Chavda, M.A., Bernal, S.A., Apperley, D.C. et al. (2 more authors) (2015) Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders. Cement and Concrete Research, 70. 21 - 28. ISSN 0008-8846
Abstract
The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength. Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A 31P/27Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium–phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2015 Elsevier. This is an author produced version of a paper subsequently published in Cement and Concrete Research. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Calcium aluminate cement; Amorphous material; CP/MAS NMR; Spectroscopy |
Dates: |
|
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: | 02 Jun 2015 15:23 |
Last Modified: | 16 Nov 2016 16:15 |
Published Version: | http://dx.doi.org/10.1016/j.cemconres.2015.01.007 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.cemconres.2015.01.007 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:86430 |