Interaction of metakaolin-phosphoric acid and their structural evolution at high temperature

Khabbouchi, Mohamed; Hosni, Khaled; Mezni, Mohamed; Zanelli, Chiara; Doggy, Mahmoud; Dondi, Michele; Srasra, Ezzeddine

doi:10.1016/j.clay.2017.07.006

Cited by 46 publications

(16 citation statements)

References 32 publications

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“…They reported that the formation of AlPO 4 at ambient temperatures is responsible for the high strength of the acidic activated cement, and it behaves as a binder, thus reinforcing the structure and enhancing the strength. This finding was also reported by Khabbouchi et al [25]; however, contrary to that of Tchakoute, berlinite was only present at elevated temperatures (750 °C, for 11 wt% P 2 O 5 and 250 °C for 17 wt% P 2 O 5 ).…”

Section: Introductionsupporting

confidence: 87%

Metakaolinite Phosphate Cementitious Matrix: Inorganic Polymer Obtained by Acidic Activation

et al. 2019

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This work aims to study an aluminosilicate phosphate cementitious matrix. The cementitious matrix was studied on paste samples. The synthesis of metakaolinite phosphate cement (MKPC) was investigated using calorimetric techniques. A systematic study was performed by emphasizing a broad range of Al/P molar ratios, covering the different behavior of the material to the extremes, as well as the optimum composition. X-ray diffraction and scanning electron microscopy revealed that the final structure was mainly an amorphous network, albeit with some non-reacted phases. The compressive strength was studied on mortars using a cement/sand ratio of 1:3. MKPC specimens with Al/P ratios close to 1/1 showed optimal behavior. MKPCs with Al/P ratios above 1/1 were characterized by high porosity and low strength, whereas MKPCs with Al/P < 1 contained an excess of phosphates. The influence of the Al/P molar ratio on compressive strength was also studied, reaching a maximum of 68 MPa for the optimum composition. Based on the results, MKPC may be a promising candidate for construction purposes.

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Section: Introductionsupporting

confidence: 87%

Metakaolinite Phosphate Cementitious Matrix: Inorganic Polymer Obtained by Acidic Activation

et al. 2019

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“…Other changes are the disappearance of the vibration band at 541 cm −1 and the appearance of the band at 713 cm −1 after heating. Similar changes were observed in previous work [16,17]. In this study, these changes are attributed to the crystallization of tridymite and phosphate minerals as shown in XRD patterns of geopolymer after heating at 1000 °C.…”

Section: Influence Of Phosphoric Acid Concentration On Mineralogy At supporting

confidence: 90%

“…Also, phosphoric acid activation of synthetic Al 2 O 3 -2SiO 2 powders showed extremely high thermal stability of phases with no sign of melting up to 1550 °C [15]. Recent work reported that the structural evolution of phases with temperature and their stability depend on the phosphate content of the matrix [16]. However, MK-based phosphate geopolymers have low thermal stability in terms of compressive strength evolution.…”

Section: Introductionmentioning

confidence: 99%

Phase and dimensional stability of volcanic ash-based phosphate inorganic polymers at elevated temperatures

Djobo

Elimbi

2020

SN Appl. Sci.

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Phosphate geopolymers are part of chemically bonded phosphate cements obtained from an aluminosilicate and phosphate solution. Their structure consisting of phosphate bonds makes them suitable for use as refractory material. This study deals with the influence of phosphoric acid concentration (6, 8 and 10 mol/L) on the stability of volcanic ash-based phosphate geopolymers exposed to 100, 600 and 1000 °C. The results reveal that the onset of crystallization is about 600 °C with the formation of aluminum phosphate (V) and tridymite, then crystallization of iron (III) phosphate (V) and hematite at 1000 °C. The degree of crystallization of these phases increases with phosphoric acid concentration. The geopolymers obtained with 8 mol/L of phosphoric acid showed the best thermal stability at 1000 °C in terms of compressive strength change. The maximum thermal linear shrinkage recorded was 3%. The major phases of all geopolymers remain stable up to 1000 °C, after which the melting of phases happens.

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“…According to some authors [ 11 , 12 ], the consolidated geopolymer is constituted of a tridimensional [Si-O-P-O-Al] network whereas others suggested [7,10] that it is composed of Temperature-dependant studies demonstrated the formation, starting from 250°C, of AlPO 4 polymorphs, crystalline SiO 2 and phosphosilicates in the case of high Si/P ratios [12,13].…”

Section: Introductionmentioning

confidence: 99%

Acid-based geopolymers: Understanding of the structural evolutions during consolidation and after thermal treatments

Mathivet

Jouin

Gharzouni

et al. 2019

Journal of Non-Crystalline Solids

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Materials such as ceramic matrix composites are developed for mechanical applications at high temperature, but their cost remains a limitation. Consequently, the use of acid-based geopolymer matrices may be an alternative to reduce costs. In this study, the sample was prepared from metakaolin and phosphoric acid. FTIR and NMR spectroscopies, XRD and thermal measurements were used to understand the structural evolution of acid-based geopolymers (binders) during consolidation and after thermal treatments. According to the results, the consolidation of the binder has been divided into four steps: the dissolution of the metakaolin, the polycondensation reactions forming AlPO 4 entities and hydrated phases, the breakdown of Si-O-Al bonds with formation of various hydrated silica *Manuscript Click here to download Manuscript: manuscript.docx Click here to view linked References

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Interaction of metakaolin-phosphoric acid and their structural evolution at high temperature

Cited by 46 publications

References 32 publications

Metakaolinite Phosphate Cementitious Matrix: Inorganic Polymer Obtained by Acidic Activation

Metakaolinite Phosphate Cementitious Matrix: Inorganic Polymer Obtained by Acidic Activation

Phase and dimensional stability of volcanic ash-based phosphate inorganic polymers at elevated temperatures

Acid-based geopolymers: Understanding of the structural evolutions during consolidation and after thermal treatments

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