Fresh and hardened properties of alkali-activated fly ash/slag pastes with superplasticizers

Jang, Jeong Gook; Lee, Namkon; Lee, Haeng‐Ki

doi:10.1016/j.conbuildmat.2013.09.048

Cited by 255 publications

(118 citation statements)

References 21 publications

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“…There are a few published studies on geopolymer mixes with a variant combination of FA and GGBS in the mixture [9,16,17,[23][24][25] and in most of these studies promising results were achieved. However, in these studies high volumes and concentrations of corrosive sodium silicate and/or sodium hydroxide have been used leading to geopolymer products with potential health and worker safety issues during application [14].…”

Section: Introductionmentioning

confidence: 99%

“…4 indicate that the setting time was considerably affected by the GGBS content in the mix. Based on a previous study [24], the setting time for FA based geopolymer without GGBS has been found to be around 1500 minutes. Setting time was significantly reduced by incorporating GGBS in the mixture, e.g.…”

Section: Setting Timementioning

confidence: 99%

“…4 indicate that the setting time was considerably affected by the GGBS content in the mix. Based on a previous study [24], the setting time for FA based …”

mentioning

confidence: 99%

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Development of geopolymer mortar under ambient temperature for in situ applications

Al-Majidi

Λαμπρόπουλος

Cundy

et al. 2016

Construction and Building Materials

266

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Geopolymer concrete technology involves production of more environmentally friendly waste material-based concrete which could be a viable solution for conventional concrete replacement. Typical fly ash-based geopolymer concrete however requires high temperature curing treatment in order to develop sufficient early strength properties, which is considered a severe limitation for cast-in-place concrete applications. Most previous studies on geopolymer concrete have focused on the properties of concretes pre-hardened by heat curing and/ or by aggressive chemical treatment (e.g. alkali activation using concentrated sodium hydroxide (NaOH)). The current study presents an extensive experimental investigation on the mechanical and microstructural properties of geopolymer concrete mixes prepared with a combination of fly ash and slag cured under ambient temperature. 'User friendly' geopolymer mixes were produced using fly ash (FA) and Ground Granulated Blast furnace Slag (GGBS) mixed together with potassium silicate with molar ratio equal to 1.2 (as the activator) and water. The results indicated that heat curing treatment can be avoided by partial replacement of fly ash with slag. The compressive strength of the examined mixes was found to be in the range of 40-50MPa for 40 % and 50 % GGBS replacement mixtures respectively. Moreover, the flexural and direct tensile strengths of geopolymer mixes are considerably improved as the GGBS content is increased.Based on FTIR and SEM/EDS analysis, the inclusion of a higher content of GGBS resulted in a denser structure by formation of more hydration products.Keywords: Fly ash, slag, ambient temperature, user friendly geopolymer mortar *Manuscript Click here to view linked References 2 IntroductionThere are many environmental issues associated with the production of Ordinary Portland cement (OPC), such as consumption of 5% of natural resources, and generation of 5-7 % of total global anthropogenic carbon dioxide emissions [1][2][3][4]. This has led to an urgent need for the development of alternative materials that may provide technically viable alternative solutions to conventional cementitious concrete, with more favourable environmental credentials. Geopolymer concrete manufacture is one of the most promising techniques which has been developed in the last few years. Utilization of geopolymer materials can reduce 80% of greenhouse gas emissions associated with material production, and overcome issues related to cement production and unregulated disposal of industrial materials by recycling these materials in geopolymer manufacture [5][6][7].Geopolymers are inorganic by-product materials, rich in silicon (Si) and aluminium Five different mixtures of geopolymer mortar proportions were examined with various ratios of GGBS to total binder (10%, 20%, 30%, 40% and 50 %, Table 2). Based on preliminary experimental studies undertaken during the current project, the optimum mix design (in terms of mechanical strength and workability) was achieved using water, alkaline activator...

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Section: Introductionmentioning

confidence: 99%

Section: Setting Timementioning

confidence: 99%

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Development of geopolymer mortar under ambient temperature for in situ applications

Al-Majidi

Λαμπρόπουλος

Cundy

et al. 2016

Construction and Building Materials

266

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“…반면, CFBC 보일러에서 발생하 는 석탄재는 탈황 과정에서 투입하는 석회석에 의해 유 리 석회(Free CaO)와 무수석고의 함량이 풍부하고 물질 자체가 자경성을 가지는 것을 특징으로 한다 6,7) . PCC 방식과 CFBC 방식에서 발생하는 석탄재는 주로 시멘 트 · 콘크리트 분야, 토목·건설 분야에서 재활용되거나 관련 연구가 활발히 진행 중에 있다 2,[8][9][10][11][12] . 국내에는 가행광산과 휴·폐광산을 합하여 약 5000개 이상의 광산이 존재하며, 이 중 지하 공동이 존재하는 광산은 약 2000개 이상으로 추정되고 있다 13) .…”

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Utilization of Circulating Fluidized Bed Combustion Ash and Related Specifications for Mine Backfills

Jang¹,

Ji²,

Ahn³

2017

Journal of the Korean Institute of Resources Recycling

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Circulating fluidized bed combustion (CFBC) ash is one of useful mineralogical resources having abundant content of free lime and anhydrite, and has a self-cementitious property. Recently, considerable interest has been gained regarding the utilization of CFBC ash, along with its use in mine backfill and reclamation. Prior to adopt the use of CFBC ash in the mine backfill technology, discussion on the technology and related specification is prerequisite in the future. This paper presents a review on studies in the emerging technology of CFBC ash utilization, and provides useful information with regard to the specifications for mine backfills utilizing CFBC ash.

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“…In contrast, silica fume incorporation reduces workability of fresh mortar, and thus requires the addition of an agent to improve workability [54]. Poly-carboxylate based agents are a type of water-reducing admixtures able to improve workability and mechanical properties of geopolymer [55][56]. In addition, drying shrinkage is an important part of alkali-activated slag in early stages and is a critical parameter for durability design of structures [4;57].…”

Section: Introductionmentioning

confidence: 99%

Effect of GGBFS and Micro-Silica on Mechanical Properties, Shrinkage and Microstructure of Alkali-Activated Fly Ash Mortar

Tajunnisa¹

2017

GEOMATE

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Performance of drying shrinkage, flow rate, mechanical properties, and microstructure of three materials -alkali-activated fly ash (FA); ground granulated blast-furnaced slag (GGBFS); and un-densified micro-silica (M) are investigated. Mixtures used herein are referred to as AAM -alkali activated materialsof four types according to composition: AAM-IV, AAM-V, AAM-VI and AAM-VII (note: types 1 through 3 were investigated in previous research) with corresponding mixture FA, GGBFS and M ratios of 47.5/47.5/5, 45/45/10, 42.5/42.5/15, 40/40/20 by weight percentage. The AAM samples were air-cured under a sealed condition for 6 days followed by unsealed curing up to the test at 18-20° C and a low relative humidity of 30-50%. The samples AAM-IV through VII were composed of a progressive decrease of fly ash and GGBFS and an increase in M content. Results show that flow rate and compressive strength increased from AAM-IV to AAM-VI; contrarily, it decreased in AAM-VII. Both flexural strength -a positive aspect -and drying shrinkage -negative as it leads to cracking -increased in all samples. Incorporation of both GGBFS and M in alkaliactivated fly ash mortar was found to improve performance compared to that incorporated solely of GGBFS in alkali-activated fly ash. The incorporation of M of certain values improves strength and flowability of AAM; conversely, it results in a higher drying shrinkage value, which leads to increased cracking. SEM and XRD results confirm these results. Unreacted particles of AAM-VI and AAM-VII appear to act as a 'microaggregate,' resulting in increased compressive and flexural strength.

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Fresh and hardened properties of alkali-activated fly ash/slag pastes with superplasticizers

Cited by 255 publications

References 21 publications

Development of geopolymer mortar under ambient temperature for in situ applications

Development of geopolymer mortar under ambient temperature for in situ applications

Utilization of Circulating Fluidized Bed Combustion Ash and Related Specifications for Mine Backfills

Effect of GGBFS and Micro-Silica on Mechanical Properties, Shrinkage and Microstructure of Alkali-Activated Fly Ash Mortar

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