scholarly journals A Chemical-Transport-Mechanics Numerical Model for Concrete under Sulfate Attack

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7710
Author(s):  
Xuandong Chen ◽  
Xin Gu ◽  
Xiaozhou Xia ◽  
Xing Li ◽  
Qing Zhang
Keyword(s):  
Numerical Model ◽  
Solid Phase ◽  
Sulfate Attack ◽  
Third Party ◽  
Time Dependent ◽  
Expansion Rate ◽  
Sulfate Concentration ◽  
Multiple Perspectives ◽  
Ion Diffusion ◽  
Sulfate Ion

Sulfate attack is one of the crucial causes for the structural performance degradation of reinforced concrete infrastructures. Herein, a comprehensive multiphase mesoscopic numerical model is proposed to systematically study the chemical reaction-diffusion-mechanical mechanism of concrete under sulfate attack. Unlike existing models, the leaching of solid-phase calcium and the dissolution of solid-phase aluminate are modeled simultaneously in the developed model by introducing dissolution equilibrium equations. Additionally, a calibrated time-dependent model of sulfate concentration is suggested as the boundary condition. The reliability of the proposed model is verified by the third-party experiments from multiple perspectives. Further investigations reveal that the sulfate attack ability is underestimated if the solid-phase calcium leaching is ignored, and the concrete expansion rate is overestimated if the dissolution of solid-phase aluminate is not modeled in the simulation. More importantly, the sulfate attack ability and the concrete expansion rate is overestimated if the time-dependent boundary of sulfate concentration is not taken into consideration. Besides, the sulfate ion diffusion trajectories validate the promoting effect of interface transition zone on the sulfate ion diffusion. The research of this paper provides a theoretical support for the durability design of concrete under sulfate attack.

Sulfate-Ion Diffusion Regularity and Reaction Mechanism of Sodium Sulfate Attack on Carbonized Concrete

2008 ◽  
Vol 400-402 ◽  
pp. 211-214
Author(s):  
Xiao Ke Li ◽  
Shun Bo Zhao ◽  
Chang Cheng Shi
Keyword(s):  
Reaction Mechanism ◽  
Sodium Sulfate ◽  
Concrete Specimen ◽  
Sulfate Solution ◽  
Sulfate Attack ◽  
Test Results ◽  
Ion Diffusion ◽  
Sulfate Ion ◽  
Titration Method ◽  
Sulfate Solutions

The experiment has been carried out to study the sodium sulfate attack on carbonized concrete. The concrete specimens with strength grade of C50 were first carbonized for 28d in the carbonation box after standard curing, and then immersed into the sodium sulfate solutions of three different concentrations. When the immersed time were up to 30d, 90d, 180d, 270d and 360d, the sulfate-ion concentrations of every layer from the surface to the inside of concrete specimen were measured by the chemical titration method. Based on the test results, the sulfate-ion diffusion regularity and the reaction mechanism of carbonized concrete are analyzed. It can be concluded that the sulfate-ion diffusion regularity and the reaction mechanism of carbonized concrete is completely different from that of un-carbonized concrete, the diffusion of sulfate-ion occupies advantage in the pore water of carbonized concrete, which increases the depth of concrete specimen attacked by sulfate solution.

Simulations on Expansive Strain of Concrete Caused by Ettringite Growth under Sulfate Attack

2011 ◽  
Vol 250-253 ◽  
pp. 1906-1911 ◽  
Author(s):  
Xiao Bao Zuo ◽  
Wei Sun
Keyword(s):  
Sulfate Solution ◽  
Sulfate Attack ◽  
Diffusion Time ◽  
Diffusion Reaction ◽  
Sulfate Ion ◽  
Reaction Equation ◽  
Ettringite Formation ◽  
Sulfate Solutions ◽  
Calcium Aluminates ◽  
Strain Responses

In order to assess theoretically the expansive strain of concrete caused by the ettringite formation and growth under the sulfate attack, some models are proposed to investigate the strain responses of concrete exposed to the sulfate solutions. Firstly, an 1-D nonlinear and nonsteady diffusion-reaction equation of sulfate ion in concrete is proposed; Secondly, based on chemical reactions between sulfate and aluminates in concrete, the expansive strain is obtained due to the ettringite growth resulting in concrete expansion. Thirdly, numerical simulations are carried out to analyze the formation process of the concrete expansive strain under the sulfate solution, and results show that the models can be used to predict the concrete responses with the diffusion time, such as the distribution concentration of sulfate ion, dissipated concentration of the calcium aluminates, expansion strain of concrete due to the formation and growth of ettringite.

scholarly journals Resveratrol-supplemented holding or re-culture media improves viability of fresh or vitrified-warmed in vitro-derived bovine embryos

2021 ◽  
Vol 10 (14) ◽  
pp. e367101422097
Author(s):  
Arianny Rafaela Neto Silva ◽  
Thaisa Campos Marques ◽  
Elisa Caroline Silva Santos ◽  
Tiago Omar Diesel ◽  
Isabelle Matos Macedo ◽  
...  
Keyword(s):  
Culture Media ◽  
Cell Number ◽  
Time Dependent ◽  
Expansion Rate ◽  
Ros Generation ◽  
Hatching Rate ◽  
Protective Effects ◽  
Bovine Embryos ◽  
In Vitro Production

The effect of resveratrol supplementation on fresh (E1) or vitrified/warmed (E2) in vitro produced bovine embryos was investigated by evaluating the time-dependent response. After in vitro production, resveratrol (0.5 µM) was added to the incubation media and after two incubation periods with or without resveratrol, blastocysts were re-cultured for 24h. The rates of re-expansion, hatching, total cell number (TCN), apoptotic cells (ACN), reactive oxygen species (ROS) and intracellular glutathione (GSH) content were evaluated. For E1, the re-expansion rate differed at 6 and 10h within and between treatments (P<0.05), as did the re-expansion rate after 24h (P<0.01). The hatching rate increased after 10h with resveratrol (P<0.01) with differences within (P<0.05), but not between treatments after 24h of re-cultivation. At E2, hatching rate differed between treatments at 24h (P<0.01), with higher TCN in resveratrol-treated blastocysts after 10h (P<0.01). Resveratrol supplementation reduced ROS generation in E1 and E2 after 10h of incubation and increased GSH content (P<0.01). These results indicate that supplementation of holding re-cultivation medium with resveratrol for treatment of fresh or vitrified/warmed in vitro produced bovine embryos has a positive and time-dependent effect. The reduction of ROS content, the increase of GSH and the anti-apoptotic ability of resveratrol are responsible for its protective effects, allowing an extension of embryo storage time before transfer to recipients.

scholarly journals Dynamic Pulse Buckling of Composite Stanchions in the Sub-Cargo Floor Area of a Civil Regional Aircraft

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3594
Author(s):  
Andrea Sellitto ◽  
Francesco Di Caprio ◽  
Michele Guida ◽  
Salvatore Saputo ◽  
Aniello Riccio
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Low Frequency ◽  
Time Dependent ◽  
Structural Behavior ◽  
Cyclic Loads ◽  
Civil Aircraft ◽  
Compressive Loads ◽  
Pulse Buckling ◽  
Implicit And Explicit

This work is focused on the investigation of the structural behavior of a composite floor beam, located in the cargo zone of a civil aircraft, subjected to cyclical low-frequency compressive loads with different amplitudes. In the first stage, the numerical models able to correctly simulate the investigated phenomenon have been defined. Different analyses have been performed, aimed to an exhaustive evaluation of the structural behavior of the test article. In particular, implicit and explicit analyses have been considered to preliminary assess the capabilities of the numerical model. Then, explicit non-linear analyses under time-dependent loads have been considered, to predict the behavior of the composite structure under cyclic loading conditions. According to the present investigation, low-frequency cyclic loads with peak values lower than the static buckling load value are not capable of triggering significant instability.

scholarly journals Cocrystal Formation through Solid-State Reaction between Ibuprofen and Nicotinamide Revealed Using THz and IR Spectroscopy with Multivariate Analysis

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 760
Author(s):  
Sae Ishihara ◽  
Yusuke Hattori ◽  
Makoto Otsuka ◽  
Tetsuo Sasaki
Keyword(s):  
Ir Spectroscopy ◽  
Solid Phase ◽  
Time Dependent ◽  
Multivariate Curve Resolution ◽  
Thz Spectroscopy ◽  
Water Molecules ◽  
Active Pharmaceutical Ingredients ◽  
Curve Resolution ◽  
Pharmaceutical Ingredients ◽  
Solid Phase Reactions

Cocrystallisation can enhance the solubility and bioavailability of active pharmaceutical ingredients (APIs); this method may be applied to improve the availability of materials that were previously considered unsuitable. Terahertz (THz) spectroscopy provides clear, substance-specific fingerprint spectra; the transparency of the THz wave allows us to probe inside a sample to identify medicinal materials. In this study, THz and infrared (IR) spectroscopy were used to characterise cocrystallisation in solid-phase reactions between ibuprofen and nicotinamide. Multivariate curve resolution with alternating least squares (MCR-ALS) was applied to both time-dependent THz and IR spectra to identify the intermolecular interactions between these cocrystallising species. The analytical results revealed cocrystal formation through a two-step reaction, in which the steps were dominated by thermal energy and water vapour, respectively. We infer that the presence of water molecules significantly lowered the activation energy of cocrystal formation.

Application of Two Phase Eulerian CFD Model to Simulate High Velocity Jet Induced Scour

2020 ◽  
Author(s):  
Nicholas S. Tavouktsoglou ◽  
Aggelos Dimakopoulos ◽  
Jeremy Spearman ◽  
Richard J. S. Whitehouse
Keyword(s):  
Numerical Model ◽  
High Velocity ◽  
Stokes Equations ◽  
Solid Phase ◽  
Three Dimensional ◽  
Water Jet ◽  
Ocean Engineering ◽  
Two Phase ◽  
Water Jets ◽  
Good Agreement

Abstract Submerged water jet causing soil excavation is a typical water-soil interaction process that occurs widely in many engineering disciplines. In hydraulic engineering for instance, a typical example would be scour downstream of headcuts, culverts, or dam spillways. In port and waterway engineering, erosion of the channel bed or quay wall by the propellers of passing ships are also typical water jet/soil interaction problems. In ocean engineering, trenching by impinging high-velocity water jets has been used as an efficient method for cable and pipeline burial. At present, physical modelling and simple prediction equations have been the main practical engineering tool for evaluating scour in these situations. However, with the increasing computational power of modern computers and the development of new Computational Fluid Dynamics (CFD) solvers, scour prediction in such engineering problems has become possible. In the present work three-dimensional (3D) numerical modelling has been applied to reproduce the capability of a pair of water jets to backfill an excavated trench. The simulations are carried out using a state-of-the-art three-dimensional Eulerian two-phase scour model based on the open source CFD software OpenFOAM. The fluid phase is resolved by solving modified Navier-Stokes equations, which take into consideration the influence of the solid phase, i.e., the soil particles. This paper first presents a validation of the numerical model against vertical jet erosion tests from the literature and conducted at HR Wallingford. The results of the model show good agreement with the experimental tests, with the numerical model predicting the scour hole depth and extent with good accuracy. The paper then presents a validation of the model’s ability to reproduce deposition which is evaluated through a comparison with settling velocity data and empirical formulations found in literature, again with the model showing good agreement. Finally, the model is applied to a prototype cable burial problem using a commercially available controlled flow jet excavator. The study found that the use of water jets can be effective (subject to confirmation of the time-scale required for real operations) for performing backfill operations but that the effectiveness is closely related to the type of sediment and selection of an appropriate jet discharge. As a result, in order for the water jet method to be effective for backfill, there is a requirement for a good description of the variation in sediment type along the trench and a requirement for the jet discharge to be varied as different sediment types are encountered.

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