Chloride Penetration into Concrete

2008 ◽  
Vol 400-402 ◽  
pp. 181-186
Author(s):  
Xiao Mei Wan ◽  
F.H. Wittmann ◽  
Tie Jun Zhao ◽  
Fu Xiang Jiang
Keyword(s):  
Mechanical Load ◽  
Compressive Load ◽  
Chloride Diffusion ◽  
Capillary Absorption ◽  
Capillary Suction ◽  
Micro Cracks ◽  
Environmental Actions ◽  
Different Types ◽  
Order Of Magnitude ◽  
Cell Test

Reinforced concrete structures may be exposed to an aggressive environment. In this case combined mechanical and environmental actions may act simultaneously and their synergetic influences have to be taken into consideration. In this contribution results of tests on two different types of concrete and mortars are presented and discussed. Capillary absorption of not carbonated and carbonated concrete has been determined. The influence of mechanical load on capillary suction has been studied separately. A moderate compressive load reduces the coefficient of capillary suction, while capillary suction is enhanced by higher mechanical loads as micro-cracks are formed. Chloride diffusion has been measured by means of the diffusion cell test. The diffusion coefficient observed in carbonated concrete is roughly speaking one order of magnitude higher than the value measured on not carbonated concrete.

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.

Self-Healing and Repairing Concrete Cracks Based on Bio-Mineralization

2014 ◽  
Vol 629-630 ◽  
pp. 494-503 ◽  
Author(s):  
Chun Xiang Qian ◽  
Mian Luo ◽  
Li Fu Ren ◽  
Rui Xing Wang ◽  
Rui Yang Li ◽  
...  
Keyword(s):  
Concrete Surface ◽  
Cellular Respiration ◽  
Self Healing ◽  
Capillary Suction ◽  
Water Permeation ◽  
Carbonate Ions ◽  
Micro Cracks ◽  
Small Cracks ◽  
The Common ◽  
The One

In this paper, three bio-mineralization mechanisms were proposed to repair cement-based materials cracks. The common feature is that the three are all induced by bacterial. A type of bacterial which can decompose urea and release carbonate ions could be applied to repair micro cracks on concrete surface when combining calcium ions. But what need to be noted is that the way of repairing cracks is passive. Some alkaliphilic bacterial spores could be added to concrete when casted and two different types of bacterial were used to realize the function of self-healing. The sources of carbonate ions made them different, the one release carbonate dioxide through its own cellular respiration, the other could transfer carbon dioxide in air to bicarbonate. Coefficient of capillary suction, apparent water permeation coefficient and area repairing rate were applied to characterize the repairing effectiveness. The tests results were that all three bio-mineralization mechanisms showed excellent repair effect to small cracks formed at early ages. When the bacteria were immobilized by ceramsite, the self-healing effect could be improved for the cracks formed at late ages.

Excitable Membrane Properties of Neurons

2020 ◽  
Author(s):  
Leonard K. Kaczmarek
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Cell Biology ◽  
Neuronal Firing ◽  
Membrane Properties ◽  
Potassium Ions ◽  
Single Action ◽  
Sodium Calcium ◽  
Different Types ◽  
Order Of Magnitude

The intrinsic electrical properties of neurons are extremely varied. For example, the width of action potentials in different neurons varies by more than an order of magnitude. In response to prolonged stimulation, some neurons generate repeated action potential hundreds of times a second, while others fire only a single action potential or adapt very rapidly. These differences result from the expression of different types of ion channels in the plasma membrane. The dominant channels that shape neuronal firing patterns are those that are selective for sodium, calcium, and potassium ions. This chapter provides a brief overview of the biophysical properties of each of these classes of channel, their role in shaping the electrical personality of a neuron, and how interactions of these channels with cytoplasmic factors shape the overall cell biology of a neuron.

scholarly journals Research on Horizontal Coefficient of Consolidation of Vietnam’s Soft Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Nu Nguyen Thi ◽  
Bui Truong Son ◽  
Do Minh Ngoc
Keyword(s):  
Experimental Study ◽  
Laboratory Tests ◽  
Soft Soil ◽  
Coefficient Of Consolidation ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Constant Rate ◽  
Different Types ◽  
Cell Test ◽  
Dissipation Test

The horizontal coefficient of consolidation is the most important parameter for designing the improvement of soil soft by prefabricated vertical drains (PVDs) combined with surcharge and vacuum preloading. This paper presents the experimental study on the horizontal coefficient of consolidation (ch) of some soft soils distributed in Vietnam. The ch value was determined by the laboratory test and CPTu dissipation test. The laboratory tests included the Rowe consolidation cell test and constant rate of strain consolidation with radial drainage test. Two types of consolidation laboratory tests were performed. The experimental results indicated that the ch value is always larger than the vertical coefficient of consolidation of soil (cv). The ratio of ch/cv depends on the consolidated pressure, type of soil, and the anisotropy of soil. The ratio of ch/cv is different in different types of soft soil in Vietnam. In the normally consolidated state, the ch/cv ratio ranges from 1.35 to 10.59. It was necessary to choose the ch value at the consolidated stress level for calculating the PVD spacing.

INFLUENCE OF SURFACTANTS ON PROPERTIES OF ELECTRORHEOLOGICAL FLUIDS CONTAINING POLYANILINE

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2461-2467 ◽  
Author(s):  
MAŁGORZATA BOCIŃSKA ◽  
HENRYK WYCIŚLIK ◽  
MARCIN OSUCHOWSKI ◽  
JANUSZ PŁOCHARSKI
Keyword(s):  
Yield Stress ◽  
Current Density ◽  
Silicone Oil ◽  
Flow Curves ◽  
Different Types ◽  
Order Of Magnitude ◽  
Dynamic Yield ◽  
Rate Of Sedimentation ◽  
Er Fluids

Sedimentation which is a natural process in most of ER fluids can be reduced by addition of surfactants that influence also other properties of the fluids. To study both the ER effect and the rate of sedimentation was the aim of the investigations. The ER fluids comprised powdered polyaniline and silicone oil to which surfactants of different polarity were added. The rate of sedimentation was measured by a sedimentation balance. The flow curves were recorded under electric field up to 2.5 kV/mm. Current density was also measured as a function of shear rate. It was found that the activity of a surfactant depends strongly on its polarity. The lipophylic surfactants stabilized the suspension very well but about 30% decrease of the dynamic yield stress was observed. The current density was reduced as well by almost one order of magnitude. The hydrophylic surfactants hardly stabilized the suspension but increase of yield stress was observed that was not followed by increase of current density. The role of different types of non-ionic surfactants was discussed.

Pre-project Comparative Environmental Assessment of Alternative Locations for a Production Facility

2019 ◽  
Vol 23 (4) ◽  
pp. 41-45
Author(s):  
V.A. Zhigulsky ◽  
D.V. Zhigulskaya ◽  
V.F. Shuisky ◽  
E.Yu. Maximova
Keyword(s):  
Environmental Assessment ◽  
Environmental Safety ◽  
Comparative Assessment ◽  
Production Facility ◽  
Technology Application ◽  
Positive Effects ◽  
Different Types ◽  
Order Of Magnitude ◽  
Two Stages ◽  
Project Company

The technology of a pre-project comparative assessment of alternative options for locating production facilities, developed by the St. Petersburg ecological project company Eco-Express-Service, is presented. Comparison of options is carried out on the basis of a multi-criteria score-rating assessment in two stages: first, the determination and comparison of values of the environmental safety criteria, then a generalized summary assessment across the totality of the criteria. To bring the obtained results into a general comparative scoring, four competitive methods are used, differing in the degree of detail of the accounting for the indicator significance of the criteria and the ratio of different types of object sites. The stages of technology application are illustrated with concrete examples. The main positive effects and advantages of its use are due to the increased environmental safety of construction and significant (by an order of magnitude) savings of the federal, regional and local budgets and investors owing eliminating unfavorable placement options for the object at the early stages of development.

Nonlinear Elastoplastic Behaviour of Intermittently Welded Stiffened Plates Under Inplane Compression

2006 ◽  
Author(s):  
Mohammad Reza Khedmati ◽  
Mehran Rastani
Keyword(s):  
Finite Element ◽  
Compressive Load ◽  
Steel Plates ◽  
Stiffened Plates ◽  
Finite Element Code ◽  
Stiffened Plate ◽  
Plate Models ◽  
Different Types ◽  
Stiffened Steel ◽  
Continuous Chain

The objective of this study is to investigate the sensitivity of the ultimate strength and failure mechanism of stiffened plates constructed by different welding methods in common. A series of detailed numerical analyses of longitudinally stiffened steel plates subjected to inplane compressive load are performed using ADINA commercial finite element code. Complete equilibrium paths are traced up to collapse for nonlinear elastoplastic response of stiffened plates. Stiffened plates analysed are imperfect and their aspect ratio, plate slenderness and column slenderness are changed in a systematic manner. Different types of stiffener are chosen for stiffened plate models. Three different stiffener-to-plate welding procedures are considered: continuous, chain intermittent and staggered intermittent fillet welding.

Influence of Sustained Load on Durability and Service Life of Reinforced Concrete Structures

2016 ◽  
Vol 711 ◽  
pp. 638-644 ◽  
Author(s):  
Peng Gang Wang ◽  
Folker H. Wittmann ◽  
Wen Pan Lu ◽  
Tie Jun Zhao
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Compressive Stress ◽  
Pore Space ◽  
Concrete Structures ◽  
Compressive Load ◽  
Sustained Load ◽  
Capillary Absorption ◽  
Reinforced Concrete Structures ◽  
Concentration Difference

The influence of an applied high compressive load on strength of concrete has been studied both theoretically and experimentally in great detail in the past. It was observed that load bearing capacity of concrete decreases under the influence of sustained compressive stress. In this contribution the influence of high sustained compressive stress on capillary absorption and on chloride penetration will be described. It was found that under the influence of moderate sustained compressive load the amount of capillary absorbed water decreases. If the sustained compressive load overcomes 50 % of the material’s strength, the rate of capillary absorption increases. This fact can be explained by reduction of the pore space under moderate compressive stress and formation and time-dependent growth of micro-cracks in the composite structure of concrete. Dissolved chloride is filtered out of the aqueous salt solution and remains accumulated in a surface near layer. In this way a high concentration difference of chloride is built up in a short time. This gradient leads to long lasting diffusion of chloride deeper into the pore space. As the diffusion coefficient of dissolved ions in the pore liquid increases with increasing applied compressive load, service life of structural elements under high compressive load will be reduced significantly when exposed to aggressive environment. This fact has to be taken into consideration if service life of reinforced concrete structures is to be predicted in a realistic way.

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 Fibrocartilage in tendons and ligaments — an adaptation to compressive load

1998 ◽  
Vol 193 (4) ◽  
pp. 481-494
Author(s):  
M. BENJAMIN ◽  
J. R. RALPHS
Keyword(s):  
Compressive Stress ◽  
Mechanical Load ◽  
Compressive Load ◽  
Type Ii Collagen ◽  
Type Ii ◽  
Joint Movement ◽  
Collagen Fibres ◽  
Wear And Tear ◽  
Compression Type

Where tendons and ligaments are subject to compression, they are frequently fibrocartilaginous. This occurs at 2 principal sites: where tendons (and sometimes ligaments) wrap around bony or fibrous pulleys, and in the region where they attach to bone, i.e. at their entheses. Wrap-around tendons are most characteristic of the limbs and are commonly wider at their point of bony contact so that the pressure is reduced. The most fibrocartilaginous tendons are heavily loaded and permanently bent around their pulleys. There is often pronounced interweaving of collagen fibres that prevents the tendons from splaying apart under compression. The fibrocartilage can be located within fascicles, or in endo- or epitenon (where it may protect blood vessels from compression or allow fascicles to slide). Fibrocartilage cells are commonly packed with intermediate filaments which could be involved in transducing mechanical load. The ECM often contains aggrecan which allows the tendon to imbibe water and withstand compression. Type II collagen may also be present, particularly in tendons that are heavily loaded. Fibrocartilage is a dynamic tissue that disappears when the tendons are rerouted surgically and can be maintained in vitro when discs of tendon are compressed. Finite element analyses provide a good correlation between its distribution and levels of compressive stress, but at some locations fibrocartilage is a sign of pathology. Enthesis fibrocartilage is most typical of tendons or ligaments that attach to the epiphyses of long bones where it may also be accompanied by sesamoid and periosteal fibrocartilages. It is characteristic of sites where the angle of attachment changes throughout the range of joint movement and it reduces wear and tear by dissipating stress concentration at the bony interface. There is a good correlation between the distribution of fibrocartilage within an enthesis and the levels of compressive stress. The complex interlocking between calcified fibrocartilage and bone contributes to the mechanical strength of the enthesis and cartilage-like molecules (e.g. aggrecan and type II collagen) in the ECM contribute to its ability to withstand compression. Pathological changes are common and are known as enthesopathies.

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