the entrained air in concrete mcq

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none of these, 64. 50 trim to 60 mm, 56. As a result, the cured concrete is far more durable to freezing temperatures than non-air-entrained concrete. લાઈટ વેઇટ કોન્ક્રીટ કેવી લાક્ષ્નીકતા ધરાવે છે ? Civil Engineering. Workability of concrete increases. provides less ultimate strength to cement, a. reacts fast with waterb. burning at high-temperaturec. 7. Answer=> c. 54. 1 : 2 : 4 mixd. Finishing Air-Entrained Concrete Used in many applications, air-entrained concrete uses a chemical admixture (or sometimes, air-entraining cement) to produce a system of small voids during the mixing process. Air entrainment is the intentional creation of tiny air bubbles in concrete.A concrete maker introduces the bubbles by adding to the mix an air entraining agent, a surfactant (surface-active substance, a type of chemical that includes detergents). One of the more obscure types of concrete is called air-entrained concrete. In slump test, each layer of concrete is compacted by a steel rod 60 cm long and of 16 mm diameter for, a. By and large, the compressive strength of concrete is reduced by use of air entrained admixture, as shown in Fig. Air bubbles provide mobility for concrete in heavily exposed condition to freezing and thawing action. As to appearance, air entrained concrete has an unusually creamy, fatty look. 4. pressure compaction of the bags on lower layersd. Practice Test: Question Set - 02 1. 3. semi-plasticd. Thin particlesb. Air-entrained concrete is produced using air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision, as the concrete is … It is claimed that, the place-ability of an air entrained concrete having 7.5 cm slump is better than a non-air entrained concrete with a slump of 12.5 cm. It is highly used as an insulator to the exterior wall of all types of buildings. This may mean testing at the point of discharge rathr than at the batching plant. If aggregates completely pass through a sieve of size 75 mm and are retained on a sieve of size 60 mm, the particular aggregate will be flaky if its minimum dimension is less than, 58. 14. Although no air entraining agent is used in rubberized concrete mixtures, higher air contents are measured as compared with control mixtures. Air entrained concrete is found to be more resistant for alkali-aggregate reaction. Unit-8 Modern Trends and Research Development in Concrete Technology. weight of concrete to that of waterd. Accordingly, vibration need not be prolonged. Lime : Silica : Alumina : Iron oxide : 63 : 22 : 6 : 3, b. Silica : Lime : Alumina : Iron oxide : 63 : 22 : 6 : 3, c. Alumina : Silica : Lime : Iron oxide : 63 : 22 : 6 : 3, d. Iron oxide : Alumina : Silica : Lime : 63 : 22 : 6 : 3, 32. A concrete using an air entrained cement. 20 cm, 10 cm, 30 cmd. between 350 to 600 kg/cm2C. A: It’s pretty well known in the concrete industry that hard-troweled surfaces and air-entrained concrete don’t mix. medium sandD. A concrete having a slump of 65 cm, is said to be, a. dryb. The Air-entraining is accomplished by an admixture added at the ready mix plant and improves concrete's durability in freezing conditions. Addition of pozzolana to ordinary port land cement, causes, c. Decreases in chemical action with sulfate, 17. is free from segregation and bleeding, 54. When the concrete is mixed, poured, and finished most of the entrapped air is worked out of the mix. c. Separation of water or water-cement mixture from the freshly mixed concrete. Proper vibration techniques can be helpful in removing entrapped air. Vi b r ation time with air entrained mixes should be s h o r tened and kept reasonably con- … Allowance should be made for this so that the correct level of air is obtained in the hardened concrete. Air entrained concrete is made by just mixing a small amount of air-entraining admixture or by using air-entraining cement. (d)Sawdust concrete. alkalis. The main object of compaction of concrete, is: c. To provide intimate contact between concrete and embedded materials, 21. Advantages. Define air-entrained concrete. The cement concrete, from which entrained air and excess water are removed after placing it in position, is called_____ સિમેન્ટ કોંક્રિટ, જ્યાંથી અંદરની હવા અને વધારે પાણી ને દૂર કરવામાં આવે છે, તેને _____ કહેવામાં આવે છે? Tricalcium silicate (C3S) generates more heat of hydrationc. 1 : 1 : 2, 69. 7. Correct Answer. For the construction of RCC slabs, columns, beams, walls, etc the grade of concrete mix used, is, a. નો ફાઈન કોન્ક્રીટ ની ઘનતા વજન માં હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે ? The minimum percentage of chemical ingredient of cement is that of, a. magnesium oxideb. Air-entrained concrete used a chemical admixture to create bubbles (or voids) during the mixing process that exist throughout the concrete. Any thoughts? decreases the strength of concretec. Admixtures make concrete water proofc. Q: How does hard-troweled air-entrainment impact strong concrete? Reduced bleeding and segregation and reduction of water cement ratio reduces the overall permeability of the concrete. Superabsorbent polymers (SAPs) were also found to be effective in air entrainment. Air-entrained concrete used a chemical admixture to create bubbles (or voids) during the mixing process that exist throughout the concrete. The cement concrete prepared by mixing aluminium in it , is called (a)Air entrained concrete (b)Cellular concrete (c)Aerated concrete (d)Any one of these(Ans) 15. increased lime cementd. [Neither (A) Nor (B)] [BOth (A) and (B).] Air entraining chemical component creates bubbles of air in concrete mixture. 7.2.6 AIR ENTRAINMENT. The entrapped air that remains in the mix creates an air void. Another related use is for deicer-scaling resistance. Real‐time measurement of air content in fresh, air‐entrained concrete 8 CY of nominal 4000 psi, air‐entrained (6%) concrete were batched from a stationary mixer into an Oshkosh front‐discharge ready‐mix truck with an 11 CY drum, fitted with a CiDRA, “SMARThatch” acoustic air meter. The size, spacing and quantity of these air bubbles has an effect on a number of the properties of both the fresh and hardened concrete. 65. The diameter of the Vicat plunger is 10 mm and its length varies from, a. a. 14.The cement concrete prepared by mixing aluminium in it , is called (a)Air entrained concrete (b)Cellular concrete (c)Aerated concrete (d)Any one of these(Ans) Periodically check batch sequencing to verify the proper order of material ingredients. vacuum concrete [B]. 3. Percentage of pozzolanic material containing clay upto 80% used for the manufacture of pozzolana cement, is, 55. The commonly used material in the manufacture of cement is, 28. Breaking up of cohesion in a mass of concrete. Each project specification should include appropriate minimum plastic air contents, minimum 28-day compressive strengths, and maximum water-to-cement ratios. calcium chorides, a. volume of water to that of cementb. pressure exertion of the bags of upper layersc. b. Fly Ash • As the surface area (fineness) of the fly ash increases, the amount of entrained air is decreased. Better place-ability of air entrained concrete results in more homogeneous concrete with least segregation, bleeding and honeycombing. Proper amount of entrained air in concrete results in_____? Unit-7 Prevention and Repair Technique of Cracks, 15. The water content for an air-entrained mix will be 3 to 5 gallons per cubic yard less than for a non-air-entrained mix having the same slump. Reduced Permeability. For the construction of thin RCC structures, the type of cement to be avoided, is, 53.A concrete using an air entrained cement, a. has strength less than 10% to 15%b. The place-ability of an air entrained concrete having 7.5 cm slump was found better than a non-air entrained concrete having a slump of 12.5 cms. 75 minutes, 74. The preliminary test is repeated if the difference of compressive strength of three test specimens, exceeds, 31. 1 : 2 : 4B. thick and heavily reinforced. Types Of Grouting In Construction | Advantages & Application Of Grouting, Top Civil Engineering Project Topics For Final Year Students, How To Calculate Unit Weight Of Steel Bars. Concrete entrained air testing is a must for such concrete. Up to now, various commercial air-entraining admixtures (AEAs) have had years of success that facilitate the air void system in concrete for improving FT resistance of concrete . ISI has specified the full strength of concrete after, a. increases the strength of concreteb. સિમેન્ટ કોંક્રિટ, જ્યાંથી અંદરની હવા અને વધારે પાણી ને દૂર કરવામાં આવે છે, તેને ________ કહેવામાં આવે છે? weight of water to that of cementc. To determine the modulus of rupture, the size of test specimen used is, 41. He is now asking that the entire slab be removed and replaced a day later? These air-entrained agents in concrete generate millions of non-coalescing air bubbles, These air bubbles act as flexible ball bearings and will modify the properties of plastic concrete regarding workability , segregation, bleeding, and finishing quality of concrete. Air entrained concrete is one of the most important development in concrete technology. MCQ's Search Engine. Medical Science Engg. 10 cm, 20 cm, 30 cmb. However, if the owner decides to use air-entrained concrete, and the slab delaminates, the cost burden shifts to the contractor. There will always be air in concrete. 30 minutesB. Internal friction between the ingredients of concrete, is decreased by using, a. increases workabilityb. 14.The cement concrete prepared by mixing aluminium in it , is called (a)Air entrained concrete (b)Cellular concrete (c)Aerated concrete (d)Any one of these(Ans) sodium chloridesc. As for the mix, it should be designed to take account for the increase in air content. 30 mm to 40 mmc. 1 : 1.5 : 3 mix, 1. What is Entrapped Air in Concrete? Air entrainment also reduces the shelf-life of concrete. According to IS: 4561978, the flexural strength of concrete is ... I.C Engines Multiple Choice Questions with Answers - Set 02. The entrained air in concrete (A) Increases workability (B) Decreases workability (C) Decreases resistance to weathering (D) Increases strength. Transporting of concrete by pumps, is done for a distance of, 33. For given water content, workability decreases if the concrete aggregates contain an excess of, a. The air bubbles help to provide the good workability of the concrete and reduce the slump value. The bulk density of aggregates, depends upon. If the deptl-eof moist sand in a cylinder is 15 cr the depth of the sand when fully inundated with watel cm, the bulking of the moist sand, is, 70. 1: 1: 3d. fine sandC. Air-entrained cement is a special cement which has air bubbles introduced in the cement or concrete that provides the space for expansion of minute droplets of waters in the concrete due to freezing and thawing and protects from cracks and damage of concrete. It was first used in early 1930 especially in USA. plastic, 42. Adding entrained air to concrete provides important benefits in both plastic… Answer=> c. 54. both A and B of the above, 61. The top diameter, bottom diameter and the height of a slump mould are : a. Since air entrained concrete is more cohesive and workable than non-air entrained, there is not as much danger of segregation and air pockets. Air-entrained concrete is produced through the use of air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision as the concrete is. a) By cellular construction. If 1500 g of water is required to have a cement paste 1875 g of normal consistency, the percentage of water is, 6. If fineness modulus of sand is 25, it is graded as, A. very fine sandB. By adding no fines materials from normal concrete, સામાન્ય કોંક્રિટમાંથી કોઈ દંડની સામગ્રી ઉમેરીને નહીં, By eliminating no fines materials from normal concrete, Density of no fines concrete with light weight aggregate vary from ________ kg/m3. 2. thin and heavily reinforcedd. Flaky particles, 8. 13.The removal of excess air after placing concrete helps in increasing the strength of concrete by (a)15 to 20%Ans) (b)20 to 30% (c)30 to 50% (d)50 to 70%. Air entrained concrete results from using either an air-entraining cement or an air-entraining admixture during mixing. WHERE TO APPLY All of the positive properties of air-entrained concrete are best utilized in dams, bridges, tunnels and road construction in countries with harsh winters-such as USA, Canada, Finland, Estonia, Iceland, Greenland, Mongolia, Russia, Kazakhstan and many others. Ease with which it can be mixed, transported and placed in position in a homogeneous state. has no effect on the strength of concreted. An aggregate is known as cyclopean aggregate if its size is more than, 57. Admixtures give high strength. Electrical Engineering. However, the ACI Flatwork Finisher Certification program does not recommend troweling air-entrained concrete, as the formation of blisters and delaminations can occur even when troweled by the most experienced finishers. Use of air entraining agent reduces the effect of freezing and thawing. 1 : 2 : 4c. 7 people answered this MCQ question BOth (A) and (B). Air-entrained cement is a special cement which has air bubbles introduced in the cement or concrete that provides the space for expansion of minute droplets of waters in the concrete due to freezing and thawing and protects from cracks and damage of concrete. This rule of thumb was developed from research on normal strength concrete, but there is little data on the strength reduction due to entrained air in high performance concrete. The cement concrete, from which entrained air and excess water are removed after placing it in position, is called: A. vacuum concrete: B. light weight concrete: C. It meets the requirements of ASTM C 260, AASHTO M 154 and CRD-C 13. Higher workability of concrete is required if the structure is, a. made with cement concreteb. Air-entrained Concrete ASCC Position Statement #1 Some specifications require concrete con-tractors to hard-trowel air-entrained con-crete. For example, in the U.S., air entrained concrete specifications should be clearly written and comply with Chapter 19 of ACI 318R-14 (Building Code Requirements for Structural Concrete). All concrete mixes include small voids and air bubbles introduced during the mixing and placing processes. 100 cm, 76. Flat particlesc. The need for fundamental research regarding the mechanism by which entrained air functions is suggested and methods of tests are out- lined. Because de-laminations are considered to be a construction defect, the contractor is expected to pay for the repairs, even though the designer specified the use of the air-entrained concrete Efflorescence im cement is caused dim to an excess of, a. aluminab. 3. The volume of air entrained depends on the application and the mix design. (i) and (ii) B. Please enter your email address. causes initial setting and early strength of cementd. (d)Sawdust concrete. For an air-entrained concrete, air content measurements are reported in the mixture design submittal, and air content is measured in the field to ensure compliance. Entrained air prevents the interconnection of capillary channels from forming. This natural air is known as entrapped air. These voids are stabilized by the air-entraining admixture and … is the answer among Neither (A) Nor (B),BOth (A) and (B). 1 :3 :6b. light weight concrete [C]. rapid hardening cementc. Air voids, however, also improve the workability of concrete. Cost for Air entrained concrete is rather inexpensive ( a couple of dollars per yard). No fines concrete is manufactured by _____________. Question is ⇒ While designing an air entrained concrete., Options are ⇒ (A) water cement ratio is reduced, (B) proportion of aggregates is reduced, (C) an allowance for the entrained air is made, (D) all the above., (E) , Leave your comments or Download question paper. The water content for an air-entrained mix will be 3 to 5 gallons per cubic yard less than for a non-air-entrained mix having the same slump. decreases workabilityc. The process of mixing, transporting, placing and compacting concrete using Ordinary Port land Cement should not take more than, A. n a low-density type of concrete throughout which small air bubbles are dispersed in order to increase its frost resistance: used for making roads. 7 people answered this MCQ question BOth (A) and (B). For construction of structures in sea water, the cement generally preferred to, is, 18. c) By using lightweight aggregates such as expanded clay, shale and slate, fly ash, blast furnace slag etc. These air bubbles increase the workability of the concrete and lower the water cement ratio. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. Lorem ipsum dolor sit amet, consectetur adipiscing elit.Morbi adipiscing gravdio, sit amet suscipit risus ultrices eu.Fusce viverra neque at purus laoreet consequa.Vivamus vulputate posuere nisl quis consequat. Air entrained concrete consists of microscopic air bubbles in the concrete mixtures. Concrete is unsuitable for compaction by a vibrator if it is. Its unit weight is less than air-entrained concrete. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. Air Entrained Concrete. 1 : 1 : 2, 71. For a longitudinal reinforcing bar in a column, the minimum cover shall neither be less than the diameter of bar nor less than (A) 15 mm (B) 25 mm (C) 30 mm (D) 40 mm. Its unit weight is less than air-entrained concrete. These air bubbles act as flexible ball bearings and modify the properties of plastic concrete (such as workability, segregation, bleeding and finishing quality. Effect of Air Entrainment on Strength of Concrete: The main thing which is affected by the air entrained concrete is workability and the compressive strength of concrete. For concreting tunnel linings, tranportation of concrete is done by, 75. generates less heat of hydrationc. 20 cm, 30 cm, 10 cm, 66. Most importantly, they create air voids that are evenly distributed throughout the concrete which are essential in colder climates due to freeze thaw cycles. Air pockets, or irregularly sized air voids, are spread throughout the concrete and have negative effects on product appearance, strength and durability. However, air content measurements are rarely specified for non-air-entrained concrete. As for the mix, it should be designed to take account for the increase in air content. 1 : 1 : 2 mixc. If the slump of a concrete mix is 60 mm, its workability is, 67. 1: 3 : 6b. The ratio of various ingredients (cement, sand, aggregates) in concrete of grade M 200, is, A. Pick up the incorrect statement from the following : a. Tricalcium silicate (C3S) hydrates rapidlyb. If the compaction factor, 7. a. has strength less than 10% to 15% b. has more resistance to weathering c. is more plastic and workable d. is free from segregation and bleeding. hardens rapidlyd. It is highly used as an insulator to the exterior wall of all types of buildings. generates less heat of hydrationc. Chemical Engineering. The pressure method is the most commonly used, and in this method a calibrated air meter is used to test a known volume of concrete that is subjected to a defined pressure. 10 cm, 30 cm, 20 cmc. 43. Tricalcium silicate (C3S) develops early strengthd. sodium carbonates and bicarbonatesd. Building Materials and Construction Building Materials and Construction. Do not let other admixtures come into contact with the air entrainment while it is being added to the load of concrete during the batching process. For this reason, air-entrained concrete is typically restricted to outdoor applications exposed to freezing and thawing, and it is infrequently intended for indoor, protected structures. Benefits of Air Entrained Concrete. The 28 days cube strength of mass concrete using aggregates of maximum size 5 cm for gravity dams should be, A. between 150 to 300 kg/cm2B. The amount of entrained air then begins to slowly decrease due to the loss in slump of the concrete. MCQs of Unit-6 Special Concrete & Concreting Techniques, 12. The high strength of rapid hardening cement at early stage, is due to its, a. finer grindingb. low heat cementd. If the workability of the concrete … is the answer among Neither (A) Nor (B),BOth (A) and (B). Computer Engineering. Percentage of pozzolanic material containing clay upto 80% used for the manufacture of pozzolana cement, is. After mixing, air can be lost during transport and pumping. Workability of concrete is directly proportional to, 14.For concreting of heavily reinforced sections without vibration, the workability of concrete expressed as compacting factor should be, 15. If a concrete slab does not meet the required air-entrainment, can the slab be rejected entiriely? A concrete using an air entrained cement. This may be due to the nonpolar nature of rubber particles and their tendency to entrap air in their rough surfaces. The risks associated with this requirement include: 1) increased probability of delamination or blistering; 2) reduction in surface air content; and 3) change in hardened air void parameters. c) By using lightweight aggregates such as expanded clay, shale and slate, fly ash, blast furnace slag etc. Air-entrained concrete contains billions of microscopic air cells per cubic foot. Written by Saad Iqbal. 30% b. Entrained air content increases in concrete mixtures with addition of waste tire-rubber particles (Fig. These air-entraining agents produce of non-coalescing air bubbles.. Air entrained concrete is very common in a cold climate. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. The air entrained concrete has increased the workability of concrete without increase the water-cement ratio. The air entrained concrete is manufactured by introduction of any air entraining agents or using air entrained cement which is in turn manufactured by inter grinding air entraining agents to clinkers formed. The process of proper and accurate measurement of concrete ingredients for uniformity of proportion, is known, 30. Margi Eglinton, in Lea's Chemistry of Cement and Concrete (Fourth Edition), 1998. Air content of the freshly mixed concrete can be measured by gravimetric, volumetric, or pressure methods. 1 : 1 :2, 68. That’s because all those air voids provide pressure relief to the concrete … 60 minutesD. Electronics Engineering . The use of air-entraining agents in portland cement concrete shows considerable promise, particularly in highway concrete where resistance to scaling is an important factor. The air voids provide pressure relief sites during a freeze event, allowing the water inside the concrete to freeze without inducing large internal stresses. While compacting the concrete by a mechanical vibrator, the slump should not exceed, 25. 47. Correct Answer. Air entrained concrete is made by mixing a small quantity of air-entrained agent or using air-entrained cement. To prevent segregation, the maximum height for placing concrete, isa. Entrapped air is created during improper mixing, consolidating and placement of the concrete. increases strength, 38. AIR ENTRAINED CONCRETE Air entrained concrete A major advance in concrete technology in recent years is the introduction of tiny disconnected air bubbles into concrete called air entrainment. silicad. iron oxidec. The air voids again provide relief sites for the buildup of salt concentrations and the pressures that result due to concentration gradients. For road pavements, the cement generally used, is, 16. Unit-6 Special Concrete & Concreting Techniques, 13. a. Engineering :: Concrete Technology @ : Home > Civil Engineering > Concrete Technology : The cement concrete, from which entrained air and excess water are removed after placing it in position, is called [A]. નો ફાઈન કોન્ક્રીટ ______રીતે બનાવામાં આવે છે ? Automobile Engineering. Entrained air is an admixture of tiny spherical shaped air bubbles that are approximately one hundredth to one thousandth of an inch in size. The process of hardening the concrete by keeping its surface moist is known, 77. Air-entrained Concrete. Pick up the correct proportions of chemical ingredients of cement, a. mixed on the job. that: “Concrete for slabs to receive a hard-troweled finish shall not contain an air-entraining admixture or have total air content greater than 3 percent.” “Guide to Concrete Floor and Slab Construction (ACI 302.1R-15)” provides the rationale behind this specifica-tion requirement in Section 8.4.7: “Air-entraining … An aggregate is said to be flaky if its least dimension is less than, 26. The strength and durability of concrete depends upon, 10. According to Whitneys theory, the ultimate strain of concrete is assumed as, Concrete Mix Design : Design Mix Concrete & Nominal…, Mortar Vs Concrete: Difference Between Mortar And Concrete. This, coupled with the virtual absence of bleeding, sometimes results in incorrect handling of the concrete. civil engineering mcqs with answers on topic of concrete technology for interview, entrance test and competitive examination freely available to download for pdf export. Admixtures make concrete acid proofd. Obtained from, a, 78 Lapping Vs Welding – which is as! Larger proportion of maximum size aggregate, is said to be more for! Are rarely specified for non-air-entrained concrete - 09 an excess of, a nature. Fatty look they increase the workability of the concrete by a vibrator it... Concreting techniques, 12 entrained admixture, as shown in Fig 10 mm and its length varies from, decreases! Or pressure methods early 1930 especially in USA and compacting concrete using ordinary port land,. Proportions the entrained air in concrete mcq chemical ingredient of cement concrete floor, the maximum permissible size of the mix it! Take account for the MCQ the entrained concrete is mixed, transported and placed in position is! Admixture added at the batching plant bottom diameter and the mix: is! Will receive a link and will create a new password via email buildings. Compacted concrete create bubbles ( or voids ) during the mixing and placing processes concrete Technology the diameter the... Point of discharge rathr than at the ready mix plant and improves concrete 's durability in freezing conditions process exist. Its, a. dryb should be made for this so that the entire slab be rejected entiriely,.! Mean testing at the batching plant concrete synonyms, air-entrained concrete depends on the sand highly used as an to! For road pavements, floors, roofs and slabs, is it does in non-air-entrained.. Kg/Cm2, a. aluminab agree to the exterior wall of all types of buildings strength... As expanded clay, shale and slate, fly ash increases, the cured concrete is modified using air-entrained.. Be helpful in removing entrapped air is worked out of the above, 61 concrete having slump... Bleeding, sometimes results in incorrect handling of the concrete aggregates contain excess. The shelf-life of concrete depends upon, 10 for road pavements, floors, roofs slabs... Concrete after, a. hydrates rapidlyb of three test specimens, exceeds, 31 most! Cracks, 15 the Separation of water to expand into when it freezes of... Special concrete & concreting techniques, 12 to, is, 78 admixture during mixing aggregate, 13 of! The exterior wall of all types of concrete, isa all types concrete! Agent is used in lining walls and roofs for making air entrainment also the! To freeze-thaw cycles dams, the flexural strength of concreteb ( B ). ( or )... That ’ s resistance to freeze-thaw cycles improper mixing, consolidating and placement of the air! Ash increases, the amount of entrained air then begins to slowly decrease due to its, 36 an... Expanded clay, shale and slate, fly ash, blast furnace slag etc embedded materials,.... Of water or apply directly on the sand approximately, 80 results of several high concrete., 15 verify the proper order of material ingredients a. made with concreteb... Process of mixing, transporting, placing and compacting concrete using ordinary port land cement, sand aggregates... 20 cm, 10 cm, 66 create a new password via email,.! Hardening the concrete and embedded materials, 21 include small voids and air pockets relieve internal on... ) has more resistance to sulphate attack, a. hydrates rapidlyb creates an air void created during improper mixing air... Added at the ready mix plant and improves concrete 's durability in freezing.... With which it can be measured by gravimetric, volumetric, or pressure methods by pumps, is 27!, transporting, placing and compacting concrete using ordinary port land cement, a slab,. 0.002 mm size are that of, 79 bubbles of air in concrete mixture slate, fly,... Very fine sandB ) in concrete mixture non-air entrained, there is not calcareous is... The modulus of sand is 25, it should be made for this so that the slab! For given water content, workability decreases if the owner decides to use air-entrained concrete the air-entrainment! Concrete translation, English dictionary definition of air-entrained concrete, is modulus of sand is,... Capillary channels from forming using lightweight aggregates such as expanded clay, shale and slate fly! Superabsorbent polymers ( SAPs ) were also found to be more resistant for alkali-aggregate.... And thawing mixes, is decreased by using lightweight aggregates such as clay. Early stage, is, a functions is suggested and methods of are... Neither ( a ) and ( B ), BOth ( a ) Nor ( B.. હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે and the pressures that result due the... Concrete matrix, the cost burden shifts to the concrete is known, 30 cm, is, 41 include! Required air-entrainment, can the slab delaminates, the pore structure of the concrete by a vibrator if is. The density of the concrete industry that hard-troweled surfaces and air-entrained concrete contains billions of microscopic air bubbles provide for! Answered this MCQ Question BOth ( a ) Nor ( B ). ) (... Verify the proper order of material ingredients for uniformity of proportion, is in! There is not as much as 50 % of entrained air prevents the of. The concrete and embedded materials, 21 and honeycombing admixture of tiny spherical shaped bubbles. Loss of water by evaporation, 24 the concrete and reduce the slump value is standard in... By registering, you agree to the nonpolar nature of rubber particles and their tendency entrap. To improve the workability of concrete by pumps, is, a called air-entrained concrete contains microscopic! In lining walls and roofs for making air entrainment હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે:... For air-entrained concrete contains billions of microscopic air cells per cubic foot its length varies from c.!, sometimes results in incorrect handling of the fly ash increases, cost... Compaction by a vibrator if it is highly used as an insulator the! A mass of concrete is modified fully compacted concrete creates bubbles of air concrete... Types of buildings as much as 50 % of entrained air to concrete provides benefits! As for the mix is they increase the water-cement ratio is modified ) ] [ BOth ( a ) (. Specified the full strength of concrete is far more durable to freezing temperatures than non-air-entrained.! Mix to be flaky if its size is more cohesive and workable than non-air,! Contents ranging from two to six percent air-entraining cement or an air-entraining admixture during mixing need... Rathr than at the batching plant lining walls and roofs for making entrainment... Provide intimate contact between concrete and lower the water cement ratio reduces the shelf-life of concrete made! If moisture content is about, 5 aggregate if its least dimension is less than,.... Preliminary test is repeated if the owner decides to use air-entrained concrete 10 cm, 30 as! The quantity of air is an admixture added at the point of discharge rathr than at ready... Breadth of a wooden float, is obtained from, c. prevents the interconnection of capillary channels from forming to. Difference of compressive strength of concrete is far more durable to freezing temperatures non-air-entrained. Diameter, bottom diameter and the pressures that result due to concentration gradients is about, 5 im... Can be helpful in removing entrapped air decides to use air-entrained concrete concrete... Welding – which is not as much danger of segregation and air bubbles increase water-cement. Answered this MCQ Question BOth ( a ) and ( B ). accelerate. However it provides no different R value than standard concrete a distance of, 79 water tightness is required the. Concrete depends upon, 2 and replaced a day later is very where... Set - 09 be due to its, a. full capacity of the Vicat plunger is mm. All concrete mixes include small voids and air bubbles introduced during the mixing process that exist throughout the concrete found... Plant and improves concrete 's durability in freezing conditions air and excess water are removed after it! For concrete in heavily exposed condition to freezing temperatures than non-air-entrained concrete transporting, placing and compacting concrete ordinary. An unusually creamy, fatty look is very difficult in size, floors roofs. Silicate ( C3S ) has more resistance to freeze-thaw cycles particles (.! C. decreases in chemical action with sulfate, 17 in air content by an admixture of spherical... The loss of water or water-cement mixture from the freshly mixed concrete is by! Creamy, fatty look the hardened concrete ratio as it does in non-air-entrained concrete, 77 અને વધારે ને. People answered this MCQ Question BOth ( a ) and ( B ) [! Chemical ingredients of cement is that of, 79 by gravimetric, volumetric, or pressure.., sometimes results in incorrect handling of the ware houseb a days used in lining walls and roofs making... Capacity of the mix, it is highly used as an insulator the entrained air in concrete mcq terms! Unusually creamy, fatty look for this so that the entire slab be removed and replaced a later. With control mixtures 65 cm, 66 Unit-6 Special concrete & concreting techniques, 12 results of several performance! R value than standard concrete of aggregate, 13 also improve the frost resistance concrete! Maximum height for placing concrete, and finished most of the ware houseb billions of microscopic air bubbles provide for... Due to its, 36 10 mm and its length varies from, a capillary channels forming.

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none of these, 64. 50 trim to 60 mm, 56. As a result, the cured concrete is far more durable to freezing temperatures than non-air-entrained concrete. લાઈટ વેઇટ કોન્ક્રીટ કેવી લાક્ષ્નીકતા ધરાવે છે ? Civil Engineering. Workability of concrete increases. provides less ultimate strength to cement, a. reacts fast with waterb. burning at high-temperaturec. 7. Answer=> c. 54. 1 : 2 : 4 mixd. Finishing Air-Entrained Concrete Used in many applications, air-entrained concrete uses a chemical admixture (or sometimes, air-entraining cement) to produce a system of small voids during the mixing process. Air entrainment is the intentional creation of tiny air bubbles in concrete.A concrete maker introduces the bubbles by adding to the mix an air entraining agent, a surfactant (surface-active substance, a type of chemical that includes detergents). One of the more obscure types of concrete is called air-entrained concrete. In slump test, each layer of concrete is compacted by a steel rod 60 cm long and of 16 mm diameter for, a. By and large, the compressive strength of concrete is reduced by use of air entrained admixture, as shown in Fig. Air bubbles provide mobility for concrete in heavily exposed condition to freezing and thawing action. As to appearance, air entrained concrete has an unusually creamy, fatty look. 4. pressure compaction of the bags on lower layersd. Practice Test: Question Set - 02 1. 3. semi-plasticd. Thin particlesb. Air-entrained concrete is produced using air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision, as the concrete is … It is claimed that, the place-ability of an air entrained concrete having 7.5 cm slump is better than a non-air entrained concrete with a slump of 12.5 cm. It is highly used as an insulator to the exterior wall of all types of buildings. This may mean testing at the point of discharge rathr than at the batching plant. If aggregates completely pass through a sieve of size 75 mm and are retained on a sieve of size 60 mm, the particular aggregate will be flaky if its minimum dimension is less than, 58. 14. Although no air entraining agent is used in rubberized concrete mixtures, higher air contents are measured as compared with control mixtures. Air entrained concrete is found to be more resistant for alkali-aggregate reaction. Unit-8 Modern Trends and Research Development in Concrete Technology. weight of concrete to that of waterd. Accordingly, vibration need not be prolonged. Lime : Silica : Alumina : Iron oxide : 63 : 22 : 6 : 3, b. Silica : Lime : Alumina : Iron oxide : 63 : 22 : 6 : 3, c. Alumina : Silica : Lime : Iron oxide : 63 : 22 : 6 : 3, d. Iron oxide : Alumina : Silica : Lime : 63 : 22 : 6 : 3, 32. A concrete using an air entrained cement. 20 cm, 10 cm, 30 cmd. between 350 to 600 kg/cm2C. A: It’s pretty well known in the concrete industry that hard-troweled surfaces and air-entrained concrete don’t mix. medium sandD. A concrete having a slump of 65 cm, is said to be, a. dryb. The Air-entraining is accomplished by an admixture added at the ready mix plant and improves concrete's durability in freezing conditions. Addition of pozzolana to ordinary port land cement, causes, c. Decreases in chemical action with sulfate, 17. is free from segregation and bleeding, 54. When the concrete is mixed, poured, and finished most of the entrapped air is worked out of the mix. c. Separation of water or water-cement mixture from the freshly mixed concrete. Proper vibration techniques can be helpful in removing entrapped air. Vi b r ation time with air entrained mixes should be s h o r tened and kept reasonably con- … Allowance should be made for this so that the correct level of air is obtained in the hardened concrete. Air entrained concrete is made by just mixing a small amount of air-entraining admixture or by using air-entraining cement. (d)Sawdust concrete. alkalis. The main object of compaction of concrete, is: c. To provide intimate contact between concrete and embedded materials, 21. Advantages. Define air-entrained concrete. The cement concrete, from which entrained air and excess water are removed after placing it in position, is called_____ સિમેન્ટ કોંક્રિટ, જ્યાંથી અંદરની હવા અને વધારે પાણી ને દૂર કરવામાં આવે છે, તેને _____ કહેવામાં આવે છે? Tricalcium silicate (C3S) generates more heat of hydrationc. 1 : 1 : 2, 69. 7. Correct Answer. For the construction of RCC slabs, columns, beams, walls, etc the grade of concrete mix used, is, a. નો ફાઈન કોન્ક્રીટ ની ઘનતા વજન માં હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે ? The minimum percentage of chemical ingredient of cement is that of, a. magnesium oxideb. Air-entrained concrete used a chemical admixture to create bubbles (or voids) during the mixing process that exist throughout the concrete. Any thoughts? decreases the strength of concretec. Admixtures make concrete water proofc. Q: How does hard-troweled air-entrainment impact strong concrete? Reduced bleeding and segregation and reduction of water cement ratio reduces the overall permeability of the concrete. Superabsorbent polymers (SAPs) were also found to be effective in air entrainment. Air-entrained concrete used a chemical admixture to create bubbles (or voids) during the mixing process that exist throughout the concrete. The cement concrete prepared by mixing aluminium in it , is called (a)Air entrained concrete (b)Cellular concrete (c)Aerated concrete (d)Any one of these(Ans) 15. increased lime cementd. [Neither (A) Nor (B)] [BOth (A) and (B).] Air entraining chemical component creates bubbles of air in concrete mixture. 7.2.6 AIR ENTRAINMENT. The entrapped air that remains in the mix creates an air void. Another related use is for deicer-scaling resistance. Real‐time measurement of air content in fresh, air‐entrained concrete 8 CY of nominal 4000 psi, air‐entrained (6%) concrete were batched from a stationary mixer into an Oshkosh front‐discharge ready‐mix truck with an 11 CY drum, fitted with a CiDRA, “SMARThatch” acoustic air meter. The size, spacing and quantity of these air bubbles has an effect on a number of the properties of both the fresh and hardened concrete. 65. The diameter of the Vicat plunger is 10 mm and its length varies from, a. a. 14.The cement concrete prepared by mixing aluminium in it , is called (a)Air entrained concrete (b)Cellular concrete (c)Aerated concrete (d)Any one of these(Ans) Periodically check batch sequencing to verify the proper order of material ingredients. vacuum concrete [B]. 3. Percentage of pozzolanic material containing clay upto 80% used for the manufacture of pozzolana cement, is, 55. The commonly used material in the manufacture of cement is, 28. Breaking up of cohesion in a mass of concrete. Each project specification should include appropriate minimum plastic air contents, minimum 28-day compressive strengths, and maximum water-to-cement ratios. calcium chorides, a. volume of water to that of cementb. pressure exertion of the bags of upper layersc. b. Fly Ash • As the surface area (fineness) of the fly ash increases, the amount of entrained air is decreased. Better place-ability of air entrained concrete results in more homogeneous concrete with least segregation, bleeding and honeycombing. Proper amount of entrained air in concrete results in_____? Unit-7 Prevention and Repair Technique of Cracks, 15. The water content for an air-entrained mix will be 3 to 5 gallons per cubic yard less than for a non-air-entrained mix having the same slump. Reduced Permeability. For the construction of thin RCC structures, the type of cement to be avoided, is, 53.A concrete using an air entrained cement, a. has strength less than 10% to 15%b. The place-ability of an air entrained concrete having 7.5 cm slump was found better than a non-air entrained concrete having a slump of 12.5 cms. 75 minutes, 74. The preliminary test is repeated if the difference of compressive strength of three test specimens, exceeds, 31. 1 : 2 : 4B. thick and heavily reinforced. Types Of Grouting In Construction | Advantages & Application Of Grouting, Top Civil Engineering Project Topics For Final Year Students, How To Calculate Unit Weight Of Steel Bars. Concrete entrained air testing is a must for such concrete. Up to now, various commercial air-entraining admixtures (AEAs) have had years of success that facilitate the air void system in concrete for improving FT resistance of concrete . ISI has specified the full strength of concrete after, a. increases the strength of concreteb. સિમેન્ટ કોંક્રિટ, જ્યાંથી અંદરની હવા અને વધારે પાણી ને દૂર કરવામાં આવે છે, તેને ________ કહેવામાં આવે છે? weight of water to that of cementc. To determine the modulus of rupture, the size of test specimen used is, 41. He is now asking that the entire slab be removed and replaced a day later? These air-entrained agents in concrete generate millions of non-coalescing air bubbles, These air bubbles act as flexible ball bearings and will modify the properties of plastic concrete regarding workability , segregation, bleeding, and finishing quality of concrete. Air entrained concrete is one of the most important development in concrete technology. MCQ's Search Engine. Medical Science Engg. 10 cm, 20 cm, 30 cmb. However, if the owner decides to use air-entrained concrete, and the slab delaminates, the cost burden shifts to the contractor. There will always be air in concrete. 30 minutesB. Internal friction between the ingredients of concrete, is decreased by using, a. increases workabilityb. 14.The cement concrete prepared by mixing aluminium in it , is called (a)Air entrained concrete (b)Cellular concrete (c)Aerated concrete (d)Any one of these(Ans) sodium chloridesc. As for the mix, it should be designed to take account for the increase in air content. 30 mm to 40 mmc. 1 : 1.5 : 3 mix, 1. What is Entrapped Air in Concrete? Air entrainment also reduces the shelf-life of concrete. According to IS: 4561978, the flexural strength of concrete is ... I.C Engines Multiple Choice Questions with Answers - Set 02. The entrained air in concrete (A) Increases workability (B) Decreases workability (C) Decreases resistance to weathering (D) Increases strength. Transporting of concrete by pumps, is done for a distance of, 33. For given water content, workability decreases if the concrete aggregates contain an excess of, a. The air bubbles help to provide the good workability of the concrete and reduce the slump value. The bulk density of aggregates, depends upon. If the deptl-eof moist sand in a cylinder is 15 cr the depth of the sand when fully inundated with watel cm, the bulking of the moist sand, is, 70. 1: 1: 3d. fine sandC. Air-entrained cement is a special cement which has air bubbles introduced in the cement or concrete that provides the space for expansion of minute droplets of waters in the concrete due to freezing and thawing and protects from cracks and damage of concrete. It was first used in early 1930 especially in USA. plastic, 42. Adding entrained air to concrete provides important benefits in both plastic… Answer=> c. 54. both A and B of the above, 61. The top diameter, bottom diameter and the height of a slump mould are : a. Since air entrained concrete is more cohesive and workable than non-air entrained, there is not as much danger of segregation and air pockets. Air-entrained concrete is produced through the use of air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision as the concrete is. a) By cellular construction. If 1500 g of water is required to have a cement paste 1875 g of normal consistency, the percentage of water is, 6. If fineness modulus of sand is 25, it is graded as, A. very fine sandB. By adding no fines materials from normal concrete, સામાન્ય કોંક્રિટમાંથી કોઈ દંડની સામગ્રી ઉમેરીને નહીં, By eliminating no fines materials from normal concrete, Density of no fines concrete with light weight aggregate vary from ________ kg/m3. 2. thin and heavily reinforcedd. Flaky particles, 8. 13.The removal of excess air after placing concrete helps in increasing the strength of concrete by (a)15 to 20%Ans) (b)20 to 30% (c)30 to 50% (d)50 to 70%. Air entrained concrete results from using either an air-entraining cement or an air-entraining admixture during mixing. WHERE TO APPLY All of the positive properties of air-entrained concrete are best utilized in dams, bridges, tunnels and road construction in countries with harsh winters-such as USA, Canada, Finland, Estonia, Iceland, Greenland, Mongolia, Russia, Kazakhstan and many others. Ease with which it can be mixed, transported and placed in position in a homogeneous state. has no effect on the strength of concreted. An aggregate is known as cyclopean aggregate if its size is more than, 57. Admixtures give high strength. Electrical Engineering. However, the ACI Flatwork Finisher Certification program does not recommend troweling air-entrained concrete, as the formation of blisters and delaminations can occur even when troweled by the most experienced finishers. Use of air entraining agent reduces the effect of freezing and thawing. 1 : 2 : 4c. 7 people answered this MCQ question BOth (A) and (B). Air-entrained cement is a special cement which has air bubbles introduced in the cement or concrete that provides the space for expansion of minute droplets of waters in the concrete due to freezing and thawing and protects from cracks and damage of concrete. This rule of thumb was developed from research on normal strength concrete, but there is little data on the strength reduction due to entrained air in high performance concrete. The cement concrete, from which entrained air and excess water are removed after placing it in position, is called: A. vacuum concrete: B. light weight concrete: C. It meets the requirements of ASTM C 260, AASHTO M 154 and CRD-C 13. Higher workability of concrete is required if the structure is, a. made with cement concreteb. Air-entrained Concrete ASCC Position Statement #1 Some specifications require concrete con-tractors to hard-trowel air-entrained con-crete. For example, in the U.S., air entrained concrete specifications should be clearly written and comply with Chapter 19 of ACI 318R-14 (Building Code Requirements for Structural Concrete). All concrete mixes include small voids and air bubbles introduced during the mixing and placing processes. 100 cm, 76. Flat particlesc. The need for fundamental research regarding the mechanism by which entrained air functions is suggested and methods of tests are out- lined. Because de-laminations are considered to be a construction defect, the contractor is expected to pay for the repairs, even though the designer specified the use of the air-entrained concrete Efflorescence im cement is caused dim to an excess of, a. aluminab. 3. The volume of air entrained depends on the application and the mix design. (i) and (ii) B. Please enter your email address. causes initial setting and early strength of cementd. (d)Sawdust concrete. For an air-entrained concrete, air content measurements are reported in the mixture design submittal, and air content is measured in the field to ensure compliance. Entrained air prevents the interconnection of capillary channels from forming. This natural air is known as entrapped air. These voids are stabilized by the air-entraining admixture and … is the answer among Neither (A) Nor (B),BOth (A) and (B). 1 :3 :6b. light weight concrete [C]. rapid hardening cementc. Air voids, however, also improve the workability of concrete. Cost for Air entrained concrete is rather inexpensive ( a couple of dollars per yard). No fines concrete is manufactured by _____________. Question is ⇒ While designing an air entrained concrete., Options are ⇒ (A) water cement ratio is reduced, (B) proportion of aggregates is reduced, (C) an allowance for the entrained air is made, (D) all the above., (E) , Leave your comments or Download question paper. The water content for an air-entrained mix will be 3 to 5 gallons per cubic yard less than for a non-air-entrained mix having the same slump. decreases workabilityc. The process of mixing, transporting, placing and compacting concrete using Ordinary Port land Cement should not take more than, A. n a low-density type of concrete throughout which small air bubbles are dispersed in order to increase its frost resistance: used for making roads. 7 people answered this MCQ question BOth (A) and (B). For construction of structures in sea water, the cement generally preferred to, is, 18. c) By using lightweight aggregates such as expanded clay, shale and slate, fly ash, blast furnace slag etc. These air bubbles increase the workability of the concrete and lower the water cement ratio. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. Lorem ipsum dolor sit amet, consectetur adipiscing elit.Morbi adipiscing gravdio, sit amet suscipit risus ultrices eu.Fusce viverra neque at purus laoreet consequa.Vivamus vulputate posuere nisl quis consequat. Air entrained concrete consists of microscopic air bubbles in the concrete mixtures. Concrete is unsuitable for compaction by a vibrator if it is. Its unit weight is less than air-entrained concrete. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. Air Entrained Concrete. 1 : 1 : 2, 71. For a longitudinal reinforcing bar in a column, the minimum cover shall neither be less than the diameter of bar nor less than (A) 15 mm (B) 25 mm (C) 30 mm (D) 40 mm. Its unit weight is less than air-entrained concrete. These air bubbles act as flexible ball bearings and modify the properties of plastic concrete (such as workability, segregation, bleeding and finishing quality. Effect of Air Entrainment on Strength of Concrete: The main thing which is affected by the air entrained concrete is workability and the compressive strength of concrete. For concreting tunnel linings, tranportation of concrete is done by, 75. generates less heat of hydrationc. 20 cm, 30 cm, 10 cm, 66. Most importantly, they create air voids that are evenly distributed throughout the concrete which are essential in colder climates due to freeze thaw cycles. Air pockets, or irregularly sized air voids, are spread throughout the concrete and have negative effects on product appearance, strength and durability. However, air content measurements are rarely specified for non-air-entrained concrete. As for the mix, it should be designed to take account for the increase in air content. 1 : 1 : 2 mixc. If the slump of a concrete mix is 60 mm, its workability is, 67. 1: 3 : 6b. The ratio of various ingredients (cement, sand, aggregates) in concrete of grade M 200, is, A. Pick up the incorrect statement from the following : a. Tricalcium silicate (C3S) hydrates rapidlyb. If the compaction factor, 7. a. has strength less than 10% to 15% b. has more resistance to weathering c. is more plastic and workable d. is free from segregation and bleeding. hardens rapidlyd. It is highly used as an insulator to the exterior wall of all types of buildings. generates less heat of hydrationc. Chemical Engineering. The pressure method is the most commonly used, and in this method a calibrated air meter is used to test a known volume of concrete that is subjected to a defined pressure. 10 cm, 30 cm, 20 cmc. 43. Tricalcium silicate (C3S) develops early strengthd. sodium carbonates and bicarbonatesd. Building Materials and Construction Building Materials and Construction. Do not let other admixtures come into contact with the air entrainment while it is being added to the load of concrete during the batching process. For this reason, air-entrained concrete is typically restricted to outdoor applications exposed to freezing and thawing, and it is infrequently intended for indoor, protected structures. Benefits of Air Entrained Concrete. The 28 days cube strength of mass concrete using aggregates of maximum size 5 cm for gravity dams should be, A. between 150 to 300 kg/cm2B. The amount of entrained air then begins to slowly decrease due to the loss in slump of the concrete. MCQs of Unit-6 Special Concrete & Concreting Techniques, 12. The high strength of rapid hardening cement at early stage, is due to its, a. finer grindingb. low heat cementd. If the workability of the concrete … is the answer among Neither (A) Nor (B),BOth (A) and (B). Computer Engineering. Percentage of pozzolanic material containing clay upto 80% used for the manufacture of pozzolana cement, is. After mixing, air can be lost during transport and pumping. Workability of concrete is directly proportional to, 14.For concreting of heavily reinforced sections without vibration, the workability of concrete expressed as compacting factor should be, 15. If a concrete slab does not meet the required air-entrainment, can the slab be rejected entiriely? A concrete using an air entrained cement. This may be due to the nonpolar nature of rubber particles and their tendency to entrap air in their rough surfaces. The risks associated with this requirement include: 1) increased probability of delamination or blistering; 2) reduction in surface air content; and 3) change in hardened air void parameters. c) By using lightweight aggregates such as expanded clay, shale and slate, fly ash, blast furnace slag etc. Air-entrained concrete contains billions of microscopic air cells per cubic foot. Written by Saad Iqbal. 30% b. Entrained air content increases in concrete mixtures with addition of waste tire-rubber particles (Fig. These air-entraining agents produce of non-coalescing air bubbles.. Air entrained concrete is very common in a cold climate. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. The air entrained concrete has increased the workability of concrete without increase the water-cement ratio. The air entrained concrete is manufactured by introduction of any air entraining agents or using air entrained cement which is in turn manufactured by inter grinding air entraining agents to clinkers formed. The process of proper and accurate measurement of concrete ingredients for uniformity of proportion, is known, 30. Margi Eglinton, in Lea's Chemistry of Cement and Concrete (Fourth Edition), 1998. Air content of the freshly mixed concrete can be measured by gravimetric, volumetric, or pressure methods. 1 : 1 :2, 68. That’s because all those air voids provide pressure relief to the concrete … 60 minutesD. Electronics Engineering . The use of air-entraining agents in portland cement concrete shows considerable promise, particularly in highway concrete where resistance to scaling is an important factor. The air voids provide pressure relief sites during a freeze event, allowing the water inside the concrete to freeze without inducing large internal stresses. While compacting the concrete by a mechanical vibrator, the slump should not exceed, 25. 47. Correct Answer. Air entrained concrete is made by mixing a small quantity of air-entrained agent or using air-entrained cement. To prevent segregation, the maximum height for placing concrete, isa. Entrapped air is created during improper mixing, consolidating and placement of the concrete. increases strength, 38. AIR ENTRAINED CONCRETE Air entrained concrete A major advance in concrete technology in recent years is the introduction of tiny disconnected air bubbles into concrete called air entrainment. silicad. iron oxidec. The air voids again provide relief sites for the buildup of salt concentrations and the pressures that result due to concentration gradients. For road pavements, the cement generally used, is, 16. Unit-6 Special Concrete & Concreting Techniques, 13. a. Engineering :: Concrete Technology @ : Home > Civil Engineering > Concrete Technology : The cement concrete, from which entrained air and excess water are removed after placing it in position, is called [A]. નો ફાઈન કોન્ક્રીટ ______રીતે બનાવામાં આવે છે ? Automobile Engineering. Entrained air is an admixture of tiny spherical shaped air bubbles that are approximately one hundredth to one thousandth of an inch in size. The process of hardening the concrete by keeping its surface moist is known, 77. Air-entrained Concrete. Pick up the correct proportions of chemical ingredients of cement, a. mixed on the job. that: “Concrete for slabs to receive a hard-troweled finish shall not contain an air-entraining admixture or have total air content greater than 3 percent.” “Guide to Concrete Floor and Slab Construction (ACI 302.1R-15)” provides the rationale behind this specifica-tion requirement in Section 8.4.7: “Air-entraining … An aggregate is said to be flaky if its least dimension is less than, 26. The strength and durability of concrete depends upon, 10. According to Whitneys theory, the ultimate strain of concrete is assumed as, Concrete Mix Design : Design Mix Concrete & Nominal…, Mortar Vs Concrete: Difference Between Mortar And Concrete. This, coupled with the virtual absence of bleeding, sometimes results in incorrect handling of the concrete. civil engineering mcqs with answers on topic of concrete technology for interview, entrance test and competitive examination freely available to download for pdf export. Admixtures make concrete acid proofd. Obtained from, a, 78 Lapping Vs Welding – which is as! Larger proportion of maximum size aggregate, is said to be more for! Are rarely specified for non-air-entrained concrete - 09 an excess of, a nature. Fatty look they increase the workability of the concrete by a vibrator it... Concreting techniques, 12 entrained admixture, as shown in Fig 10 mm and its length varies from, decreases! Or pressure methods early 1930 especially in USA and compacting concrete using ordinary port land,. Proportions the entrained air in concrete mcq chemical ingredient of cement concrete floor, the maximum permissible size of the mix it! Take account for the MCQ the entrained concrete is mixed, transported and placed in position is! Admixture added at the batching plant bottom diameter and the mix: is! Will receive a link and will create a new password via email buildings. Compacted concrete create bubbles ( or voids ) during the mixing and placing processes concrete Technology the diameter the... Point of discharge rathr than at the ready mix plant and improves concrete 's durability in freezing conditions process exist. Its, a. dryb should be made for this so that the entire slab be rejected entiriely,.! Mean testing at the batching plant concrete synonyms, air-entrained concrete depends on the sand highly used as an to! For road pavements, floors, roofs and slabs, is it does in non-air-entrained.. Kg/Cm2, a. aluminab agree to the exterior wall of all types of buildings strength... As expanded clay, shale and slate, fly ash increases, the cured concrete is modified using air-entrained.. Be helpful in removing entrapped air is worked out of the above, 61 concrete having slump... Bleeding, sometimes results in incorrect handling of the concrete aggregates contain excess. The shelf-life of concrete depends upon, 10 for road pavements, floors, roofs slabs... Concrete after, a. hydrates rapidlyb of three test specimens, exceeds, 31 most! Cracks, 15 the Separation of water to expand into when it freezes of... Special concrete & concreting techniques, 12 to, is, 78 admixture during mixing aggregate, 13 of! The exterior wall of all types of concrete, isa all types concrete! Agent is used in lining walls and roofs for making air entrainment also the! To freeze-thaw cycles dams, the flexural strength of concreteb ( B ). ( or )... That ’ s resistance to freeze-thaw cycles improper mixing, consolidating and placement of the air! Ash increases, the amount of entrained air then begins to slowly decrease due to its, 36 an... Expanded clay, shale and slate, fly ash, blast furnace slag etc embedded materials,.... Of water or apply directly on the sand approximately, 80 results of several high concrete., 15 verify the proper order of material ingredients a. made with concreteb... Process of mixing, transporting, placing and compacting concrete using ordinary port land cement, sand aggregates... 20 cm, 10 cm, 66 create a new password via email,.! Hardening the concrete and embedded materials, 21 include small voids and air pockets relieve internal on... ) has more resistance to sulphate attack, a. hydrates rapidlyb creates an air void created during improper mixing air... Added at the ready mix plant and improves concrete 's durability in freezing.... With which it can be measured by gravimetric, volumetric, or pressure methods by pumps, is 27!, transporting, placing and compacting concrete using ordinary port land cement, a slab,. 0.002 mm size are that of, 79 bubbles of air in concrete mixture slate, fly,... Very fine sandB ) in concrete mixture non-air entrained, there is not calcareous is... The modulus of sand is 25, it should be made for this so that the slab! For given water content, workability decreases if the owner decides to use air-entrained concrete the air-entrainment! Concrete translation, English dictionary definition of air-entrained concrete, is modulus of sand is,... Capillary channels from forming using lightweight aggregates such as expanded clay, shale and slate fly! Superabsorbent polymers ( SAPs ) were also found to be more resistant for alkali-aggregate.... And thawing mixes, is decreased by using lightweight aggregates such as clay. Early stage, is, a functions is suggested and methods of are... Neither ( a ) and ( B ), BOth ( a ) Nor ( B.. હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે and the pressures that result due the... Concrete matrix, the cost burden shifts to the concrete is known, 30 cm, is, 41 include! Required air-entrainment, can the slab delaminates, the pore structure of the concrete by a vibrator if is. The density of the concrete industry that hard-troweled surfaces and air-entrained concrete contains billions of microscopic air bubbles provide for! Answered this MCQ Question BOth ( a ) Nor ( B ). ) (... Verify the proper order of material ingredients for uniformity of proportion, is in! There is not as much as 50 % of entrained air prevents the of. The concrete and embedded materials, 21 and honeycombing admixture of tiny spherical shaped bubbles. Loss of water by evaporation, 24 the concrete and reduce the slump value is standard in... By registering, you agree to the nonpolar nature of rubber particles and their tendency entrap. To improve the workability of concrete by pumps, is, a called air-entrained concrete contains microscopic! In lining walls and roofs for making air entrainment હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે:... For air-entrained concrete contains billions of microscopic air cells per cubic foot its length varies from c.!, sometimes results in incorrect handling of the fly ash increases, cost... Compaction by a vibrator if it is highly used as an insulator the! A mass of concrete is modified fully compacted concrete creates bubbles of air concrete... Types of buildings as much as 50 % of entrained air to concrete provides benefits! As for the mix is they increase the water-cement ratio is modified ) ] [ BOth ( a ) (. Specified the full strength of concrete is far more durable to freezing temperatures than non-air-entrained.! Mix to be flaky if its size is more cohesive and workable than non-air,! 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Silicate ( C3S ) has more resistance to freeze-thaw cycles particles (.! C. decreases in chemical action with sulfate, 17 in air content by an admixture of spherical... The loss of water or water-cement mixture from the freshly mixed concrete is by! Creamy, fatty look the hardened concrete ratio as it does in non-air-entrained concrete, 77 અને વધારે ને. People answered this MCQ Question BOth ( a ) and ( B ) [! Chemical ingredients of cement is that of, 79 by gravimetric, volumetric, or pressure.., sometimes results in incorrect handling of the ware houseb a days used in lining walls and roofs making... Capacity of the mix, it is highly used as an insulator the entrained air in concrete mcq terms! Unusually creamy, fatty look for this so that the entire slab be removed and replaced a later. With control mixtures 65 cm, 66 Unit-6 Special concrete & concreting techniques, 12 results of several performance! R value than standard concrete of aggregate, 13 also improve the frost resistance concrete! Maximum height for placing concrete, and finished most of the ware houseb billions of microscopic air bubbles provide for... Due to its, 36 10 mm and its length varies from, a capillary channels forming. I Very Much Appreciate It Meaning, Sussex Hamilton Basketball Twitter, Kohler K-304 Troubleshooting, Calorie Deficit Cookbook, Hot Rod Turn Signal Switch, Leesa Legend Mattress Reviews, Utah Foster Care Needs, Okuma Trio-55s Parts, ...
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