Hydration kinetics and performance of sodium carbonate-activated slag-based systems containing reactive MgO and metakaolin under carbonation

Aktürk, Büşra; Abolfathi, Mehrnosh; Ulukaya, Serhan; Kizilkanat, Ahmet B.; Hooper, Thomas J. N.; Gu, Lei; Yang, En-Hua; Unluer, Cise

doi:10.1016/j.cemconcomp.2022.104617

Cited by 22 publications

(5 citation statements)

References 97 publications

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“…The mass loss at this temperature range was identified as 5.2%, 7.1%, 6.5%, and 7% for N8M0, N8M30, N12M0, and N12M30 specimens, respectively. This mass loss can be attributed to the free water from liquid activator and in the pore network of gel structure 86,87 . The evaporation of physico‐chemical bound water from sodium/(sodium‐calcium) aluminosilicates was determined up to temperatures of ~400°C.…”

Section: Resultsmentioning

confidence: 99%

“…This mass loss can be attributed to the free water from liquid activator and in the pore network of gel structure. 86,87 The evaporation of physicochemical bound water from sodium/(sodium-calcium) aluminosilicates was determined up to temperatures of $400 C. The mass loss caused due to the loss of physico-chemical bound water was determined as 4.6%, 3.3%, 5.1%, and 5.0% for N8M0, N8M30, N12M0, and N12M30 specimens, respectively. The minor peak observed from 450 C to 600 C is associated with dehydroxylation of OH groups and polycondensation process of geopolymer gels.…”

Section: Tga and Dtamentioning

confidence: 99%

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The effect of marble powder on physico‐mechanical and microstructural properties of kaolin‐based geopolymer pastes

Kaya

Köksal

Bayram

et al. 2022

Structural Concrete

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As an alternative to ordinary Portland cement (OPC), alkali‐activated materials (AAMs) have more recently been studied and found to have certain suitability in reducing ecological footprint of OPC binding systems. Nonetheless, due to recent concerns over the availability of certain precursors used AAMs (such as the reduction of coal fly ash availability), this study utilized marble powder in various quantities to replace the naturally available kaolin as precursor. This composite use of natural precursors has been entertained to assimilate the production of carbon zero AAMs. To evaluate the physico‐mechanical and microstructural characteristics of the materials, 48 mixes with different sodium (Na) concentrations, curing temperatures, and marble powder content have been used. The results show that rising curing temperature is more effective than other variables, such as the Na and marble powder content on the physico‐mechanical performance of tested geopolymers. In this regard, it is found that a very high Na content can have adverse effect on the properties, potentially due to altered Na/Si, Na/Al ratio in the mixes. Furthermore, the inclusion of marble powder is found to be effective in decreasing the overall porosity up to ~31% and enhancing the physico‐mechanical properties of the specimens cured at 20 and 80°C. Nonetheless, results show that when specimens containing marble powder are exposed to higher curing temperatures (above 80°C) the presence of marble powder adversely affects physico‐mechanical properties. It is concluded that this phenomenon is caused by the dehydration of chemically bound water in higher temperatures when marble powder is used. This result is further confirmed by microstructural tests.

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Section: Resultsmentioning

confidence: 99%

Section: Tga and Dtamentioning

confidence: 99%

The effect of marble powder on physico‐mechanical and microstructural properties of kaolin‐based geopolymer pastes

Kaya

Köksal

Bayram

et al. 2022

Structural Concrete

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“…Active MgO finds extensive use in ordinary Portland concrete, particularly hydraulic concrete [23]. In this context, MgO reacts with water to produce Mg(OH) 2 gel, experiencing a volume expansion of approximately 118%.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

Liu,

Tian,

et al. 2024

Buildings

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The hydration mechanism and strength development of alkaline salt-activated cementitious materials primarily rely on the alkaline activators and mineral admixtures employed. However, the impact of increased Mg2+, Al3+, and Si4+ resulting from the addition of MgO and steel slag (SS) on the hydration mechanism of these systems remains undetermined. This study delves into the hydration mechanism and mechanical properties of a Na2CO3-MgO-activated regenerated micropowder-slag-based cementitious material system. Mechanical properties were assessed by measuring dry shrinkage and compressive strength at various ages, up to 28 days. The reaction mechanism was scrutinized using X-ray diffraction and a thermogravimetric analysis. The main reaction products contributing to the strength development are C-S-H, C-(A)-S-H gel, and hydrotalcite. Other carbonate-containing phases make smaller contributions. The findings reveal that when SS usage is at 10%, it yields higher early strength compared to ordinary samples. Samples incorporating MgO and SS achieved strengths similar to or surpassing those of the control samples. A noteworthy observation is the synergistic excitation effect between sodium carbonate (NC) and MgO, leading to the generation of a significant amount of gelling substances. These substances fill the pores of the structure, resulting in the formation of a dense microstructure. Consequently, the enhanced interaction between NC and MgO contributes to the overall strength development of the cementitious material.

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“…At an early age, adding MK to the cement paste increases the pozzolanic reaction rate and CH consumption rate. − The reaction of AS 2 (SiO 2 and Al 2 O 3 ) is performed in MK, CH, and water . The different hydration products are generated with the difference in the AS 2 /CH ratio and reaction temperature, including tobermorite (CSH-I), calcium aluminate melilite hydrate (C 2 ASH 8 ), tetracalcium aluminate hydrate (C 4 AH 13 ), and tricalcium aluminate hydrate (C 3 AH 6 ). , However, the pozzolanic reaction process and CH removal mechanism of the nanoscale is still unrevealed, which needs in-depth research. In this work, the process of CH removal by MK was studied at the atom scale.…”

Section: Introductionmentioning

confidence: 99%

Molecular Insight into the Pozzolanic Reaction of Metakaolin and Calcium Hydroxide

et al. 2023

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The reaction mechanism of the pozzolanic reaction of metakaolin (MK) from the atomic point of view has not yet been explored. To explain the process and mechanism of the pozzolanic reaction from the atomic point of view, molecular insight into the pozzolanic reaction of MK and calcium hydroxide (CH) was analyzed through the reaction molecular dynamics (MD) simulation. The results show that the pozzolanic reaction of MK and CH can be essentially regarded as the CH decomposition and penetration into MK. Also, the structure evolution after the pozzolanic reaction shows that the water molecules cannot penetrate the MK structure till the participation of Ca2+ and OH– ions of CH. The Ca2+ and OH– ions have strong interaction with MK and drill into the MK structure, followed by the destruction of a part of the MK structure and water penetration. The final structure of CH removed by MK can be regarded as the precursor of the CASH gel structure.

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Hydration kinetics and performance of sodium carbonate-activated slag-based systems containing reactive MgO and metakaolin under carbonation

Cited by 22 publications

References 97 publications

The effect of marble powder on physico‐mechanical and microstructural properties of kaolin‐based geopolymer pastes

The effect of marble powder on physico‐mechanical and microstructural properties of kaolin‐based geopolymer pastes

Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

Molecular Insight into the Pozzolanic Reaction of Metakaolin and Calcium Hydroxide

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