The durability analysis of concrete structures in contact to external sulfate solutions requires the definition of a proper diffusionreaction model, for the computation. It occurs when concrete comes in contact with water containing sulfates so 4. Physical salt attack on concrete, part 2 aci spring 2012 convention march 18 21, dallas, tx r. Sulfates can be found in some soils especially when arid conditions exist, in seawater, and in wastewater treatment plants.
Sulphate attack in concrete, its effects, causes and. Sulfate damage to concrete floors on sulfatebearing hardcore. Relationship between coefficient of permeability and watercement ratio ref 4. How to build and setup a concrete foundation for garages, houses, room additions, etc part 1 duration. The primary variable in the research was the introduction of silica fume as a 12%. Troxell, et al reported the effect of sulphate water on concrete. For deleterious sulfate attack to occur in a ground floor slab, the concrete must be of.
Effects of substances on concrete and guide to protective. Accelerated test for measuring sulfate resistance of. Durability of concrete exposed to leaching and external. 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. Pozzolan concrete durability on sulphate attack ahcene. He is also a fellow of astm, and the engineering institute of canada. Soil and concrete samples may be taken to measure the sulphate content and help identify root cause of the sulphate attack. Concrete mixtures i, j, k, and l were air entrained with average air contents of about 5%, the wb ratio was 0. Sulphate attack on concrete process and control of. Sulphate attack prevention sulphate attack is the decline of concrete over a period of time, as a result of a chemical reaction between sulphate ions and the components of hardened concrete. Internal sulphate attack is commonly characterized as any sulphate attack caused by sulphate originating from within the concrete i. 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. Cement and concrete research institute cbi, drottning kristinas vag 26, stockholm. The potential for this form of attack should also be taken into account when designing castin place structures that carry flowing water, eg culverts.
Aci 318 identifies four exposure classes for sulfate as s0, s1, s2 and s3 table 4. The volume of the resulting gypsum is greater than the sum of its. This lack of information has led to confusion and contradictory views regarding the mechanisms of concrete deterioration due to physical sulphate attack. Sulphate attack might show itself in different forms depending upon the chemical form of the sulfate and the atmospheric environment which the concrete is exposed to. Sulfate in the soil and concrete foundations concrete.
Evolution of damage due to sulphate attack in cement mortar with and without. Sulphate attack on concrete magazine of concrete research. Sulphate attack on concrete is a chemical process where sulphate ions attack components of cement paste. In the french standard on concrete nf en 2061 17, the maximum proportion of. This process adversely affects concrete exposed to these damaging stimuli. It is clear that the nonbinder thaumasite can be formed. As these reactions may lead to cracking, spalling or strength loss of concrete structures, appropriate test methods are needed to determine the resistance of concrete under sulfate exposure. Their role in concrete durability march 99 attackpenetration has been the subject of much research in recent years.
Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. Corrosion of reinforcing steel is the most common cause of concrete. The sulphates react with the concrete causing it to expand. Test methods for resistance of concrete to sulfate attack. Solution of the sulfates of various bases including sodium, potassium, magnesium and calcium react with hydrated cement paste forming gypsum or a compound called ettringite sulphoaluminate which leads to the expansion and disruption of the concrete and mortar this process is referred as sulphate attack. Sulphate attack on concrete has the potential to cause serious damage or structural failures. The destruction of concrete under sulphate attack is particularly related to expansion, however, the dissolution of cement matrix may by considerable.
Sulphate attack sulphate attack is a twophased process. Aggressive substances can compromise the durability of concrete. Sulfate attack is the reaction between sulfate ions in the pore solution of concrete and constituents in the concrete that result in formation of new reaction products with a relatively large molar volume. We define sulfate attack as destructive chemical action and damage. Types of sulphate attack in concrete influences and sources.
The following summary discusses potential causes of concrete deterioration and the factors that influence them. In both cases, the consequence is some volume expansion owing to the delayed formation of ettringite, which is. The problem occurs when the fill material hardcore beneath the slab contains sulphates and these migrate into the concrete. Thaumasite form of sulfate attack tsa the thaumasite form of sulfate attack often abbreviated to tsa requires a source of sulfate and also of carbonate.
Laboratory and field evaluations of external sulfate attack. Sulfate attack comprises a series of chemical reactions between sulfate ions and the components of hardened concrete. Sulphate attack is the result of interaction between sulphate ions and hydrated cement products. Concrete sulphate attack in a sulfatefree environment. 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.
In order to determine the severity of the attack, sulphate to cement ratio within the. Relationship between concrete strength and wc ratio at various ages ref 3. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate attack. Concrete can deteriorate for a variety of reasons, and concrete damage is often the result of a combination of factors. Sulphate attack on ground floor slabs is a very serious problem which can cause structural damage to the main walls of a building. The sulphate attack can have an internal origin which means the attack occurs without any contribution from the surrounding environment and external. External sulfate attack of concrete is a major problem that can appear in regions where concrete is exposed to soil or water containing sulfates, leading to softening and cracking of the concrete. Nevertheless, the formation of ettringite by sulphate attack on concrete can lead to severe damage.
The sulphate attack can have an internal origin which means the attack occurs without any. Sulfate attack is another possible deterioration mechanism of concrete. Concrete sulphate attack in a sulfatefree environment authors. Effects of substances on concrete and guide to protective treatments concrete technology by beatrix kerkhoff fig. Tsa can attack concretes containing a wide range of different cements including those that are resistant to the conventional form of sulfate attack. Mpa cement fact sheet 2 thaumasite form of sulfate attack. External sulphate attack field aspects and lab tests springerlink. 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. Shown are concrete beams exposed to highconcentration sulfate soilssolutions.
Sulfate attack on concrete provides a comprehensive reference to this important subject. Effect of external and internal sulphate on compressive. If sufficient new phases are formed, stresses can be induced in the concrete to such an extent that the concrete can undergo cracking. Sulphate attack on concrete process and control of sulphate attack. The use of fly ash is well documented as a sound and economical method of achieving sulphate resistance. Concrete can be damaged by fire, aggregate expansion, sea water effects, bacterial corrosion, calcium leaching, physical damage and chemical damage from carbonatation, chlorides, sulfates and nondistilled water.
Concrete mix design and binder type have an important influence on concrete performance in sulphate environments. The research addresses the mitigation of sulphate attack on concrete as it is considered one of the major degradationcausing phenomenons in the durability of concrete. Pozzolan concrete durability on sulphate attack pdf free. Anderson award winner, and a member of numerous aci committees including c232 on fly ash and c201 on durability. So, the situation is that, in homes 10 ro 20 years old, no structural damage has occurred and no concrete needs to be replaced. Due to a soluble source being incorporated into the concrete at the time of mixing, gypsum in the aggregate, for example.
Thaumasite is a calcium silicate carbonate sulphate hydrate casio 3 caco 3 caso 4 15h 2 o, which can coexists with ettringite, gypsum, or can occur on its own. 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. Durability of metakaolin concrete to sulfate attack pdf. The characteristics of the concrete slab maybe noted. Sulphates combine with soluble calcium hydroxide, generated from the hydration of portland cement, to form calcium sulphate or gypsum. Sulfate damage pdf, 756kb, 40 pages this file may not be suitable for users of assistive technology. Damage modelling in concrete subject to sulfate attack core. Sulfate attack is a common form of concrete deterioration. Sulphate present in alkali soils and waters are known to cause deterioration of many concrete structures.
Investigating sulphate attack in floor slabs building. Effect of chloride and sulfate contamination in soils on. In following the procedure described in astm e 632, the performance of concrete under sulfate attack needs to be divided into several phenomena and therefore several tests had to be developed. 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. Thaumasite can occur rarely as a natural mineral as an alteration product of limestones. Sodium sulphate attacks calcium hydroxide and forms gypsum that becomes more than doubles the volume. Sulphate attack is caused when sulphates contained within the concrete aggregate contain sulphates or the hardcore subbase below the concrete contains sulphates. These concrete mixtures were used to investigate the effect of wb ratio on the durability of mk concrete to sulfate attack. Testing to evaluate the resistance of concrete to external sulphate attack. Pdf mitigating sulphate attack in high performance. The types of disruption observed during sulphate attack on mortars or concretes, and the chemical processes involved, are summarized.
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