Deicing salts are a major cause of corrosion of reinforcing steel in concrete. Chloride attack chloride attack is one of the most important aspects while dealing with durability of concrete. Concrete can deteriorate for a variety of reasons, and concrete damage is often the result of a combination of factors. Chloride attack on concrete is one of the important aspects of durability of concrete. Chloride attack on concrete structures is one of the most important phenomena we consider when we deal with the durability of concrete. Studies on concrete degradation in aggressive environment. Statistics have indicated that over 40% of failure of structures is due to corrosion of steel. The acid attack test on concrete cube was conducted by immersing the cubes in the. Xianming shi, yajun liu, matthew mooney, michael berry, barrett hubbard, laura fay, andrea beth leonard 9. In the case of humic acid, reaction products formed on the surface of concrete are mainly insoluble and tend to impede further attack. So researchers looked for a test method that would accelerate this migration. Chloride content test for concrete determines the level of chloride ions and ingress of the chloride ion which destroys the protective layer of steel.
C1 readymixed concrete 5 5 recycledconcreteaggregaterca recycled aggregate is made by processing inorganic material previously used in construction. Several cases of acid attack on concrete in the uk are described by eglinton 1975 6. 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. 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. When chloride ions ingress and carbonation take place simultaneously in concrete. Soluble salts, mostly with calcium, are subsequently leached out, whereas insoluble salts along with amorphous hydrogels, remain in the corroded layer.
Sulfate attack is a complex form of deterioration that has damaged concrete structures throughout the world. An effective concrete repair and protection system was required for the concrete elements of the bridge to complement other strengthening work and. Mineral admixtures were used as a partial replacement for ordinary portland cement c,a 8. This research hasnt been cited in any other publications. Combined attack simulates concrete deterioration in marine environments more realistically.
It is important to recognise the two stages in the compaction process because, with vibration. The following summary discusses potential causes of concrete deterioration and the factors that influence them. Damages associated with chloride attack the main problem involving the corrosion of the steel is the spalling of the concrete cover. Statistics have indicated that over 40% of failure of structures is due to corrosion of reinforcement a. Also, since high temperatures usually accelerate chemical attack, better protection is required than for normal temperatures. Maintenance of concrete bridges deteriorated by chloride. Salt has scaled the concrete surface behind a coating of latex paint. Also, the figure shows that bs total chloride limit for this type of concrete is not. Laboratory and field evaluations of external sulfate attack. Air drying for at least 28 days following curing helps concrete resist attack from sugar solutions. Chloride ingress into concrete is generally held to follow ficks second law of diffusion, forming a chloride profile with depth into the concrete. Sulphate attack on concrete magazine of concrete research. Chloride content test for concrete structure durability. Testing chloride penetration resistance of concrete.
In the presence of oxygen and water, chloride attack corrodes the steel reducing the strength of the structure drastically. Shown are concrete beams exposed to highconcentration sulfate soilssolutions. This article points out some of the conditions that lead to chemical attack on hardened concre t e. 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.
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. Potential chemical attack on concrete foundations due to groundwater chemistry conference paper pdf available july 2014 with 2,935 reads how we measure reads. Fresh concrete corrodes aluminum with subsequent release of hydrogen. One of the factors that affect the concrete structures durability is the corrosion in reinforcement steel. Chloride attack in wetting and drying exposure concrete. Analysis of total chloride content in concrete sciencedirect. Chemical resistance chart for concrete ambient temperature and maximum concentration apply, unless otherwise noted. 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.
Relationship between coefficient of permeability and watercement ratio ref 4. Pdf potential chemical attack on concrete foundations due. Effect of chloridebased deicers on reinforced concrete. 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. The service life of reinforced concrete structures is. Chloride attacks on concrete structures ctlgroupqatar.
Compaction of concrete is, therefore, a twostage process figure 1. 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. Consideration of the concrete durability should take into account sulphate attack which may be significantly various. It primarily affects the reinforcement of concrete and cause corrosion. The destruction of concrete under sulphate attack is particularly related to expansion, however, the dissolution of cement matrix may by considerable. Among all sources of failure of concrete structures, the chloride attack accounts 40% contribution. First the aggregate particles are set in motion and slump to fill the form giving a level top surface. This video talks about sources for chlorides and how the chlorides attack the passive layer in concrete and the following steps. Chloride content of portland cement concrete powder by a. After the chemical reaction, the concrete loses its properties and deteriorates. The mean compressive strength required at a specific age, usually 28 days, determines the nominal watercement ratio of the mix. The formation of the steel concrete composite has enabled the construction of taller buildings, longer bridges, more environmentally friendly and more architecturally. The sulphuric acid attacks both the cement phase and the carbonate aggregate. Pdf effect of carbonation, chloride and sulphate attacks.
Sugar solutions and sugarcontaining food products may cause deterioration. Cracking in mass concrete will normally occur when tensile stresses are developed which exceed the tensile strength of the concrete. It is a permitted constituent in some types of concrete. Concrete used in the modern era is a mixture of water, cement, aggregates and, where required, admixtures plasticisers, superplasticisers, etc. Their role in concrete durability march 99 attackpenetration has been the subject of much research in recent years. 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. Compressive strength it is one of the most important properties of concrete and influences many other describable properties of the hardened concrete. Trace amounts of sugar in freshly mixed concrete are sufficient to retard the setting, but dry sugar has no effect on hardened concrete. 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. Recycled concrete aggregate rca principally contains crushed concrete.
The compounds present in cement concrete are attacked by many salt solutions and. These threshold chloride values can be approximated to about 0. Relationship between concrete strength and wc ratio at various ages ref 3. Concrete mix design and binder type have an important influence on concrete performance in sulphate environments. By concrete construction staff download the pdf version of this article. Maininfluences, cement and concrete research, 1998, vol. Understanding chemical attacks and permeation properties. Chloride limits are expressed on the basis of the weight of portland cement. 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. 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. Pozzolan concrete durability on sulphate attack sciencedirect. 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.
Chloride attack is a major deterioration factor for concrete structures in japan. Analysis of total chloride content in concrete article pdf available in case studies in construction materials 3c. Chemical attack of strong chloride solutions on concrete. Chemical attack on concrete transportation research board. Sulphate attack on concrete process and control of sulphate attack. 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. The video defines the chloride threshold level, the initiation. The main effect of chloride attack is the corrosion of reinforcement that induces the strength of the. The paste is composed of cement, water, and entrained air and ordinarily constitutes 20 to 40 percent of the total volume. Attack of concrete materials, advanced materials re search, issn. The silica fume affects negatively the resistance to this attack. The mode of attack relies on salts and other corrosive substances, carried by moisture, being absorbed into the.
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. Often the trouble comes from using a poor quality of concrete, but frequently good concrete has been unintentionally subjected to conditions that lead to. Concrete basicsaims to provide a clear, concise explanation of all aspects of making quality concrete. Cracking in mass concrete structures is undesir able as it affects the watertightness, durability, appearance, and internal stresses of t,he structures. Physical salt attack on concrete foundation stem wall by sodium sulfate.
Maximum chloride ion content of concrete aci 318 maximum type of member cl prestressed concrete 0. Chlorides can be introduced into the concrete either during or after construction as follows. 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 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. Evaluating effect of chloride attack and concrete cover on. 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. It cannot be determined directly in a time frame that would be useful as a quality control measure. He is also a fellow of astm, and the engineering institute of canada. When considering durability of concrete, chloride attack is the most imminent enemy. In buildings, concrete is used for footings, foundations, columns, beams, girders, wall slabs, and roof unitsin short, all important building elements. Different types of chemical attacks and their effects on concrete structures are explained below. At present, concrete and reinforced concrete are gaining ground in all sectors of construction including construction in the extreme north, on shelves.
Chloride attack on concrete structures cause and prevention. 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 induced corrosion of reinforcement steel in concrete. The penetration of the concrete by chloride ions, however, is a slow process. Sulphate attack on concrete has the potential to cause serious damage or structural failures. The alkaline environment is created by the hydration of the cement in concrete. The chlorides exist in concrete during the casting process due to the following reasons. Chlorination is a major process governing the initiation and advancement of the injurious corrosion of steel bars. However, several factors influence concrete resistance against chlorides and sulphates. Effects of substances on concrete and guide to protective treatments concrete technology by beatrix kerkhoff fig. 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. Aci 318 defines exposure classes ec within each exposure category based on the severity of exposure. The types of disruption observed during sulphate attack on mortars or concretes, and the chemical processes involved, are summarized.
Chloride attack evaluation on concrete compositions according to brazilian standard abnt nbr 6118 specification. When a concrete structure is prone to chemical actions its durability gets affected. Components of concrete concrete is made up of two components, aggregates and paste. The life of structure reduces and it can lead to failure of structures. Structures in potentially aggressive environments must be designed to. But due to chloride attack on concrete, reinforcement steel gets corroded. He includes mistakes discovered at the design stage, ones that. Oct 11, 2001 sulfate attack on concrete provides a comprehensive reference to this important subject. Portland cement concrete, on storing in strong solutions of sodium or potassium chloride, forms sodium or potassium hydroxide, enough to cause. It is responsible for almost 40% of failure of concrete structures. 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 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.
Effects of substances on concrete and guide to protective. In the literature, this is referred as physical attack 2. Increasing severity is represented by higher numerical value in the ec designation. Aggressive substances can compromise the durability of concrete. Anderson award winner, and a member of numerous aci committees including c232 on fly ash and c201 on durability. Pdf chloride attack evaluation on concrete compositions.
Cement,additionsandadmixtures concrete may contain one. 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. 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. Effect of chloride based deicers on reinforced concrete structures july 2010 6. Occurrence of acidic ground conditions is dealt with in section c2. Page 1 of 6 1 continuous long term exposure 2 short termintermittent exposure penetration. Sulphate attack on concrete is a chemical breakdown mechanism. Chloride migration through concrete, even in high watercement ratio concrete, is a very slow process. The most common causes of corrosion of concrete structures include. Best practices guidelines for concrete construction. Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste.
Severe sulfuric acid attack on selfcompacting concrete. Now, several researches on the chlorination of concrete structures have been ongoing around the world. This research compares singleion attack and combined attack. Chemical attack on hardened concrete concrete construction. 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. 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. Concrete has a great variety of applications because it not only meets structural demands but also lends itself readily to architectural treatment. Carbonation and chloride of concrete development bureau.
Concrete basicsaddresses the needs of unskilled and semiskilled persons undertaking general concreting projects including home and handyman projects. The chemicals may cause cracking of concrete, volume change and deterioration of structure. Corrosion of reinforcing steel is the most common cause of concrete. The ability of chloride ions to penetrate the concrete must then be known for design as well as quality control purposes. Chemical attack on concrete transportation research.
Corrosion of reinforced concrete rc structures is one of the significant causes of deterioration of reinforced concrete rc structures. Physical salt attack on concrete, part 2 aci spring 2012 convention march 18 21, dallas, tx r. This phenomenon does not occur because of the physical and chemical protection that concrete offers. Case studies in reinforced and prestressed concrete presents a selection of the authors firsthand experience with incidents related to reinforced and prestressed concrete structures.
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