Physical and Chemical Deterioration of Reinforced Concrete Reefs in Tongyeong Reefs Coastal Waters, Korea

2008 ◽  
Vol 42 (3) ◽  
pp. 110-118 ◽  
Author(s):  
H. S. Kim ◽  
C. G. Kim ◽  
W. B. Na ◽  
J. Woo ◽  
J. K. Kim
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Dissolved Oxygen ◽  
Extreme Event ◽  
Chemical Properties ◽  
Chloride Concentration ◽  
Concrete Cover ◽  
Marine Habitat ◽  
Seawater Salinity ◽  
Physical And Chemical

As part of a marine habitat enhancement project, the physical and chemical deterioration of reinforced concrete reefs that were fully immersed in Tongyeong waters of Korea was investigated. For the investigation, marine environmental factors such as seawater, salinity, pH, dissolved oxygen, sea-bottom materials, and water depth of the targeted sites were surveyed from 1997 to 2001. Then, four reinforced concrete reefs from four different sites were recovered and tested by using various destructive and nondestructive methods. Based on the observations and test results, it was seen that the reinforced concrete reefs have sound physical and chemical properties, except for chloride concentration and its associated factors. However, because of the lack of dissolved oxygen in the targeted seawaters and its continuous supply, it is concluded that the originally designed service life will be achieved, and in fact the concrete reefs will have an even longer service life than expected. By considering an extreme event such as impact loading under installation and construction, a new minimum concrete cover depth of 40 mm is introduced into practice.

Analysis on Concrete Neutralization and Life Evaluation of Reinforced Concrete Chimney

2013 ◽  
Vol 671-674 ◽  
pp. 1672-1675
Author(s):  
Yan Hui Li ◽  
Yang Yang Zhang ◽  
Jing Cun Wei ◽  
Yun Feng Wu
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Concrete Structure ◽  
Concrete Cover ◽  
Initiation Time ◽  
Reinforcement Corrosion ◽  
Single Factor ◽  
Routine Examination ◽  
Life Evaluation ◽  
Reinforced Concrete Chimney

Through calculation and analysis on routine examination and neutralization of reinforced concrete chimney, the service life of concrete structure was evaluated only considering neutralization of concrete single factor. The results show that the neutralization of the reinforced concrete chimney was serious than that of other similar projects. The initiation time of reinforcement corrosion were 19.3a, cracking time of concrete cover were 27.35a.

Corrosion effects on seismic capacity of reinforced concrete structures

2019 ◽  
Vol 37 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Antonio Bossio ◽  
Francesco Fabbrocino ◽  
Tullio Monetta ◽  
Gian Piero Lignola ◽  
Andrea Prota ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Seismic Behavior ◽  
Concrete Cover ◽  
Residual Service Life ◽  
Seismic Capacity ◽  
Rc Structures ◽  
Behavior Simulation ◽  
Cover Cracking ◽  
Rc Structure

AbstractRecently, corrosion prevention and monitoring of reinforced concrete (RC) structures became an important issue for seismic assessment of such kind of structures. Therefore, it is important to develop adequate models to represent material degradation into seismic behavior simulation of RC structures. Because of its effects, corrosion represents the most important form of degradation for materials and structures, both for wide diffusion and the amount of danger it presents. To understand the corrosion process is critical in order to design RC structures that are able to guarantee the required service life and in order to understand the residual service life and strength of an existing structure. The seismic behavior of a corroded framed RC structure is analyzed by means of push-over analyses, which allow understanding the development of the global behavior of the structure. Three different degrees of corrosion penetration were simulated, by means of the reduction of bars and stirrups’ diameters and concrete cover cracking and spalling, and three different configurations of corrosion, depending on the number of corroded frames and sides of the structural elements.

scholarly journals Prediction of the Service Life of a Reinforced Concrete Column under Chloride Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Mohammad K. Alkam ◽  
Maha Alqam
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Chloride Ion ◽  
Threshold Value ◽  
Concrete Cover ◽  
Ion Concentration ◽  
Critical Threshold ◽  
Concrete Column ◽  
Reinforced Concrete Column ◽  
Chloride Environment

In the present investigation, service life of a reinforced concrete column exposed to chloride environment has been predicted. This study has been based on numerical simulation of chloride ion diffusion in a concrete column during its anticipated life span. The simulation process has included the concrete cover replacement whenever chloride ion concentration has reached the critical threshold value at the reinforcement surface. Repair scheduling of the concrete column under consideration has been discussed. Effects of the concrete cover thickness and the water cement ratio on the service life of the concrete column at hand have been presented. A new approach for arranging locations of reinforcement steel bars has been introduced. This approach is intended to prolong the service life of the concrete column under consideration against chloride induced corrosion.

scholarly journals Improving the Mechanical Performance of Shell Precast Concrete Blocks for Coastal Protection Structures of Hydraulic Works

2021 ◽  
Vol 11 (1) ◽  
pp. 6787-6791
Author(s):  
N. Viet Duc
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
High Performance ◽  
Mechanical Performance ◽  
Precast Concrete ◽  
Reference Beam ◽  
Concrete Cover ◽  
Fiber Reinforced Concrete ◽  
Bending Test ◽  
Coastal Protection

Although the use of concrete and reinforced concrete for construction has been widespread, more studies are needed on marine structures exposed directly to corrosive environments to prolong their service life. This paper proposes a new type of shell precast concrete block for coastal structures, studying a beam consisting of 15mm High-Performance Glass Fiber-Reinforced Concrete (HPGFRC) at the bottom and 45mm Traditional Concrete (TC) for the rest of the structure. Steel bar reinforcements were placed at the bottom with a concrete cover of 25mm to avoid abrupt failure. The strength classes of HPGFRC and TC were 60MPa and 30MPa respectively. A reference beam consisting of TC only was also prepared for comparison. The four-point flexural bending test results showed that the first cracking strength of the proposed beam was 20% higher, as HPGFRC performed better on tension than TC. Additionally, HPGFRC's maximum strength was 25% greater than TC's. Furthermore, HPGFRC possessed more durable characteristics such as waterproof grade, abrasion resistance, and shrinkage than TC, promising to protect the reinforcement from the aggressive marine environment and corrosion, prolonging the service life of the structure.

scholarly journals Numerical analysis of reinforced concrete beam subject to pitting corrosion

2022 ◽  
Vol 22 (1) ◽  
pp. 201-222
Author(s):  
Éverton Souza Ramos ◽  
Rogério Carrazedo
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Pitting Corrosion ◽  
Numerical Study ◽  
Reinforced Concrete Beam ◽  
Concrete Cover ◽  
Structural Element ◽  
Deterministic Models ◽  
Faraday’S Law ◽  
Parametric Analyses

Abstract This paper presents a numerical study about the effects of chloride-induced corrosion on the service life of structures. A two-dimensional geometrically nonlinear mechanical model based on Finite Element Method (FEM) was developed for reinforced concrete structures. The corrosion initiation stage was evaluated by Fick's diffusion laws. The corrosion propagation was carried out by deterministic models based on Faraday's law. Pitting corrosion was simulated in the reinforcements by pit elements, distributed longitudinally on the steel rebars, which degrade the physical properties over time. The service life was determined by the crack width.Two parametric analyses were performed. In the first analysis, five models were created with a variablecover thickness and water/cement ratio (w/c). In the second analysis, the reduction in yield stress due to corrosion was considered.The results showed that the concrete cover thicknessand the w/c ratio significantly influence the service life. The reduction of the cover thickness from 30 mm to 25 mm resulted in 21.26% reduction in service life, whilethe increase in the w/c ratio from 0.50 to 0.55 caused 32.98% reduction in service life of the structural element analyzed.

scholarly journals Calculation method for the service life of Chinese historical reinforced concrete buildings

2020 ◽  
Vol 319 ◽  
pp. 06006
Author(s):  
Hui Jin ◽  
Qing Chun
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Calculation Method ◽  
Assessment Method ◽  
Concrete Cover ◽  
Rc Buildings ◽  
Specific Calculation ◽  
Cover Cracking ◽  
Durability Assessment ◽  
Steel Rebars

Almost all of the existed studies on the corrosion of rebars were based on round-section rebars. However, the square-section steel rebars were widely used in China from 1912 to 1949, and there was no specific calculation model or durability assessment method for this type of historical buildings. In this study, based on the original configuration design of this kind of structures, the experiments of the corrosion-induced cover cracking of a certain number of reinforced concrete members with square-section rebars were carried out with the electrochemical acceleration method. The average rust depths of the square-section rebars at the critical corrosion-induced cover cracking moment were obtained. Then, the calculation method of critical rust depth of steel rebars at the concrete cover cracking moment was presented with data fitting method. Finally, combining with predication of carbonization life of concrete, a calculation method of the service life for Chinese historical RC buildings using square-section rebars was proposed. The research results can provide the basis for the durability assessment and conservation for Chinese historical RC buildings.

scholarly journals Diel vertical migration of Cladocera in a compartment of a tropical reservoir

2018 ◽  
Vol 30 (0) ◽  
Author(s):  
Erika dos Santos Silva ◽  
Odete Rocha ◽  
Maria José dos Santos-Wisniewski
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Chlorophyll A ◽  
Vertical Migration ◽  
Variable Temperature ◽  
Chemical Properties ◽  
Migration Pattern ◽  
Limiting Factor ◽  
Tropical Reservoir ◽  
Physical And Chemical

Abstract Aim This study seeks to analyze the vertical migration pattern of Cladocera species as related with the physical and chemical parameters of the water. Methods Samplings were carried out at 3-h intervals for 24 h in January 15 on the Sapucaí River compartment of Furnas reservoir, Minas Gerais State, Brazil. These samples were taken at five depths, from the surface to the near-bottom layer (0, 2, 4, 6, 8, and 9 m) totalizing 54 samplings for each limnological variable (temperature, pH, dissolved oxygen, electrical conductivity, chlorophyll-a content, Index of Trophic State, water transparency and Cladocera populations abundance). The samplings were performed at the limnetic region at a point with total depth of 9 meters. Results Water column thermal and chemical stratifications and thermocline occurrences were registered in the middle of the day. Among the 14 Cladocera species, only Ceriodaphnia cornuta and C. silvestrii displayed a significant migration pattern, which was mainly related to chlorophyll-a and dissolved oxygen concentrations. Diaphanosoma birgei and D. spinulosum are found at high densities near the surface and low ones in depth. The migration of Diaphanosoma was directly related to the concentration of chlorophyll a and pH, thus acting as a limiting factor. Feeding at high temperatures in the surface layer and assimilating at lower ones in depth, usually confer metabolic advantages to the vertically migratory species. Conclusions In this study, a well-defined pattern of vertical migration was found for two Cladocera species and its possible causes were hypothesized. To the species with less locomotory capacity, thermal and chemical stratifications can act as barriers to migration and distribution through the water column. This pattern may probably be found for zooplankton species in other compartments of Furnas reservoir, with similar physical and chemical properties.

Evaluation of Additional Protection Methods to Control Reinforcement Corrosion

2016 ◽  
Vol 711 ◽  
pp. 37-44 ◽  
Author(s):  
Fabio Bolzoni ◽  
Silvia Beretta ◽  
Andrea Brenna ◽  
Maria Vittoria Diamanti ◽  
Luciano Lazzari ◽  
...  
Keyword(s):  
Service Life ◽  
Limit State ◽  
Chloride Concentration ◽  
Concrete Cover ◽  
Reinforcement Corrosion ◽  
Simplified Approach ◽  
Model Code ◽  
Open Questions ◽  
Additional Protection ◽  
Prevention Methods

The prevention of reinforcement corrosion is primarily achieved by using high quality concrete, adequate concrete cover and suitable casting and curing. Additional prevention methods are adopted when severe environmental conditions occur on structures requiring very long service life. While existing standards, EN 206 or Eurocode 2, adopt prescriptive approach, performance based methods can improve the evaluation of the service life and enable the comparison of available design options. The reliability of the prediction is very important and even widely used models (e.g. fib Model Code) still have open questions. In this paper different additional protection are evaluated: corrosion inhibitors, stainless steel rebars, concrete coatings. A simplified approach is used, considering that the serviceability limit state, i.e. initiation of corrosion in chloride containing environments, can be modeled through the analytical solution of the 2nd Fick’s law of diffusion. The main factors influencing corrosion initiation (critical chlorides concentration, chlorides diffusion coefficient, surface chloride concentration, concrete cover) are represented by distribution of values and the probability distribution of service life is evaluated by Monte Carlo simulation.

scholarly journals Service Life Prediction and Lateral Bearing Capacity Analysis of Piles Considering Coupled Corrosion-Temperature Deterioration Processes

2021 ◽  
Vol 9 (6) ◽  
pp. 614
Author(s):  
Yue Li ◽  
Youliang Chen ◽  
Wei Shao ◽  
Juhui Zhang ◽  
Shaoming Liao ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Bearing Capacity ◽  
Chloride Concentration ◽  
Probabilistic Methods ◽  
Stiffness Degradation ◽  
Chloride Diffusion ◽  
Capacity Analysis ◽  
Chloride Diffusion Coefficient ◽  
Degradation Coefficient

High temperatures can enhance the chloride diffusion coefficient and this poses a threat to reinforced concrete (RC) piles. This study intends to propose predictive models that can evaluate the service life and lateral bearing behaviour of reinforced concrete piles subjected to marine environments and varying temperatures. The models show that temperature can accelerate the diffusion rate of chloride and increase the concentration of free chloride in concrete. The distribution law of chloride concentration is obtained by considering the ageing effect as well. Deterministic and probabilistic models are proposed to assess the time to corrosion initiation and propagation. The stiffness degradation coefficient is introduced in the analysis of the lateral bearing capacity of RC piles. The results show that high temperature can decrease the service life of piles and the life spans obtained from deterministic and probabilistic methods are similar; however, the predictions of the latter are more conservative. Temperature can enhance the current density and boost corrosion products, which leads to pile cracking. The rust appearing on the steel surface would make the stiffness degradation coefficient drop sharply. The lateral bearing capacity analysis is conducted from the perspectives of shear force, displacement and bearing moment of the piles.

Release Text on the Humus Soil Pellets

2012 ◽  
Vol 610-613 ◽  
pp. 3096-3101
Author(s):  
Jun Yin ◽  
Lei Wu ◽  
Zhi Sheng Liu ◽  
Jian Hui Wang ◽  
Hai Lu ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Complex Structure ◽  
Chemical Properties ◽  
Hydroxyl Groups ◽  
High Concentration ◽  
Weight Percentage ◽  
Highly Active ◽  
Oxygen Conditions ◽  
Physical And Chemical ◽  
Humus Soil

In this article, texted the humus soil pellets by means of SEM-EDAX. Analyze the release of organic matter at different dissolved oxygen conditions and the content of TOC changes after being used for different duration. Systematically studied on the physical and chemical properties of the filler and it’s released highly active organic nutrient composition. Further reveals the principle of humus activated sludge process how to deal with the high concentration organic wastewater. The results show that the humus soil pellets has a complex structure and irregular, containing large quantities of animal bone debris and plant fragments, and its main elements are C, Si, O. Three elements of the weight percentage reached 88.69%, atomic hundreds of content reached 93.52%.The humus soil pellets released organic substances at different dissolved oxygen conditions are different. Released substance under low dissolved oxygen conditions are mostly short-chain polar organic functional groups such as methyl, carboxyl and hydroxyl groups.

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