Nsulfate attack in concrete pdf

Pdf recovery from sulfate attack in concrete via electrokinetic. Sulfate attacks are a primary chemical attack of concrete, and thus analyzing their impact can help to elucidate the durability of concrete structures. Download it once and read it on your kindle device, pc, phones or tablets. The mechanism of sulfate attack on portland cement concrete is not well understood. He confirmed the influence of the type of cement on the resistance to. 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. Aas concrete was also reported to have a superior durability in aggressive environments as compared to opc. Sulfate, sulfateresistance, sulfate attack, delayed ettringite formation, def, concrete distress. Thaumasite sulfate attack in cement mortars exposed to. Most concrete specifications restrict the use of calcium chloride or admixtures containing calcium chloride to plain unreinforced concrete and ban it for structural concrete that contains embedded metal. Moisture makes this reaction happen and can cause serious structural damage to both wall slabs and walls in buildings. This has limited confidence that can be placed in and hence the reliability of existing standard tests and models to predict performance and service life of concrete subjected to sulfate attack.

Relationship between coefficient of permeability and watercement ratio ref 4. Chlorination is a major process governing the initiation and advancement of the injurious corrosion of steel bars. Test methods for resistance of concrete to sulfate attack. 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. Sodium sulphate attacks calcium hydroxide and forms gypsum that becomes more than doubles the volume. Their role in concrete durability march 99 attackpenetration has been the subject of much research in recent years. Relationship between concrete strength and wc ratio at various ages ref 3. Upon hydration, the main reaction products are a calcium silicate gels and calcium hydroxide caoh2 or ch in cement chemistry. In 1962, i had the privilege of knowing him, and i profited from his wealth of knowledge of cement. Research sulfate resistance of cementcontaining composition. This book provides a comprehensive reference to this important subject, covering. Concrete can deteriorate for a variety of reasons, and concrete damage is often the result of a combination of factors.

Experiment analysis of concretes mechanical property. 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. Chloride attack chloride attack is one of the most important aspects while dealing with durability of concrete. Page 1 of 6 1 continuous long term exposure 2 short termintermittent exposure 200 and. Sulfate attack on concrete modern concrete technology book 1 kindle edition by odler, ivan. Concrete mix design and binder type have an important influence on concrete performance in sulphate environments. Use features like bookmarks, note taking and highlighting while reading sulfate attack on concrete modern. The effect of recycled concrete aggregate rca on concrete performance against external sulfate attack esa is not yet fully known. Cement is composed of mainly two minerals tricalcium silicates c3s and dicalcium silicates c2s. Materials science of concrete, sulfate attack mechanism, pp. In fact the literature contains contradictory results with some studies indicating that chloride reduces tsa, while others show the. 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. In this paper, recycled aggregate concretes rac with 0, 50.

Ettringite formation and sulfate attack on concrete by m. Use of alkaliactivated slag aas in concrete manufacturing has environmental benefits as its production requires less energy than ordinary portland cement opc and it utilises industrial byproducts. Sulfate attack is one of several mechanisms of concrete deterioration. Effects of substances on concrete and guide to protective. 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. Effect of accelerating admixture on properties of concrete. A similar phenomenon can be found in portland cement pc concrete elements partially exposed to sulfate environments. Corrosion of reinforced concrete rc structures is one of the significant causes of deterioration of reinforced concrete rc structures. The durability analysis of concrete structures in contact to external sulfate solutions requires the definition of a proper diffusionreaction model, for the computation. Sulfate attack on concrete provides a comprehensive reference to this important subject.

This has limited the confidence that can be placed in the reliability of existing standard tests and models to predict performance and service life of concrete subjected to sulfate attack. These are transported to the concrete in various concentrations in water, together with cations, the more common of which are calcium, magnesium and sodium. Sulfate attack is a complex form of deterioration that has damaged concrete structures throughout the world. He is also a fellow of astm, and the engineering institute of canada. Snydera amaterials and structural systems division engineering laboratory bmaterials measurement science division. In this research, sodium nitrite is used as accelerating admixture in the dosage range of 1% to 3% by weight of cement. 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. The following summary discusses potential causes of concrete deterioration and the factors that influence them. In hardened cement, c3a reacts with sulfate ions in the presence of calcium hydroxide to form gypsum, leading to degradation of concrete into a noncohesive granular mass and disruptive expansion 25. Mineral admixtures were used as a partial replacement for ordinary portland cement c,a 8. Physical sulfate attack on concrete lininga field case analysis. The internal sulfate attack is characterized by a delayed mobilization of cement sulfates, and it leads to the generalized deterioration of the concrete. Without requiring much effort from your part, the gout diet guides you stepbystep on how to remove gout quickly and efficiently.

Sulphate attack on concrete process and control of. Sulphate attack is a chemical break down mechanism where suphate ion attacks on components of cement paste. Fly ash increases resistance to sulphate attack august 95 strong water reducer and aids in reducing water cementitious ratio. Pdf physical sulfate attack on concrete lininga field case analysis. Now, several researches on the chlorination of concrete structures have been ongoing around the world. 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. High sulfate attack resistance of reinforced concrete flumes. Sulphate attack in concrete, its effects, causes and. The types of disruption observed during sulphate attack on mortars or concretes, and the chemical processes involved, are summarized. In this article we demonstrated the study results of sulfate attack in cementclay solutions with an additive ashes and sodium sulfate. Physical salt attack on concrete, part 2 aci spring 2012 convention march 18 21, dallas, tx r. An enormous contribution in the field of sulfate attack on concrete was made by thorvaldson in the 1950s. Statistics have indicated that over 40% of failure of structures is due to corrosion of steel. The sulfate attack in concrete by degradation of iron.

Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste. However, variability in chemical composition of slag may have an. The term sulfate attack, as used here, means deterioration of concrete involving any type of sulfate interactions with cement paste independently of the curing. Corrosion of reinforcing steel is the most common cause of concrete. This publication discusses the effects of many substances on concrete and provides guidelines to protective treatments. Sulfate attacks happen to ground floor slabs, this issue generally affects properties from the 1950s and 1960s but c. The effect of cement type on behavior of reinforced. Influence of internal curing and viscosity modifiers on resistance to sulfate attack dale p. Evaluating effect of chloride attack and concrete cover on. Pdf in the tunnels of the chengkun railway in china, concrete failure can usually be observed from the effect of sulfates.

Anderson award winner, and a member of numerous aci committees including c232 on fly ash and c201 on durability. Sulphate attack on concrete magazine of concrete research. Sulfate attack on concrete modern concrete technology. Laboratory and field evaluations of external sulfate attack. Damage modelling in concrete subject to sulfate attack core. Lowering watercementitious ratio significantly can lead to more sulphate resisting concrete. Cement is composed of mainly two minerals tricalcium silicates and dicalcium silicates. To ensure the most durable concrete possible, fly ash is an essential ingredient when the project will be. The first line of defense against chemical attack is to use quality concrete with maximum chemical resistance. Upon hydration, the main reaction products are a calcium silicate gels csh and calcium hydroxide caoh2 or ch in cement chemistry. 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.