Effect of MgO, Mg-Al-NO3 LDH and calcined LDH-CO3 on chloride resistance of alkali activated fly ash and slag blends

Liu, Tao; Chen, Yuxuan; Yu, Qingliang; Fan, Jianfeng; Brouwers, Hjh Jos

doi:10.1016/j.conbuildmat.2020.118865

Cited by 40 publications

(13 citation statements)

References 45 publications

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“…The emerging structural properties of layered double hydroxides (LDH) make them potential candidates for applications as smart functional additives in hydrated cement, producing high-performance materials. − The LDH structure consists of stacked layers formed by hydroxyl octahedra with embedded divalent (M 2+ ) and trivalent (M 3+ ) metal cations, represented by the formula , where A n – represents the charge-compensating anions in the interlamellar domain. , LDH-type phases are normally obtained in cement during hydration reactions to form the AFm phase ( ). In this case, A n – can be an exchangeable singly charged anion (e.g., chloride and nitrate) or half of a doubly charged anion (e.g., sulfate, carbonate, and aluminosilicate).…”

Section: Introductionmentioning

confidence: 99%

MgAl-Layered Double Hydroxide Nanoparticles as Smart Nanofillers To Control the Rheological Properties and the Residual Porosity of Cement-Based Materials

Almeida

Santos

Rosa

et al. 2022

ACS Appl. Nano Mater.

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Nanotechnology in building materials has still not been widely explored, despite its great potential in developing a new generation of smart and eco-efficient cementitious materials based on the addition of nanoparticles. In this context, layered double hydroxides (LDH) are a family of anionic clays that can regenerate their nanostructure after thermal decomposition to the corresponding mixed oxides (MO). This memory effect involves the reversible recrystallization of the LDH nanoparticles from nanocrystalline MO in contact with water or anionic solutions. It has shown promise in the immobilization of different anions, such as chloride and carbonate, that could compromise the durability of reinforced concrete. This study proposes the incorporation of nanocrystalline MO in the cementitious matrix to control the rheological properties of the paste and reduce the porosity of the cement because the regeneration of the lamellar nanostructure occurs by the dissolution and reprecipitation of LDH nanoparticles inside the pores formed during the consolidation of the paste. Time-resolved wide-angle X-ray scattering (WAXS) was used to study the mechanism of regeneration of the LDH structure following contact of the MO with the cement pore solution. The results showed that the regeneration of the LDH, which occurs by an aggregative growth of anisotropic nanoparticles, changed the rheological behavior by increasing the elastic modulus (G′) and consequently contributing to the consolidation of the paste, demonstrating the potential of these materials for application in threedimensional (3D) printing. Regarding the pore structure of the hydrated cement, a porosity reduction of up to 20% was observed with the addition of 2.0 wt % of MO. Furthermore, after 28 days of hydration, the specific surface area of the cement was reduced from 60 to 36 m 2 g −1 with the incorporation of 1.0 wt % of MO. The use of LDH nanoparticles as a cement smart nanofiller proved to be advantageous in the kinetic control of cement curing and improvement of the porous structure of the hydrated cement.

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Section: Introductionmentioning

confidence: 99%

MgAl-Layered Double Hydroxide Nanoparticles as Smart Nanofillers To Control the Rheological Properties and the Residual Porosity of Cement-Based Materials

Almeida

Santos

Rosa

et al. 2022

ACS Appl. Nano Mater.

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“…S Luo et al [98] also obtained the same porous structure in CLDH, as shown in Figure 6C. Different heating rates have been used in LDH calcination; a heating rate of 10 • C/min was used in Mg/Al LDH by several authors [99][100][101][102] and a heating rate of 5 • C /min was used by [103]. It is known that if the heating rate is slower, the thermal effects are better observed (better porous structure).…”

Section: Thermal Behaviour Of Hydrotalcite By Sem/temmentioning

confidence: 81%

Review of the Application of Hydrotalcite as CO2 Sinks for Climate Change Mitigation

2022

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In recent decades, the environmental impact caused by greenhouse gases, especially CO2, has driven many countries to reduce the concentration of these gases. The study and development of new designs that maximise the efficiency of CO2 capture continue to be topical. This paper presents a review of the application of hydrotalcites as CO2 sinks. There are several parameters that can make hydrotalcites suitable for use as CO2 sinks. The first question is the use of calcined or uncalcined hydrotalcite as well as the temperature at which it is calcined, since the calcination conditions (temperature, rate and duration) are important parameters determining structure recovery. Other aspects were also analysed: (i) the influence of the pH of the synthesis; (ii) the molar ratio of its main elements; (iii) ways to increase the specific area of hydrotalcites; (iv) pressure, temperature, humidity and time in CO2 absorption; and (v) combined use of hydrotalcites and cement-based materials. A summary of the results obtained so far in terms of CO2 capture with the parameters described above is presented. This work can be used as a guide to address CO2 capture with hydrotalcites by showing where the information gaps are and where researchers should apply their efforts.

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“…The improvement of elasticity and yield strength was based on the synthesis technique and the percentage of reinforcements. In ceramic reinforcements, the flexibility was improved by grain refinements, texture modification, and nonbasal slip systems [27]. The yield strength is mainly enhanced by homogeneous distribution of reinforcements, grain refinement, and limited pores in the fly ash-reinforced composites.…”

Section: Resultsmentioning

confidence: 99%

Mechanical and Wear Behaviour of Nano‐Fly Ash Particle‐Reinforced Mg Metal Matrix Composites Fabricated by Stir Casting Technique

Santhosh¹,

Natrayan

Kaliappan

et al. 2022

Journal of Nanomaterials

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In recent years, magnesium-based alloys and composites have great attention in automobile, structural, and biomedical industries due to their desirable characteristics such as lower density, low elastic modulus, high specific strength, better damping properties, and excellent castability. The pure magnesium was used as a matrix material and reinforced with fly ash fillers of different compositions with a weight percentage of 2.5%, 5%, and 7.5% to compare with the pure magnesium. The three different weights (wt%) of fly ash/Mg samples were prepared using the bottom pouring stir casting method. Fabricated samples sliding wear characteristics and mechanical behaviour (ASTM standard) were studied. Wear, tensile, and hardness results portray that 7.5 wt% fly ash composites possess better elongation and hardness and good wear resistance. The tensile strength values were improved by 42% in sample 4 compared with pure Mg. Hardness values were also improved by 21% in sample 4 compared with pure Mg. The wear rate and coefficient of friction are also reduced by the increased weight percentage of fly ash reinforcement. SEM images display casted pure magnesium’s morphology and wear-tested samples’ worn surface characteristics.

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Effect of MgO, Mg-Al-NO3 LDH and calcined LDH-CO3 on chloride resistance of alkali activated fly ash and slag blends

Cited by 40 publications

References 45 publications

MgAl-Layered Double Hydroxide Nanoparticles as Smart Nanofillers To Control the Rheological Properties and the Residual Porosity of Cement-Based Materials

MgAl-Layered Double Hydroxide Nanoparticles as Smart Nanofillers To Control the Rheological Properties and the Residual Porosity of Cement-Based Materials

Review of the Application of Hydrotalcite as CO2 Sinks for Climate Change Mitigation

Mechanical and Wear Behaviour of Nano‐Fly Ash Particle‐Reinforced Mg Metal Matrix Composites Fabricated by Stir Casting Technique

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