Structure and properties of new eco-material obtained by phosphoric acid attack of natural Tunisian clay

Louati, S.; Hajjaji, W.; Baklouti, Samir; Samet, B.

doi:10.1016/j.clay.2014.07.015

Cited by 86 publications

(33 citation statements)

References 21 publications

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“…Louati et al [12], although they all used H3PO4 without additional Al to activate the aluminosilicate precursors for synthesis of silico-aluminophosphate geopolymers. These spectral changes can be attributed to the effect of phosphate activation on the MK particles.…”

Section: X-ray Diffractionmentioning

confidence: 99%

“…The last phase transition was the formation of mullite from residual, fully dehydroxylated MK particles at 980 to 1010 ºC [44], and is especially prominent in the raw MK particles. For all geopolymer samples, such a peak is less significant, indicating that the raw MK particles had reacted with the phosphate activating solution to synthesize new gels: silico-alumino-phosphate (S-A-P) gel [16] and amorphous or semi-crystalline aluminum phosphate compounds [12,17].…”

Section: Thermogravimetrymentioning

confidence: 99%

“…However, an alternative activation approach for the aluminosilicate sources is phosphate activation [9,10], which involves an analogous acid-activated reaction process involving phosphoric acid. The mechanism of phosphate-activated geopolymerization starts with the dealumination of the aluminosilicate source (i.e., dealumination reaction) into the acidic aqueous environment, following the polycondensation of free aluminate, silicate, and phosphate units to generate Si-O-Al, Si-O-P and/or Al-O-P bonds in silico-alumino-phosphate (S-A-P) gels [11,12]; the structures of these gels are far from fully understood, and the chemical details of the mechanisms involved require further investigation.…”

Section: Introductionmentioning

confidence: 99%

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Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers

Wang

Provis

Dai

2018

Cement and Concrete Composites

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An aluminosilicate precursor, such as metakaolin, can be transformed into a cement-like geopolymer binder via a phosphate activation approach. This paper identifies the effect of the addition of aluminum species into the phosphate activating solution on the formation of such geopolymers, from the fresh to the hardened state. Activating solutions with Al/P molar ratios of 0, 0.1, and 0.3 were prepared by blending monoaluminum phosphate (MAP) and orthophosphoric acid (OPA). The rheological properties, fluidity, and setting times of the fresh geopolymer pastes and the compressive strength of the hardened geopolymer matrices were studied. Liquid-state 27 Al and 31 P nuclear magnetic resonance (NMR) measurements for the chemical environments of Al and P, and spectroscopic, thermal, and microscopic analyses revealed that the soluble aluminum in the phosphate activating solution played an important role during the geopolymerization process. Seeding of aluminum species through inclusion in the activating solution allowed a rapid sol/gel transition that improved the rheological properties and setting time of the fresh geopolymer pastes at ambient temperature. However, although the increased concentration of aluminum phosphate oligomers promoted by the soluble aluminum addition contributed to the formation of a compact matrix with high early strength, it hinders the ongoing reaction of metakaolin in the later period, which has a detrimental influence on ongoing strength development beyond 7 days of curing.

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Section: X-ray Diffractionmentioning

confidence: 99%

Section: Thermogravimetrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers

Wang

Provis

Dai

2018

Cement and Concrete Composites

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“…Previous research showed that the updated Si-O-Al linkage (i.e., Al-O-P) can balance the charge due to the aluminum chemical shift ranging from octahedral or/and pentahedral coordination to tetradentate form (Cao et al, 2005). However, many studies indicated that the hexa-coordinated aluminum dominates in SAP geopolymers (Davidovits, 2011;Louati et al, 2014Louati et al, , 2016. It should be noted that an amorphous Si-Al-P structure was reported in AAS geopolymer wherein the tetrahedral P was identified to occupy a proportion of site of silicate .…”

Section: Sap Geopolymermentioning

confidence: 99%

“…Besides, the natural aluminosilicate materials like Tunisian clay and metakaolin were also investigated when activated by phosphate acid with various Si/P molar ratios (Douiri et al, 2014;Louati et al, 2014). A shift in the wide broad band from 18-30 • (2θ) to 22-35 • (2θ) was observed in both calcined clay and synthesized geopolymers, as well as the diffraction intensity changed in some crystalline peaks e.g., aluminum phosphate (AlPO 4 ), augelite (Al 2 (PO 4 )(OH) 3 ), and monetite (CaHPO 4 ).…”

Section: Sap Geopolymermentioning

confidence: 99%

Silico-Aluminophosphate and Alkali-Aluminosilicate Geopolymers: A Comparative Review

2019

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Chemically activated materials (often termed as geopolymer) have received attracting attentions in civil, material and environmental research fields as a toolkit alternative to traditional Portland cement in specific applications. This paper presents a comparative review on silico-aluminophosphate (SAP) geopolymers in terms of definition, chemistries involved during geopolymerization, mechanical performance, durability, environmental impacts, and their potentials in applications relative to conventional alkali-aluminosilicate (AAS) geopolymers. Recommendations for future applications are also highlighted. It is found that S-A-P gels with six-coordinated aluminum environment dominate in SAP geopolymers, while the aluminum in N-A-S-H gels formed in the AAS geopolymers is characterized by four-coordinated features. Besides, the slow performance development of SAP geopolymer matrix under ambient temperature curing can be compensated through incorporating additional countermeasures (e.g., metal sources) which allow the tailored design of such geopolymers for certain in-situ applications. Generally, the calcium-bearing C-(A)-S-H gels co-existing with N-A-S-H gels are dominant in AAS geopolymers, while the S-A-P gels enhanced by phosphate-containing crystalline/amorphous phases are the main products in SAP geopolymers. The SAP geopolymers show their environmental friendliness relative to the AAS geopolymers due to the utilization of phosphate activators that require lower production energy relative to silicate-containing activators. However, the higher cost of phosphate activators may confine the applications of SAP geopolymers in some exquisite or special fields.

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Screening of Factors Influencing Phosphate-Based Geopolymers Consolidation Time, Using Plackett-Burman Design

Zribi¹,

Samet²,

Baklouti³

2019

Lecture Notes in Mechanical Engineering

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Structure and properties of new eco-material obtained by phosphoric acid attack of natural Tunisian clay

Cited by 86 publications

References 21 publications

Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers

Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers

Silico-Aluminophosphate and Alkali-Aluminosilicate Geopolymers: A Comparative Review

Screening of Factors Influencing Phosphate-Based Geopolymers Consolidation Time, Using Plackett-Burman Design

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