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PUMICE STONE

PUMICE STONE. AHMAD BADNJKI 995****7500. What is Pumice? *Pumice is a unique rock, noted for its light weight and low density (dry pumice can float in water). It is a type of igneous rock full of bubble holes that forms during explosive volcanic eruptions.

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PUMICE STONE

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  1. PUMICE STONE AHMAD BADNJKI 995****7500

  2. What is Pumice? *Pumice is a unique rock, noted for its light weight and low density (dry pumice can float in water). It is a type of igneous rock full of bubble holes that forms during explosive volcanic eruptions. *Pumice has a very low specific gravity giving the rock an ability to float on wate * Pumice is typically light colored.

  3. How Does Pumice Form? *Pumice is naturally formed, made by environmental circumstances. *Pumice is formed by lava coming into contact with water. This occurs most often with volcanoes near or under water. The pore spaces (known as vesicles) in pumice are a clue to how it forms. *The vesicles are actually gas bubbles that were trapped in the rock during the rapid cooling of a gas-rich frothy magma. The material cools so quickly that atoms in the melt are not able to arrange themselves into a crystalline structure. Thus, pumice is an amorphous volcanic glass known as a "mineraloid.“

  4. How Does Pumice Form? *Pumice is a foamed-glass stone that is hard yet friable, non-crystalline in structure, and naturally calcined—a combination of characteristics that make pumice powders and aggregates incredibly useful to a variety of industries. *Large eruptions can blanket the landscape around the volcano with over 100 meters of pumice and launch dust and ash high into the atmosphere “Pumice Raft”.

  5. Chemical Properties *Pumice is not created equally—it varies greatly in its chemical properties (and effectivenes) from deposit to deposit, but essentially, pumice is primarily Silicon Dioxide (Amorphous Aluminum Silicate), some Aluminum Oxide, and trace amounts of other oxides. *http://www.hesspumice.com/pumice-pages/why-pumice/superior-quality-pumice.html.

  6. Uses of Pumice *The largest use of pumice in the United States is the production of lightweight concrete blocks and other lightweight concrete products. When this concrete is mixed, the vesicles remain partially filled with air. That reduces the weight of the block. Lighter blocks can reduce the structural steel requirements of a building or reduce the foundation requirements. The trapped air also gives the blocks a greater insulating value. *https://geology.com/rocks/pumice.shtml

  7. Uses of Pumice *The second most common use of pumice is in landscaping and horticulture. The pumice is used as a decorative ground cover in landscaping and planters. It is used as drainage rock and soil conditioner in plantings. Pumice and scoria are also popular rocks for use as substrates in hydroponic gardening. *https://geology.com/rocks/pumice.shtml

  8. Pumice as aggregate MOUSTEFA HOSSAINI

  9. Pumice is a light weight aggregate Pumice is a very light and porous volcanic rock used as light weight aggregate which formed by the sudden cooling of molten volcanic matter and can find in many parts of the world. Nearly three-quarters of all pumice that is produced annually is used in lightweight construction materials like concrete. The remaining pumice produced is used in horticulture, landscaping and the manufacture of abrasives.

  10. Chemical properties of pumice aggregate The high percentage of silicon-oxide gives the pumice its abrasive quality, thus it exhibits a chemical composition which can easily corrode steel. The Al2O3 in the structure makes the pumice highly resistant to heat. Some of the minerals like, Na2O and K2O which give the pumice the reaction sought after by the textiles industry. Constituent of pumice

  11. How do we produce pumice aggregate NO CRUSHING NO BLASTING ONLY GRADING WASHING WHEN NEEDED Thus; No high energy requirement

  12. Properties of a concrete with pumice aggregate 1. Light weight concrete One of the most significant of the advantages of pumice aggregate concrete is its lightweight quality. Up to one-third (25-35%) lighter than conventional sand-and-gravel concrete. 2. Low thermal conductivity concrete Thermal conductivity is the measurement of the heat transfer ability of the material itself. The thermal conductivity of solid matter is higher than that of air. Therefore, the higher the porosity is, the lower the thermal conductivity will be. This provides lese loose heat.

  13. Properties of a concrete with Pumice aggregate - It has low density. - Reduce the dead load of a structure. - Freeze/thaw resistance is high due to the low capillary action. - It is a good sound proofing due to its excellent sound proofing properties. - Better fire resistance with high melting point. - low specific gravity.

  14. Normal concrete and Pumice aggregate concrete

  15. Water Absorption All aggregates, whether natural and artificial absorb water but water absorption of volcanic pumice aggregate is far much higher than normal aggregate. One of the major problems in pumice concrete is the high water absorption characteristic of aggregates due to their porous structure. Pumice aggregate can easily absorb the mix water or float during the mixing and in both cases the workability of the mixture can deteriorate but this problem usually overcome by Prewetting the aggregates. Prewetting minimize the mixing water being absorbed by the aggregate.

  16. Pumice Aggregate need a Pozzolan It’s also important to know that pumice or light weight aggregates are reactive (high silica content) and need a pozzolan to mitigate alkali-silica reaction. If lightweight aggregates are used with Portland cement without the mitigating effects of a reactive pozzolan, the concrete inevitably develops a nasty ASR problem. A reaction between the silica content in the aggregate and the alkali in the hydrated cement paste.

  17. Reference - Basic Properties of Pumice Aggregate; ISSN 0974-5904, Volume 08, No. 04 R S MURALITHARAN AND V RAMASAMY - Effect of prewetting methods on some fresh and hardened properties of concrete with pumice aggregate,NihatKabay,FevziyeAkoz,Yıldız Technical University - Properties of Pumice Lightweight Aggregate, *Mang,uriu Geoffrey N. MutkuRaphael.N. OyawaWalter.O. AbuodhaSilvester.O. Department of Civil Engineering University of Nairobi.

  18. Alkali-AggregateReaction(precautionstorestrict) Beyhan GÜVERCİN 27245297996

  19. DEFINITION • ASR is the closed reaction between the hydroxyl (OH-) ions in the concrete pore water and the materials containing some reactive silica in the concrete aggregate (Eşitlik1).

  20. As a result of the reaction, due to the pressure caused by expansion due to the formation of a water that can hold an unlimited amount of water, cracks occur in the concrete. • Because ASR is a slow-moving reaction like other reactions, the damage to the internal structure of the concrete due to expansion becomes visible after a few years.

  21. Alkali-Silica Reaction (ASR) is the reaction of alkalis in Portland cement which is one of the main constituents of concrete with reactive silicate minerals which can be found in aggregate. As a result of this reaction, cracks occur in the concrete and the tensile strength of the concrete is reduced. This reaction, particularly in concrete structures such as bridges, tunnels and viaducts, concrete sleepers, concrete sleepers used in railways, road pavement, parking lots, paving stones used in pavements, and concrete elements exposed to environmental conditions such as borders, is a cause. Among the factors affecting the formation of this reaction are the mineralogical composition of the aggregate used, as well as the amount of alkali oxides in the cement used. However, other factors such as the relative humidity of the medium (RH), the pH of the concrete pore water, the porosity of the concrete and the properties of the additives included in the mixture also play an important role in the development of the reaction.

  22. FACTORS AFFECTING THE ALKALI-SILICA REACTION • Alkaline content in cement • Amount of reactive silica in the aggregate • Environmentalconditions (HumidityandTemperature)

  23. A.Alkaline Content InCement • In each cement havea raw material-induced alkali. • The equivalent (total) alkaline content in the cement is calculated by the formula ASTM C 150 (Na2O + 0,658 K2O). • Alkaline-containing cements of more than 0.6% form alkali-silica gel when used together with reactive silicate aggregates. • Other than cement; mineral additives, chemical additives and de-icers can also carry alkali to the concrete system!

  24. B. Amount Of ReactiveSilicaIn The Aggregate • The type and amount of the constituent components determine the reactivity of the aggregate. • Reactive silica dispersed within the aggregate grain causes harmful expansion in both cement paste and aggregate and disrupts the integrity of the concrete.

  25. C. Environmentalconditions (HumidityandTemperature) • In addition to the chemical structure of the materials used for the realization of the Alkali-Silica Reaction, the ambient conditions must also meet certain conditions. • The humidity in the environment helps both the formation of the reaction and the volumetric expansion. • Temperature is effective on reaction speed, ASR occurs at higher temperatures.

  26. The fact that the ASR causes damage to the concrete is only possible with the presence of water. Otherwise, the reaction product gel does not cause the formation of internal tensile stresses in the concrete. The minimum humidity required to start the reaction is 85% at 20oC.

  27. PrecautionsToRestrict • In order for the alkaline-silica reaction to show its harmful effects on concrete, it is necessary to have three levels in theenviroment; • Adequatehumidity • High content of alkali hydroxide • A critical amount of reactive silica in the aggregate

  28. In order to avoid the alkaline-silica reaction, the amount of alkali contained in the concrete must be very low or the aggregates should not contain any reactive silica to initiate such a reaction. According to ASTM standards, the amount of Na2O + 0.66 K2O ”in the cement to be used in the construction of concrete should not be more than 0.6%.

  29. One of the most effective methods to prevent the formation of alkali-silica reaction is to use pozzolanic materials in addition to concrete components. Pozzolanic materials contain highly active silica. The active silica reacts with the free lime in the mortar and provides the formation of new tobermorite gels. Thanks to the newly formed tobermorite gels, the concrete element has a more dense structure, thus making it difficult for the moisture input to enter the structural element. In addition, the alkali content of the binders should be low and the alkali must be avoided from the external sources. In other words, the pH of the water should not be too high. For this purpose, pozzolonic additives such as fly ash, silica fume and blast furnace slag should be used.

  30. In recent years, lithium-based lithium carbonate, lithium nitrate and lithium fluoride have been used in the reduction of ASR reactions in additives such as. • A low w/c ratio in concrete production and the impermeability of concrete may have a reducing effect on ASR. As less water enters the impermeable concrete, the amount of water that alkali-silica gels can absorb is reduced.

  31. REFERENCES • http://yunus.hacettepe.edu.tr/~adil/asrturk.html • http://eds.b.ebscohost.com/eds/pdfviewer/pdfviewer?vid=0&sid=0eb795d6-3deb-4a83-997c-505efadf93d4%40sessionmgr101 • https://www.cimsa.com.tr/ca/docs/4FE58AA58E3A4B7B85FA9E4EE011A8/1C95011D95AA45EE8FF1B55A4D3290A6.pdf • http://www.betonvecimento.com/beton-2/alkali-silika-reaksiyonu

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