Physical sulfate attack on concrete types of external sulfate attack being covered in new draft revision to c201. The occurrence of sulphate attack on a concrete floor slab should be taken seriously as the stability of the structure is put at risk. Investigation of resistance of cement paste to sulfate attack. A lower water cement ratio results in obviously better resistance against sulfate attack for both precast and castinsitu concrete. Effects of substances on concrete and guide to protective. The following summary discusses potential causes of concrete deterioration and the factors that influence them. Soil and concrete samples may be taken to measure the sulphate content and help identify root cause of the sulphate attack. The authors describe chloride ions penetration in concrete structures as a significant threat to the durability of concrete structures. Sulphate attack is a process in which sulphates react with various phases of hydrated cement paste leading to deterioration of the concrete matrix through spalling, softening, and mass loss, which may lead to expansion and loose strength and elasticity. Sulfates can attack concrete by reacting with hydrated compounds in the. Internal sulphate attack takes place due to the source of sulphate being. Sulphate attack on concrete process and control of sulphate. Sulphate attack on a ground floor concrete slab is a very serious problem.
Ettringite formation and sulfate attack on concrete. Based on the obtained data in this study, the use of natural volcanic pozzolan replacing 5% by weight of cement in the mixture of high performance concrete influences positively the durability specimens concrete cured in sulphate environment. When the concrete is in soil and groundwater with dissolved sulfate, it will be destroyed by sulphate attack. There are apparently two chemical reactions involved in sulfate attack on concrete. Laboratory and field evaluations of external sulfate attack. Increases resistance to sulfate attack sulfate attack is a twophased process sulfates combine with calcium hydroxide generated during cement hydration to form calcium sulfate gypsum. Experimental studies on effects of sulphate resistance on. Sulfate attack, volcanic concrete system, granite rock powder, river sand, corrosion of reinforcement cite this article.
Throughout this study, it was possible to evaluate the effect of sulphate attack on concrete mixes by testing the changes in strength, height, and mass, in addition to observing the optical appearance of the test samples, as shown in figure 7. It occurs when concrete comes in contact with water containing sulfates so 4. Concrete can deteriorate for a variety of reasons, and concrete damage is often the result of a combination of factors. Sulphates can be found in some soils especially when arid conditions exist, in seawater, and in wastewater treatment plants. Concrete, sulphate attack, ettringite, delayed ettringite formation. Sulphate attack on concrete process and control of. The first line of defense against chemical attack is to use quality concrete with maximum chemical resistance. Where porous concrete is in contact with saturated. Innovative green cementitious systems using offspec fly ash. This is as a result of the presence of free lime caoh2 in the concrete after cement has undergone hydration.
Concrete in sulfate rich environments or solutions has been usually examined for chemical sulfate attack 12. Sulfate attack and reinforcement corrosion in concrete with. It is known that the concrete resistance to sulfates can be significantly improved producing a dense waterproof concrete. One of the main causes is leakage of sulphates into the concrete floor slab from the material below.
Tsa can attack concretes containing a wide range of different cements including those that are resistant to the conventional form of sulfate attack. However, not necessarily any ettringiterelated expansion is related to sulfate attack. 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. He is author or coauthor of numerous papers on concrete technology and cement chemistry. Sulphate attack increase in the volume of cement paste in concrete or mortar due to the chemical reaction between the products of hcp and solution containing sulphates. Sulphate attack on concrete is a chemical process where sulphate ions attack components of cement paste. Deterioration mechanism of sulfate attack on concrete. Therefore, if sulfate attack chemical characteristic xa1 xa2 xa3 so 4 2 mgl 200 and 15 and sulfate attack of concrete control of thaumasite formation in concrete.
The experimental part of the paper summarizes the testing methods, chemical characterization techniques and materials analyses used to evaluate the chemical composition, strength and longterm performance for cementitious powders, mortars and concrete samples with different. The characteristics of the concrete slab maybe noted. These chemicals are encountered by almost all concrete structures. Upon hydration, the main reaction products are calcium silicate gels and calcium hydroxide caoh2, written as ch in cement chemistry notation. Especially tunnel sites provide a great potential for concrete damaging processes as. Attack is the result of sulphates found within the soils under wet conditions reacting with the concrete, causing expansion which results in cracking and distortion of the. Identify concrete deterioration due to sulphate attack. Sulfate damage to concrete typically starts at the surface exposed to the sulfate environment and sulfate containing salt that forms on the concrete surface. Concrete is being used as a construction material in aggressive environment since long days. Consideration of the concrete durability should take into account sulphate attack which may be significantly various.
Concrete made with cements high in tricalci um aluminate c 3 a are affected by most forms of sulfate attack 7. The sulfate attack in concrete by degradation of iron sulfides and the effect of the host rock servando chinchonpaya 1 izelman oliveira 2 antonio aguado 3 servando chinchon 4 abstract in this study we deal with the problems of durability of concrete made with reactive aggregates, and more particularly those containing oxidizable iron sulfides. Powers, john lawler, koray tureyen wiss, janney, elstner associates, inc. The compounds responsible for sulphate attack on concrete are watersoluble sulphate containing salts, such as alkaliearth calcium, magnesium and alkali sodium, potassium sulphates. Sulphate attack is a common form of concrete deterioration. Structures in potentially aggressive environments must be designed to recognise the risk of sulphate attack, and specific precautions taken in the design process to manage that risk. Chemical sulfate attack sulfate ingress sulfate attack requires intimate contact between sulfate anions and the cement paste of the concrete. Sulphate attack on concrete process and control of sulphate attack. Composition of portland cement was less important as it relates to performance in sulfate solutions.
Mpa cement fact sheet 2 thaumasite form of sulfate attack. Sulphate attack is the reaction between concrete constituents and sulphate ions in the pore solution of concrete that results in the production of new product with a fairly large molar volume the sulphate attack can have an internal origin which means the attack occurs without any contribution from the surrounding environment and external origin in which sulphate in soil or groundwater. Sulfate attack is a common form of concrete deterioration. Therefore, if sulfate attack chemical characteristic xa1 xa2 xa3 so 4 2 mgl 200 and 15 and sulphate attack. The orientation of chemical reactions of sulfate attack on cement concrete was theoretically determined as well as the critical sulfate ion concentration and the. External sulfate attack on concrete may lead to cracking, spalling, increased permeability, and strength loss. Concrete deterioration caused by sulfuric acid attack. Corrosion of steel in embedded concrete with volcanic aggregates due to sulfate attack, international journal of civil engineering and technology, 72, 2016, pp.
Accelerated test for measuring sulfate resistance of. Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. Analysis of durability of asvanced cementitious materials. Moisture is necessary for this reaction which can cause serious structural damage to both walls and wall slabs in buildings. Overview of sulfate attack in concrete, describing conventional sulfate attack, delayed ettringite formation and thaumasite. Due to a soluble source being incorporated into the concrete at the time of mixing, gypsum in the aggregate, for example. Sulphate attacks are of two types external or internal. Sulfate with the presence of water and cementitious paste will result in a process called sulfate attack. The expansion is directly connected with formation of.
Mpa cement fact sheet 2 thaumasite form of sulfate attack on. The deterioration of reinforced concrete by sulfate attack causes the reinforcing steel to be exposed to the action of aggressive agents starting the corrosion of the reinforcement 1. Concrete mix design and binder type have an important influence on concrete performance in sulphate environments. The rate of attack on good quality concrete is relatively slow. Nov 28, 2015 other sources of sulphate which can cause sulphate attack include. Mineral admixtures were used as a partial replacement for ordinary portland cement c,a 8. In hardened concrete, cah can react with sulphate salt from outside, forming calcium sulphoaluminate in the framework of hcp. Pozzolan concrete durability on sulphate attack sciencedirect. The types of disruption observed during sulphate attack on mortars or concretes, and the chemical processes involved, are summarized. Sulphate attack is the result of interaction between sulphate ions and hydrated cement products. The degree to which this attack can occur depends on water penetration as referred to above, the sulphate salt and its concentration and type eg sodium or magnesium, the means by which the salt develops in the concrete. Groundwater is a natural sulfate source to which buried concrete.
Once the sulphates and concrete are in contact, react with each other. For the past decades concrete degradation by various processes as the thaumasite form of sulphate attack tsa and alkaliaggregate reactions aar have repeatedly been discussed in the literature lopezbuendia et al. Sulfate attack is a complex form of deterioration that has damaged concrete structures throughout the world. Carbonation occurs when carbon dioxide in the environment penetrates into the concrete. Physical sulphate attack on concrete semantic scholar. Sulfate resistance of concrete is largely determined by the permeability of the concrete and by the reactivity of the hydration products present. Jan 14, 2017 the factors that mitigate or delay sulfate chemical attack in concrete can be aci 201. Sulphate attack on concrete ash development association of. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate attack.
Ettringite formation and sulfate attack on concrete synopsis. External attack thaumasite formation 1 thaumasite has the composition. Current approach and research needs dr ewan a byars centre for cement and concrete university of sheffield this paper discusses the current approach taken in bre special digest 1 to the specification. It is generally said that the deterioration depth of concrete due to acid attack including sulfuric acid attack is proportional to the square root of the exposure time, according to sakamoto 1972, pavlik 1994, and so on, as follows. The destruction of concrete under sulphate attack is particularly related to expansion, however, the dissolution of cement matrix may by considerable. Types of sulphate attack in concrete influences and sources. Sulphate attack on concrete magazine of concrete research. Sulphate attack the end result of sulphate attack can be excessive expansion, delamination, cracking, and loss of strength. The salt crystallization process was a major cause of concrete distress compared with the traditional hypothesis of chemical reaction of. Download sulfate attack on concrete book pdf epub mobi tuebl.
Sulfate attacks typically happen to ground floor slabs. Analysis of durability of asvanced cementitious materials for. The main effects of the chemical attack are volume change. The use of fly ash is well documented as a sound and economical method of achieving sulphate resistance. What is sulfate attack sulfate attack on concrete is a chemical breakdown mechanism where. Quick notes series for concrete technology from amaze concrete. Sulphates are highly soluble salts in the form of sodium sulphate, calcium sulphate, potassium sulphate, and magnesium sulphate.
An aci technical publication american concrete institute. This lack of information has led to confusion and contradictory views regarding the mechanisms of concrete deterioration due to physical sulphate attack. Research on sulfate attack mechanism of cement concrete based. Seawater oxidation of sulphate minerals in clay adjacent to the concrete this can produce sulphuric acid which reacts with the concrete bacterial action in sewers anaerobic bacterial produce sulphur dioxide which dissolves in water and then oxidizes to form sulfuric acid in masonry, sulphates present in bricks and can be gradually released over a long period of time, causing sulphate attack of mortar. The deterioration of reinforced concrete by sulfate attack causes the reinforcing steel to be exposed to the action of aggressive agents starting the. Download sulfate attack on concrete book pdf epub mobi. The effect of attack of chloride and sulphate on ground. Current knowledge of external sulfate attack white rose research. Sulfate damage to concrete floors on sulfatebearing hardcore. Degradation mechanism of concrete subjected to external sulfate. A concrete structure exposed to a rich sulfate environment or contained sulfate salts in its mix constituents water, aggregates, or cement can degrade rapidly and causes reduction of strength. It occurs when concrete comes in contact with water containing sulphates so4. The sulfates of greatest concern for the durability of concrete are salts found in natural soils and groundwaters such as sulfates of sodium, potassium, magnesium, and calcium.
Beside the strength criteria of concrete there is also the case of durability of these concrete and its proneness to chemical attack, especially sulphate attack. This publication discusses the effects of many substances on concrete and provides guidelines to protective treatments. Ettringite formation and sulfate attack on concrete by m. It can have endogenous origin developing without any contribution from the environment or exogenous origins such as sulfates contained in the soils or in liquids germain, 2008. Sulfate attack and reinforcement corrosion in concrete. No deleterious level of sulfate attack has been found where an intervening dampproof membrane separates the. Effect of magnesium sulphate on selfcompacting concrete. These are transported to the concrete in various concentrations in water, together with cations, the more common of which are calcium, magnesium and sodium. In this part have described sulphate attack in concrete and details. This reaction produces crystals, which force the concrete. At present, the mechanism of chemical sulfate attack on cement based materials is relatively well known. For deleterious sulfate attack to occur in a ground floor slab, the concrete must be of a type susceptible to sulfate attack and it must be in direct contact with hardcore that contains a substantial amount of sulfates and moisture. Corrosion of reinforcing steel is the most common cause of concrete.
The sulfate attack in concrete by degradation of iron. The compounds present in cement concrete are attacked by many salt solutions and acids. Sulfate attack is a term used to describe a series of deleterious chemical reactions between sulfate ions and the components of hardened concrete, principally the cement matrix, caused by exposure of concrete to sulfates and moisture skalny et al. Sulfates may permeate concrete and react with existing hydration. Sulphate attack chemical attack internal sulphate already in concrete at casting time p hysical attack salt crystallization salt hydration deterioration external sulphate enters concrete system from outside diffusion into and within microstructure conditions for formation of ettringite at later ages heat treatment delayed ettringite formation. Internal sulphate attack is commonly characterized as any sulphate attack caused by sulphate originating from within the concrete i. The more common form of chemical attack is the leaching out of cement and action of sulphate, seawater and natural slightly acidic water.
Sulfate attack is another possible deterioration mechanism of concrete. 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 with components of concrete. The present uk codes of practice based on bre digest 250 reflect the technical information available for various binders currently used in the uk. Sulphate attack is a major difficulty which has a local effect on the constructional materials, specially the concrete. For deleterious sulfate attack to occur in a ground floor slab, the concrete. The volume of this gypsum is greater than the sum of its components causing internal pressure and expansion, which fractures the concrete. Sulphate attack on concrete has the potential to cause serious damage or structural failures. Mario collepardi is professor of materials science and technology at the politecnico di milano, milan, italy. Sulphate attack on concrete can appear in different forms depending on chemical form of the sulphate and atmospheric environment which the concrete is exposed to. The term sulfate attack, as used here, means deterioration of concrete involving any type of sulfate interactions with cement paste independently of the curing.
First, the sulfate reacts with free calcium hydroxide which is libera ted during the hydration of the cement to form calcium sulfate gypsum. In both cases, the consequence is some volume expansion owing to the delayed formation of ettringite, which is an expansive. The most reactive phases of cement paste are alumunoferrite hydrate phases afm and calcium hydroxide. Investigating sulphate attack in floor slabs building. Sulfate attack on concrete provides a comprehensive reference to this important subject.
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