Physico-chemical, mechanical, microstructure and durability characteristics of alkali activated Egyptian slag

Heikal, Mohamed; Nassar, Mostafa Y.; El-Sayed, Gamal O.; Ibrahim, Sahar M.

doi:10.1016/j.conbuildmat.2014.07.026

Cited by 99 publications

(33 citation statements)

References 56 publications

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“…16. This trend is in accordance with that of previous studies, emphasizing the dosage of activating agent as a paramount factor in improving the early age performance of blended mixtures [54][55][56][57].…”

Section: Effect Of Chemical Activationsupporting

confidence: 93%

Effect of chemical and thermal activation on the microstructural and mechanical properties of more sustainable UHPC

Abdulkareem

Fraj

Bouasker

et al. 2018

Construction and Building Materials

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This paper investigates the influence of the content of blast furnace slag (BFS) on the microstructural and mechanical properties of non-activated and activated ultra-high performance concrete (UHPC). Three volume-substitution rates of cement with BFS were explored (30% for UHPC 2 , 50% for UHPC 3 and 80% for UHPC 4) and two activation methods, chemical and thermal, were tested. Results show that with 30% of BFS, heterogeneous nucleation prevailed over dilution, accelerating the hydration reaction of cement and increasing the amount of C-S-H formed. C-S-H decreased the porosity of UHPC 2 by 18% and 20% respectively at 3 and 90 days. The compressive strengths of UHPC 1 (without BFS) and UHPC 2 were very similar. For high BFS contents, the dilution effect prevailed and there was less portlandite, which decreased the amount of hydrated products, particularly at early age. As a result, the porosity of UHPC 3 and UHPC 4 was more than twofold higher than that of UHPC 1. To boost the hydration reaction of blended UHPC with a high BFS content, KOH was added. The use of [KOH] 3 significantly increased the amount of hydrated products, reducing the porosity of UHPC 4 1.6-fold at 3 days and increasing its compressive strength by 42% at the same age. However, this activation mode was not enough to ensure the required compressive strength of UHPC 1. Thermal activation at 90°C for 2 days was therefore tested. Results showed the acceleration of the reaction of solid components, which increased the consumption of portlandite and hence the development of hydrated products. This resulted in improving the packing density of blended UHPC, decreasing its porosity and enhancing its compressive strength. In comparison with reference concrete at 90 days, the compressive strength of UHPC 3-T increased by 7% and that of UHPC 4 was 12.5% lower.

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Section: Effect Of Chemical Activationsupporting

confidence: 93%

Effect of chemical and thermal activation on the microstructural and mechanical properties of more sustainable UHPC

Abdulkareem

Fraj

Bouasker

et al. 2018

Construction and Building Materials

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“…Addition of fly ash to GBFS also improves the mechanical properties; the activated fly ash is particularly durable and highly resistant to aggressive solutions like 5% MgSO 4 . Unlike that the compressive strength of OPC increases up to 28 days then decrease gradually due to the formation of expanding and softening ettringite hydrated products [Heikal et al, 2014]. Alkali-activated GBFS improves the durability and the resistance to chemical attack.…”

Section: Resistance To Magnesium Sulphate Solutionmentioning

confidence: 91%

“…Which may deposit in the open pores that increase the bulk density of the activated slag, this increasing of alkali activator enhances the bulk density of the investigated pastes. The alkali activator enhance the production of higher concentration of [SiO 4 ] -4 which increases the rate of hydration and formation of more C-S-H as shown in Figure (1) [Heikal et al, 2014]. As the amount of alkali activator content increases, the bulk density accordingly increases.…”

Section: Bulk Densitymentioning

confidence: 92%

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Preparation and Characterization of Geopolymer Cement

Kisha

Sayed

Salah

et al. 2016

Journal of Scientific Research in Science

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Effect of some artificial pozzolana such as ground granulate blast furnace slag (GGBFS), cement kiln bypass dust (CKD), silica fume (SF), and fly ash (FA) on geopolymer composition and its resistance to sulphate attack was studied. Various mixes are prepared using different liquid/solid ratios (L/S) by weight. Sodium hydroxide pellets (SH) and commercial sodium silicate liquid (SSL) are used as an activator which was dissolved in the mixing water. The hydration characteristics of the different mixes have been tested via determination of bulk density, total porosity, combined water, compressive strength, and XRD analysis at different time intervals from 1 up to 180 days in water. The results show that the combined water content of the alkali-activated GBFS pastes gradually increases up to 180 days in all mixes. The bulk density increases and the total porosity decreases, as a result of addition of the pozzolanic materials. The compressive strength also increases up to 180 days. All mixes showed good stability of its compressive strength values in 5 % MgSO 4 solution. The data show that SF1 (85% GGBFS+15% SF) activated by (0.5 mol/kg SSL, and 2.5 M SH), and S3 (100% GGBFS) activated by (0.5 mol/kg SSL, and 2.5 M SH) are the most appropriate binding materials (geopolymer cement) that have good different properties so that they can be used as alternative binding materials to the ordinary Portland cement.

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“…The use of a granular nanostructured aggregate as a carrier of a hydrophobizing additive is promising for the production of products with increased hydrophobicity due to the fact that it, firstly, itself has a hydrophobizing effect on the concrete matrix due to its impregnation with solutions of sodium polysilicates during heat activation of the aggregate, secondly, its prolonged action is designed to minimize the negative impact of aggregate content on the process of concrete hardening [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Hydrophobization of Concrete Using Granular Nanostructured Aggregate

Ogurtsova

Строкова

Labuzova

2017

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The possibility of giving hydrophobical properties to the fine-grained concrete matrix by using a granular nanostructured aggregate (GNA) with a hydrophobizing additive is investigated in this work. GNA is obtained by granulating the silica raw material with an alkaline component. The introduction of a hydrophobizing additive into the raw mix of GNA allows to encapsulate it reducing the negative effect on hydration processes, the intensity of migration of moisture and efflorescence in concrete and, consequently, improving the performance characteristics of fine-grained concrete products. The hydrophobizing ability of a solution of sodium polysilicates formed in the core of GNA during concrete heat and moisture treatment is proved. The analysis of IR spectra after the impregnation of cement stone samples with a solution of sodium polysilicates showed an increase in the degree of hydration and the formation of framework water aluminosilicates. Atmospheric processes modelling showed that the use of GNA on the basis of gaize with calcium stearate and on the basis of fly ash with GKZh-11 makes it possible to increase the resistance of fine-grained concrete to the atmospheric effect of the medium, namely, the outwashing of readily soluble compounds.

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Physico-chemical, mechanical, microstructure and durability characteristics of alkali activated Egyptian slag

Cited by 99 publications

References 56 publications

Effect of chemical and thermal activation on the microstructural and mechanical properties of more sustainable UHPC

Effect of chemical and thermal activation on the microstructural and mechanical properties of more sustainable UHPC

Preparation and Characterization of Geopolymer Cement

Hydrophobization of Concrete Using Granular Nanostructured Aggregate

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