scholarly journals Service Life Modeling of Concrete with SCMs Using Effective Diffusion Coefficient and a New Binding Model

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 967
Author(s):  
Mukhtar Oluwaseun Oluwaseun Azeez ◽  
Ahmed Abd El Fattah
Keyword(s):  
Diffusion Coefficient ◽  
Service Life ◽  
Binding Capacity ◽  
Effective Diffusion ◽  
Supplementary Cementitious Materials ◽  
Binding Model ◽  
Exposure Site ◽  
Free Chloride ◽  
Binding Data ◽  
Concrete Blocks

This paper presents a new algorithm that predicts the service life of concrete contains supplementary cementitious materials, SCMs, and determines time of corrosion initiation. The algorithm drives effective diffusivity from an apparent diffusion model, using experimental binding data performed in the lab, temperature, free ion concentration, and carbonation, and generates free chloride profiles for concrete with and without SCMs by using Fick’s law in a finite element model. Adjusting diffusion coefficient at each step of the solution, by addressing the impact of different parameters, simplifies the algorithm and reduces calculation time without jeopardizing the results’ quality. Results generated by the model compare well to the performance of concrete blocks constructed in an exposure site on the east coast of Saudi Arabia. The exposure site hosted five different mixes of Portland cement and SCMs, and the concrete blocks were exposed to harsh weather over the period of two years. Linear polarization and chloride profiling assessed the performance of the mixes against corrosion activities. Lab work identified the performance of the mixes through binding capacity and chloride profiling. Statistical analysis evidenced the accuracy of the model through correlation and regression analysis. Furthermore, a new proposed binding model, produced from binding data in different studies, alters the experimental binding data in the algorithm to decouple the solution from experimental values. The algorithm proves its accuracy when compared to the experimental free chloride profile. The proposed transport model proves that using effective diffusion and binding capacity are enough to generate reliable results, and the effective diffusion can be calibrated with environmental conditions such as temperature, age, and carbonation. Finally, the algorithm presents its features in an object-oriented programming using C# and user friendly web interface.

scholarly journals Field Validation of Concrete Transport Property Measurement Methods

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1166 ◽  
Author(s):  
Ahmed Abd El Fattah ◽  
Ibrahim Al-Duais ◽  
Kyle Riding ◽  
Michael Thomas ◽  
Salah Al-Dulaijan ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Corrosion Inhibitors ◽  
Effective Diffusion ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Exposure Site

Reinforcing steel corrosion, caused by chloride ingress into concrete, is the leading cause of reinforced concrete deterioration. One of the main findings in the literature for reducing chloride ingress is the improvement of the durability characteristics of concrete by the addition of supplementary cementitious materials (SCMs) and/or chemical agents to concrete mixtures. In this study, standard ASTM tests—such as rapid chloride permeability (RCPT), bulk diffusion and sorptivity tests—were used to measure concrete properties such as porosity, sorptivity, salt diffusion, and permeability. Eight different mixtures, prepared with different SCMs and corrosion inhibitors, were tested. Apparent and effective chloride diffusion coefficients were calculated using bound chloride isotherms and time-dependent decrease in diffusion. Diffusion coefficients decreased with time, especially with the addition of SCMs and corrosion inhibitors. The apparent diffusion coefficient calculated using the error function was slightly lower than the effective diffusion coefficient; however, there was a linear trend between the two. The formation factor was found to correlate with the effective diffusion coefficient. The results of the laboratory tests were compared and benchmarked to their counterparts in the marine exposure site in the Arabian Gulf in order to identify laboratory key tests to predict concrete durability. The overall performance of concrete containing SCMs, especially fly ash, were the best among the other mixtures in the laboratory and the field.

Experimental Research on Chloride-Induced Service Life of Sturctures under Loading Capacity Criterion

2012 ◽  
Vol 601 ◽  
pp. 227-231 ◽  
Author(s):  
Fu Xue Sun ◽  
Yun Hui Zhu
Keyword(s):  
Diffusion Coefficient ◽  
Service Life ◽  
Effective Diffusion ◽  
Chloride Ion ◽  
Test Model ◽  
Loading Capacity ◽  
Loading Test ◽  
Accelerated Corrosion ◽  
Actual Structure ◽  
Chloride Environment

The whole service life of reinforcement concrete structure under chloride environment was devided into two stages according to mechanism of degradation. Using diffusion test, content of chloride ion was tested to decide diffusion coefficient for different age and damped exponential of diffusion coefficient. Then, through using effective diffusion coeffient into solution of the Fick’s Second Law, service life of the first stage was predicted. For corrosion propogation phase, loading test was carried out to construct relationship between loading capacity of corroded test model and accelerated corrosion time. When using this relationship to actual structure, we calculated the service life of the second stage. These methods and results can be considered as reference to eveluate service life of structure under the samilar environment.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

The stirring of the medium by bull spermatozoa

1963 ◽  
Vol 157 (969) ◽  
pp. 461-472 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Short Range ◽  
Short Range Order ◽  
Effective Diffusion ◽  
Sperm Head ◽  
Special Shape ◽  
Bull Semen ◽  
Sperm Density ◽  
Bull Sperm ◽  
Diffusion Coefficient Of Oxygen

1. Bull semen diluted 1/5 or 1/10 respired at the same rate whether the manometers were stationary or shaken. 2. Respirometric experiments using a manometer flask of special shape showed that bull sperm suspensions achieve this result by increasing the effective diffusion coefficient of oxygen in the suspending medium by 900%. 3. The hypothesis is put forward ( a ) that these results are caused by the existence of short-range order, as opposed to disorder, in bull sperm suspensions, even at comparatively low sperm densities (dilution 1/8 to 1/20); ( b ) that this order produces group sperm velocities greater than those of isolated spermatozoa; and ( c ) that as a result, larger volumes of the suspending medium are convected with the ordered sperm groups, causing an augmented ‘diffusion’ of oxygen. 4. This hypothesis was examined by taking photomicrographs of sperm suspensions at different dilutions and temperatures and determining from them the distributions of (i) the distance between pairs of nearest spermatozoa; (ii) the angle of inclination of a sperm head relative to that of the spermatozoon nearest to it; and (iii) the relative position of the nearest spermatozoon. 5. Comparison of the observed distributions and the corresponding random ones showed that the spermatozoa attracted each other, so that transient sperm groups were formed, in which the spermatozoa tended to swim in the same direction. A reduction in temperature or sperm density decreased the sperm order.

Diffusion of Zinc in Two-Phase Mg-Al Alloy

2007 ◽  
Vol 263 ◽  
pp. 189-194
Author(s):  
Ivo Stloukal ◽  
Jiří Čermák
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Residual Activity ◽  
Diffusion Path ◽  
Al Alloy ◽  
Serial Sectioning ◽  
Two Phase ◽  
Interphase Boundaries ◽  
The Mean

Coefficient of 65Zn heterodiffusion in Mg17Al12 intermetallic and in eutectic alloy Mg - 33.4 wt. % Al was measured in the temperature region 598 – 698 K using serial sectioning and residual activity methods. Diffusion coefficient of 65Zn in the intermetallic can be written as DI = 1.7 × 10-2 m2 s-1 exp (-155.0 kJ mol-1 / RT). At temperatures T ≥ 648 K, where the mean diffusion path was greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Def = 2.7 × 10-2 m2 s-1 exp (-155.1 kJ mol-1 / RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Db (623 K) = 1.6 × 10-12 m2 s-1 and Db (598 K) = 4.4 × 10-13 m2 s-1.

scholarly journals Diffusion of calcium ions in retinal rods. A theoretical calculation.

1981 ◽  
Vol 77 (4) ◽  
pp. 475-487 ◽  
Author(s):  
S McLaughlin ◽  
J Brown
Keyword(s):  
Diffusion Coefficient ◽  
Adsorption Isotherm ◽  
Calcium Ions ◽  
Outer Segment ◽  
Effective Diffusion ◽  
Langmuir Adsorption Isotherm ◽  
Diffuse Double Layer ◽  
Langmuir Adsorption ◽  
Retinal Rods ◽  
Disk Membrane

The Fick diffusion equation is combined with the Langmuir adsorption isotherm and the relevant equations from the Gouy-Chapman theory of the electrical diffuse double layer to demonstrate that the effective diffusion coefficient of calcium ions, both in the cytoplasm of the rod outer segment and within the aqueous space bounded by the disk membrane, should be reduced by a factor of 10-100 because these ions adsorb to phospholipids present in the disk membrane.

scholarly journals Effects after 1500 Hardening Days on the Microstructure and Durability-Related Parameters of Mortars Produced by the Incorporation of Waste Glass Powder as a Clinker Replacement

2021 ◽  
Vol 13 (7) ◽  
pp. 3979
Author(s):  
Rosa María Tremiño ◽  
Teresa Real-Herraiz ◽  
Viviana Letelier ◽  
Fernando G. Branco ◽  
José Marcos Ortega
Keyword(s):  
Diffusion Coefficient ◽  
Water Absorption ◽  
Glass Powder ◽  
Cementitious Materials ◽  
Cement Industry ◽  
Waste Glass ◽  
Supplementary Cementitious Materials ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Waste Glass Powder

One of the ways of lessening the CO2 emissions of cement industry consists of replacing clinkers with supplementary cementitious materials. The required service life of real construction elements is long, so it is useful to characterize the performance of these materials in the very long term. Here, the influence of incorporating waste glass powder as a supplementary cementitious material, regarding the microstructure and durability of mortars after 1500 hardening days (approximately 4 years), compared with reference mortars without additions, was studied. The percentages of clinker replacement by glass powder were 10% and 20%. The microstructure was studied using impedance spectroscopy and mercury intrusion porosimetry. Differential thermal and X-ray diffraction analyses were performed for assessing the pozzolanic activity of glass powder at the end of the time period studied. Water absorption after immersion, the steady-state diffusion coefficient, and length change were also determined. In view of the results obtained, the microstructure of mortars that incorporated waste glass powder was more refined compared with the reference specimens. The global solid fraction and pores volume were very similar for all of the studied series. The addition of waste glass powder reduced the chloride diffusion coefficient of the mortars, without worsening their behaviour regarding water absorption after immersion.

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