Kaolin-based geopolymers: Effect of mechanical activation and curing process

Please cite this article in press as: B.B. Diffo Kenne, et al., Effect of the rate of calcination of kaolin on the properties of metakaolin-based geopolymers, J. Asian Ceram. Soc. (2014), http://dx. a b s t r a c tKaolin samples of the same mass were treated at 700 • C for the same duration of 30 min by varying the rate of calcination (1, 2.5, 5, 10, 15 and 20 • C/min) in order to obtain metakaolins which were used to produce geopolymers. Depending on the nature of each type of material, kaolin, metakaolins and geopolymers were characterized using thermal analysis, chemical analysis, XRD, FTIR, particle size distribution, specific surface area, bulk density, setting time and compressive strength. FTIR and XRD analyses showed that metakaolins except at 1 • C/min contained residual kaolinite whose quantity increased with the rate of calcination of kaolin and which influenced the characteristics of geopolymers. Thus as the rate of calcination of kaolin increased, the setting time increased (226 min (rate of 1 • C/min)-773 min (rate of 20 • C/min)) while the compressive strength reduced (49.4 MPa (rate of 1 • C/min)-20.8 MPa (rate of 20 • C/min)). From the obtained results the production of geopolymers having high compressive strength along with low setting time requires that the calcination of kaolin be carried out at a low rate.

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“…In fact geopolymers can be synthesized between kaolin and alkali activator solution. However, kaolinite always shows low reactivity [36,37].…”

Section: Ftirmentioning

confidence: 98%

Effect of the rate of calcination of kaolin on the properties of metakaolin-based geopolymers

Diffo

Elimbi

Cyr

et al. 2015

Journal of Asian Ceramic Societies

129

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“…The mechanical activation of fly-ash by milling was conducted in order to promote a decrease in particle size. According to Hounsi et al 33,36 , the decrease of particle size is related to an increase of the surface and, consequently, an increase of the contact area of the FA particles with the activator solutions. This promotes particle dissolution and the release of Si and Al rich species to the system, increasing the formation of the N-A-S-H gel.…”

Section: Mechanical Activation Of the Brazilian Fly-ashmentioning

confidence: 99%

Effect of Curing Temperature, Activator Solution Composition and Particle Size in Brazilian Fly-Ash Based Geopolymer Production

et al. 2019

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The geopolymer binder is a relatively new class of inorganic binding material of elevated mechanical strength and good chemical properties. This can be produced using clay minerals or byproducts of the industrial processes, such as metakaolin, fly-ash and blast furnace slag. In this work, geopolymers were produced by alkaline activation of a Brazilian fly-ash with simple and compound solutions (NaOH and NaOH + Na 2 SiO 3). The hardened specimens presented values of the mechanical strength close to 48 MPa when the activator used presented SiO 2 /Na 2 O ration close to 1.0 after 24 h of curing at 65 °C. The increase of the temperature to 90 °C favored the reactions of the N-AS -H gel (geopolymer) formation and compression strength increased to values close to 90 MPa after 24 h. It has been found that physical properties, such as density and porosity, varied when different SiO 2 /Na 2 O rations was present in alkaline solutions. Time, temperature of curing and particle size of fly-ash modified the mechanical and physical proprieties of hardened inorganic binder. Was observed the diffraction phases related to zeolitic phases and carbonate new bands of absorption were related to reactions of Na2O in excess with atmospheric CO 2. The variation of SiO 2 /Na 2 O modified the microstructural of the hardened specimens.

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“…Alkali-activated materials (geopolymers, alkali-activated fly ashes, slags) are a new type of binder that utilise industrial byproducts (fly ashes and slags), kaolin, rice husk ashes, different soils and so on (Bakharev et al, 1999;He et al, 2013;Hounsi et al, 2013;Steveson and Sagoe-Crentsil, 2005). The production of geopolymers results in lower carbon dioxide emissions, making these materials 'greener' than ordinary Portland cement (OPC) binders (McLellan et al, 2011;Papa et al, 2014;Turner and Collins, 2013;Van Deventer et al, 2010;Yang et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Temperature rise and initial shrinkage of alkali-activated fly ash cement pastes

Shekhovtsova

Kovtun

Kearsley

2016

Advances in Cement Research

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This paper reports on core temperature development and initial shrinkage of fly ash cement pastes activated with sodium hydroxide solution at different concentrations during elevated-temperature curing at 60°C. The results indicate that a high sodium hydroxide concentration might result in a substantial rise in the core temperature of samples, dependent on the mould size and ratio of paste to oven volume. An increase in alkali concentration was also found to increase the initial shrinkage of the pastes during elevated-temperature curing. Excessive initial shrinkage and temperature increase might lead to the appearance of internal stresses in the pastes, which can affect the material performance. mass of mould with sample after elevatedtemperature curing (g) m m mass of empty mould (g) T p peak temperature (°C) t p time of appearance of peak temperature after the start of elevated-temperature curing (min) Notation

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Kaolin-based geopolymers: Effect of mechanical activation and curing process

Cited by 88 publications

References 27 publications

Effect of the rate of calcination of kaolin on the properties of metakaolin-based geopolymers

Effect of the rate of calcination of kaolin on the properties of metakaolin-based geopolymers

Effect of Curing Temperature, Activator Solution Composition and Particle Size in Brazilian Fly-Ash Based Geopolymer Production

Temperature rise and initial shrinkage of alkali-activated fly ash cement pastes

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