly Ash to Mitigate Alkali Silica Reactions in …

KEYWORDS: Class C fly ash, alkali silica reactivity, ASR ABSTRACT High-calcium fly ashes, classified as Cla ss C by ASTM International (ASTM) C618 ... reduction in expansion continued as the fly ash content increased. INTRODUCTION This project was initially designed as a 3-year study to perform a comprehensive

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

When fly ash content is increased to 55% and 65% by weight of cement, the ultrasonic pulse velocity drops to 4287 and 4283 m/s respectively. ... The analysis of concrete microstructure revealed that fly ash particles are covered with amorphous SiO 2 and alkali reaction product. Fly ash contains 49.8% of amorphous SiO 2, which reacts with NaOH ...

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Alkali Content of Fly Ash Measuring and Testing Strategies …

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).

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Mechanical Properties, Microstructure, and Chloride Content of Alkali

The aim of the present study is to investigate the potential of sea water as a feasible alternative to produce alkali-activated fly ash material. The alkali-activated fly ash binder was fabricated by employing conventional pure water, tap water, and sea water based alkali activating solution. The characteristics of alkali-activated materials were examined by …

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Alkali Content of Fly Ash – Measuring and Testing Strategies for …

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

To avoid the flash-setting problem and improve fluidity, three alkali-activated slag formulations with different fly ash content, together with the presence of five admixtures (vinyl copolymer, …

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

Coal fly ash contains essential constituents for cement production, such as Ca, Si, Al, and Fe. Application of coal-fired ash to produce clinker at high doses may reduce the limestone content in the raw mix.

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Alkali and sulfate effects on mechanical properties and …

Scientific Reports - Alkali and sulfate effects on mechanical properties and microscopic mechanisms of slag and fly ash geopolymers Skip to main content Thank you for visiting nature.

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Final Report April 2015

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 execution and reporting.

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Evaluation on reactivity of fly ash from different sources in alkali

The aluminum content in fly ash is primarily found within the glassy phase and various crystalline constituents, including mullite and albite. ... reflecting the reactivity of fly ash in alkali-activation processes, ranges from 4.52 to 24.90 in this work. The R value exhibits high predictive accuracy for estimating the strengths development of ...

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Properties of alkali-activated fly ash: high performance to lightweight

Alkali-activated lime fly ash pastes with high levels of fly ash in an alkali-activated system have been described by Shi (Citation 1996a, Citation 1996b). The alkali activation catalysis of hydration reaction in slags (which contain about 50% calcium) is reported with and without fly ash (Soong et al. Citation 2006 ).

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Setting, Strength, and Autogenous Shrinkage of Alkali …

This paper focuses on the development of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) paste mixtures in order to determine their suitability for making concretes. ... A negative linear …

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Coal fly ash alkalis content characterization by means of a full

Then, a long-term durability indicator of concrete could be the coal fly ash alkali content. Such alkali ions are provided by the Portland cement, but also by the coal fly ash when is used as a main cement constituent. In this work, fly ashes from the combustion of a South African coal were investigated. The scope of this paper is to deep in ...

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Effects of Composition Type and Activator on Fly Ash-Based Alkali

The optimum alkali-equivalent content in fly ash A was AE% = 7%, with the best compressive strength 38.58 MPa at 20% slag substitution amount. The mix proportion with the second-best compressive strength occurred in fly ash C, at AE% = 8%. The compressive strength was 36.63 MPa when the slag substitution amount was 20%.

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Workability, rheology, and geopolymerization of fly ash …

The effect of alkali dosage (A/F), water-binder ratio (w/b), and modulus (Ms) on the performance of fly ash geopolymer (FAG) was reported. The rheology of Na 2 SiO 3 /NaOH …

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High calcium fly ash-auto glass powder alkali-activated pastes

1. Introduction. Fly ash-based geopolymer is formed through the chemical reaction between the alkaline activator solutions and fly ash. Alkaline activators can be a combination of alkali hydroxide and alkali silicate, such as sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3).Geopolymer products are formed during the curing process achievable at low …

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Toughness study of polyacrylamide-modified slag/fly ash-based alkali

This study investigated the mechanical properties and toughness of slag/fly ash-based alkali-activated cementitious materials (AASF) by incorporating PAM with different molecular weights and dosages. ... The water-to-binder ratio was 0.45, the alkali content (Na 2 O as a percentage of the powder materials) was 8 %, and the activator modulus was ...

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Mechanical property and microstructure of fly ash-based …

Fly ash is a silicate glass body characterized by high silicon and aluminum content, and low calcium content, making it significantly less reactive compared to slag glass bodies with low silicon, high calcium, and moderate aluminum content. The glass network in fly ash contains a higher proportion of [SiO 4] 4-and [AlO 4] 5-ions, which ...

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Effects of Composition Type and Activator on Fly Ash-Based …

The optimum alkali-equivalent content in fly ash A was AE% = 7%, with the best compressive strength 38.58 MPa at 20% slag substitution amount. The mix proportion with the second-best …

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Fly ash properties, characterization, and applications: A review

Class F fly ash is pozzolanic brought out from either anthracite or bituminous burning of coal. The total amount of SiO 2, Al 2 O 3, and Fe 2 O 3 must be greater than 70%. …

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Evaluation of the Effect of Portland Cement Alkali Content, Fly Ash

Abstract. The effects of portland cement alkali content, and replacement of portland cement with Class F fly ash, slag, or silica fume on alkali-silica reactivity (ASR) were studied by measuring the expansion of mortar bars made with Pyrex glass and stored over water at 38°C. Expansions were negligible with portland cements having alkali contents of 0.40% Na2O …

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Thermally stimulated stiffening and fly ash's alkaline activation by …

This study demonstrates how the use of fly ash (FA) enables enhanced thermal stiffening, and rapid alkali-activation in the presence of portlandite (Ca(OH) 2, CH). In general, blends of CH and FA exhibit less structural build-up at low temperatures, but upon reaching a trigger temperature of 75 °C, these blends achieve rapid stiffening, at ...

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Alkali Content of Fly Ash – Measuring and Testing Strategies for …

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 …

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Fly ash properties, characterization, and applications: A review

The dispersion of fly ash in water results in an alkaline pH from 10 to 13. At high pH, ... 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 lower than 10% creating potential limitations in ...

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Synchronous hot-pressed metakaolin-fly ash based geopolymer

This is due to an increase in alkali content relative to the silica-alumina ratio, which effectively promotes the hydration reactions of SHPMFG, thereby enhancing its compressive strength. ... of modulus ratio and dosage of alkali-activated solution on the properties and micro-structural characteristics of alkali-activated fly ash mortars ...

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