The role of curing temperature and reactive aluminum species on characteristics of phosphate geopolymer

Djobo, Jean Noël Yankwa; Moustapha,; Ndjonnou, L P T; Etame, K K; Stephan, Dietmar

doi:10.1039/d2ra04562a

Cited by 12 publications

(11 citation statements)

References 35 publications

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“…That trend has been observed in the literature with other type of raw materials where heat curing was less beneficial for 28 d strength than room temperature curing 6,28 . That was explained to be due to the type of reaction mechanism ongoing which corresponds to the dissolution‐inhibition‐precipitation for the calcium modified phosphate geopolymer and dissolution‐enhancement‐precipitation for the controle phosphate geopolymer 11,29,30 . Further in the calcium modified phosphate geopolymer series, the type of phase formed can also forster that behavior.…”

Section: Discussionsupporting

confidence: 64%

“…6,28 That was explained to be due to the type of reaction mechanism ongoing which corresponds to the dissolution-inhibition-precipitation for the calcium modified phosphate geopolymer and dissolutionenhancement-precipitation for the controle phosphate geopolymer. 11,29,30 Further in the calcium modified phosphate geopolymer series, the type of phase formed can also forster that behavior. This holds as CH is soluble in high pH, and the results show that as the dosage of CH increased, the pH also increased rapidly because of the neutralization reaction.…”

Section: Discussionmentioning

confidence: 99%

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Early age properties and water resistance of calcium hydroxide modified volcanic ash‐based phosphate geopolymer binders

Djobo,

Hirsch,

Stephan

2023

Int J Ceramic Engine & Sci

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This work aims to improve the early age characteristics and water resistance of volcanic ash‐based phosphate geopolymer materials by modifying the chemistry of the binder with calcium hydroxide (CH). Phosphate geopolymer binders with Ca/P molar ratios ranging from 0.49 to 0.80 were prepared. Then the early and late age physical properties were then determined. The hardened binder was characterized by various analytical techniques involving XRD, TGA‐DSC and SEM‐EDS. The results showed that the use of CH decreases the initial setting time from several hours to less than 5 min. At the same time, the 1 d compressive strength was increased from 0 to 15 MPa with the increase in the Ca/P molar ratio. Moreover, the slow dissolution rate of volcanic ash was responsible for the low strength at an early age but beneficial to improving the geopolymerisation with time. This favored the high strength of the control phosphate geopolymer, which reached 52.5 MPa at 56d and was higher than those with CH (28.5‐45.2 MPa). However, the control phosphate geopolymer had poor water resistance, with strength retention ranging from 21–57% compared to 76–90% for phosphate geopolymer with CH. This is because of the leaching of the reactive phase underwater that inhibits further reaction progress. In addition, the modification of the binder chemistry with CH leads to the formation of new calcium phosphate phases that also contribute to enhancing water resistance.This article is protected by copyright. All rights reserved

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Early age properties and water resistance of calcium hydroxide modified volcanic ash‐based phosphate geopolymer binders

Djobo,

Hirsch,

Stephan

2023

Int J Ceramic Engine & Sci

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“…The search for an alternative source of PA is of great importance. Some studies have been interested in alternating the activator with other phosphates rich in aluminum elements [9,18,19,33,[43][44][45][46][47]. Secondly, the reaction between the PA solution and aluminosilicates is highly exothermic [5].…”

Section: Acidic Versus Alkaline Activatorsmentioning

confidence: 99%

“…The microstructure and performance of acid-based geopolymers are also highly dependent on the precursors and activators' physicochemical properties. These properties include particle size [7], curing temperature [8,9], molar concentration of the acid [5,[10][11][12], activator dilution [13], and chemical composition [14].…”

Section: Introductionmentioning

confidence: 99%

“…However, environmental and economic concerns are driving efforts to replace MK partially due to the high temperatures required for its production and the exploitation of natural resources to supply kaolinite [6]. Fly ash (FA) [5,[15][16][17][18][19][20][21][22], volcanic ash (VA) [9,[23][24][25], calcined clay [26], burnt brick residue [27], bauxite [28], laterite [28,29], and mine tailings (MT) [30] were tested, alone or in blends, to reduce the required amount of MK and provide a recycling opportunity for these residues.…”

Section: Introductionmentioning

confidence: 99%

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Acid Activation in Low-Carbon Binders: A Systematic Literature Review

Park,

Pimenta,

Bezerra

2023

Buildings

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Geopolymers have emerged as an alternative binding material to Ordinary Portland Cement (OPC). Recently, there has been an increase in studies exploring the synthesis of these materials using acid activation rather than traditional alkaline activation. This approach offers benefits such as good strength at an early age, better thermal properties, and a chemical activator that emits less carbon to be produced. In addition, it provides resistance to efflorescence and leaching, which are common challenges associated with alkali-activated products. This work analyzed the scientific advances in acid activation in synthesizing an alternative binder to OPC. To this end, a systematic review of the last five years of scientific literature was carried out using the Systematic Review for Engineering and Experiments (SREE) method. The results show a notable increase in research focused on acid activation over the last few years. The acid activators were always phosphate solutions, mainly phosphoric acid. Metakaolin was the most tested precursor, followed by fly ash, and volcanic ash. The research requires improvements in the methodological quality, providing data on molar ratios (Al/P, Si/Al, and Si/P), Liquid/Solid mass ratio, activator solution molarity, and curing process, in addition to statistical treatment and comparison of results. There exists a paucity of diversity in the examined precursors, activators, and additives. Future research developments need to clarify the behavior of mechanical resistance over time, better curing process, water resistance, durability, and the role of iron, magnesium, and calcium silicates and/or oxides. The paper identifies the main research gaps in the area and functions as a database, guiding researchers in selecting raw materials, dosing methodology, and curing processes.

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Engineering Properties of Geopolymer Mortars Containing Industrial Steel Shavings

Gülmez

Koçkal

2023

Iran J Sci Technol Trans Civ Eng

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The role of curing temperature and reactive aluminum species on characteristics of phosphate geopolymer

Abstract: The diluted phosphoric acid and mild curing temperature foster the dissolution–enhancement–precipitation–condensation mechanism. While the dissolution–inhibition–precipitation–condensation mechanism occurs in the presence of any setting accelerator.

Cited by 12 publications

References 35 publications

Early age properties and water resistance of calcium hydroxide modified volcanic ash‐based phosphate geopolymer binders

Early age properties and water resistance of calcium hydroxide modified volcanic ash‐based phosphate geopolymer binders

Acid Activation in Low-Carbon Binders: A Systematic Literature Review

Engineering Properties of Geopolymer Mortars Containing Industrial Steel Shavings

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