Chemo-Micro-Dilatation Modeling of Carbonation Shrinkage Phenomenon of the Porous Mortars

In this paper, we investigate the CO2 carbonation on porous materials such as the cement paste mortar. Our scientific goal is to model the CO2 carbonation effect on the porous cement mortar by the micro-dilatation theory and to determine the chemo-mechanical stress development due to the chemical reactions. In fact, this phenomenon will modify not only the pH value of the cement paste but also the micro-structure due to collapsing pore-network. Based upon the micro-dilatation theory originally proposed by Cowin and Nunziato, four unknown parameters related to the micro-structure will be determined for the cement mortar using the semi-empirical method and numerical modeling. The experimental carbonation tests on two different types of cement paste (CEMI and CEMIII) have been realized to capture carbonated affected zones and to measure their shrinkage deformations.

Download Full-text

An Efficient Approach of Predicting the Elastic Property of Hydrating Cement Paste

Frontiers in Materials ◽

10.3389/fmats.2021.729644 ◽

2021 ◽

Vol 8 ◽

Author(s):

Baoyu Ma ◽

Guansuo Dui ◽

Zhenglin Jia ◽

Bo Yang ◽

Chunyan Yang ◽

...

Keyword(s):

Elastic Properties ◽

Cement Paste ◽

Volume Fraction ◽

Solid Volume Fraction ◽

Empirical Method ◽

Elastic Behavior ◽

Engineering Practice ◽

Proposed Model ◽

Hydration Model ◽

Semi Empirical

Although elastic properties of hydrating cement paste are crucial in concrete engineering practice, there are only a few widely available models for engineers to predict the elastic behavior of hydrating cement paste. Therefore, in this paper, we derive an analytical model to efficiently predict the elastic properties (e.g., Young’s modulus) of hydrating cement paste. Notably, the proposed model provides the prediction of hydration, percolation, and homogenization of the cement paste, enabling the study of the early age elasticity evolution in cement paste. A hydration model considering the mineral composition and the initial w/c ratio was used, while the percolation threshold was calculated adopting a phenomenological semi-empirical method describing the effects of the solid volume fraction and the w/c ratio. An efficient mixing rule based on the degree of solid connectivity was then adopted to calculate the elastic properties of the hydrating cement paste. Moreover, for ordinary Portland cement, a simplified model was built using Powers’ hydration model. The obtained modeling results are following experimental data and other numerical results available in the literature.

Download Full-text

Modeling the Effects of O-sulfonation on the CID of Serine

10.26434/chemrxiv.11783628.v2 ◽

2020 ◽

Author(s):

Kenneth Lucas ◽

George Barnes

Keyword(s):

Sulfo Group ◽

High Energy ◽

Empirical Method ◽

Side Chain ◽

Energy Structure ◽

Direct Dynamics ◽

Theoretical Mass ◽

Intermolecular Proton Transfer ◽

Dynamics Simulations ◽

Semi Empirical

We present the results of direct dynamics simulations and DFT calculations aimed at elucidating the effect of \textit{O}-sulfonation on the collision induced dissociation for serine. Towards this end, direct dynamics simulations of both serine and sulfoserine were performed at multiple collision energies and theoretical mass spectra obtained. Comparisons to experimental results are favorable for both systems. Peaks related to the sulfo group are identified and the reaction dynamics explored. In particular, three significant peaks (m\z 106, 88, and 81) seen in the theoretical mass spectrum directly related to the sulfo group are analyzed as well as major peaks shared by both systems. Our analysis shows that the m\z 106 peaks result from intramolecular rearrangements, intermolecular proton transfer among complexes composed of initial fragmentation products, and at high energy side-chain fragmentation. The \mz 88 peak was found to contain multiple constitutional isomers, including a previously unconsidered, low energy structure. It was also seen that the RM1 semi empirical method was not able to obtain all of the major peaks seen in experiment for sulfoserine. In contrast, PM6 did obtain all major experimental peaks.

Download Full-text

Theoretical investigation of Ramachandran plot of N-formyl-L-alanine-amide

10.31221/osf.io/8gbdp ◽

2019 ◽

Author(s):

Chem Int

Keyword(s):

Genetic Algorithm ◽

Theoretical Investigation ◽

Energy Analysis ◽

Empirical Method ◽

Conformational Space ◽

Ramachandran Plot ◽

Global Minima ◽

Reasonable Time ◽

Semi Empirical

The full conformational space of N-formyl-L-alanine-amide was explored by the semi-empirical method AM1 coupled to the Multi Niche Crowding (MNC) genetic algorithm implemented in a package of programs developed in our laboratory. The structural and energy analysis of the resulting conformational space E(,ψ) exhibits 5 regions or minima ɣL, ɣD, ɛL, D and αD. The technique provides better detection of local and global minima within a reasonable time.

Download Full-text

Radiation protection instrumentation. Semi-empirical method for performance evaluation of detection and radionuclide identification

10.3403/30320911u ◽

2017 ◽

Keyword(s):

Performance Evaluation ◽

Radiation Protection ◽

Empirical Method ◽

Semi Empirical

Download Full-text

Radiation protection instrumentation. Semi-empirical method for performance evaluation of detection and radionuclide identification

10.3403/30320911 ◽

2017 ◽

Keyword(s):

Performance Evaluation ◽

Radiation Protection ◽

Empirical Method ◽

Semi Empirical

Download Full-text

Preparation of Electric- and Magnetic-Activated Water and Its Influence on the Workability and Mechanical Properties of Cement Mortar

Sustainability ◽

10.3390/su13084546 ◽

2021 ◽

Vol 13 (8) ◽

pp. 4546

Author(s):

Kaiyue Zhao ◽

Peng Zhang ◽

Bing Wang ◽

Yupeng Tian ◽

Shanbin Xue ◽

...

Keyword(s):

Magnetic Field ◽

Mechanical Properties ◽

Compressive Strength ◽

Flexural Strength ◽

Cement Paste ◽

Cement Mortar ◽

Environmental Issues ◽

Chemical Admixtures ◽

Untreated Water ◽

Alternating Voltage

Cement-based materials prepared with activated water induced by a magnetic field or electric field represent a possible solution to environmental issues caused by the worldwide utilization of chemical admixtures. In this contribution, electric- and magnetic-activated water have been produced. The workability and mechanical properties of cement mortar prepared with this activated water have been investigated. The results indicate that the pH and absorbance (Abs) values of the water varied as the electric and magnetic field changed, and their values increased significantly, exhibiting improved activity compared with that of the untreated water. In addition, activated water still retains activity within 30 min of the resting time. The fluidity of the cement paste prepared with electric-activated water was significantly larger than that of the untreated paste. However, the level of improvement differed with the worst performance resulting from cement paste prepared with alternating voltage activated water. In terms of mechanical properties, both compressive strength and flexural strength obtained its maximum values at 280 mT with two processing cycles. The compressive strength increased 26% as the curing time increased from 7 days to 28 days and flexural strength increased by 31%. In addition, through the introduction of magnetic-activated water into cement mortar, the mechanical strength can be maintained without losing its workability when the amount of cement is reduced.

Download Full-text

How Good Is the STW Sensor? An Account from a Larger Shipping Company

Journal of Marine Science and Engineering ◽

10.3390/jmse9050465 ◽

2021 ◽

Vol 9 (5) ◽

pp. 465

Author(s):

Angelos Ikonomakis ◽

Ulrik Dam Nielsen ◽

Klaus Kähler Holst ◽

Jesper Dietz ◽

Roberto Galeazzi

Keyword(s):

High Frequency ◽

Additional Data ◽

Empirical Method ◽

Influential Factor ◽

Sensor Data ◽

Sea State ◽

Shipping Company ◽

Frequency Sensor ◽

Semi Empirical

This paper examines the statistical properties and the quality of the speed through water (STW) measurement based on data extracted from almost 200 container ships of Maersk Line’s fleet for 3 years of operation. The analysis uses high-frequency sensor data along with additional data sources derived from external providers. The interest of the study has its background in the accuracy of STW measurement as the most important parameter in the assessment of a ship’s performance analysis. The paper contains a thorough analysis of the measurements assumed to be related with the STW error, along with a descriptive decomposition of the main variables by sea region including sea state, vessel class, vessel IMO number and manufacturer of the speed-log installed in each ship. The paper suggests a semi-empirical method using a threshold to identify potential error in a ship’s STW measurement. The study revealed that the sea region is the most influential factor for the STW accuracy and that 26% of the ships of the dataset’s fleet warrant further investigation.

Download Full-text

On the Estimation of Reliability of Weighted Weibull Distribution: A Comparative Study

International Journal of Statistics and Probability ◽

10.5539/ijsp.v5n4p1 ◽

2016 ◽

Vol 5 (4) ◽

pp. 1

Author(s):

Bander Al-Zahrani

Keyword(s):

Maximum Likelihood ◽

Weibull Distribution ◽

Real Data ◽

Reliability Function ◽

Nonparametric Methods ◽

Empirical Method ◽

Density Estimator ◽

Bayes Estimators ◽

Unknown Parameters ◽

Data Set

The paper gives a description of estimation for the reliability function of weighted Weibull distribution. The maximum likelihood estimators for the unknown parameters are obtained. Nonparametric methods such as empirical method, kernel density estimator and a modified shrinkage estimator are provided. The Markov chain Monte Carlo method is used to compute the Bayes estimators assuming gamma and Jeffrey priors. The performance of the maximum likelihood, nonparametric methods and Bayesian estimators is assessed through a real data set.

Download Full-text