Wang, Y.-S., Provis, J.L. orcid.org/0000-0003-3372-8922 and Dai, J.-G. (2018) Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers. Cement and Concrete Composites, 93. pp. 186-195. ISSN 0958-9465
Abstract
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 27Al and 31P 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.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 Elsevier. This is an author produced version of a paper subsequently published in Cement and Concrete Composites. Uploaded in accordance with the publisher's self-archiving policy. Article available under the terms of the CC-BY-NC-ND licence (https://creativecommons.org/licenses/by-nc-nd/4.0/). |
Keywords: | Silico-aluminophosphate geopolymer; Metakaolin; Phosphate activating solution; Soluble aluminum; Setting time; Rheology |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Materials Science and Engineering (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 11 Jun 2019 14:24 |
Last Modified: | 20 Jul 2019 00:43 |
Status: | Published |
Publisher: | Elsevier |
Refereed: | Yes |
Identification Number: | 10.1016/j.cemconcomp.2018.07.011 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:146695 |