Assessment of pozzolanic activity of calcined coal-series kaolin

Liu, Yuanyuan; Lei, Shaomin; Lin, Min; Li, Yang; Zhao, Yupei; Fan, Yanming

doi:10.1016/j.clay.2017.03.038

Cited by 112 publications

(32 citation statements)

References 29 publications

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“…Thermal treatment of kaolin clays gives rise to formation of amorphous material which can produce reactive silicate and aluminate species. These species are capable of reacting with calcium hydroxide solution that forms during cement hydration to generate stable insoluble compounds (calcium-silicate-hydrate and calcium-aluminate-hydrate) which possesses cementitious properties [8,12,14,15]. Apart from CO 2 emission reduction, other advantages of substituting some portion of cement with metakaolin have been documented to include lower heat of hydration, higher density, improved strength and resistance to degradation mechanisms [11].…”

Section: Introductionmentioning

confidence: 99%

Characterization of raw and thermally treated Nigerian kaolinite-containing clays using instrumental techniques

et al. 2020

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Thermal behavior, surface area, oxide, mineralogical composition, and structural functional groups of raw and thermally treated five local kaolin clays [Ijero-Ekiti (IJ), Ikere-Ekiti (IK), Isan-Ekiti (IS), Abusoro (AB) and Odigbo (OD)] from two states in SouthWest Nigeria were studied in order to determine their potential uses. These properties were measured using thermogravimetric analysis coupled with differential thermal analysis (TGA/DTA), surface area and porosity analysis, X-ray fluorescence (XRF), X-Ray Diffractometry (XRD) and Fourier Transform infra-red spectroscopy (FTIR) respectively. The TGA/ DTA showed major mass losses and broad endothermic bands at temperatures 390-700 °C, which were associated with dehydroxylation of kaolinite and other clay minerals. Thermal treatment increased the surface area of the raw clays. The XRF results showed oxides of kaolinite, illite, quartz, feldspar, hematite, anatase and the phases were confirmed by XRD. The FTIR spectra displayed the characteristic absorption bands of the minerals. Combining the obtained results, Ijero-Ekiti clay was identified as feldspar (albite)-quartz containing clay, Ikere-Ekiti and Isan-Ekiti clays as kaolinite-dominated clays, Abusoro clay as kaolinite-illite-montmorillonite-containing clay and Odigbo clay as kaolinite-illite-containing clay. The TGA/DTA, XRD and FTIR indicated that crystalline kaolinite in the clays were converted into amorphous metakaolinite after thermal treatment. Based on the properties displayed, clays from IK, IS, AB and OD deposits can be thermally treated to form useful supplementary cementitious and geopolymer materials to make binders in building and construction while clay from IJ deposit can be a potential raw material for ceramic production.

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Section: Introductionmentioning

confidence: 99%

Characterization of raw and thermally treated Nigerian kaolinite-containing clays using instrumental techniques

et al. 2020

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“…The last effect was recorded in the DTA curve was exothermic peaks at 990 °C, which was related to recrystallization and mullite formation according to the following reaction: (2Al2O3⋅3SiO2) → 2(3Al2O3•2SiO2) + 5SiO2. The mullite formation reduced reactivity and pozzolanic characteristic of the calcined products [10].…”

Section: Characterization Of Waste Kaolinmentioning

confidence: 99%

Preliminary Investigation of Pozzolanic Properties of Calcined Waste Kaolin

Huang¹,

Deng²,

Wang³

et al. 2018

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Current research aims to investigate the influence of calcination temperature on the pozzolanic activity of the waste kaolin and the impact of calcination products on Portland cement hydration. The raw material with approximately 85 % kaolinite was calcined to temperatures ranging between 500 and 1000 °C. The clay and its calcined products were characterized by TGA-DTA, SEM-EDS, XRD, FT-IR and BET. The pozzolanic activity of the calcined products was assessed by electrical conductivity test and compressive strength in mortars with 30 % substitution of Portland cement. The effect of calcined products on Portland cement hydration was characterized by XRD and SEM. The results showed that the calcination temperature had an important influence on mineral phase transition and the pozzolanic activity of calcined products. The degree of disorder and pozzolanic activity of calcined products at 800 °C was the highest at temperatures ranging from 500 and 1000 °C. The impact of calcined products on the hydration of blended systems was a combination of a filler effect at early ages and the pozzolanic reaction at later. The experimental results indicated that calcined products of waste kaolin constituted a potential source of high reactivity pozzolanic materials.

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“…There have been numerous studies along these lines, both on the optimum conditions for activation processes in which inert materials taken from coal mining waste is transformed into a material with pozzolanic properties and on its behavior in binary cements (Alujas et al, 2015;Liu et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Influence of ZnO on the activation of kaolinite-based coal waste: Pozzolanic activity and mineralogy in the pozzolan/lime system

García-Giménez

Villa

Martínez-Ramírez

et al. 2018

Applied Clay Science

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One inconvenience presented by the thermal activation of kaolinite-based wastes is their low content of metakaolinite, a highly pozzolanic product listed in current standards for the manufacture of commercial cements. The addition of a chemical activator during the thermal activation process is a priority line of research to increase the reactivity of the recycled metakaolinite. In this paper, an additional chemical activator, ZnO, is studied and its effect on both pozzolanic properties and the evolution of mineralogical phases in the thermal activation of coal waste with a reaction time of up to 90 days in the pozzolan/lime system. To do so, activation temperatures of between 550ºC/650ºC were selected and additions of chemical activator (ZnO) in percentages of between 0.0% and 3.0% by weight of coal waste, because it is an activator with a positive effect on a 100% natural kaolinite. The results showed that the incorporation of ZnO inhibited the reactivity of the recycled metakaolinite and in consequence, the capacity of the metakaolinite to react with the surrounding lime; even more so when the content of added chemical activator was raised, albeit with some exceptions, in the samples activated at 550ºC and 650ºC with 0.5% of chemical activator. In none of the cases under analysis was the chemical activator able to improve the properties of the metakaolinite in comparison with the properties of the reference sample activated only with temperature. The hydrated phases that appeared in the pozzolanic reaction were tetracalcium aluminate hydrate, stratlingite, monosulfoaluminate hydrate and LDH (phyllosilicate/carbonate).

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Assessment of pozzolanic activity of calcined coal-series kaolin

Cited by 112 publications

References 29 publications

Characterization of raw and thermally treated Nigerian kaolinite-containing clays using instrumental techniques

Characterization of raw and thermally treated Nigerian kaolinite-containing clays using instrumental techniques

Preliminary Investigation of Pozzolanic Properties of Calcined Waste Kaolin

Influence of ZnO on the activation of kaolinite-based coal waste: Pozzolanic activity and mineralogy in the pozzolan/lime system

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