File Name: durability and permeability of concrete .zip
Metrics details. Assessment of concrete cover quality is necessary for proper maintenance of concrete structures. Concrete durability is evaluated primarily based on chloride penetrability, neutralization and other external factors. The present study attempts to analyze concrete quality and its mass transfer resistance performance by measuring the air permeability and its relation with concrete durability indicators like chloride diffusion and neutralization.
The applicability of air permeability as a durability indicator is validated using concrete with different materials, parameters and curing conditions. The tests are conducted on laboratory prepared concrete as well as for concrete exposed to actual marine conditions. From the experimental results, it is found that air permeability coefficient, neutralization coefficient and chloride ion diffusion coefficient have high correlation. It is suggested that air permeability could be considered as an alternative to estimate mass transfer resistance of concrete and as a concrete durability indicator.
Evaluation of concrete quality up to the depth of concrete cover is necessary for proper maintenance of reinforced concrete structures. One of the employed methods to analyze the existing concrete performance is the compressive strength. However, compressive strength alone cannot be an indicator for mass transfer resistance of concrete. Permeability of concrete is a major indicator of its performance in terms of durability.
Carbon dioxide, chloride ion and water ingress are the primary cause of detrimental effects in concrete. Their penetration into concrete is governed by the pore structure. Hence air permeability and water permeability can be indicators for the magnitude of penetration of carbon dioxide or chloride ion.
Air permeability is said to be highly correlated with porosity and pore size distribution of concrete and can be used as a measure of porosity and pore connectivity Halamickova et al. Air permeability coefficient has high correlation with neutralization progress, water cement ratio, cement type and curing conditions Basheer et al. Studies on air permeability and its relation to chloride diffusion are few and rather complicated. It is reported that chloride ion diffusion coefficient has a possibility of greatly varying between salt immersion test and in actual concrete structure.
Due to such variations, evaluation of penetration of chloride ion into actual concrete structure should be considered for safer structures Yamaji Diffusion coefficient is time dependent and decreases over time Halamickova et al. This makes it difficult to evaluate chloride ion penetration into concrete by various methods. However, long-term resistance to chloride ion penetration is unclear. Since, supplementary cementitious materials like fly ash and Portland blast furnace cement are excellent in resistance to chloride ion penetration Osborne ; Thomas and Bamforth ; McCarthy and Dhir ; Berndt , studies on their relation between air permeability and chloride diffusion is important.
In case of air permeability, factors affecting measurement are pore structure and moisture content in concrete. On the other hand, it is considered that penetration of chloride ion into concrete is governed by the capillary absorption, permeability and diffusion by concentration gradient depending on several factors and each has its own testing methods Basheer et al.
In the electrophoretic test method chloride ion migration test for evaluation of chloride ion penetration, concrete specimen is subjected to water saturated condition. Hence, air permeability coefficient can be possibly used to evaluate D e. Also, assessment of chloride diffusion by electrophoretic test has its own drawbacks owing to complexity and time consumption Truc et al. All the facts put together, present study aims at evaluating mass transfer resistance performance of concrete by measurement of air permeability.
The correlation between air permeability and other durability indicators were examined for possible application of air permeability as a durability indicator on a wide range of conditions.
Since D a can be estimated from D e using established equations, a good correlation between air permeability and D e facilitates easy estimation of D a. Hence, the study aims to find the correlation between air permeability and D e. This provides an indirect estimation of chloride diffusion coefficient by air permeability. The relation between air permeability and neutralization, chloride diffusion by salt immersion test, porosity, cement types and curing conditions have been studied extensively.
However, there are no substantial reports on correlation between air permeability and chloride diffusion coefficient by electrophoretic test especially for both laboratory tests and actual marine structures. Laboratory tests to determine neutralization coefficient, chloride diffusion coefficient by electrophoretic test of chloride ion D e , apparent diffusion coefficient by salt immersion test D a and air permeability were employed.
The relation between air permeability and chloride diffusion in concrete exposed to marine conditions was also analyzed. In particular, measurement of D a and D e in actual marine environment, at deeper sections of concrete cores where chloride ions not penetrated was also performed.
The experimental procedure for each is explained. Average of three samples was taken for compressive strength MPa: megapascal. The variation of air permeability result with different relative humidity was experimented and reported by Care and Derkx and Villani et al.
However, in this study, this condition was adopted to match the conditions of laboratory during the air permeability experiment. The sides of specimens were coated with epoxy and taped with aluminum, except top and bottom surface to promote air flow into specimen. Compressed air was introduced into the chamber.
When the amount of permeated air became constant, the amount of air permeation was measured by the water substitution method Fig. Salt immersion test and determination of diffusion coefficient were done according to JIS A and JSCE-G respectively for specimens both water and atmosphere cured. These specimens were coated with epoxy on the sides except opposite surfaces.
Mercury intrusion porosimetry was employed to determine the pore size distribution of each concrete. In this experiment, concrete cores of actual structure in marine environment were used as specimens.
The year-old concrete structures were constructed using B type Portland blast furnace cement and partial replacement of cement by fly ash. Compressive strength was Tests were carried out by using cut slices of the concrete core as shown in Fig. Measurement of penetrated chloride ion was carried out in accordance with JIS A Air permeability, salt immersion, electrophoretic test and porosity tests were carried out similar to the procedures explained in Sect.
The relationship between air permeability and water binder ratio of concretes are shown in Fig. The difference in curing conditions is also projected in the graphs. Regardless of cement types used, air permeability is lesser for water cured specimens than atmosphere cured similar to other findings Mu et al.
Permeability coefficient in any cement types, decreases with increase in compression strength regardless of curing conditions. Hence blended concrete requires water curing for longer curing periods. OPC has relatively higher content of cement and hence produces higher amounts of calcium hydroxide. This is thought to be the cause for reduced neutralization. By comparing the relationship between air permeability coefficient and the neutralization coefficients shown in Fig.
But those studies showed rather less correlation between air permeability and neutralization suggesting that estimation would be better considering compressive strength. A similar argument is made by Hui-sheng et al. Corresponding to decrease in air permeability coefficient in any of the cement type, D a decreases Fig. Fairly good correlation is found between diffusion coefficient and air permeability for all cement types.
According to Sugiyama et al. As in Fig. According to Ramezanianpour and Malhotra and Guneyisi et al. Concrete with slag shows superior resistance to chloride penetration Yildirim et al. Hence from the observations, it can be understood that chloride penetration is much strongly governed by chemical processes ion transfer and physical adsorption by charge interaction, concentration gradient, and immobilization rather than physical processes advection alone.
From the observations, when estimating the chloride ion apparent diffusion coefficient by permeability coefficient, it is necessary to take into account at least the cement type and curing conditions. Within the scope of the results shown in Fig. In the case of atmosphere cured concrete subjected to vacuum during air permeability test and later saturated when subjected to electrophoretic test changes the internal conditions of concrete; from dry concrete including unreacted cement to saturated concrete with possible rehydration reaction.
This results in varied air permeability results before and after the tests. Hence, this is thought to be one of the reasons for low correlation for atmosphere cured concrete. The degree of saturation highly effects chloride diffusion Nielsen and Geiker Overall result shows lower permeability for water cured specimens than atmosphere cured Care and Derkx The possibility of estimating D e without considering cement types by permeability coefficient can be considered but moisture condition and curing are accountable.
However, further investigation is recommended to clearly understand the correlation and possible estimation by air permeability. The difference in apparent diffusion coefficient between sea condition and immersion test is due to time dependent declination of diffusion coefficient due to the long-term hydration reaction of cement or blended cements Takewaka and Matsumoto ; Costa and Appleton However, there are several other factors to be considered for marine exposed concrete.
This makes it more complicated to arrive at relationship between permeability and chloride penetration. D e seems to be higher for higher air permeability in any concrete. Although the measured points are few, it is suggested that air permeability coefficient and D e have significant correlation, unlike D a or D c. Sharif et al. These findings show that air permeability can be an alternative to chloride diffusion obtained by electrophoretic test.
Air permeability versus chloride diffusion coefficient by salt immersion test D a and chloride diffusion coefficient of marine exposed concrete D c for exposed concrete. Air permeability versus effective chloride diffusion coefficient D e for exposed concrete. Specimens which were water cured showed high correlation regardless of cement types and water cement ratio in Fig. And, this relationship differs from Fig. It is a well-known fact that air permeability is influenced by water content in concrete and that pre-conditioning is required which makes the test often sensitive Zaharieva et al.
The difference in slope of correlation between Figs. In case of laboratory prepared atmosphere cured concrete, low correlation was observed between air permeability and D e due to the changes in pore structure of concrete when concrete is transferred from air permeability test to electrophoretic test because of possible rehydration reaction of cement in the process of electrophoretic test of chloride ion and saturated water processing.
The results of air permeability depend on degree of saturation of specimen under test and how it is dried Sugiyama et al. Hence, estimation of D e by air permeability for laboratory prepared concrete and actual structure exposed to marine conditions is possible by considering the effect of water content ratio. From these results, D e can be estimated by measurement of air permeability regardless of cement type or concrete properties, but water content should be considered.
Effects of pore structure on diffusion coefficient of BBC and FAC in existing structure is evaluated as a relationship between volume of pores for a range of pore diameter and respective diffusion coefficients by linear approximation method depicting correlation coefficient R 2.
This work is licensed under a Creative Commons Attribution 4. You may also start an advanced similarity search for this article. Technical support: soporte. The present study analyzes these two factors. The results of low-pressure water testing to evaluate permeability and analyses to determine compressive strength and pore size distribution showed that self-compacting concrete has lower capillary porosity than traditional concrete, which would explain its greater resistance to water penetration.
Water is often added to concrete placing for easy workability and finishability in construction site. The additional mixing water can help easy mixing and workability but causes increased porosity, which yields degradation of durability and structural performances. In this paper, cement mortar samples with 0. Several durability tests including strength, chloride diffusion, air permeability, saturation, and moisture diffusion are performed, and they are analyzed with changed porosity. The changing ratios and patterns of durability performance are evaluated considering pore size distribution, total porosity, and additional water content. Usually deteriorating agents which can cause steel corrosion like chloride ions and carbon dioxide intrude into concrete through pores or their connectivity [ 1 — 3 ].
The ability of concrete to withstand the conditions for which it is designed without deterioration for a long period of years is known as durability. Durability of concrete may be defined as the ability of concrete to resist weathering action, chemical attack, and abrasion while maintaining its desired engineering properties. Durability is defined as the capability of concrete to resist weathering action, chemical attack and abrasion while maintaining its desired engineering properties. It normally refers to the duration or life span of trouble-free performance. Different concretes require different degrees of durability depending on the exposure environment and properties desired. For example, concrete exposed to tidal seawater will have different requirements than indoor concrete.
Durability is the ability to last a long time without significant deterioration. A durable material helps the environment by conserving resources and reducing wastes and the environmental impacts of repair and replacement. The production of replacement building materials depletes natural resources and can produce air and water pollution. Concrete resists weathering action, chemical attack, and abrasion while maintaining its desired engineering properties. Different concretes require different degrees of durability depending on the exposure environment and the properties desired.
The change of the gas permeability of concrete with age and the effect of defined moisture conditions were investigated.
Сьюзан объяснила, что перехватываемые сообщения обычно исходят от правительств потенциально враждебных стран, политических фракций, террористических групп, многие из которых действуют на территории США. Эти сообщения обычно бывают зашифрованы: на тот случай, если они попадут не в те руки, - а благодаря КОМИНТ это обычно так и происходит. Сьюзан сообщила Дэвиду, что ее работа заключается в изучении шифров, взламывании их ручными методами и передаче расшифрованных сообщений руководству. Но это было не совсем. Сьюзан переживала из-за того, что ей пришлось солгать любимому человеку, но у нее не было другого выхода. Все, что она сказала, было правдой еще несколько лет назад, но с тех пор положение в АН Б изменилось. Да и весь мир криптографии изменился.
Информация, которую он выдал… Она резко подняла голову.
В следующую секунду, со сломанными шейными позвонками, он сполз на пол. ГЛАВА 61 Джабба лежал на спине, верхняя часть туловища скрывалась под разобранным компьютером. Во рту у него был фонарик в виде авторучки, в руке - паяльник, а на животе лежала большая схема компьютера. Он только что установил новый комплект аттенюаторов на неисправную материнскую плату, когда внезапно ожил его мобильный.
Дэвид даже вздрогнул. Он смотрел в ее глаза, надеясь увидеть в них насмешливые искорки. Но их там не. - Сью… зан, - заикаясь, начал. - Я… я не понимаю.
Он будет оставаться в таком состоянии, пока она не вернется и вновь не введет пароль. Затем Сьюзан сунула ноги в туфли и последовала за коммандером. - Какого черта ему здесь надо? - спросил Стратмор, как только они с Сьюзан оказались за дверью Третьего узла.
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