scholarly journals Correlation between diffusion coefficient values of chloride ions obtained through column and ion migration tests in cementitious matrices with varying contents of silica fume and mortar

2022 ◽  
Vol 15 (3) ◽  
Author(s):  
Silas de Andrade Pinto ◽  
Sandro Lemos Machado ◽  
Daniel Véras Ribeiro
Keyword(s):  
Silica Fume ◽  
Coarse Aggregate ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Transport Mechanisms ◽  
Ion Diffusion ◽  
Column Tests ◽  
Ion Migration ◽  
Chloride Migration ◽  
Chloride Ion Diffusion

Abstract Corrosion is one of the main phenomena that lead to pathological manifestations in reinforced concrete structures under aggressive environments. with the chloride ion being the most responsible for its occurrence. In this way, understanding the transport mechanisms of this ion through the microstructure of the concrete is of fundamental importance to prevent or delay the penetration of these aggressive agents to guarantee a durable structure. In the literature, there are extensive studies concerning the diffusion of chlorides in concrete and the influence of pozzolanic additions in this mechanism. However, only a few correlate the different methods of analysis. This work aims to determine the chloride ion diffusion coefficients in concrete containing various levels of silica fume (5%, 10%, and 15%) or varying the mortar content (54%, 80%, and 100%), and compares the results obtained through column tests and chloride migration tests. It was observed that, although the techniques used were quite distinct, the diffusion values obtained were similar, contributing to the validation of both techniques. Furthermore, the variation in the mortar ratio causes a reduction in the interfacial transition zone of coarse aggregate/mortars and an increase in the content of aluminates, which promotes a similar effect to the use of silica fume.

scholarly journals Bentonite replacing part of cement concrete for resistance to chloride ion attack

2019 ◽  
Vol 136 ◽  
pp. 03011
Author(s):  
Jie Luo ◽  
Chuanchang Li ◽  
Yafei Ma ◽  
Lei Wang
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Ion Diffusion ◽  
Natural Pozzolan ◽  
Cement Production ◽  
Chloride Ion Penetration ◽  
Chloride Migration ◽  
Chloride Ion Diffusion

Bentonite is known as a kind of natural pozzolan that can improve the mechanical properties of cementitious materials and reduce the overall CO2 output of cement production. This study is designed to evaluate the feasibility of using bentonite as a substitute for cement in concrete and analyze the effect of bentonite on resisting chloride ion penetration. The concrete was replaced by equal-quality bentonite for 0%, 5%, 10%, 15% and 20% cement respectively, and the water-cement ratio, fine and coarse aggregate content remained constant. The results indicated that as the bentonite content increased, the compressive strength of the mixes increased first and then decreased. The sample containing 10% bentonite got a higher compressive strength than the other samples. The rapid chloride migration (RCM) tests showed that the samples containing bentonite had better resistance to chloride ion attack than samples without bentonite against chloride, especially the sample containing 10% bentonite. It can be concluded that the concrete with 10% bentonite can improve the resistance to chloride ion diffusion with high compressive strength.

Experimental Study on Mix Design of Chloride Resistant Cementitious Spacers

2014 ◽  
Vol 629-630 ◽  
pp. 351-357
Author(s):  
Chen Huang ◽  
Wen Ying Guo ◽  
Yi Bo Yang ◽  
Hui Zhao ◽  
Zhen Jie Li ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Design Method ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Mix Design ◽  
Easy Access ◽  
Ion Diffusion ◽  
Electric Flux ◽  
Chloride Environment ◽  
Chloride Ion Diffusion

Chloride resistant HPC and protective cover are two basic measurements to improve the durability of concrete in chloride environment. Though it provides crucial cover for concrete to resist chloride ions, spacer has limited chloride resistant ability, which is overlooked by past researchers. Cementitious spacers are easy access for chloride ions to penetrate into concrete resulting in reduction of structural durability. To improve cementitious spacers’ performance, a systematic study was conducted. Test results showed that there was major difference between mortar and concrete in terms of chloride coulomb electric flux but minor difference in terms of chloride ion diffusion coefficient, which implied using chloride ion diffusion coefficient as spacer’s durability indicator was preferable; parameters of mix design had a similar influence on mortar and concrete and, with the same mixing parameters, the strength and chloride resistant ability of mortar were weaker than concrete’s; it was feasible to develop the mix design of chloride resistant cementitious spacers based on concrete’s design method with certain adjustments, such as using stricter mix proportion, adding small-size coarse aggregate, lowering water-binder ratio and optimizing the binder proportion, to achieve higher strength and durability.

scholarly journals FUNDAMENTAL STUDY ON CHLORIDE ION DIFFUSION AND STEEL CORROSION IN SILICA FUME CONCRETE

2011 ◽  
Vol 65 (1) ◽  
pp. 360-367
Author(s):  
Shinichi KAWAHARA ◽  
Tatsuhiko SAEKI ◽  
Tsuyoshi SHIMA ◽  
Hironori YOSHIZAWA
Keyword(s):  
Silica Fume ◽  
Steel Corrosion ◽  
Chloride Ion ◽  
Ion Diffusion ◽  
Fundamental Study ◽  
Chloride Ion Diffusion

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 Influence of Pore Size and Fatigue Loading on NaCl Transport Properties in C-S-H Nanopores: A Molecular Dynamics Simulation

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 700 ◽  
Author(s):  
Qingyu Cao ◽  
Yidong Xu ◽  
Jianke Fang ◽  
Yufeng Song ◽  
Yao Wang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Transport Properties ◽  
Diffusion Rate ◽  
Chloride Ion ◽  
Fatigue Loading ◽  
Chloride Ions ◽  
Water Molecules ◽  
Ion Diffusion ◽  
Chloride Ion Diffusion

The transport properties of chloride ions in cement-based materials are one of the major deterioration mechanisms for reinforced concrete (RC) structures. This paper investigates the influence of pore size and fatigue loading on the transport properties of NaCl in C-S-H nanopores using molecular dynamics (MD) simulations. Molecular models of C-S-H, NaCl solution, and C-S-H nanopores with different pore diameters are established on a microscopic scale. The distribution of the chloride ion diffusion rate and the diffusion coefficient of each particle are obtained by statistically calculating the variation of atomic displacement with time. The results indicate that the chloride ion diffusion rate perpendicular to C-S-H nanopores under fatigue loading is 4 times faster than that without fatigue loading. Moreover, the diffusion coefficient of water molecules and chloride ions in C-S-H nanopores increases under fatigue loading compared with those without fatigue loading. The diffusion coefficient of water molecules in C-S-H nanopores with a pore size of 3 nm obtained from the MD simulation is 1.794 × 10−9 m2/s, which is slightly lower than that obtained from the experiment.

Chloride Ion Diffusion of Phosphoaluminate Cement Concrete

2009 ◽  
Vol 79-82 ◽  
pp. 99-102 ◽  
Author(s):  
Zhu Ding ◽  
Feng Xing ◽  
Ming Zhang ◽  
Peng Liu
Keyword(s):  
Portland Cement ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Hydration Products ◽  
Portland Cement Concrete ◽  
Ion Diffusion ◽  
Cement Concrete ◽  
Dense Microstructure ◽  
Corrosion Of Steel ◽  
Chloride Ion Diffusion

Penetration and diffusion of chloride ions in concrete can lead to the corrosion of steel bar and shorten the service life of concrete structures. Phosphoaluminate cement (PAC) is a new cementitious material which has many special properties compared to Portland cement (PC). In the study, chloride ion diffusion in PAC concrete was tested with RCM method. The phase composition and morphology of hydration products, pore volume of hardened paste cured for 28d were analyzed with X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The results show that chloride ion diffusion coefficient of PAC concrete is much lower than that of Portland cement concrete under the same test conditions. The hydration products of PAC are main micro-crystalline phase and gel of phosphate and/or phophoaluminate, which formed a dense microstructure. There is no calcium hydroxide produced in the PAC hydration system. In hardened PAC paste, chloride ions might replace the atom group [OH] - and [PO4]3- of hydrates and become stable compounds. The resistance to chloride ion diffusion of PAC concrete will increase with the hydration age, because its microstructure becomes denser with the hydration age increasing.

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.

Research on the Concrete Performance in the Marine Environment

2013 ◽  
Vol 345 ◽  
pp. 184-188 ◽  
Author(s):  
Yi Dan Song ◽  
Juan Hong Liu ◽  
Fa Xing Yi ◽  
Bo Xu ◽  
Peng Ge
Keyword(s):  
Marine Environment ◽  
Chloride Solution ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Mineral Admixture ◽  
Ion Diffusion ◽  
Freezing And Thawing ◽  
Binder Ratio ◽  
Chloride Ion Diffusion ◽  
Water Binder Ratio

This paper mainly studied effects of NaCl,MgSO4 soaking experiments,carbonation and freezing and thawing cycle on concrete intensity.The results show:When the concrete is completely soaked in chloride solution,the concrete of high slump of the same strength grade has high compressive intensity.With the improvement of the concentration of chloride ions solution,the chloride ion diffusion coefficient of concrete is increasing as well;for the structure in marine environment,low water-binder ratio and high mineral admixture can improve most of performances of concrete.

Sea Sand Concrete Chloride Ion Diffusion and Combination of Curing

2012 ◽  
Vol 174-177 ◽  
pp. 358-361
Author(s):  
Jian Bin Chen ◽  
Guo Liang Zhang ◽  
Li Wei Mo ◽  
Jun Zhe Liu ◽  
Zhi Min He
Keyword(s):  
Chloride Ion ◽  
Chloride Ions ◽  
Water Soluble ◽  
Ion Concentration ◽  
Ion Diffusion ◽  
Binding Characteristics ◽  
Fly Ash Concrete ◽  
Sea Sand ◽  
Chloride Ion Diffusion

The concentration of chloride ion in concrete has been an important part of the study of reinforcement corrosion, while the microstructure of concrete on the concentration of chloride ions play an important role, in order to evaluate the sea sand for ordinary concrete and fly ash concrete microstructure andmineral composition, we use the 28 days of age in sea sand Mohr method for the determination of the different types of water-soluble chloride ion concentration to the chloride ion binding characteristics in the study of sea sand in concrete

Permeability of Anti-Chloride Ion of Fly Ash Recycled Concrete

2011 ◽  
Vol 317-319 ◽  
pp. 544-547
Author(s):  
Ai Jiu Chen ◽  
Jing Wang ◽  
Zhan Fang Ge ◽  
Ming Wu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Coarse Aggregate ◽  
Chloride Ion ◽  
Reducing Agent ◽  
Polypropylene Fibre ◽  
Recycled Concrete ◽  
Ion Diffusion ◽  
The North ◽  
Chloride Ion Diffusion

Adding fly ash to recycled concrete with super-substitute technique, comparing the 28d strength of fly ash recycled concrete(FARC) with the 28d strength of ordinary recycled concrete(ORC), the compressive strength of fly ash recycled concrete slightly decreased with the increase of the fly ash and the admixture of renewable aggregate. Along with the increase of mixing amount of the air entraining and water-reducing agent, the compressive strength of fly ash recycled concrete tends to reduce. The order of the factors that affect the chloride ion diffusion coefficient of recycled concrete is fly ash admixture→mixing amount of the air entraining and water-reducing agent→admixture of recycled coarse aggregate→polypropylene fibre admixture, which provides a basis for the application of recycled concrete engineering in the environment which is affected by chlorine salt in the north frigid area .

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