Retracted: Effect of Reactive Magnesium Oxide on Properties of Alkali-Activated Slag-Cement Pastes

Abdel‐Gawwad, Hamdy A.

doi:10.1061/(asce)mt.1943-5533.0001207

Cited by 21 publications

(23 citation statements)

References 42 publications

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“…More recently, NT has attracted considerable scientific interest, due to the new potential uses of particles in nanometer (10 -9 m) scale; the advent of NT has brought in various types of nano-materials (NMs), which may have good applications in civil engineering, especially concrete production, due to their major effects: size effect, surface effect, and interface effect [1][2][3][4]. It was stated that [5], ''the fineness of cement affects it's reactivity with water and generally the finer the cement the more rapidly it will react''.…”

Section: Introductionmentioning

confidence: 99%

Chemical and Engineering Properties of Blended Cement Containing Micro- and Nano-silica

Ahmed¹,

Sabrah²,

Mohamed³

et al. 2017

AJCHE

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Nano-technology (NT) and nano-materials (NMs) has attracted considerable scientific attention, due to the new potential uses of nano-particles (NPs), which can change the concrete world. There is a great interest in replacing a long time used materials in concrete structure by NMs to improve the different properties of concrete. In this study, the hydration characteristics and microstructure of cement pastes and mortars with and without nano-silica (NS) were studied. Blended cement mix containing 10 mass, % silica fume (SF) was prepared, then the cement mix was partially replaced by NS up 1.5 mass, %. The results show that, NS increases the water of consistency and final setting time The values of chemically combined water, free lime, bulk density and compressive strength prove that, NS up to 1% seems to be an effective mineral additive for blending with OPC to improve its chemical and engineering properties. This is mainly attributed to that; NS behaves not only as filler to improve microstructure, but also as pozzolanic material (PZM). The formation of more hydrated silicates in presence of NS was confirmed by XRD, DTA, IR and SEM examinations. At 1.5 mass, % NS, the density and strength are reduced but still higher than those of 0.0 and 0.5% NS. Also, the results indicate that, the substitution of blended cement mix (OPC+10% SF) with 1 mass, % NS gives a reasonable hydration characteristics and improved engineering properties more than those of 0.0 and 0.5% NS at all hydration ages up to 90 days. Therefore, this level of NS is suggested to be the most suitable replacement level.

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Section: Introductionmentioning

confidence: 99%

Chemical and Engineering Properties of Blended Cement Containing Micro- and Nano-silica

Ahmed¹,

Sabrah²,

Mohamed³

et al. 2017

AJCHE

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“…A lack of brucide formation in the presence of magnesia was also observed earlier for the blastfurnace slag-based binders. e hydrolysis of MgO on the Figure 8 [36,37]. Peaks marked as "CSH" and detected at around 29 o θ were identified as originating from a mix of poorly crystalline sodium-and aluminum-substituted calcium silicate hydrate C-(N)-A-S-H based on the earlier study by Walkley at al.…”

Section: Test Results and Discussionmentioning

confidence: 89%

“…Consequently, formation of C-(N)-A-S-H gel could be retarded due to the presence of sulphate ions in the pore solution which could repel the negative charge on the aluminosilicates. is would in turn obstruct condensation reactions and would lower the degree of ash solubilization due to the slight decline of pH [37]. Sulphate could also accelerate the conversion of Ca-(N)-A-S-H gel into zeolites, Abdel-Gawwad [37], which was confirmed by detection of zeolite-like "Z" peaks in the XRD analysis.…”

Section: Test Results and Discussionmentioning

confidence: 89%

“…is would in turn obstruct condensation reactions and would lower the degree of ash solubilization due to the slight decline of pH [37]. Sulphate could also accelerate the conversion of Ca-(N)-A-S-H gel into zeolites, Abdel-Gawwad [37], which was confirmed by detection of zeolite-like "Z" peaks in the XRD analysis. Existence of nanometer-sized crystalline zeolite structures in generally XRD-amorphous geopolymer gels has been suggested by others [39].…”

Section: Test Results and Discussionmentioning

confidence: 89%

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Interaction of Magnesia with Limestone‐Metakaolin‐Calcium Hydroxide Ternary Alkali‐Activated Systems

Ćwirzeń

Metsäpelto

Habermehl-Cwirzen

2018

Advances in Materials Science and Engineering

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The effect of magnesia on ternary systems composed of limestone, metakaolin and calcium hydroxide, alkali activated with sodium silicate, sodium hydroxide, and sodium sulphate was studied by determination of the compressive strength, X-ray powder diffraction (XRD), thermogravimetry (TG), and scanning electron microscope (SEM). Pastes activated with sodium silicate and sodium sulphate showed strength regression caused by a formation of an unstable prone to cracking geopolymer gel. The presence of magnesia in sodium hydroxide-activated system hindered this trend by promoting a formation of more stable crystalline phases intermixed with brucide. In general, magnesia densified the binder matrix by promoting a formation of amorphous phases while sodium hydroxide produced the most porous microstructure containing high amount of crystalline phases.

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“…When MgO is added, the MgO particles hydrolyzes and reacts with the Si–O and Al–O to form magnesium silicate hydrate (M–S–H) or hydrotalcite‐like phases . In alkali‐activated systems, magnesium may play a role in partly compensating shrinkage caused by hydration (activation reaction) of slag due to the formation of hydrotalcite‐like phases . Jin et al found that the effectiveness of MgO in shrinkage reduction was highly dependent on the reactivity and content of MgO in AAS pastes.…”

Section: Discussionmentioning

confidence: 99%

Autogenous and drying shrinkage of alkali‐activated slag mortars

et al. 2019

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Shrinkage of alkali-activated slag (AAS) cement is a critical issue for its industrial application. This study investigated the mechanisms and effectiveness of shrinkagereducing agent (SRA) and magnesia expansive agent on reducing autogenous and drying shrinkage of AAS mortars that were activated by liquid sodium silicate (LSS) solution with modulus (SiO 2 /Na 2 O molar ratio) of 0-1.5. The results showed that the autogenous shrinkage of AAS mortars increased with the increase of LSS modulus from 0 to 0.5, then decreased as modulus increased up to 1.5. The drying shrinkage consistently increased with the increase in the modulus of LSS. The oxyalkylene alcohol-based SRA could significantly reduce the autogenous and drying shrinkage of AAS mortars while the magnesia expensive agent was comparatively less effective.The autogenous shrinkage of AAS mortars was inversely proportional to the internal relative humidity, while the drying shrinkage was more related to the mass loss of samples. Mathematical models were established to describe the autogenous and drying shrinkage behavior of AAS mortars. K E Y W O R D Sadditives, alkali activation, alkali-activated slag, shrinkage 4964 | HU et al.

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Retracted: Effect of Reactive Magnesium Oxide on Properties of Alkali-Activated Slag-Cement Pastes

Cited by 21 publications

References 42 publications

Chemical and Engineering Properties of Blended Cement Containing Micro- and Nano-silica

Chemical and Engineering Properties of Blended Cement Containing Micro- and Nano-silica

Interaction of Magnesia with Limestone‐Metakaolin‐Calcium Hydroxide Ternary Alkali‐Activated Systems

Autogenous and drying shrinkage of alkali‐activated slag mortars

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