Potassium alkali concentration and heat treatment affected metakaolin-based geopolymer

Tippayasam, Chayanee; Balyore, Pongpob; Thavorniti, Parjaree; Kamseu, Elie; Leonelli, Cristina; Chindaprasirt, Prinya; Chaysuwan, Duangrudee

doi:10.1016/j.conbuildmat.2015.11.027

Cited by 58 publications

(15 citation statements)

References 22 publications

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“…After geopolymerization, the chemical environment around regular arranged chain structures of the Si-O bond altered, along with the formation of Al-O-Si bonds. Subsequently, the strong asymmetrical stretching vibration peak of the Si-O bond in metakaolin (1100 cm −1 ) all shifted to a lower wavenumber (to 1010 cm −1 ) for all the curing temperatures [ 31 ]. This indicated that the solidification process of the geopolymer is also a chemical reaction, with the generation of a new substance.…”

Section: Resultsmentioning

confidence: 99%

Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer

et al. 2016

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The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was found that the optimal geopolymer was prepared with metakaolin, sodium hydroxide, sodium silicate and water, with the molar ratio of SiO2:Al2O3:Na2O:NaOH:H2O being 3.4:1.1:0.5:1.0:11.8. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were adopted to investigate the influence of curing conditions on the mechanical properties and microstructures of the geopolymers. The best curing condition was 60 °C for 168 h, and this alkali activated metakaolin-based geopolymer showed the highest compression strength at 52.26 MPa. In addition, hollow micro-sphere glass beads were mixed with metakaolin particles to improve the thermal insulation properties of the alkali activated metakaolin-based geopolymer. These results suggest that a suitable volume ratio of metakaolin to hollow micro-sphere glass beads in alkali activated metakaolin-based geopolymers was 6:1, which achieved a thermal conductivity of 0.37 W/mK and compressive strength of 50 MPa. By adjusting to a milder curing condition, as-prepared alkali activated metakaolin-based geopolymers could find widespread applications in concrete thermal protection.

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Section: Resultsmentioning

confidence: 99%

Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer

et al. 2016

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“…The alkaline solution used was a mixture of required amounts of potassium silicate and aqueous solution of potassium hydroxide (10 M). The silica modulus (Ms) or molar ratio of SiO 2 /K 2 O and H 2 O/K 2 O were fixed at 1.55 and 13.27, respectively [27,28]. This solution was prepared 1 h before use to enable equilibration and cooling.…”

Section: Preparation Of the Alkali-silicate Activatormentioning

confidence: 99%

Mechanical and microstructural properties of geopolymer mortars from meta-halloysite: effect of titanium dioxide TiO2 (anatase and rutile) content

et al. 2020

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This study aimed to investigate the effect of Titanium Dioxide TiO 2 (anatase and rutile) on mechanical and microstructural properties of meta-halloysite based geopolymer mortars namely GMHA and GMHR series. Meta-halloysite received 2.5, 5.0, 7.5 and 10 wt% of anatase or rutile as addition before calcination and geopolymerization. The raw materials and the end products were characterized using XRD, FTIR, ESEM and MIP analyses. The flexural strength increases from 6.90 to 9.13 MPa and from 6.90 to 12.33 MPa for GMHA and GMHR series respectively. The cumulative pore volume decreases from 102.2 to 84.2 mm 3 g −1 and from 102.2 to 51.3 mm 3 g −1 for GMHA and GMHR products respectively. Both matrices present micrographs with very low capillaries pores and fractured surfaces that confirmed the enhancement of the mechanical properties. It was concluded that TiO 2 in both forms is beneficial for the reduction of porosity and densification of geopolymer matrices. Rutile enabled more compact and denser geopolymer structure compared to anatase. The aforementioned results showed the efficiency of both fine TiO 2 particles to improve the geopolymer network significant for its durability.

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“…In other words, absorption peak of the Si–O bonds turned into low wave numbers with the increment of NaOH molar concentration, which suggests a lengthening of the Si–O bond, a reduction in the bond angle. The regularly arranged chain structure of Si–O bonds was broken and silicon was replaced by aluminum to form Si–O–Al bonds in alkaline atmosphere [37]. In Figure 7 where the slag content was 30%, the interactions between SiO 2 and Al 2 O 3 enhance with the increase in CaO dosage and absorption peak of the Si–O bonds turned into low wave numbers with increase in slag content.…”

Section: Resultsmentioning

confidence: 99%

Preparation and Reaction Mechanism Characterization of Alkali-activated Coal Gangue–Slag Materials

Zhu

Cheng

et al. 2019

Materials

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In this paper, slag is used as a calcium source to make alkali-activated coal gangue–slag (AACGS) based material. The reaction mechanism of AACGS materials was discussed in depth by means of XRD, FT-IR, 29Si MAS-NMR (nuclear magnetic resonance) and SEM-EDS (energy dispersive spectrometer). The experimental results show that coal gangue can be used as a raw material for preparing alkali-activated materials. The liquid–solid ratio is the most influential factor on AACGS paste fluidity and strength, followed by slag content. As the modulus of sodium hydroxide increases, the depolymerization process of the reactant precursor is accelerated, but the high sodium hydroxide concentration inhibits the occurrence of the early coal gangue–slag polycondensation reaction, and exerts little effect on the 28 d compressive strength. Ca2+ in the slag promotes exchange with Na+, and the product is converted from N-A-S-H gel to C-(A)-S-H gel, and C-(A)-S-H is formed with higher Ca/Si ratio with the increase of slag content. The slight replacement of coal gangue by slag can greatly improve the reaction process and the strength of AACGS materials.

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Potassium alkali concentration and heat treatment affected metakaolin-based geopolymer

Cited by 58 publications

References 22 publications

Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer

Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer

Mechanical and microstructural properties of geopolymer mortars from meta-halloysite: effect of titanium dioxide TiO2 (anatase and rutile) content

Preparation and Reaction Mechanism Characterization of Alkali-activated Coal Gangue–Slag Materials

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