Chloride initiates the corrosion of embedded reinforcements, which not only produces signs of deterioration on the concrete surface, such as rusting, cracking and spalling, but also reduces the loadcarrying capacity. This phenomenon does not occur because of the physical and chemical protection that concrete offers. Structures in potentially aggressive environments must be designed to. Although properly made concre t e is inherently a rugged, durable mat e r ial, there are many physical and chemical forces in the enviro n m e n t which can contribute to its deteri o ration. It is responsible for almost 40% of failure of concrete structures. Damages associated with chloride attack the main problem involving the corrosion of the steel is the spalling of the concrete cover. Potential chemical attack on concrete foundations due to groundwater chemistry conference paper pdf available july 2014 with 2,935 reads how we measure reads. Corrosion of reinforced concrete rc structures is one of the significant causes of deterioration of reinforced concrete rc structures. As a result of carbonation and chloride attack, the structural integrity of the bridge needed to be reinstated as the steel reinforcement had corroded significantly and the concrete had spalled. The life of structure reduces and it can lead to failure of structures. Latterly the need for concrete in construction has led to its combination with steel reinforcing bars to provide tensile strength not readily available to concrete in isolation.
Among all sources of failure of concrete structures, the chloride attack accounts 40% contribution. Case studies in reinforced and prestressed concrete presents a selection of the authors firsthand experience with incidents related to reinforced and prestressed concrete structures. Evaluating effect of chloride attack and concrete cover on. Chemical attack of strong chloride solutions on concrete. Sulfate attack is particularly complex because the source of sulfates can be external or internal delayed ettringite formation, and the distress can be chemical in nature, due to alteration of hydration of products, or physical in. Also, the figure shows that bs total chloride limit for this type of concrete is not. They found that when an electrical current was applied to a concrete specimen it increased and accelerated the rate at which the chlorides migrated into concrete. He includes mistakes discovered at the design stage, ones that. The net result of chloride attack is the corrosion of steel reinforcement, leading to cracking and spalling of concrete and in some cases catastrophic structural failure as the load bearing capacity of the concrete is compromised. Effect of chloride based deicers on reinforced concrete structures july 2010 6. Anderson award winner, and a member of numerous aci committees including c232 on fly ash and c201 on durability. Relationship between coefficient of permeability and watercement ratio ref 4. Physical salt attack on concrete, part 2 aci spring 2012 convention march 18 21, dallas, tx r.
Chloride attacks on concrete structures ctlgroupqatar. Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. Sulphate attack on concrete process and control of sulphate attack. The main effect of chloride attack is the corrosion of reinforcement that induces the strength of the. Effects of substances on concrete and guide to protective treatments concrete technology by beatrix kerkhoff fig. Mineral admixtures were used as a partial replacement for ordinary portland cement c,a 8. Cracking in mass concrete will normally occur when tensile stresses are developed which exceed the tensile strength of the concrete. It cannot be determined directly in a time frame that would be useful as a quality control measure.
Laboratory and field evaluations of external sulfate attack. Understanding chemical attacks and permeation properties of concrete 1st saudi concrete conference, 14 may 2016 riyadh, jeddah and khobar ksa abu saleh mohammod phd, mict general manager pudlo middle east building materials l. By concrete construction staff download the pdf version of this article. Components of concrete concrete is made up of two components, aggregates and paste. The mean compressive strength required at a specific age, usually 28 days, determines the nominal watercement ratio of the mix. Relationship between concrete strength and wc ratio at various ages ref 3. The following summary discusses potential causes of concrete deterioration and the factors that influence them.
Analysis of total chloride content in concrete sciencedirect. The most common causes of corrosion of concrete structures include. Their role in concrete durability march 99 attackpenetration has been the subject of much research in recent years. Carbonation and chloride of concrete development bureau. Chloride ingress into concrete is generally held to follow ficks second law of diffusion, forming a chloride profile with depth into the concrete.
Recycled concrete aggregate rca principally contains crushed concrete. Page 1 of 6 1 continuous long term exposure 2 short termintermittent exposure penetration. Physical salt attack on concrete foundation stem wall by sodium sulfate. Sulphate attack on concrete is a chemical breakdown mechanism. Maininfluences, cement and concrete research, 1998, vol. Chloride induced corrosion of reinforcement steel in concrete. Chlorides can be introduced into the concrete either during or after construction as follows. Chemical resistance chart for concrete ambient temperature and maximum concentration apply, unless otherwise noted. In buildings, concrete is used for footings, foundations, columns, beams, girders, wall slabs, and roof unitsin short, all important building elements. Chemical attack on hardened concrete concrete construction. Sulphate attack on concrete has the potential to cause serious damage or structural failures. Chloride attack is a major deterioration factor for concrete structures in japan. The chemicals may cause cracking of concrete, volume change and deterioration of structure.
Xianming shi, yajun liu, matthew mooney, michael berry, barrett hubbard, laura fay, andrea beth leonard 9. Chloride attack poses a significant threat to reinforced concrete especially for structures in marine environments or those that. Chloride attack in wetting and drying exposure concrete. The chlorides exist in concrete during the casting process due to the following reasons. Chloride content of portland cement concrete powder by a. The acid attack test on concrete cube was conducted by immersing the cubes in the. An effective concrete repair and protection system was required for the concrete elements of the bridge to complement other strengthening work and. The oxide resulting from the corrosion is very porous and takes up to 10 times the volume of the steel which causes the breakup of the concrete. The mechanism of chlorideinduced corrosion of steel embedded in concrete, the ingress of chlorides into the concrete, and the threshold chloride content for corrosion to occur are discussed.
After the chemical reaction, the concrete loses its properties and deteriorates. The compounds responsible for sulphate attack on concrete are watersoluble sulphatecontaining salts, such as alkaliearth calcium, magnesium and alkali sodium, potassium sulphates that are capable of chemically reacting. The destruction of concrete under sulphate attack is particularly related to expansion, however, the dissolution of cement matrix may by considerable. Understanding chemical attacks and permeation properties. So researchers looked for a test method that would accelerate this migration. This research compares singleion attack and combined attack. When a concrete structure is prone to chemical actions its durability gets affected. The mode of attack relies on salts and other corrosive substances, carried by moisture, being absorbed into the. Oct 11, 2001 sulfate attack on concrete provides a comprehensive reference to this important subject. The ability of chloride ions to penetrate the concrete must then be known for design as well as quality control purposes. The service life of reinforced concrete structures is.
He is also a fellow of astm, and the engineering institute of canada. Corrosion of reinforcing steel is the most common cause of concrete. When chloride ions ingress and carbonation take place simultaneously in concrete. First the aggregate particles are set in motion and slump to fill the form giving a level top surface. Founded in 1904 and headquartered in farmington hills, michigan, usa, the american concrete institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensusbased standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design. At present, concrete and reinforced concrete are gaining ground in all sectors of construction including construction in the extreme north, on shelves. C1 readymixed concrete 5 5 recycledconcreteaggregaterca recycled aggregate is made by processing inorganic material previously used in construction. Chloride content test for concrete determines the level of chloride ions and ingress of the chloride ion which destroys the protective layer of steel. Attack of concrete materials, advanced materials re search, issn. Concrete basicsaddresses the needs of unskilled and semiskilled persons undertaking general concreting projects including home and handyman projects.
Shown are concrete beams exposed to highconcentration sulfate soilssolutions. Fresh concrete corrodes aluminum with subsequent release of hydrogen. Hydrochloric acid attack on concrete the chemicals formed as the products of reaction between hydrochloric acid and hydrated cement phases are some soluble salts and some insoluble salts. Also, since high temperatures usually accelerate chemical attack, better protection is required than for normal temperatures. Now, several researches on the chlorination of concrete structures have been ongoing around the world. Compressive strength it is one of the most important properties of concrete and influences many other describable properties of the hardened concrete. Aggressive substances can compromise the durability of concrete. Salt has scaled the concrete surface behind a coating of latex paint. Maintenance of concrete bridges deteriorated by chloride.
Several cases of acid attack on concrete in the uk are described by eglinton 1975 6. Effect of chloridebased deicers on reinforced concrete. Neville 1995 according to the author, the chloride attack on concrete is different from other mechanisms of deterioration because the primary action of chlorides is to cause corrosion of steel reinforcement and it is only as a consequence of this corrosion that the surrounding concrete is damaged. Chloride attack on concrete structures is one of the most important phenomena we consider when we deal with the durability of concrete. In the literature, this is referred as physical attack 2. Increasing severity is represented by higher numerical value in the ec designation. Testing chloride penetration resistance of concrete. The video defines the chloride threshold level, the initiation.
Deicing salts are a major cause of corrosion of reinforcing steel in concrete. Consideration of the concrete durability should take into account sulphate attack which may be significantly various. The binding of chloride ions by cement compounds and the associated effect of using different cements, both portland and blended, as well as other factors influencing corrosion, are considered. Occurrence of acidic ground conditions is dealt with in section c2. Often the trouble comes from using a poor quality of concrete, but frequently good concrete has been unintentionally subjected to conditions that lead to. This article points out some of the conditions that lead to chemical attack on hardened concre t e. Cracking in mass concrete structures is undesir able as it affects the watertightness, durability, appearance, and internal stresses of t,he structures. The formation of the steel concrete composite has enabled the construction of taller buildings, longer bridges, more environmentally friendly and more architecturally. Chloride migration through concrete, even in high watercement ratio concrete, is a very slow process. Maximum chloride ion content of concrete aci 318 maximum type of member cl prestressed concrete 0. Chlorination is a major process governing the initiation and advancement of the injurious corrosion of steel bars. Concrete basicsaims to provide a clear, concise explanation of all aspects of making quality concrete. The penetration of the concrete by chloride ions, however, is a slow process.
Sulfate attack is a complex form of deterioration that has damaged concrete structures throughout the world. It is a permitted constituent in some types of concrete. Compaction of concrete is, therefore, a twostage process figure 1. The types of disruption observed during sulphate attack on mortars or concretes, and the chemical processes involved, are summarized. Analysis of total chloride content in concrete article pdf available in case studies in construction materials 3c. Though hno 3 is not as strong as h 2 so 4, its effect on concrete at brief exposure is more destructive since it transforms ch into highly soluble calcium nitrate salt and low soluble calcium nitroaluminate hydrate nitric acid attack is a typical acidic corrosion for shrinkage of the corroded layer due to leaching of highly soluble calcium nitrate.
In the presence of oxygen and water, chloride attack corrodes the steel reducing the strength of the structure drastically. Air drying for at least 28 days following curing helps concrete resist attack from sugar solutions. Effects of substances on concrete and guide to protective. Combined attack simulates concrete deterioration in marine environments more realistically. These threshold chloride values can be approximated to about 0. This video talks about sources for chlorides and how the chlorides attack the passive layer in concrete and the following steps. Introduction chloride ions ingress and carbonation, which start from concrete surface and progress toward internal concrete, can both lead to accelerated corrosion of steel bars in concrete.
The compounds present in cement concrete are attacked by many salt solutions and. For portland cement concrete, the gain in strength is sanewhat reduced, but not for slag cement concrete, canpared with the same types of concrete stored in pure water. Chloride attack evaluation on concrete compositions according to brazilian standard abnt nbr 6118 specification. The sulphuric acid attacks both the cement phase and the carbonate aggregate. Pdf potential chemical attack on concrete foundations due. Trace amounts of sugar in freshly mixed concrete are sufficient to retard the setting, but dry sugar has no effect on hardened concrete. Chloride attack on concrete is one of the important aspects of durability of concrete. Concrete can deteriorate for a variety of reasons, and concrete damage is often the result of a combination of factors. The silica fume affects negatively the resistance to this attack. The attack of chloride on concrete structures can be happened either from inside of the concrete or through the ingress of chloride from outside to the inside of concrete structures. Pozzolan concrete durability on sulphate attack sciencedirect.
Chloride attack on concrete structures cause and prevention. Soluble salts, mostly with calcium, are subsequently leached out, whereas insoluble salts along with amorphous hydrogels, remain in the corroded layer. Cement,additionsandadmixtures concrete may contain one. Chloride content test for concrete structure durability.
Severe sulfuric acid attack on selfcompacting concrete. Acid attack test the concrete cube specimens of various concrete mixtures of size 150 mm were cast and after 28 days of water curing, the specimens were removed from the curing tank and allowed to dry for one day. Chemical attack on concrete transportation research board. The main cause for deterioration of reinforced concrete structures is the corrosion of the embedded steel, in particular when exposedto marine environments or deicing salts, due to the action of chloride.
Chloride attack in wetting and drying exposure by concrete construction staff a brine with a high content of calcium chloride is leaking through the concrete linings of a potash shaft and causing severe deterioration of the concrete linings. The paste is composed of cement, water, and entrained air and ordinarily constitutes 20 to 40 percent of the total volume. Concrete mix design and binder type have an important influence on concrete performance in sulphate environments. Chemical attack on concrete transportation research. Sugar solutions and sugarcontaining food products may cause deterioration. Studies on concrete degradation in aggressive environment. Concrete used in the modern era is a mixture of water, cement, aggregates and, where required, admixtures plasticisers, superplasticisers, etc. Chloride limits are expressed on the basis of the weight of portland cement. Different types of chemical attacks and their effects on concrete structures are explained below. Statistics have indicated that over 40% of failure of structures is due to corrosion of reinforcement a. However, several factors influence concrete resistance against chlorides and sulphates. But due to chloride attack on concrete, reinforcement steel gets corroded. One of the factors that affect the concrete structures durability is the corrosion in reinforcement steel. Sulphate attack on concrete magazine of concrete research.
Pdf effect of carbonation, chloride and sulphate attacks. The alkaline environment is created by the hydration of the cement in concrete. Dec 01, 2012 1,2,3 chloride attack is one of the most important aspects for consideration when we deal with the durability of concrete. Chloride attack chloride attack is one of the most important aspects while dealing with durability of concrete. This research hasnt been cited in any other publications. When considering durability of concrete, chloride attack is the most imminent enemy. Aci 318 defines exposure classes ec within each exposure category based on the severity of exposure. Best practices guidelines for concrete construction. Chemistry of chloride attack on concrete i should appreciate very much, if you, dear reader, would pleas e to communicate to me, or to professor arne hillerborg, any experience that points to the pos sibi lit y that damage to concrete is caused by chlorides in a way, which is not covered up in this short study. It primarily affects the reinforcement of concrete and cause corrosion. Pdf chloride attack evaluation on concrete compositions. In the case of humic acid, reaction products formed on the surface of concrete are mainly insoluble and tend to impede further attack. The mechanism of chloride induced corrosion of steel embedded in concrete, the ingress of chlorides into the concrete, and the threshold chloride content for corrosion to occur are discussed. Statistics have indicated that over 40% of failure of structures is due to corrosion of steel.
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