Evaluation of activated high volume fly ash systems using Na 2 SO 4 , lime and quicklime in mortars with high loss on ignition fly ashes

Abstract

Article available under the terms of the CC-BY-NC-ND licence (https://creativecommons.org/licenses/by-nc-nd/4.0/) eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. The effect of sodium sulfate, added as an activator, is significant in terms of compressive strength at early age for two of the fly ashes studied; in this case, the parameter used to correlate with the compressive strength evolution is the amount of portlandite consumed through pozzolanic reactions. However, sodium sulfate does not have the same effect on fly ashes with a high amount of Fe 2 O 3 , in which portlandite consumption is much lower.

Influence of selected activating methods on hydration processes of mixtures containing high and very high amount of fly ash

“…Velandia et al [84] investigated reactivity of different high losses on ignition fly ashes (used as 50% of cement replacement) in the presence of lime and quicklime. They showed that the properties of fly ash, especially content of amorphous phases and grain size, as well as the amount and the type of used activator influence reactivity of fly ash.…”

“…However, in case of steam curing at 60°C the compressive strength was similar as for the nonactivated reference. Velandia et al [84] showed that in case of 50% cement replacement by fly ash, activation of such systems by Na 2 SO 4 gives better compressive strength on early days as compared to activating by lime and quicklime. This relationship was observed mainly in case of fly ashes containing low amount of Fe 2 O 3 ; thus, the authors of Influence of selected activating methods on hydration processes... [84] concluded that the content of Fe 2 O 3 in fly ash affected activation process.…”

“…Velandia et al [84] showed that in case of 50% cement replacement by fly ash, activation of such systems by Na 2 SO 4 gives better compressive strength on early days as compared to activating by lime and quicklime. This relationship was observed mainly in case of fly ashes containing low amount of Fe 2 O 3 ; thus, the authors of Influence of selected activating methods on hydration processes... [84] concluded that the content of Fe 2 O 3 in fly ash affected activation process. Donatello et al [16] showed that 2-days compressive strength of mixture containing about 80% of Class F fly ash was about two times higher than the result registered for about 80% of sand (both mixtures activated by Na 2 SO 4 ).…”

“…Results obtained by different researchers give contradictory informations about the possibility of ettringite formation in the presence of Na 2 SO 4 . For example formation of ettringite was observed in [84] (50% of cement replacement by fly ash). Donatello et al [19] noted the presence of small amount of ettringite during early stages of hydration of mixture containing higher amount, i.e.…”

Increasing the Dimensional Stability of Cao-Feox-Al2o3-Sio2 Alkali-Activated Materials: On the Swelling Potential of Calcium Oxide-Rich Admixtures

“…However, the scarce literature on the effects of Ca 2+ during alkali activation is focused on systems with lowiron content (Yuan et al, 2014;Velandia et al, 2016), whereas appreciable levels of iron will increase the complexity of the mechanisms involved. Daux et al (1997) studied the dissolution of basaltic glasses and observed that Fe species are dissolved and precipitated faster than Si and Al.…”