Microstructure and microanalysis of hardened cement pastes involving ground granulated blast-furnace slag

150

ReuseUnless 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. Abstract: The effects on composite cements of the aluminium content of slag plus that of additional sulphate, has been investigated. Samples containing cement or composites with 40% replacement by one of 2 different slags, differing in aluminium contents, were prepared. A further blended sample was prepared with additional anhydrite replacing 3%w/w of binder. Slag blended mortars showed comparable strengths to the neat cement system at later ages. Adding slag changed the hydration kinetics of the clinker phases. The addition of sulphate had no effect on slag reactivity but increased that of alite. Slags richer in aluminium resulted in greater incorporation of aluminium into C-S-H and encouraged the presence of hemicarbonate over monocarbonate. The Ca/Si ratios of the C-S-H formed were comparable between the two blends, being marginally lower than that of the neat system. The addition of anhydrite resulted in the adsorption of sulphate onto the C-S-H, plus stabilisation of ettringite. Corresponding Author 8 9 The Role of the Alumina Content of Slag, plus the Presence of AdditionalAbstract 10 The effects on composite cements of the aluminium content of slag plus that of additional sulphate, 11 has been investigated. Samples containing cement or composites with 40% replacement by one of 2 12 different slags, differing in aluminium contents, were prepared. A further blended sample was 13 prepared with additional anhydrite replacing 3%w/w of binder. Slag blended mortars showed 14 comparable strengths to the neat cement system at later ages. Adding slag changed the hydration 15 kinetics of the clinker phases. The addition of sulphate had no effect on slag reactivity but increased 16 that of alite. Slags richer in aluminium resulted in greater incorporation of aluminium into C-S-H and 17 encouraged the presence of hemicarbonate over monocarbonate.

supporting

confidence: 80%

The role of the alumina content of slag, plus the presence of additional sulfate on the hydration and microstructure of Portland cement-slag blends

Whittaker

Zając

Haha

et al. 2014

150

“…The major changes are related to the C-S-H composition which tends to have lower Ca/Si and higher Al/Si ratios than in PC paste [3]. These modifications in the C-S-H composition have been associated with a change in morphology of C-S-H. At high replacement of slag or fly ash, the morphology of C-S-H was changed from fibrillar to foil-like morphology [4,5]. It is not clear how such changes in morphology or, more importantly, how the distribution of hydrates from the reaction of SCM changes the overall porosity.…”

Section: Introductionmentioning

confidence: 95%

“…Nevertheless, earlier studies indicate that there is an optimal replacement of SCM above which the refinement and the reduction of the pore volume are not occurring [19] which, as a consequence, decreases the mechanical properties of the paste [20,21]. It has also been reported that the degree of reaction of fly ash [19,22,23] or slag [5] may decrease when they are present at higher replacement levels. This paper reports on the development of the pore structure in slag-PC and fly ash-PC systems and on the filling ability of the hydrates from SCM reaction.…”

Section: Introductionmentioning

confidence: 95%

Evolution of pore structure in blended systems

Berodier

Scrivener

2015

253

a b s t r a c t a r t i c l e i n f oIn this study, the effect of SCM in the cement paste was isolated by using ternary systems combining Portland cement, quartz and SCM. The results show clear differences in how the hydrates from the reaction of clinker, slag and fly ash fill space. The reaction of slag is more efficient than that of fly ash in modifying the porosity. Our results indicate that Portland cement (PC), slag and fly ash reactions are limited at later ages by the lack of water-filled capillary pores. The higher the space available, with increasing the water/solids ratio, the later the reaction is limited. This explains the lower degree of reaction of SCM in blended systems at high replacement levels.

“…Richardson and Groves [43] found sub-micrometer sized crystals of this phase dispersed through C-S-H gel. X-ray microanalysis of AAS cement done by Wang and Scrivener [44] showed that Mg/Al ratio of the hydrotalcite-type phase was 2.2 which is very close to Mg/Al ratio of 2.0 of the hydrotalcite identified by XRD analysis (Fig.…”

Section: Edsmentioning

confidence: 99%

“…4) in this study. According to Richardson and Groves [43], Al can replace the bridging Si in the dreierketten C-S-H structure. Assuming that pentrameric chains predominate in C-S-H structure, the presence of Al in all the bridging sites would result in an Al/Si ratio of 0.25 [33].…”

Section: Edsmentioning

confidence: 99%

Chemical acceleration of a neutral granulated blast-furnace slag activated by sodium carbonate

Kovtun

Kearsley

Shekhovtsova

2015

133

This paper presents results of a study on chemical acceleration of a neutral granulated blastfurnace slag activated using sodium carbonate. As strength development of alkali-activated slag cements containing neutral GBFS and sodium carbonate as activator at room temperature is known to be slow, three accelerators were investigated: sodium hydroxide, ordinary Portland cement and a combination of silica fume and slaked lime. In all cements, the main hydration product is C-(A)-S-H, but its structure varies between tobermorite and riversideite depending on the accelerator used. Calcite and gaylussite are present in all systems and they were formed due to either cation exchange reaction between the slag and the activator, or carbonation. With accelerators, compressive strength up to 15 MPa can be achieved within 24 hours in comparison to 2.5 MPa after 48 hours for a mix without an accelerator.