scholarly journals The Influence Mechanism of Ettringite Crystals and Microstructure Characteristics on the Strength of Calcium-Based Stabilized Soil

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1359
Author(s):  
Youmin Han ◽  
Junwu Xia ◽  
Hongfei Chang ◽  
Jun Xu
Keyword(s):  
Space Structure ◽  
X Ray Diffraction ◽  
Testing Methods ◽  
Lower Strength ◽  
Soil Particles ◽  
X Ray ◽  
Microstructure Characteristics ◽  
Influence Mechanism ◽  
Stabilized Soil ◽  
Network Space

To reveal the influence mechanism of ettringite (AFt) crystals and microstructure characteristics on the strength of calcium-based stabilized soil, the strengths and microscopic properties of seven groups of stabilized soil samples were studied systematically through unconfined compressive strength, scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG), and Fourier transform infrared spectroscopy (FTIR) testing methods. The results indicate that the strength of the cement-stabilized soil is relatively high because abundant calcium silicate hydrate (CSH) gels coat the outer surface of soil particles to cement together. For the cement–gypsum-stabilized soil, superabundant thick and long AFt crystals make the pores in soil particles larger, and the sample becomes looser, resulting in lower strength than that of the cement-stabilized soil. However, the strength of the cement–gypsum–lime-stabilized soil is slightly stronger than that of the cement-stabilized soil, for the reason that the appropriate amount of fine AFt crystals fill the macropores between soil particles to form a network space structure and sufficient CSH gels cement the soil particles and the AFt crystals network space structure tightly together. It could be suggested that the components of calcium-based stabilizer should consider the optimal production balance between CSH gels and fine AFt crystals.

scholarly journals Strength Performance and Microstructure of Calcium Sulfoaluminate Cement-Stabilized Soft Soil

2021 ◽  
Vol 13 (4) ◽  
pp. 2295
Author(s):  
Hailong Liu ◽  
Jiuye Zhao ◽  
Yu Wang ◽  
Nangai Yi ◽  
Chunyi Cui
Keyword(s):  
Soft Soil ◽  
Hydration Product ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Strength Performance ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Stabilized Soil ◽  
Calcium Silicates ◽  
Hydrated Calcium

Calcium sulfoaluminate cement (CSA) was used to stabilize a type of marine soft soil in Dalian China. Unconfined compressive strength (UCS) of CSA-stabilized soil was tested and compared to ordinary Portland cement (OPC); meanwhile the influence of amounts of gypsum in CSA and cement contents in stabilized soils on the strength of stabilized soils were investigated. X-ray diffraction (XRD) tests were employed to detect generated hydration products, and scanning electron microscopy (SEM) was conducted to analyze microstructures of CSA-stabilized soils. The results showed that UCS of CSA-stabilized soils at 1, 3, and 28 d firstly increased and then decreased with contents of gypsum increasing from 0 to 40 wt.%, and CSA-stabilized soils exhibited the highest UCS when the content of gypsum equaled 25 wt.%. When the mixing amounts of OPC and CSA were the same, CSA-stabilized soils had a significantly higher early strength (1 and 3 d) than OPC. For CSA-stabilized soil with 0 wt.% gypsum, monosulfate (AFm) was detected as a major hydration product. As for CSA-stabilized soil with certain amounts of gypsum, the intensity of ettringite (Aft) was significantly higher than that in the sample hydrating without gypsum, but a tiny peak of AFm also could be detected in the sample with 15 wt.% gypsum at 28 d. Additionally, the intensity of AFt increased with the contents of gypsum increasing from 0 to 25 wt.%. When contents of gypsum increased from 25 to 40 wt.%, the intensity of AFt tended to decrease slightly, and residual gypsum could be detected in the sample with 40 wt.% gypsum at 28 d. In the microstructure of OPC-stabilized soils, hexagonal plate-shaped calcium hydroxide (CH) constituted skeleton structures, and clusters of hydrated calcium silicates (C-S-H) gel adhered to particles of soils. In the microstructure of CSA-stabilized soils, AFt constituted skeleton structures, and the crystalline sizes of ettringite increased with contents of gypsum increasing; meanwhile, clusters of the aluminum hydroxide (AH3) phase could be observed to adhere to particles of soils and strengthen the interaction.

Microstructure characteristics of non-monodisperse quantum dots: on the potential of transmission electron microscopy combined with X-ray diffraction

CrystEngComm ◽  
2020 ◽  
Vol 22 (21) ◽  
pp. 3644-3655
Author(s):  
Stefan Neumann ◽  
Christina Menter ◽  
Ahmed Salaheldin Mahmoud ◽  
Doris Segets ◽  
David Rafaja
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Characteristics ◽  
Scale Bridging ◽  
Transmission Electron ◽  
Hot Injection

Capability of TEM and XRD to reveal scale-bridging information about the microstructure of non-monodisperse quantum dots is illustrated on the CdSe quantum dots synthesized using an automated hot-injection method.

Advantages of a Redefinition of Variable-Space in Direct-Space Structure Solution from Powder X-Ray Diffraction Data

ChemPhysChem ◽  
2007 ◽  
Vol 8 (5) ◽  
pp. 650-653 ◽  
Author(s):  
Zhongfu Zhou ◽  
Veronique Siegler ◽  
Eugene Y. Cheung ◽  
Scott Habershon ◽  
Kenneth D. M. Harris ◽  
...  
Keyword(s):  
Diffraction Data ◽  
Space Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Solution ◽  
Variable Space

scholarly journals Structure and composition of soils

2010 ◽  
Vol 4 (4) ◽  
pp. 259-263 ◽  
Author(s):  
Snezana Nenadovic ◽  
Milos Nenadovic ◽  
Ljiljana Kljajevic ◽  
Vladimir Pavlovic ◽  
Aleksandar Djordjevic ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Porous Structure ◽  
X Ray Diffraction ◽  
Scanning Electronic Microscopy ◽  
Electronic Microscopy ◽  
Characterization Methods ◽  
Soil Particles ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force

This paper presents a study of soils structure and composition using up to date technique, such as scanning electronic microscopy, atomic force microscopy, X-ray diffraction, X-ray fluorescence, as well as some other characterization methods. It was shown that soil particles have porous structure and dimensions in the range from several millimeters to several hundreds of nanometers and consist of different minerals such as kaolin, quartz and feldspate.

scholarly journals Epoxy Resin’s Influence in Metakaolin-Based Geopolymer’s Antiseawater Corrosion Performance

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Wenrui Bian ◽  
Zhongchang Wang ◽  
Mo Zhang
Keyword(s):  
Compressive Strength ◽  
Corrosion Resistance ◽  
Epoxy Resin ◽  
Polymerization Process ◽  
X Ray Diffraction ◽  
Compact Structure ◽  
X Ray ◽  
Influence Mechanism ◽  
Seawater Corrosion ◽  
Average Compressive Strength

To obtain the influence mechanism of epoxy resin content, curing time, and other external factors on the compressive strength and seawater corrosion resistance of geopolymer, the NaOH and Na2SiO3 were used as activators; the effect of epoxy resin concentration on the corrosion resistance of metakaolin-based geopolymer was investigated by experiments. The mechanism of epoxy resin concentration affecting the polymerization process and the properties of geopolymer was analyzed by X-ray diffraction, scanning electron microscopy-energy spectrum, and Fourier transform infrared spectroscopy. It was shown that the epoxy resin slowed down the polymerization. The presence of epoxy resin had a beneficial effect on compact structure. Furthermore, compared with the noncorrosive specimen, mixed with 30% specimen’s average compressive strength increased by 4.77MPa and 4.24MPa after curing for 1d and 3d and soaking for 56d.

Microstructure Characteristics of Fe-xCr-C Hardfacing Alloys

2012 ◽  
Vol 472-475 ◽  
pp. 165-168
Author(s):  
Lin Zong ◽  
Zheng Jun Liu
Keyword(s):  
Solid Solution ◽  
Optical Microscopy ◽  
Arc Welding ◽  
Room Temperature ◽  
Gas Tungsten Arc Welding ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Characteristics ◽  
Gas Tungsten Arc ◽  
Gtaw Process

A series of Fe-xCr-C hardfacing alloys were successfully fabricated on a substrate of 20g steel by gas tungsten arc welding (GTAW) process. These claddings were disigned to observe hypoeutectic, near-eutectic, and hypereutectic structures with various Cr3C2 and M7C3 carbides at room temperature. According to X-ray diffraction(XRD) and optical microscopy (OM), the hypoeutectic and eutectic composites include the Fe-Cr solid solution(α+A) and Cr3C2 carbides. Hypereutectic structures consist of α+A+M+M7C3 respectively. The cladding of hypereutectic microstructure with great amounts of primary M7C3 carbides had the highest hardness of the all conditions.

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