Effect of Slag Addition on Mechanical Properties of Fly ash Based Geopolymers

Marcin, Michal; Sisol, Martin; Brezani, I.

doi:10.1016/j.proeng.2016.07.380

Cited by 15 publications

(9 citation statements)

References 8 publications

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“…For example, Nath et al [ 8 ] and Saha et al [ 9 ] found that the setting time for a fly ash geopolymer was shortened, and the compressive strength was increased when slag powder was incorporated into the fly ash geopolymer. Similarly, Marcin et al [ 10 ] and Song et al [ 11 ] found similar phenomena when they studied fly ash geopolymer mortar. Yip et al [ 12 ] found that the strength of an alkali-activated geopolymer first increased and then decreased with increasing metakaolin content, and the optimum content was 80%.…”

Section: Introductionsupporting

confidence: 53%

Macroscopic Properties and Pore Structure Fractal Characteristics of Alkali-Activated Metakaolin–Slag Composite Cementitious Materials

Zhan

Cheng

2022

Polymers

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To investigate the effects of slag and Na2O content on the macroscopic properties and pore structure characteristics of alkali-activated metakaolin–slag (AAMS) composite cementitious materials, this study used X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDS), and mercury-pressure (MIP) tests for characterization and analyzed the hydration product compositions, microstructures, and pore structure characteristics of AAMS composite cementitious materials. The relationships between the fractal dimension and the pore structure parameters, compressive strengths, and drying shrinkage rates of AAMS composite cementitious materials were investigated with the thermodynamic fractal model. The results showed that at the age of 28 d, the compressive strength and drying shrinkage of the AAMS composite binder increased by 20.57% and 215.11%, respectively, when the slag content increased from 0 to 50%. When the Na2O content increased from 8% to 12%, the compressive strength and drying shrinkage of the AAMS composite increased by 24.37% and 129.40%, respectively. The compressive strengths of AAMS composite cementitious materials increased with increasing slag content and Na2O content, but the drying shrinkage of the system increased, and the volume stability worsened. Microscopic analyses showed that with increases in the slag and Na2O contents, the hydration products of AAMS composite cementitious materials increased, and C-A-S-H and N-A-S-H filled each other so that the internal structures of AAMS composite cementitious materials were denser, and the porosities were significantly reduced. By comparing and analyzing the Menger sponge model and the fractal model based on the thermodynamic relationships, it was found that the fractal model based on the thermodynamic relationship better reflected the pore size distribution over the whole pore size determination range, and the correlation coefficients R2 were above 0.99, indicating that the fractal dimension calculated by the fractal model based on the thermodynamic relationship provided a comprehensive evaluation index for the pore structure characteristics of AAMS composite cementitious materials, and the fractal dimension correlated well with the pore structure parameters, compressive strengths, and drying shrinkage rates of cementitious materials.

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Section: Introductionsupporting

confidence: 53%

Macroscopic Properties and Pore Structure Fractal Characteristics of Alkali-Activated Metakaolin–Slag Composite Cementitious Materials

Zhan

Cheng

2022

Polymers

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“…The interaction mechanism can be mainly demonstrated as: (1) modifying the nanostructure and chemical composition of different reaction products, (2) triggering or suppressing the formation of crystalline phases within reaction products, and (3) homogenising the chemical composition and microstructure [13]. Furthermore, the microstructure and mechanical properties of AAFS are strongly dependent on various factors including the relative amount of fly ash and slag [15,16], and activator type and concentration [17][18][19]. The AAFS mixture with a high slag content shows a high reaction rate and a dense microstructure due to the soluble Ca from slag, which would promote the generation of C-A-S-H gels and result in a quicker setting as well as a higher strength than the mixture with a low slag content [20,21].…”

Section: Introductionmentioning

confidence: 99%

“…The residual fly ash particles have the highest elastic modulus and hardness, followed by reaction products (N-A-S-H gels) and pores [29][30][31][32]. The elastic modulus of N-A-S-H gels in AAF is stable at around [16][17][18] GPa, independent of the curing procedure and the molar ratio of alkaline activator [29][30][31]. In regard to AAS, the unreacted slag exhibits the highest hardness and elastic modulus, attributing to the crystalline impurities [12,23].…”

Section: Introductionmentioning

confidence: 99%

Multiscale micromechanical analysis of alkali-activated fly ash-slag paste

Fang

Zhang

2020

Cement and Concrete Research

126

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Current demand for highly sustainable concrete, e.g. alkali-activated fly ash-slag (AAFS) concrete, urges understanding the links between microstructure and micromechanical properties of this binder. This paper presents a systematic investigation into the microstructure and micromechanical properties of AAFS paste from nanoscale to micro-scale. Nanoindentation was used to evaluate the micromechanical properties, while the microstructure was characterised using 29 Si nuclear magnetic resonance, Fourier transform infrared spectroscopy, backscattered electron microscopy, and mercury intrusion porosimetry. The results indicate that N-AS -H gels have a relatively low elastic modulus due to their high level of structural disorder and gel porosity, while the C-AS -H gels and N-C-AS -H gels with a low level of structural disorder and gel porosity have a relatively high elastic modulus. The elasticity of reaction products and their relative volumetric proportions mainly determine the macroscopic elasticity of AAFS paste, while the porosity and pore size distribution primarily condition its macroscopic strength.

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“…Metakaolin (Table 3) is composed of 43.58% Al 2 O 3 and 63.36% SiO 2 which characterizes it as a predominant source of aluminum in proportion [15][16][17][18]. e use of fly ash waste from burning charcoal as a source of Si and Al favors the geopolymerization reaction and guarantees good durability for the geopolymer [19][20][21][22][23].…”

Section: Methodsmentioning

confidence: 99%

An Assessment of Reuse of Light Ash from Bayer Process Fluidized Bed Boilers in Geopolymer Synthesis at Ambient Temperature

Brito

Silva

Santa

et al. 2018

Advances in Materials Science and Engineering

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Sustainable civil construction in the future, besides having low energy consumption and greenhouse gas emissions, must also adopt the principle of reusing wastes generated in the production chain that impact the environment. The aluminum production chain includes refining using the Bayer process. One of the main wastes produced by the Bayer process that has an impact on the environment is fly ash. Geopolymers are cementitious materials with a three-dimensional structure formed by the chemical activation of aluminosilicates. According to studies, some are proving to be appropriate sources of Al and Si in the geopolymerization reaction. The research reported here sought to assess the possibility of reusing fly ash characteristic of the operational temperature and pressure conditions of Bayer process boilers in geopolymer synthesis. Geopolymerization reaction was conducted at an ambient temperature of 30°C, and the activator used was sodium hydroxide (NaOH) 15 molar and sodium silicate (Na2SiO3) alkaline 10 molar. Fly ash and metakaolin were used as sources of Al and Si. XRD, XRF, and SEM Techniques were used for characterizing the raw materials and geopolymers. As a study parameter, the mole ratios utilized followed data from the literature described by Davidovits (year), so that the best results of the geopolymer samples were obtained in the 2.5 to 3.23 range. Resistance to mechanical compression reached 25 MPa in 24 hours of curing and 44 MPa after 28 days of curing at ambient temperature.

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Effect of Slag Addition on Mechanical Properties of Fly ash Based Geopolymers

Cited by 15 publications

References 8 publications

Macroscopic Properties and Pore Structure Fractal Characteristics of Alkali-Activated Metakaolin–Slag Composite Cementitious Materials

Macroscopic Properties and Pore Structure Fractal Characteristics of Alkali-Activated Metakaolin–Slag Composite Cementitious Materials

Multiscale micromechanical analysis of alkali-activated fly ash-slag paste

An Assessment of Reuse of Light Ash from Bayer Process Fluidized Bed Boilers in Geopolymer Synthesis at Ambient Temperature

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