Effect of the addition of ammonium molybdate on metakaolin-based geopolymer formation: Shrinkage and crystallization

Vidal, L.; Joussein, Emmanuel; Colas, Maggy; Absi, Joseph; Rossignol, Sylvie

doi:10.1016/j.powtec.2015.02.012

Cited by 17 publications

(4 citation statements)

References 44 publications

(57 reference statements)

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“…The complementarity of the experimental techniques used in this study allowed us to highlight the thermal variation, and stability, of the mineral matrix of the geopolymer despite its amorphous nature. It should be noted that even if above 900°C the material crystallizes into kalsilite, then leucite, it retains its overall mechanical properties and physical integrity up to 1400°C 58 …”

Section: Discussionmentioning

confidence: 99%

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Temperature stability of a pure metakaolin based K‐geopolymer: Part 1. Variations in the amorphous mineral network

et al. 2020

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The thermal behavior of a model MK based K‐geopolymer (Si/Al = 1.38 and K/Al = 0.68; obtained by alkaline activation of a very pure metakaolin) was investigated between room temperature and 1400°C in order to evaluate its potentiality for high‐temperature applications. The purpose of our study was to monitor the behavior of a geopolymer during a temperature rise in order to better understand its variations with respect to temperature. The works from the present paper focus only variations in the internal structure of the mineral matrix. The results presented here show that the amorphous mineral matrix is preserved up to 900°C. The results also show that there is a densification of the internal structure of tetrahedral network during heating, due to changes in the Q3 environments in fully‐connected Q4 for both silicates and aluminates. Thus, our work provides a new more precise vision of the 3D geopolymeric mineral matrix for which the silicoaluminous network is not exclusively composed of Q4 entities, contrary to what is frequently encountered in the literature before.

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Section: Discussionmentioning

confidence: 99%

“…It should be noted that even if above 900°C the material crystallizes into kalsilite, then leucite, it retains its overall mechanical properties and physical integrity up to 1400°C. 58…”

Section: Geopolymer Thermal Stabilitymentioning

confidence: 99%

Temperature stability of a pure metakaolin based K‐geopolymer: Part 1. Variations in the amorphous mineral network

et al. 2020

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“…What is more, the hydration sphere, total cation, and stability of aluminium species are stated to be key factors affecting the sensitivity of geopolymers with a metakaolin dependent ambient temperature drying shrinkage. The supplement of a minute quantity up to 1.6% ammonium molybdate slims down of shrinkage at higher temperature [79]. Geopolymers manufactured by sand do not found pursue the predictable tendency concerning shrinkage as well as a supplement of an around 10% sand do not allow the disintegration of specimens upon when subjected to thermal action at 110 • C [80].…”

Section: Introductionmentioning

confidence: 90%

Fire Resistance Behaviour of Geopolymer Concrete: An Overview

2021

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Even though, an innovative inorganic family of geopolymer concretes are eye-catching potential building materials, it is quite essential to comprehend the fire and thermal resistance of these structural materials at a very high temperature and also when experiencing fire with a view to make certain not only the safety and security of lives and properties but also to establish them as more sustainable edifice materials for future. The experimental and field observations of degree of cracking, spalling and loss of strength within the geopolymer concretes subsequent to exposure at elevated temperature and incidences of occurrences of disastrous fires extend an indication of their resistance against such severely catastrophic conditions. The impact of heat and fire on mechanical attributes viz., mechanical-compressive strength, flexural behavior, elastic modulus; durability—thermal shrinkage; chemical stability; the impact of thermal creep on compressive strength; and microstructure properties—XRD, FTIR, NMR, SEM as well as physico-chemical modifications of geopolymer composites subsequent to their exposures at elevated temperatures is reviewed in depth. The present scientific state-of-the-art review manuscript aimed to assess the fire and thermal resistance of geopolymer concrete along with its thermo-chemistry at a towering temperature in order to introduce this novel, most modern, user and eco-benign construction materials as potentially promising, sustainable, durable, thermal and fire-resistant building materials promoting their optimal and apposite applications for construction and infrastructure industries.

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“…Composite systems of alkali activated fly ash and slag have better performance than any single system [ 23 , 24 ]. When the slag content is more than 0.7, the setting time decreases significantly, while the shrinkage cracks on the surface of the specimen increase [ 25 , 26 ]. Research has shown that increasing the content of fly ash in fly ash slag mixed cementitious material will prolong the setting time, reduce the drying shrinkage and compressive strength, and improve the processing performance.…”

Section: Introductionmentioning

confidence: 99%

Experimental Research on Mechanical and Shrinkage Properties of Alkali Activated Low-Carbon Green Concrete

Gao

Huang

et al. 2022

Materials

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This paper describes orthogonal experiments to investigat the effects of content of fly ash and slag, sol ratio, modulus of sodium silicate and expander on the compressive strength and shrinkage of alkali activated low-carbon green concrete (AAGC) of different ages. The microstructures and hydration product compositions of AAGC with different proportions were further studied by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Mercury Intrusion Porosimetry (MIP). The results show that with an increase of fly ash content, the compressive strength of AAGC gradually decreases, the decline of compressive strength at 28 d is smaller than that of 7 d, and the shrinkage strain gradually increases at 28 d. As the sol ratio increases, the compressive strength increases first and then decreases. When the sol ratio is 0.42, the compressive strength is maximal at 28 d; the same is true for compressive strength at 7 d. Additionally, an increase of sol ratio can reduce the shrinkage strain at 28 d. Finally, when the sol ratio was 0.46, the shrinkage decreased by 30.5% compared with 0.40 at 28 d. As the modulus of sodium silicate (Ms) increases, the compressive strength first increases and then decreases. When Ms is 1.4, the compressive strength reaches the maximum. As Ms increases, the shrinkage strain decreases first and then increases at 28 d. When Ms is 1.0, the shrinkage strain is the maximum at 28 d. Finally, with an increase in the content of expander, the compressive strength decreases at 7 d and 28 d, and the shrinkage strain decreases at 28 d. The shrinkage strain at 28 d is the minimum with 9% content. AAGC mixed with a small amount of fly ash and expander has more hydration products and significantly reduced cracks. In addition, the proportion of small hole volume of AAGC increases, while the proportion of large hole volume decreases. AAGC mixed with fly ash and slag without expander has more unhydrated particles and its structure is loose.

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Effect of the addition of ammonium molybdate on metakaolin-based geopolymer formation: Shrinkage and crystallization

Cited by 17 publications

References 44 publications

Temperature stability of a pure metakaolin based K‐geopolymer: Part 1. Variations in the amorphous mineral network

Temperature stability of a pure metakaolin based K‐geopolymer: Part 1. Variations in the amorphous mineral network

Fire Resistance Behaviour of Geopolymer Concrete: An Overview

Experimental Research on Mechanical and Shrinkage Properties of Alkali Activated Low-Carbon Green Concrete

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