Dry powder alkali-activated slag cements

Kovtun, Maxim; Kearsley, Elsabé P.; Shekhovtsova, Julia

doi:10.1680/adcr.14.00078

Cited by 10 publications

(16 citation statements)

References 2 publications

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“…The water/binder ratio was kept constant at 0.26 [18] and the moulds filled with AAS cement paste were not submerged into water between measurements to avoid alkali leaching.…”

Section: Sample Synthesis and Tests Proceduresmentioning

confidence: 99%

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

Kovtun

Kearsley

Shekhovtsova

2015

Cement and Concrete Research

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133

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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.

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“…The water/binder ratio was kept constant at 0.26 [18] and the moulds filled with AAS cement paste were not submerged into water between measurements to avoid alkali leaching.…”

Section: Sample Synthesis and Tests Proceduresmentioning

confidence: 99%

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

Kovtun

Kearsley

Shekhovtsova

2015

Cement and Concrete Research

Self Cite

133

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“…For instance, Ye et al [25] used an LS-based superplasticizer in a one-part red mud-based geopolymer paste to reduce the water/solid ratio from 0.55 to 0.45. Also, Kovtun et al [26] used LS superplasticizer to improve workability of one-part alkali-activated blast-furnace slag. Another example is the study by Yang et al [27], in which a polycarboxylate-based superplasticizer was used in one-part alkali-activated blast-furnace slag.…”

Section: Introductionmentioning

confidence: 99%

Suitability of commercial superplasticizers for one-part alkali-activated blast-furnace slag mortar

Luukkonen

Abdollahnejad

Ohenoja

et al. 2019

Journal of Sustainable Cement-Based Materials

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Alkali-activated materials are a low-CO2 alternative for Portland cement in construction. However, one major issue in their use is the poor or varying functionality of the currently available commercial superplasticizers. Especially for one-part ("just add water") alkali-activated materials, the number of studies is limited. In this study, one-part alkali-activated mortar was prepared from blast furnace slag by using solid sodium hydroxide as an activator and microsilica as an additional silica source. Comparison of commonly used superplasticizer types revealed that lignosulfonate, melamine, and naphthalene-based superplasticizers are more efficient than the currently most used polyacrylate and polycarboxylatesuperplasticizers. Lignosulfonate-based superplasticizer was overall bestperforming: it improved significantly the workability (+41% spread, -51% yield stress, -27% viscosity), setting time (+70%), and compressive strength (+19%) at a 0.5 wt% dose. When the amount of water and superplasticizer were optimized, compressive strength of mortar could be doubled (from 19 to 38 MPa at 28 d).

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“…Portland cement accounts for approximately 7-8% of the total CO2 emitted globally (approximately 0.8 tonnes of CO2 is released per tonne of clinker manufactured) (Duchesne et al, 2010;Garcia-Lodeiro et al, 2016c;Olivier et al, 2015;Palomo et al, 2007). The inherent advantage of hybrid alkaline cements, over their alkali activated counterparts is that they do not require the addition of highly alkaline (and usually expensive) chemicals, but rely on a safe source of alkali formed in situ to facilitate both the dissolution of any amorphous (glassy) phases present in the source materials, as well as hydration at ambient temperature (Donatello et al, 2013;Donatello et al, 2014b;Kovtun et al, 2015;Shekhovtsova et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Chemical and mechanical activation of hybrid fly ash cement

Toit

Kearsley

Donald³

et al. 2018

Advances in Cement Research

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Hybrid fly ash cement is a binder with a composition between that of pozzolanic fly ash cement and alkali-activated fly ash cement. Its production requires less cement clinker than ordinary Portland cement, facilitating a much-needed reduction in the carbon dioxide footprint related to the production of high-clinker-containing cement. Research on activation methods is required to overcome the low early age strength and slow strength development in hybrid fly ash cements. In this study the activation of a South African siliceous fly ash (70%) for use along with Portland cement (30%) in a hybrid alkaline binder was investigated. Both chemical (the addition of sodium sulfate) and mechanical (milling) activation of fly ash was studied. The aim of this work was to develop a better understanding of the characteristics of compressive strength development of hybrid fly ash cement mortars over an extended curing period of up to a year. The results indicated that the combination of mechanical and chemical activation (sodium sulfate) can be considered a viable solution to improving early strength and slow strength development, so that hybrid cements are able to comply with the strength requirements of the BS EN 197 cement specification.

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Dry powder alkali-activated slag cements

Cited by 10 publications

References 2 publications

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

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

Suitability of commercial superplasticizers for one-part alkali-activated blast-furnace slag mortar

Chemical and mechanical activation of hybrid fly ash cement

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