Research on the Mechanical Properties and NMR Characteristics of Cement Mortar during Freeze‐Thaw Cycles

Liu, Taoying; Wang, Yunmin; Zhou, Keping; Gao, Feng; Xie, Shucheng

doi:10.1155/2019/6805480

Cited by 11 publications

(3 citation statements)

References 27 publications

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“…A magnetic field produced by the spin of a positively charged atomic nucleus is known as nuclear magnetism. Measureable signals can be produced by the interaction of the magnetic field generated by spin nuclear magnetism with the applied magnetic field [32][33][34]. A magnetic field can be produced by the hydrogen proton spin.…”

Section: The Principle Of Nuclear Magnetic Resonance Testing Pore Str...mentioning

confidence: 99%

Study on Mechanical Properties and Microscopic Mechanism of PVA-Modified Recycled Brick Aggregate Concrete

Qiu,

Zhang,

Qin

et al. 2024

Sustainability

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This paper addresses a range of environmental issues stemming from the improper disposal of construction waste and its low recycling rate by examining the effects and mechanisms of polyvinyl alcohol (PVA) solution in modifying recycled aggregates. Basic physical properties, energy-dispersive spectroscopy (EDS), X-Ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to study these effects and mechanisms. Tests on basic mechanical properties were performed to assess the impact of aggregate modification and the brick-concrete ratio on recycled brick-aggregate concrete’s mechanical characteristics. Nuclear magnetic resonance and microhardness tests were performed to analyze the influence exerted by PVA modification on the interfacial transition zone (ITZ), microstructure, and pore structure, thus exploring the connection between modified recycled-brick-aggregate concrete’s microstructure and its icromechanical properties. The findings show that the water absorption and crushing index of recycled aggregates (RA) immersed in a 10% PVA solution for 24 h decrease significantly, while the apparent density increases most notably. This phenomenon can be ascribed to the development of a PVA coating on the exterior of the reused aggregates. The optimal mechanical properties for recycled brick aggregate concrete (RAC) occur when the replacement rate is 30% and the brick-concrete ratio is 1:1. The compressive strength is 44.2 MPa, the bending strength is 15.6 MPa, and the splitting tensile strength is 3.85 MPa. Additionally, the modification with PVA results in a higher percentage of transition pores, while simultaneously reducing the percentage of macropores. There is an uptick in the frequency of harmless and less harmful pores, and a declining proportion of harmful and more harmful pores. The ITZ’s structural morphology in the RAC is effectively improved by the coating structure formed through the bonding of the polymer with cement hydration products, and PVA modification reduces the thickness of this zone.

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Section: The Principle Of Nuclear Magnetic Resonance Testing Pore Str...mentioning

confidence: 99%

Study on Mechanical Properties and Microscopic Mechanism of PVA-Modified Recycled Brick Aggregate Concrete

Qiu,

Zhang,

Qin

et al. 2024

Sustainability

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“…Cheng et al [22] studied the porous damage of rock under freezethaw, carried out SEM and NMR technology tests on siltstone under different freeze-thaw times, and analyzed the distribution characteristics of the pore structure of siltstone. Liu et al [23] used NMR technology to study the mechanical properties, pore size, and distribution of cement mortar in freeze-thaw times. Wang et al [24,25] used NMR to study natural pumice concrete after freeze-thaw times.…”

Section: Introductionmentioning

confidence: 99%

Mechanism Analysis of the Influence of Freeze-Thaw on the Damage and Debonding Evolution of Sandstone-Concrete Interface

et al. 2022

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During tunnel construction in cold regions, the good adhesion of surrounding rock-lining interface is one of the important preconditions to evaluate the durability of tunnel lining. However, the repeated fatigue damage between rock and concrete due to the freeze-thaw action leads to debonding at the interface, which significantly affects the protective effect of shotcrete. Accordingly, based on the combination of sandstone-concrete as the object, through the development of sandstone-concrete interface freeze-thaw cycling test, and combining the nuclear magnetic resonance (NMR) test and scanning electron microscopy (SEM) analysis, the mechanism of debonding by freeze-thaw damage at the sandstone-concrete interface was systematically revealed. The conclusions drawn are as follows: (1) With the increase of freeze-thaw times, the content of micropores and macropores at the interface gradually increases, while the content of mesoporous gradually decreases. At the same time, the decrease of freeze-thaw temperature also aggravates the growth of interface cracks, and the freeze-thaw damage of interface is closely related to the minimum freeze-thaw temperature. (2) The damage of the sandstone side becomes more serious under multiple freeze-thaw actions. Concrete as a water retaining plate inhibits the migration of water to its interior, and a pot cover effect exists at the interface to provide better storage space for water accumulation. (3) The C-S-H group is the main source of the bond force of sandstone-concrete interface, and the freeze-thaw effect aggravates the fracture of the C-S-H group, which leads to the interface debonding. This study could provide an experimental basis and theoretical support for systematically recognizing the evolution mechanism of freeze-thaw damage and debonding of shotcrete in tunnels in cold regions.

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“…Interestingly, the mechanical strength 12 and the owability 19 is found to decrease with the increase of the CNTs in the cement paste matrix. Other factors affecting the physical and mechanical 20 properties of such concretes are the density and the types of pure or impure silicates 6 , sulphates and aluminates 21 compounds 6,11,22 , water to cement ratio 10,23,24 , and calcium to silicon ratio [25][26][27] .…”

Section: Introductionmentioning

confidence: 99%

Influence of CNTs, ZnO, Gd2O3 and SiO2 on Calcium Silicate Hydrate: A Raman spectroscopic study

Azeem

2021

Preprint

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Raman spectra are collated from the cement paste matrices of CNTs, ZnO, Gd2O3, and SiO2. The spectra show that CNTs do not take part in hydration process and therefore concentration of calcium silicate hydrate (CSH) is unchanged in CNT-OPC matrix. The metal oxides, on the other hand, have shown significant effects on the CSH concentration. The CSH concentration increases with the increase of ZnO weight percent in the matrix whereas spectra collected from Gd2O3 matrix shows the strongest CSH vibrational bands. Moreover, vibrational bands of CaCO3 also become weak in the matrices with Gd2O3. The addition of SiO2 however had opposite effects that is by increasing the weight percent of SiO2 in the matrix, the CSH concentration is decreased. Since CSH acts a glue in a binder, the study shows that its concentration can be controlled by adding foreign elements. Such binders are expected to show improved strength and durability.

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Research on the Mechanical Properties and NMR Characteristics of Cement Mortar during Freeze‐Thaw Cycles

Cited by 11 publications

References 27 publications

Study on Mechanical Properties and Microscopic Mechanism of PVA-Modified Recycled Brick Aggregate Concrete

Study on Mechanical Properties and Microscopic Mechanism of PVA-Modified Recycled Brick Aggregate Concrete

Mechanism Analysis of the Influence of Freeze-Thaw on the Damage and Debonding Evolution of Sandstone-Concrete Interface

Influence of CNTs, ZnO, Gd2O3 and SiO2 on Calcium Silicate Hydrate: A Raman spectroscopic study

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