Cement is composed of mainly two minerals tricalcium silicates and dicalcium silicates. 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. The concentration of sulfate ions in concrete was not enough to form new a phase of gypsum. Presence of sulfate ions in concrete structures trigger an increase in porosity, expansion, and cracking. Investigating sulphate attack in floor slabs building. Deterioration process of concrete exposed to internal. The slow progress of the external sulfate attack and the large size and criticality of typical structures affected by this phenomenon establish numerical modeling as a key tool to assess the future evolution of concrete structures exposed to sulfate rich environments. Upon hydration, the main reaction products are a calcium silicate gels and calcium hydroxide caoh2 or ch in cement chemistry. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate. The paper compares the sulphate ion attack resistance in several mixtures of highperformance concrete. Concrete structures erected in sulfate richenvironment suffer great extent of damage as a result of sulfate attack. Cements have long been known to undergo deterioration in sulfate rich service environments. Sulfate ions dissolved in water react with the tricalcium.
This report gives guidance on sulfate attack damage to houses from the past use of sulfate bearing hardcore and infill material. Most of the soil types contains sulphates in the form of calcium, magnesium, sodium, ammonium and potassium. Due to a soluble source being incorporated into the concrete at the time of mixing, gypsum in the aggregate, for example. Sodium sulphate attacks calcium hydroxide and forms gypsum that becomes more than doubles the volume.
Use of bacillus species bacteria in protecting the. The compounds responsible for sulphate attack on concrete are watersoluble sulphate containing salts, such as alkaliearth calcium, magnesium and alkali sodium, potassium sulphates that are capable of chemically reacting. Since it is the calcium silicate hydrate in concrete that provides most of the strength. 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. It occurs when concrete comes in contact with water containing sulfates so 4. Evolution of damage due to sulphate attack in cement mortar with and without. We were asked if we could carry out another investigation into potential sulphate attack in a floor slab this week. 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. Shown are concrete beams exposed to highconcentration sulfate soilssolutions. Without the passive film, the steel would corrode at rates at least 1,000 times higher aci 222 2001.
Troxell, et al reported the effect of sulphate water on concrete. Calcium chloride or admixtures containing high quantities of calcium chloride should not be used in concrete that is to be exposed to sulfate attack. The aim of this study is to experimentally investigate the effect of replacing 5% of cement by natural volcanic pozzolan in the mixture of high performance concrete hpc on the compressive strength, permeability to the chlorine ions, sulphate resistance and ultrasonic pulse velocity of specimens exposed to solutions of 5% sodium sulphate. The primary variable in the research was the introduction of silica fume as a 12%.
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. Sulfates in solution in contact with concrete can cause chemical changes to the cement, which can cause significant microstructural effects leading to the weakening of the cement binder chemical sulfate attack. Sulfate attacks happen to ground floor slabs, this issue generally affects properties from the 1950s and 1960s but c. 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. The use of fly ash is well documented as a sound and economical method of achieving sulphate resistance. For deleterious sulfate attack to occur in a ground floor slab, the concrete. External sulphate attack field aspects and lab tests springerlink. The types of disruption observed during sulphate attack on mortars or concretes, and the chemical processes involved, are summarized.
Sulfates can be found in some soils especially when arid conditions exist, in seawater, and in wastewater treatment plants. Yet the mechanism of attack has not been universally agreed and, arguably of even greater importance, test procedures to measure sulfate attack and specifications for sulfate resistant formulations are not agreed, or are disputed. Increasing severity is represented by higher numerical value in the ec designation. Testing to evaluate the resistance of concrete to external sulphate attack. Conclusion in addition to producing airentrained concrete with a moderate water content not more than 0. Pozzolan concrete durability on sulphate attack pdf free. Sulphate attack on concrete ash development association of. Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. Sulfate attack is a common form of concrete deterioration. Internal sulfate attack occurs when a source of sulfate is incorporated in the concrete when mixing like excess gypsum in cement, sulfate in the aggregate, water or. Pdf physical sulphate attack on concrete semantic scholar. It has been shown that calcium chloride reduces sulfate resistance regardless of the type of cement used.
Chloride attack chloride attack is one of the most important aspects while dealing with durability of concrete. Effects of substances on concrete and guide to protective. Sulphate attack on concrete magazine of concrete research. Fly ash increases resistance to sulphate attack august 95 strong water reducer and aids in reducing water cementitious ratio. Sulphate attack on concrete process and control of.
Their role in concrete durability march 99 once these ions reach the steel they depassivate the area surrounding the steel and in the presence of airwater, the steel commences to corrode. Ettringite was the main reason for the expansion damage of concrete. Sulphate attack in concrete, its effects, causes and. Hello everyone, in the last lecture we were talking about different aspects of durability and the fact that the control of the water. The destruction of concrete under sulphate attack is particularly related to expansion, however, the dissolution of cement matrix may by considerable. Sulphate present in alkali soils and waters are known to cause deterioration of many concrete structures. The research shows that performance needs to be divided into several phenomena. Effect of external and internal sulphate on compressive. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate attack. The cement hydration products normally present, mainly calcium silicate hydrate and calcium hydroxide, are decomposed as a result of both sulfate attack and of carbonation. In this study, the effect of chloride ions on sulfate attack and effect of sulfate ions on chloride attack were. Moisture makes this reaction happen and can cause serious structural damage to both wall slabs and walls in buildings. Analysis of durability of asvanced cementitious materials. Internal sulphate attack is commonly characterized as any sulphate attack caused by sulphate originating from within the concrete i.
This lack of information has led to confusion and contradictory views regarding the mechanisms of concrete deterioration due to physical sulphate attack. Aci 318 defines exposure classes ec within each exposure category based on the severity of exposure. Pdf mitigating sulphate attack in high performance. Sulfate attack on concrete provides a comprehensive reference to this important subject. During the process of internal sulfate attack, the content of gypsum decreased and the content of ettringite increased. Sulfate attack on concrete modern concrete technology. If sufficient new phases are formed, stresses can be induced in the concrete to such an extent that the concrete can undergo cracking. More recent study observed the performance of concrete under sulphate attack.
The acid component attacks the main constituents of hydrated cement, altering the compounds to a form which can no longer provide strength or protection to the reinforcement. Aggressive substances can compromise the durability of concrete. Carbonation occurs when carbon dioxide in the environment penetrates into the concrete to react with calcium hydroxide to form calcium carbonate. Concrete mixtures i, j, k, and l were air entrained with average air contents of about 5%, the wb ratio was 0. Sulfate attack and reinforcement corrosion in concrete with. Overview of sulfate attack in concrete, describing conventional sulfate attack, delayed ettringite formation and thaumasite.
When a concrete structure is built on these types of soils, they may attack the concrete. Concrete mix design and binder type have an important influence on concrete performance in sulphate environments. Concrete is susceptible to attack by actual acid sulfate soils. 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 scenario was that the property, a 1960s bungalow in a nottinghamshire village, had recently been subject to a homebuyers survey report, which raised concerns with regard to potential sulphate attack in the solid concrete floors.
Cement is composed of mainly two minerals tricalcium silicates c3s and dicalcium silicates c2s. The papers presented in this volume were included in a threepart session sponsored by aci committee 201, durability of concrete, about sulfate attack on concrete at the aci convention in philadelphia, pa, on october 2324, 2016. Mpa cement fact sheet 2 thaumasite form of sulfate attack. Statistics have indicated that over 40% of failure of structures is due to corrosion of steel. The internal sulfate attack is characterized by a delayed mobilization of cement sulfates, and it leads to the generalized deterioration of the concrete.
Soils containing sodium, potassium, magnesium, and calcium sulphate are the main sources of sulphate ions in groundwater 1, 2. Numerical assessment of external sulfate attack in. Sulfate damage to concrete floors on sulfatebearing hardcore. Portland cement concrete can be attacked by solutions containing sulphate ions, such. Upon hydration, the main reaction products are a calcium silicate gels csh and calcium hydroxide caoh2 or ch in cement chemistry. Effects of substances on concrete and guide to protective treatments concrete technology by beatrix kerkhoff fig. Accelerated test for measuring sulfate resistance of. 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. Effect of combined sulfatechloride ttack on concrete.
Anderson award winner, and a member of numerous aci committees including c232 on fly ash and c201 on durability. Sulphate attack on concrete process and control of sulphate attack. Durability of metakaolin concrete to sulfate attack pdf. The products of corrosion are greater in volume up to 600% than the. The corrosion tests were not performed with the actual concretes, but with model mortars. The deterioration of reinforced concrete by sulfate attack causes the reinforcing steel to be exposed to the action of aggressive agents starting the.
Lowering watercementitious ratio significantly can lead to more sulphate resisting concrete. These concrete mixtures were used to investigate the effect of wb ratio on the durability of mk concrete to sulfate attack. Carbonation occurs when carbon dioxide in the environment penetrates into the concrete to. Because of concrete s inherent protection, reinforcing steel does not corrode in the majority of concrete elements and structures. Sulphate attack on concrete has the potential to cause serious damage or structural failures. Physical salt attack on concrete, part 2 aci spring 2012 convention march 18 21, dallas, tx r. He is also a fellow of astm, and the engineering institute of canada. Sulfate solutions can also cause damage to porous cementitious materials through crystallization and recrystallization salt attack. Suleiman ii coauthorship statement iii acknowledgments v table of contents vi list of tables ix list of figures xii chapter one 1. Interaction of chloride sulfate ions on concrete deterioration is ery complicated. To ensure the most durable concrete possible, fly ash is an essential ingredient when the project will be. Sulfate resistance of concrete is largely determined by the permeability of the concrete and by the reactivity of the hydration products present.
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