scholarly journals Limitations of sorptivity and water permeability for the estimation of the chloride penetration rate in concrete regarding the accomplishment of prescriptive design for durability in the marine environment

2018 ◽  
Vol 8 (3) ◽  
pp. 301-316
Author(s):  
Yury A Villagrán Zaccardi ◽  
María E Sosa ◽  
Ángel A Di Maio
Keyword(s):  
Marine Environment ◽  
Diffusion Rate ◽  
Penetration Rate ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Capillary Absorption ◽  
Chloride Ingress ◽  
Water Penetration ◽  
Conventional Concrete

This paper presents an analysis of experimental data from conventional concrete regarding sorptivity and penetrability under pressure comparing these parameters to chloride diffusion rate determined in the laboratory and in actual marine environment. Prescriptions for durability assurance of reinforced concrete structures is based on the qualitative characterization of transport properties. For the specific case of the marine environment, it is required to assess the resistance of concrete to chloride ingress. The results show the limitations of both parameters as prescriptive indexes, with capillary absorption rate showing some advantages over water penetration under pressure.

scholarly journals Mechanical and durability assessment of cement-based and alkali-activated coating mortars in an aggressive marine environment

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Salar Lashkari ◽  
Farzad Yazdipanah ◽  
Mahyar Shahri ◽  
Prabir Sarker
Keyword(s):  
Silica Fume ◽  
Marine Environment ◽  
Strength Test ◽  
High Rate ◽  
Chloride Diffusion ◽  
Strength Development ◽  
Diffusion Resistance ◽  
Capillary Absorption ◽  
Durability Analysis ◽  
Alkali Activated

AbstractCoatings are used as practical solutions against the intrusion of corrosive ions into concrete structures, particularly, in the harsh marine environment. In the present study, the effectiveness of using cement-based and geopolymer-based coatings produced using by-product materials has been evaluated. Silica fume and GGBFS at their optimum dosages were incorporated into mortar mixtures as a cement replacement, and mixtures of NaOH or KOH and sodium silicate solutions were used in the alkali-activated mortars. Shrinkage test, RCMT, and capillary absorption test as common experiments for durability analysis, as well as tests related to the mechanical and bonding properties including compressive strength test, pull-off test, and shear bonding strength test were carried out on the specimens. According to the results, both geopolymer and cement-based mortars improved the compressive and bonding strengths, and chloride diffusion resistance of coatings compared to the OPC mortar. Silica fume was found to be more effective in the strength development of mortars at young ages, while GGBFS was more responsible for acting as a filler and producing further gel in the older ages. The major drawback with geopolymer mortars is the high rate of water absorption and shrinkage coefficient in the early hours, which shows the importance of curing of these mortars at young ages. Overall, the mix design produced with 30% GGBFS and 7.5% silica fume showed the highest durability and mechanical properties and proved to be more compatible with the harsh environment of the Persian Gulf.

The Chloride Ion Penetration Model Coupled with Temperature and Moisture Transfer in Marine Environment

2012 ◽  
Vol 591-593 ◽  
pp. 2422-2427
Author(s):  
Juan Zhao
Keyword(s):  
Marine Environment ◽  
Moisture Transfer ◽  
Regional Climate ◽  
Chloride Ion ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Tidal Zone ◽  
Analog Simulation ◽  
Chloride Ion Penetration ◽  
Ion Penetration

Considering the complexity of the chloride ion penetration in concrete exposed to marine environment, an integrated chloride penetration model coupled with temperature and moisture transfer is proposed. The governing equations and parameters embody fully the cross-impacts among thermal conduction, moisture transfer and chloride ion penetration. Furthermore, the four exposure conditions are classified based on the different contact with the aggressive marine environment, and then the micro-climate condition on the concrete surface is investigated according to the regional climate characteristics, therefore, a comprehensive analog simulation to the chloride penetration process is proposed. To demonstrate that the proposed numerical model can correctly simulate the chloride diffusion in concrete, the integrated chloride diffusion model is applied in reproducing a real experiment, finally the model gives good agreement with the experimental profiles, and it is proved the tidal zone exposure results in a more severe attack on the reinforcement

scholarly journals Influence of Pore Structure on Chloride Penetration in Cement Pastes Subject to Wetting-Drying Cycles

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Honglei Chang ◽  
Zhiwu Zuo ◽  
Mingyue Qu ◽  
Fei Wang ◽  
Zhi Ge ◽  
...  
Keyword(s):  
Pore Structure ◽  
Penetration Rate ◽  
Error Function ◽  
Chloride Concentration ◽  
Total Porosity ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cement Pastes ◽  
The Matrix

Copious studies have discovered a phenomenon that a chloride concentration peak appears on the surface of concrete under cyclic drying-wetting environments. In such cases, the chloride diffusion coefficient (D) obtained through directly fitting the standard error function of Fick’s second law is no longer accurate. The more reliable D obtained by the method proposed by Andrade is employed in this research to investigate the influence of pore structure on chloride penetration rate of pastes. The results show that both the effective coefficient (Deff) and the apparent coefficient (Dapp) increase with total porosity, the most probable pore size, and water absorption porosity, suggesting that the increase of the three pore structure parameters accelerates chloride penetration rate under cyclic wetting-drying condition. The increase of the three parameters makes more room available and eases the difficulty for salt solution to enter the matrix and thus leads to the augmentation of chloride transporting in matrix.

scholarly journals Mechanical Behavior and Chloride Penetration of Precracked Reinforced Concrete Beams with Externally Bonded CFRP Exposed to Marine Environment

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Yan Xie ◽  
Kunhua Guan ◽  
Lei Zhan ◽  
Qichen Wang
Keyword(s):  
Reinforced Concrete ◽  
Marine Environment ◽  
Chloride Penetration ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Chloride Diffusion ◽  
Accelerated Ageing ◽  
Rc Beams ◽  
Cfrp Sheets ◽  
Externally Bonded

Cracked reinforced concrete (RC) beams can be repaired effectively by using externally bonded CFRP sheets. However, when the strengthened beams are subjected to marine environment, long-term performance will be affected by the material and the interface deterioration of concrete and CFRP. Therefore, to evaluate the service life of the strengthened beams, this study investigates the behavior of precracked RC beams strengthened with CFRP sheets exposed to marine environment. Accelerated ageing experiments were carried out by exposing specimens to cyclic wetting in sea water and drying in 40°C air for 3 months and 6 months, respectively. After the environment exposure, four-point bending test was conducted and then the diffusion of chlorides in the strengthened beams was analysed. The results show that the bonding behavior of the adhesive was weakened and the ductility of the strengthened beams was slightly reduced due to the marine environment. But there is no obvious strength difference between the strengthened beams suffered from marine environment for 3 months and 6 months. Besides, the precracks in the RC beams accelerated the chloride diffusion, while CFRP bonding reduced the chloride penetration. In addition, NEL method was employed to validate the effect of the cracks on chloride permeability. The results showed that the chloride diffusion coefficients increased with the depth of the cracks.

Chloride Diffusion in Blended Cement Concrete Made with Quartzite Recycled Aggregate

2012 ◽  
Vol 1488 ◽  
Author(s):  
Claudio J. Zega ◽  
Yury A. Villagrán-Zaccardi ◽  
Ángel A. Di Maio
Keyword(s):  
Blended Cement ◽  
Recycled Concrete ◽  
Water Soluble ◽  
Recycled Aggregate ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Chloride Diffusion Coefficient ◽  
Conventional Concrete ◽  
Concrete Production ◽  
The Relationship

ABSTRACTUsing waste materials as aggregate for new concrete production is a growing tendency, because of several environmental problems. Recycled coarse aggregate (RCA) obtained from crushing waste concrete has lower density and greater absorption than natural aggregate, because of the higher porosity of the mortar attached to the RCA particles. Compressive strength level achieved in recycled concrete may be similar to that of conventional concrete. On the other hand, durable performance of recycled concrete is variable, and diverse evidence can be found in literature for different durability issues. In this paper, chloride ingress in conventional and recycled concrete, made with quartzite aggregate and blended Portland cement is evaluated when immersed in NaCl solution. Two strength levels (21 and 35 MPa) and two contents of RCA (25 and 75%), as substitute of natural quartzite aggregate, were considered. The chloride diffusion coefficient and the relationship between water-soluble chloride and bound chloride are analyzed.

Corrosion Rate Evolution in Concrete Structures with Hydrophobic Agents Exposed to the Marine Environment

2011 ◽  
Vol 374-377 ◽  
pp. 1320-1324
Author(s):  
Wei Qun Cao ◽  
Hong Fan ◽  
Tie Jun Zhao
Keyword(s):  
Reinforced Concrete ◽  
Corrosion Rate ◽  
Marine Environment ◽  
Concrete Structures ◽  
Protective Layer ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Reinforced Concrete Structures ◽  
Chloride Diffusion Coefficient ◽  
Capillary Suction

In many cases, service life of reinforced concrete structures is severely limited by chloride penetration until the steel reinforcement. Today, concrete with high resistance with respect to chloride penetration can be produced by internal hydrophobic treatment. The aim of this study was to fill this gap in regards to reinforced concrete structures inserted in a marine environment. Results indicated the efficacy of the hydrophobic agents in cases where capillary suction is the mechanism of water penetration. However, when the transport mechanism is permeability this product is not advisable. Moreover, it was demonstrated that the chloride diffusion coefficient is reduced by the hydrophobic agents, and the corrosion rate of reinforcement could be well protected in the treated concrete with hydrophobic agents of silane. The durability of reinforced structures can be considerably increased and can be accurately designed by the application of an appropriate and optimized protective layer.

scholarly journals Experimental Study on the Evaluation of Physical Performance and Durability of Cement Mortar Mixed with Water Repellent Impregnated Natural Zeolite

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3288 ◽  
Author(s):  
Chang Bok Yoon ◽  
Han Seung Lee
Keyword(s):  
Natural Zeolite ◽  
Test Specimen ◽  
Cement Mortar ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Water Repellent ◽  
Chloride Diffusion Coefficient ◽  
Accelerated Carbonation ◽  
Penetration Test ◽  
Water Penetration

To complement the shortcomings of concrete surface treatment technology and improve the durability of concrete structure, the purpose of this study was to impregnate water-repellent performance into natural zeolite, which has many pores inside, to achieve water-repellent performance inside concrete. The physical performance and durability of cement mortar mixed with water-repellent natural zeolite was evaluated. Cement mortars were prepared by mixing ZWR1%, 3%, and 5% (ZWR: Zeolite + Water Repellent impregnation) in cement powder, and compressive strength, contact angle, water penetration test, resistance chloride penetration test, chloride diffusion coefficient, and accelerated carbonation test were evaluated. When the mixing ratio of ZWR increased, the compressive strength of the test specimen was reduced compared to OPC. In contact angle measurement, water penetration test, chloride penetration resistance test, chloride diffusion coefficient, and accelerated carbonation test, the ZWR-containing samples showed superior properties compared to OPC. It was found that the durability test results improved as the amount of mixing was increased, and the durability of the test specimen containing 5% ZWR was found to be the best.

Modeling of chloride penetration in concrete structures under freeze-thaw cycles

2019 ◽  
Vol 38 (1) ◽  
pp. 127-147 ◽  
Author(s):  
H’mida Hamidane ◽  
Ayman Ababneh ◽  
Ali Messabhia ◽  
Yunping Xi
Keyword(s):  
Finite Element ◽  
Temperature Variation ◽  
Concrete Structures ◽  
Chloride Penetration ◽  
Life Assessment ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Variable Boundary ◽  
Content Type ◽  
Freeze Thaw

Purpose The purpose of this paper is to develop a method for predicting the chloride ingress into concrete structures, with an emphasis on the low temperature range where freeze-thaw cycles may cause damage. Design/methodology/approach The different phenomena that contribute to the rate and amount of transported chlorides into concrete, i.e., heat transfer, moisture transport and chloride diffusion are modeled using a two-dimensional nonlinear time dependent finite element method. In modeling the chloride transport, a modified version of Fick’s second law is used, in which processes of diffusion and convection due to water movement are taken into account. Besides, the effect of freeze-thaw cycles is directly incorporated in the governing equation and linked to temperature variation using a coupling term that is determined in this study. The proposed finite element model and its associated program are capable of handling pertinent material nonlinearities and variable boundary conditions that simulate real exposure situations. Findings The numerical performance of the model was examined through few examples to investigate its ability to simulate chloride penetration under freeze-thaw cycles and its sensitivity to factors controlling freeze-thaw damage. It was also proved that yearly temperature variation models to be used in service life assessment should take into account its cyclic nature to obtain realistic predictions. Originality/value The model proved promising and suitable for chloride penetration in cold climates.

scholarly journals Explicitly Assessing the Durability of RC Structures Considering Spatial Variability and Correlation

2021 ◽  
Vol 6 (11) ◽  
pp. 156
Author(s):  
Cao Wang
Keyword(s):  
Spatial Variability ◽  
Structural Properties ◽  
Marine Environment ◽  
Vital Role ◽  
Concrete Cover ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Chloride Diffusion Coefficient ◽  
Rc Structures ◽  
Durability Design

The durability design of reinforced concrete (RC) structures that are exposed to aggressive environmental attacks (e.g., corrosion due to chloride ingress in marine environment) plays a vital role in ensuring the structural serviceability within a reference period of interest. Existing approaches for the durability design and assessment of RC structures have, for the most part, not considered the spatial distribution of corrosion-related structural properties. In this paper, a closed-form approach is developed for durability assessment of RC structures, where the structural dimension, spatial variability, and correlation of structural properties such as the concrete cover thickness and the chloride diffusion coefficient are taken into account. The corrosion and crack initiations of an emerged tube tunnel segment that was used in the Hong Kong-Zhuhai-Macau bridge project were assessed to demonstrate the applicability of the proposed approach. The accuracy of the method was verified through a comparison with Monte Carlo simulation results based on two-dimensional random field modeling. The proposed method can be used to efficiently assess the durability performance of RC structures in the marine environment and has the potential to become an efficient tool to guide the durability design of RC structures subjected to corrosion.

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