scholarly journals Effect of Fly Ash as Cement Replacement on Chloride Diffusion, Chloride Binding Capacity, and Micro-Properties of Concrete in a Water Soaking Environment

2020 ◽  
Vol 10 (18) ◽  
pp. 6271 ◽  
Author(s):  
Jun Liu ◽  
Jiaying Liu ◽  
Zhenyu Huang ◽  
Jihua Zhu ◽  
Wei Liu ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Binding Capacity ◽  
Chloride Ion ◽  
Chloride Content ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Binding ◽  
Test Results ◽  
New Equation

This paper experimentally studies the effects of fly ash on the diffusion, bonding, and micro-properties of chloride penetration in concrete in a water soaking environment based on the natural diffusion law. Different fly ash replacement ratio of cement in normal concrete was investigated. The effect of fly ash on chloride transportation, diffusion, coefficient, free chloride content, and binding chloride content were quantified, and the concrete porosity and microstructure were also reported through mercury intrusion perimetry and scanning electron microscopy, respectively. It was concluded from the test results that fly ash particles and hydration products (filling and pozzolanic effects) led to the densification of microstructures in concrete. The addition of fly ash greatly reduced the deposition of chloride ions. The chloride ion diffusion coefficient considerably decreased with increasing fly ash replacement, and fly ash benefits the binding of chloride in concrete. Additionally, a new equation is proposed to predict chloride binding capacity based on the test results.

scholarly journals Concrete with Improved Chloride Binding and Chloride Resistivity by Blended Cements

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Katalin Kopecskó ◽  
György L. Balázs
Keyword(s):  
Binding Capacity ◽  
Experimental Studies ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Ion Binding ◽  
Chloride Binding ◽  
Test Results ◽  
Blended Cements ◽  
Water To Cement Ratio ◽  
Selection Of

Durability and service life of concrete structures can be endangered by chloride ions. Two phenomena help to keep control of chloride effects. On one hand cements are able to bind chloride ions by their aluminate clinker phases or by the clinker substituting materials. On the other hand resistivity of concrete against chloride penetration can be improved by careful selection of concrete constituents and production. Detailed results of two series of extensive experimental studies are presented herein. Chloride ion binding capacity of tested cements in decreasing sequence was the following: (1) CEM III/B 32,5 N-S; (2) CEM III/A 32,5 N; (3) CEM II/B 32,5 R; (4) CEM II/B-M (V-L) 32,5 R; (5) CEM I 42,5 N. Test results indicated that the increasing substitution of clinkers by GGBS improves the chloride resistivity in concrete made with the same water to cement ratio. The application of air entraining agent increases considerably the values of Dnssm. Based on the migration coefficients (Dnssm) the following sequence of efficiency was found (from the best): CEM III/B 32,5 N > CEM V/A (S-V) 32,5 N > CEM III/A 32,5 N > CEM II/B-S 42,5 R > CEM II/A-S 42,5 N > CEM I 42,5 N.

scholarly journals Chloride Binding Capacity and Its Effect on the Microstructure of Mortar Made with Marine Sand

2021 ◽  
Vol 13 (8) ◽  
pp. 4169
Author(s):  
Congtao Sun ◽  
Ming Sun ◽  
Tao Tao ◽  
Feng Qu ◽  
Gongxun Wang ◽  
...  
Keyword(s):  
Binding Capacity ◽  
Chloride Content ◽  
Chloride Ions ◽  
Fine Aggregate ◽  
Chloride Binding ◽  
River Sand ◽  
Total Chloride ◽  
Curing Period ◽  
Marine Sand ◽  
Bound Chloride

Chloride binding capacity and its effect on the microstructure of mortar made with marine sand (MS), washed MS (WMS) and river sand (RS) were investigated in this study. The chloride contents, hydration products, micromorphology and pore structures of mortars were analyzed. The results showed that there was a diffusion trend for chloride ions from the surface of fine aggregate to cement hydrated products. During the whole curing period, the free chloride content in the mortars made by MS and WMS increased firstly, then decreased and stabilized finally with time. However, the total chloride content of three types of mortar hardly changed. The bound chloride content in the mortars made by MS and WMS slightly increased with time, and the bound chloride content included the MS, the WMS and the RS arranged from high to low. C3A·CaCl2·10H2O (Friedel’s salt) was formed at the early age and existed throughout the curing period. Moreover, the volume of fine capillary pore with a size of 10–100 nm increased in the MS and WMS mortar.

scholarly journals Experimental Study on Chloride Ion Diffusion in Concrete under Uniaxial and Biaxial Sustained Stress

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5717
Author(s):  
Xiaokang Cheng ◽  
Jianxin Peng ◽  
C.S. Cai ◽  
Jianren Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Compressive Stress ◽  
Stress Level ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Chloride Ion Diffusion

The existence of axial and lateral compressive stress affect the diffusion of chloride ions in concrete will lead to the performance degradation of concrete structure. This paper experimentally studied the chloride diffusivity properties of uniaxial and biaxial sustained compressive stress under one-dimensional chloride solution erosion. The influence of different sustained compressive stress states on chloride ion diffusivity is evaluated by testing chloride concentration in concrete. The experiment results show that the existence of sustained compressive stress does not always inhibit the diffusion of chloride ions in concrete, and the numerical value of sustained compressive stress level can affect the diffusion law of chloride ions in concrete. It is found that the chloride concentration decreases most when the lateral compressive stress level is close to 0.15 times the compressive strength of concrete. In addition, the sustained compressive stress has a significant effect on chloride ion diffusion of concrete with high water/cement ratio. Then, the chloride diffusion coefficient model under uniaxial and biaxial sustained compressive stress is established based on the apparent chloride diffusion coefficient. Finally, the results demonstrate that the chloride diffusion coefficient model is reasonable and feasible by comparing the experimental data in the opening literature with the calculated values from the developed model.

scholarly journals Evaluation of Chloride Resistance of Early-Strength Concrete Using Blended Binder and Polycarboxylate-Based Chemical Admixture

2020 ◽  
Vol 10 (8) ◽  
pp. 2972 ◽  
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee
Keyword(s):  
Compressive Strength ◽  
Diffusion Coefficient ◽  
Portland Cement ◽  
Chloride Ion ◽  
Strength Criterion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Characteristic Strength ◽  
Early Strength

The mixing proportions of concrete were examined with regard to the durability performance and early strength in coastal areas. Research was conducted to improve the C24 mix (characteristic strength of 24 MPa). C35 concrete (characteristic strength of 35 MPa) was selected as a comparison group, as it exhibits the minimum proposed strength criterion for concrete in the marine environment. To secure the early strength of the C24 concrete, 50% of the total ordinary Portland cement (OPC) binder was replaced with early Portland cement (EPC); and to provide durability, 20% was substituted with ground granulated blast-furnace slag (GGBS). In addition, a polycarboxylate (PC)-based superplasticizer was used to reduce the unit water content. The compressive strength, chloride ion diffusion coefficient, chloride penetration depth, and pore structure were evaluated. After one day, the compressive strength improved by 40% when using EPC and GGBS, and an average increase of 20% was observed over 91 days. EPC and GGBS also reduced the overall porosity, which may increase the watertightness of concrete. The salt resistance performance was improved because the rapid early development of strength increased the watertightness of the surface and immobilization of chloride ions, decreasing the chloride diffusion coefficient by 50%.

scholarly journals Chloride Resistance of Portland Cement-Based Mortar Incorporating High Aluminate Cement and Calcium Carbonate

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 359 ◽  
Author(s):  
Yunsu Lee ◽  
Seungmin Lim ◽  
Hanseung Lee
Keyword(s):  
Diffusion Coefficient ◽  
Calcium Carbonate ◽  
Pore Volume ◽  
Binding Capacity ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Chloride Binding ◽  
Chloride Resistance ◽  
Aluminate Cement ◽  
Capillary Pore

Whether chloride resistance is highly influenced by chloride binding capacity remains unknown. In this study, the chloride resistance of Portland cement-based mortar incorporating aluminate cement and calcium carbonate was investigated considering the chloride binding capacity, pore structures and chloride diffusion coefficient from non-steady state chloride migration and natural chloride diffusion. The cement hydrates were investigated using X-ray diffraction and thermogravimetric analysis. The chloride binding capacity was evaluated based on the chloride adsorption from the solutions using the adsorption isotherm. The aluminate cement, as an available alumina source, can stimulate the formulation of layered double hydroxides, which in turn can increase the chloride binding capacity. The results of mercury intrusion porosimetry show that non-substituted (control) and substituted (only aluminate cement) specimens have capillary pore volume 8.9 vol % and 8.2 vol %, respectively. However, the specimen substituted with aluminate cement and calcium carbonate shows a higher capillary volume (12.9 vol %), which correlates with the chloride diffusion coefficient. Although the specimen substituted with calcium carbonate has a higher chloride binding capacity than the control, it does not necessarily affect the decrease in the chloride diffusion coefficient. The capillary pore volume can affect not only the chloride diffusion but also the chloride adsorption.

Research on Chloride Diffusion Model in Pre-Stressed Concrete with Sulfate Attack

2012 ◽  
Vol 166-169 ◽  
pp. 1935-1940
Author(s):  
Rong Gui Liu ◽  
Jing Li ◽  
Huan Li
Keyword(s):  
Diffusion Coefficient ◽  
Binding Capacity ◽  
Chloride Ion ◽  
Sulfate Attack ◽  
Ion Concentration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Influence Of Water ◽  
Binder Ratio ◽  
Chloride Environment

Chloride diffusion coefficient is significant to the durability of pre-stressed concrete in chloride environment. The factors which influence chloride diffusion coefficient in pre-stressed concrete structures eroded by chloride ion is of great importance, including porosity, chloride ion binding capacity and the stress of pre-stressed concrete etc. Based on the Fick’s second law and existing models, the model of chloride ion diffusion in pre-stressed concrete with sulfate attack is established. It is analyzed that the influence of water-binder ratio and sulfate ion concentration and erosion time on concentration distribution of chloride ion in concrete. Compared to test data and project examples, it is confirmed that the model is useful.

Experimental Study and Numerical Analysis on Chloride Diffusion Coefficient of Concrete with Various Water-Cement Ratios

2017 ◽  
Vol 726 ◽  
pp. 547-552
Author(s):  
Zheng Ren ◽  
Lian Zhen Xiao ◽  
Wen Chong Shi
Keyword(s):  
Diffusion Coefficient ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Chloride Ion Diffusion

A rapid chloride ion diffusion coefficient measurement (RCM) was used in this study. The influence of water-cement ratios of 0.30, 0.35 and 0.40 at various ages (3, 7, 14, 28 and 56 days) on chloride ion diffusion coefficient of the concretes and pastes was studied and analyzed. The results show that, with the increase of curing ages, the chloride ion diffusion coefficient of different water-cement ratio of each specimen is decreased. In the early age, the chloride ion diffusion coefficient of the paste with the water-cement ratio of 0.40 is 2~3 times of the paste with water-cement ratio of 0.30 and 0.35, and with the increase of curing age, this difference is gradually decreased. Additionally, the chloride ion diffusion coefficient of the cement paste is 1~2 times of the concrete with same water-cement ratio at different ages. Based on the actual experiment boundary conditions, the process of chloride ions diffusion and permeability was simulated by COMSOL software, and the simulation result was analyzed to predict the permeability of concrete.

Effect of Mineral Admixtures on Chloride Binding Mechanism in Concrete

2012 ◽  
Vol 204-208 ◽  
pp. 3716-3719
Author(s):  
Qiao Zhu ◽  
Yi Chen ◽  
Lin Hua Jiang
Keyword(s):  
Fly Ash ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Chloride Binding ◽  
Stray Current ◽  
Total Chloride ◽  
Free Chloride ◽  
The Stability

The chloride binding mechanisms of different mineral admixtures under the condition of stray current and NaCl solute were researched. The electric potential titration was used to measure the content of total chloride ions and free chloride ions. The results show that using of mineral admixture could effectively inhibit the destructive action of the stray current to the stability of bound chloride ion in cement paste. Among all, the most effective mix proportion on chloride-induced corrosion is the mixture with only slag, then the double mixing of fly ash and slag, the last comes the mixture with only fly ash.

Concentration Distribution of Chloride Ion in Cracked Concrete

2013 ◽  
Vol 351-352 ◽  
pp. 1581-1584
Author(s):  
Bo Yu ◽  
Zhong Hui Huang ◽  
Ming Wu ◽  
Hui Liang Sun ◽  
Lu Feng Yang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Concentration Distribution ◽  
Chloride Ion ◽  
Diffusion Path ◽  
Chloride Ions ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cracked Concrete ◽  
Ions Transport

Cracks provide diffusion path for chloride ions transport from the external environment into the concrete, resulting in the durability degradation of concrete structures. In this paper, the boundary condition of cracked concrete and chloride diffusion coefficient in crack were analyzed. The time-dependent chloride diffusion model was established based on the time-dependent chloride diffusion coefficient and the Ficks second law of diffusion. The influence of crack on the concentration distribution of chloride ion in cracked concrete was quantificationally investigated.

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