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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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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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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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 …

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

The main obstacle to advancing FA-based printable formulations is the low rate of structural build-up during curing and inadequate mechanical properties in the hardened state due to the low reactivity of fly ash (FA) [[16], [17], [18], [19]].To improve the early structural build-up of alkali-activated fly ash (AAF) mixtures, portlandite (Ca(OH)₂, CH) can be incorporated.

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Bond between alkali-activated steel slag/fly ash lightweight …

The effects of SS on the bond strength and the microstructure of the interface between alkali-activated SS/fly ash (FA) lightweight mortar (ASFm) and concrete substrates was studied. The SS contents, namely, the mass ratio of SS to the summation of FA and SS, were 0 %, 20 %, 40 %, 60 %, and 80 %. ... This phenomenon is principally attributed to ...

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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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Influence of the Fly Ash Content on the Fresh and Hardened

A study on the influence of the inclusion of slag or fly ash and five types of superplasticizers on the fresh and hardened properties of alkali-activated cements is presented. Three alkali-activated slag formulations with different fly ash content (0, 15, and 30%) in the presence of five admixtures (vinyl copolymer, melamine, and three polycarboxylates with …

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

Fly ash and granulated blast furnace slag contain abundant volcanic ash components such as calcium oxide, silicon dioxide, and aluminum oxide. Fly ash also contains a large amount of …

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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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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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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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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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Evaluation and beneficiation of high sulfur and high alkali fly …

Low alkali and low calcium fly ash is often used for the prevention of ASR [23], [24]. For this purpose, the standard guide for ASR mitigation, ASTM C1778 [23], recommends the use of fly ash with alkali content (Na 2 O eq) less than 4.0% and prefers fly ashes with alkali content less than 3.0%. HSAFA typically contains alkali contents well ...

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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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Effect and mechanism of the salt-alkali composite for the …

Mechanical model and strength development evolution of high content fly ash–cement grouting material. Constr. Build. Mater., 398 ... early-age hydration and microstructure of alkali-activated GGBFS-Fly ash-limestone mixtures. Cem. Concr. Compos., 124 (2021), Article 104244, 10.1016/j.cemconcomp.2021.104244. View PDF View article View in ...

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Effects of fly ash and lithium compounds on the water-soluble alkali

This study uses fly ash to replace partial cement. NaOH is used to increase alkali content of cement to 1.0% Na 2 O eq.LiOH and LiNO 3 are added separately to obtain several Li/(Na + K) molar ratios to fabricate cement specimens cured at 38 °C in a relative humidity environment. This study aims to observe the diachronic changes of water-soluble alkali and …

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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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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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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-Silica potential in fly-ash-based geopolymer concrete

The production of OPC requires up to 95% clinker content, which is a major contributor to the world's carbon dioxide ... Yang M, Paudel SR, Asa E (2020) Comparison of pore structure in alkali-activated fly ash geopolymer and ordinary concrete due to alkali-silica reaction using micro-computed tomography. Constr Build Mater 236:117524.

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Influence of the Fly Ash Content on the Fresh and …

A study on the influence of the inclusion of slag or fly ash and five types of superplasticizers on the fresh and hardened properties of alkali-activated cements is presented. Three alkali-activated slag formulations with different fly …

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

The addition of slag as a secondary precursor in fly ash-based alkali-activated materials contributed to the refinement of pore structure and thus restricted the transport of chloride ions in the concrete [28]. ... It meant that the chloride permeability resistance of AAFS concretes decreased with an increase in the content of fly ash.

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Deterioration mechanism of alkali-activated slag and fly ash …

When the fly ash content or alkali dosage was too high, fly ash cannot be activated properly and excessive moisture was consumed, reducing the overall density. The internal pore structure was more susceptible to frost heave forces during freeze-thaw cycles, resulting in a faster decline in the relative dynamic modulus [ 33 ].

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Evaluation on reactivity of fly ash from different sources in alkali

Fly ash has good pozzolanic activity and contains reactive Al and Si components, it has the potential to dissolve under alkaline conditions to form a dense green gel, i.e. alkali …

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