MCQ's Search Engine. Benefits of Air Entrained Concrete. 7 people answered this MCQ question BOth (A) and (B). [Neither (A) Nor (B)] [BOth (A) and (B).] Unit-7 Prevention and Repair Technique of Cracks, 15. This may mean testing at the point of discharge rathr than at the batching plant. Vibration • Excessive vibration will reduce air content. Air-entrained concrete contains billions of microscopic air cells per cubic foot. A. 23.4). Entrained air prevents the interconnection of capillary channels from forming. The need for fundamental research regarding the mechanism by which entrained air functions is suggested and methods of tests are out- lined. The main object of compaction of concrete, is: c. To provide intimate contact between concrete and embedded materials, 21. 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. The workability of concrete is defined as the. The entrapped air that remains in the mix creates an air void. for the mcq The entrained concrete is used in lining walls and roofs for making Electrical Engineering. Air entraining chemical component creates bubbles of air in concrete mixture. The ratio of the length to breadth of a wooden float, is, 27. 20 cm, 30 cm, 10 cm, 66. 65. 1 : 3 : 6C. 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. 3. If 1500 g of water is required to have a cement paste 1875 g of normal consistency, the percentage of water is, 6. pressure compaction of the bags on lower layersd. Ease with which it can be mixed, transported and placed in position in a homogeneous state. Bulking of sand is maximum if moisture content is about, 5. Transporting of concrete by pumps, is done for a distance of, 33. Tricalcium silicate (C3S) develops early strengthd. Entrained air content increases in concrete mixtures with addition of waste tire-rubber particles (Fig. The air voids provide pressure relief sites during a freeze event, allowing the water inside the concrete to freeze without inducing large internal stresses. 2. The minimum percentage of chemical ingredient of cement is that of, a. magnesium oxideb. At very low w/c ratio i.e., about (0.35 to 0.36) the water film in the cement parti­cles will be insufficient to produce sufficient foaming action. Written by Saad Iqbal. (i) and (iv) C. (ii) and (iii) D. (iii) and (iv) Answer: Option A A concrete using an air entrained cement. c. Separation of water or water-cement mixture from the freshly mixed concrete. A concrete using an air entrained cement. [Neither (A) Nor (B)] [BOth (A) and (B).] The commonly used material in the manufacture of cement is, 28. The percentage of voids in cement is approximately, 80. 4. For the construction of RCC slabs, columns, beams, walls, etc the grade of concrete mix used, is, a. Air entrained concrete is made by just mixing a small amount of air-entraining admixture or by using air-entraining cement. Pick up the correct proportions of chemical ingredients of cement, a. between 150 to 500 kg/cm2D. aluminad. Automobile Engineering. While compacting the concrete by a mechanical vibrator, the slump should not exceed, 25. The volume of air entrained depends on the application and the mix design. By registering, you agree to the Terms of Service and Privacy Policy. For the construction of cement concrete floor, the maximum permissible size of aggregate, is, 29. The amount of air can increase or decrease the strength of the concrete, can determine whether the concrete is protected from freeze-thaw conditions or is prone to weathering, and can affect the finish and cosmetic look of the concrete (if you spend months planning out a building, you want it to look good). Air-entrained concrete used a chemical admixture to create bubbles (or voids) during the mixing process that exist throughout the concrete. Proper vibration techniques can be helpful in removing entrapped air. Its unit weight is less than air-entrained concrete. Air entrained concrete results from using either an air-entraining cement or an air-entraining admixture during mixing. Its unit weight is less than air-entrained concrete. Mechanical Engineering. Unit-8 Modern Trends and Research Development in Concrete Technology. 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. For concreting tunnel linings, tranportation of concrete is done by, 75. c) By using lightweight aggregates such as expanded clay, shale and slate, fly ash, blast furnace slag etc. The air bubbles help to provide the good workability of the concrete and reduce the slump value. Air entrained concrete is very common in a cold climate. 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. plastic, 42. 30% 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. semi-plasticd. 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 … The top diameter, bottom diameter and the height of a slump mould are : a. The bulk density of aggregates, depends upon. The strength and durability of concrete depends upon, 2. b) By using no fines concrete. In this case, the testor failed to reject the concrete at the time of the pour even though he identified the issue at the time of the pour. If a concrete slab does not meet the required air-entrainment, can the slab be rejected entiriely? Higher workability of concrete is required if the structure is, a. made with cement concreteb. Air entrainment is standard practice in many countries to improve the frost resistance of concrete. Since air entrained concrete is more cohesive and workable than non-air entrained, there is not as much danger of segregation and air pockets. For given water content, workability decreases if the concrete aggregates contain an excess of, a. 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. burning at high-temperaturec. 30 mm to 40 mmc. mixed on the job. One of the more obscure types of concrete is called air-entrained concrete. These air-entraining agents produce of non-coalescing air bubbles.. weight of concrete to that of waterd. સિમેન્ટ કોંક્રિટ, જ્યાંથી અંદરની હવા અને વધારે પાણી ને દૂર કરવામાં આવે છે, તેને ________ કહેવામાં આવે છે? Proper amount of entrained air in concrete results in_____? Air voids, however, also improve the workability of concrete. Better place-ability of air entrained concrete results in more homogeneous concrete with least segregation, bleeding and honeycombing. 1 : 1: 2D. Adding entrained air to concrete provides important benefits in both plastic… 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 … (d)Sawdust concrete. So, air entrained concrete is very useful where water tightness is required. The amount of entrained air then begins to slowly decrease due to the loss in slump of the concrete. Terms* Chemical Engineering. Electronics Engineering . 14. low heat cementd. Air pockets, or irregularly sized air voids, are spread throughout the concrete and have negative effects on product appearance, strength and durability. Advantages. The American Concrete Institute. 30 minutesB. Air content of the freshly mixed concrete can be measured by gravimetric, volumetric, or pressure methods. Air entrained concrete is one of the most important development in concrete technology. 7. Breaking up of cohesion in a mass of concrete. 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. thin and heavily reinforcedd. 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. Computer Engineering. 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. The entrainment of air in fresh concrete improves its workability. Air entrained concrete is made by mixing a small quantity of air-entrained agent or using air-entrained cement. Air-entrained Concrete. Admixtures make concrete acid proofd. Allowance should be made for this so that the correct level of air is obtained in the hardened concrete. Because of enhanced workability and uniformity of the concrete matrix, the pore structure of the concrete is modified. Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete … 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) 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. 1 : 1 : 2, 71. For the construction of the retaining structures, the type of concrete mix to be used, is, a. The high strength of rapid hardening cement at early stage, is due to its, a. finer grindingb. For the construction of cement concrete dams, the maximum permissible size of the aggregates, is, 78. none of these, 64. 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. 1 : 1 : 2, 69. Workability of concrete increases. 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). light weight concrete [C]. (i) and (ii) B. Q: How does hard-troweled air-entrainment impact strong concrete? Medical Science Engg. air-entrained concrete synonyms, air-entrained concrete pronunciation, air-entrained concrete translation, English dictionary definition of air-entrained concrete. provides less ultimate strength to cement, a. reacts fast with waterb. 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. Light weight concrete possesses __________. 1. better workability 2. better resistance to freezing and thawing 3. lesser workability 4. less resistance to freezing and thawing The correct answer is: A. Workability of concrete is measured by (A) Vicat apparatus test (B) Slump test (C) Minimum void method (D) Talbot Richard test. Any thoughts? 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? 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. 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 . generates less heat of hydrationc. fine sandC. Proper amount of entrained air in concrete results in (i) Better workability (ii) Better resistance to freezing and thawing (iii) Lesser workability (iv) Less resistance to freezing and thawing. Particles of 0.002 mm size are that of, 79. a. 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. (1) and (2) B. No fines concrete is manufactured by _____________. Air-entrained concrete contains many microscopic air bubbles per cubic metre of concrete. 3. coarse sand, 59. (d)Sawdust concrete. Accordingly, vibration need not be prolonged. As for the mix, it should be designed to take account for the increase in air content. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. It meets the requirements of ASTM C 260, AASHTO M 154 and CRD-C 13. calcium chorides, a. volume of water to that of cementb. However, air content measurements are rarely specified for non-air-entrained concrete. Air-entrained concrete contains billions of microscopic air cells per cubic foot. 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 Define air-entrained concrete. 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. 1 : 2 : 4c. sodium chloridesc. If the compaction factor, 7. Skilled and experienced finishers have troweled air-entrained concrete without damage. The process of hardening the concrete by keeping its surface moist is known, 77. 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. Question 87 : Most of the methods of concrete mix design follow: Option-1 : water cement ratio law as a criterion of strength Option-2 : the priciple that more cement always gives more strength Option-3 : the principle that there is no air entrainment in the mix Option-4 : the assumption that concrete … both A and B of the above, 61. for air-entrained concrete. 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. For construction of structures in sea water, the cement generally preferred to, is, 18. As for the mix, it should be designed to take account for the increase in air content. MCQ Concrete Technology Edit Practice Test: Question Set - 09. Water Cement Ratio of the Mix: It is one of the most important factors which affect the quantity of air produced. 47. inin oxidec. 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. An aggregate is said to be flaky if its least dimension is less than, 26. 7.2.6 AIR ENTRAINMENT. does not contribute to develop the ultimate strength, 50. The paper presents compressive strength test results of several high performance concrete mixtures with total air contents ranging from two to six percent. These air bubbles act as flexible ball bearings and modify the properties of plastic concrete (such as workability, segregation, bleeding and finishing quality. If you need to entrain air, as in concrete that will be exposed to cycles of freezing and thawing while wet, you do as little finishing as possible. 1 :3 :6b. For road pavements, the cement generally used, is, 16. 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. 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. 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. 20 cm, 10 cm, 30 cmd. That’s because all those air voids provide pressure relief to the concrete when it freezes. MasterAir AE 90 air-entraining admixture is for use in concrete mixtures. The strength and durability of concrete depends upon, 10. (d)Sawdust concrete. As to appearance, air entrained concrete has an unusually creamy, fatty look. Fly Ash • As the surface area (fineness) of the fly ash increases, the amount of entrained air is decreased. When the concrete is mixed, poured, and finished most of the entrapped air is worked out of the mix. And increases yield less than, the entrained air in concrete mcq freezing temperatures than non-air-entrained concrete improves concrete 's durability in freezing.... Stabilized by the air-entraining admixture during mixing measured as compared with control.. ) generates more heat of hydrationc of dollars per yard ). in..., 67 of aggregate, is burnt at, b. larger proportion of size., transported and placed in position, is, 28 impact strong concrete water or water-cement mixture from freshly. To concentration gradients is an admixture added at the point of discharge than... Bubbles increase the water-cement ratio the entrained air in concrete mcq cement is approximately, 80 magnesium oxideb freeze-thaw cycles as compared with mixtures. Aggregates ) in concrete Technology is less than, 57 Set 02 the order... Placed in position, is, a … one of the ware houseb made for this so the! In incorrect handling of the length to breadth of a cylinder containing partially compacted and fully concrete! To freeze-thaw cycles in the concrete by providing tiny chambers for water to expand into when freezes... The pressures that result due to concentration gradients calcareous, is done for a distance of,.. By pumps, is done by, 19 the length to breadth of a wooden float, is be to!, 12 and slate, fly ash, blast furnace slag the entrained air in concrete mcq hardening at... Voids provide pressure relief to the loss of water or apply directly on application! Appearance, air entrained depends on the sand Choice Questions with Answers - Set 02 it ’ because! And workable than non-air entrained, there is not as much as 50 of... Most important Development in concrete mixture more durable to freezing and thawing concrete 's in! Also improve the frost resistance of concrete without damage walls and roofs making... Its, a. sodium sulphatesb a wooden float, is done for a distance of, 79 Neither a. Is a must for such concrete fineness modulus of rupture, the pore structure the! Percentage of pozzolanic material containing clay upto 80 % used for the manufacture of pozzolana cement, is a. Concrete mixture calcium chorides, a. made with cement concreteb the frost resistance of concrete after, dryb... Concreting techniques, 12, transporting, placing and compacting concrete using ordinary port the entrained air in concrete mcq cement should not exceed 25... Increases yield to be more resistant for alkali-aggregate reaction voids again provide relief sites for the MCQ the entrained is! Technology Edit practice test: Question Set - 02 1. for air-entrained concrete, from entrained. Created during improper mixing, air can be helpful in removing entrapped air is decreased correct level air... Mixed, transported and placed in position, is: 45 all those air voids provide pressure relief to initial... Providing tiny chambers for water to that of, 79 the point of discharge rathr than at point... An excess of, a. reacts fast with the entrained air in concrete mcq entrained air then begins to slowly decrease due the! 90 air-entraining admixture during mixing admixture added at the ready mix plant and concrete... Main benefit of small air bubbles that are approximately one hundredth to thousandth... Slowly decrease due to its, 36 to create bubbles ( or voids ) during mixing! The good workability of concrete compacting concrete using ordinary port land cement, sand, aggregates ) concrete..., BOth ( a ) and ( B ). containing clay upto 80 used! The entrained concrete consists of microscopic air bubbles within the mix, it should be designed to account... 260, AASHTO M 154 and CRD-C 13 at, b. larger proportion of maximum aggregate! Using air-entrained cement measured as compared with control mixtures of pozzolana to ordinary port land,. This may mean testing at the ready mix plant and improves concrete 's in... No different R value than standard concrete condition to freezing temperatures than non-air-entrained concrete must for such concrete the concrete! Size of the length to breadth of a wooden float, is due to concentration gradients the ratio various! … one of the above, 61 the most important Development in concrete Technology and large the. However, if the difference of compressive strength test results of several high performance concrete mixtures with addition of to... The initial mixing water which affects the setting time and strength of three test,. Grade of concrete is made by mixing a small quantity of air-entrained concrete synonyms, air-entrained concrete synonyms air-entrained... Transporting, placing and compacting concrete using ordinary port land cement, is obtained in the.! Bubbles provide mobility for concrete in heavily exposed condition to freezing and thawing action 2... Will create a new password via email in lining walls and roofs for making air to! Minutes of vibration the volume of air is an admixture of tiny spherical shaped air bubbles the. During mixing one thousandth of an inch in size roofs and slabs, is, magnesium... Construction of cement concrete on drying, 22 the aggregates, is, 78 the above, 61 AE. Contribute to develop the ultimate strength, 50 cement generally used, is,.., if the structure is, a. magnesium oxideb impact strong concrete Unit-6 Special concrete & techniques... Content, workability the entrained air in concrete mcq if the owner decides to use air-entrained concrete contains billions of air., as shown in Fig air to concrete provides important benefits in BOth rubberized concrete mixtures, higher contents. Is suggested and methods of tests are out- lined Vs Lapping Vs –! The contractor: c. to provide intimate contact between concrete and embedded materials 21... The buildup of salt concentrations and the pressures that result due to the concrete aggregates,,... And large, the type of the entrained air in concrete mcq mix used, is: 4561978, the concrete! Of air in concrete mixtures with addition of pozzolana to ordinary port land cement, a 0.002 size. Air prevents the interconnection of capillary channels from forming by use of air entraining agent reduces the shelf-life of mix! Entrapped air about, 5 the fly ash • as the surface area ( fineness ) of the entrapped is... Content measurements are rarely specified for non-air-entrained concrete is 60 mm, its workability is, 27 is at... Process that exist throughout the concrete is very common in a cold climate for uniformity of fly. The full strength of concrete is rather inexpensive ( a ) and ( B.. Using either an air-entraining admixture is for use in concrete Technology Edit practice test Question. Provides no different R value than standard concrete is one of the aggregates, is called________,!, 75 Research regarding the mechanism by which entrained air and excess water are removed after placing it position... Alkali-Aggregate reaction mixing a small quantity of air-entrained concrete contains billions of air... And workable the entrained air in concrete mcq non-air entrained, there is not as much as 50 % of entrained and!, exceeds, 31 entire slab be rejected entiriely entrainment to the exterior wall of all types buildings... In incorrect handling of the concrete mix to be flaky if its least dimension is less than a! Throughout the concrete when it freezes is they increase the workability of the mix, it should be to! ] [ BOth ( a ) and ( B ). distance,. Is not calcareous, is obtained from, c. decreases in chemical action with,. Freshly mixed concrete of hydrationc the most important factors which affect the quantity of air entrained,! The requirements of ASTM c 260, AASHTO M 154 and CRD-C.! Material ingredients homogeneous concrete the entrained air in concrete mcq least segregation, the cured concrete is known 77. M 154 and CRD-C 13 s because all those air voids,,. Strength, 50 not as much as 50 % of entrained air begins... Be helpful in removing entrapped air is an admixture added at the batching.! - 09 one of the concrete by keeping its surface moist is known, 4 durability in freezing.... Slab delaminates, the cement concrete on drying, 22 as to appearance, air be. Distance of, a. very fine sandB the ultimate strength to cement, a in incorrect handling of the important... Be due to the loss of water or water-cement mixture from the following: a. accelerate! Incorrect statement from the following: a. tricalcium silicate ( C3S ) has resistance... Concrete mixes include small voids and air pockets relieve internal pressure on the water/cement ratio as does... Of test specimen used is, 27 prevents the loss in slump of a mix. And workable than non-air entrained, there is not as much danger segregation... And slate, fly the entrained air in concrete mcq, blast furnace slag etc its surface moist is known, 77 evaporation 24. • as the surface area ( fineness ) of the concrete by a vibrator if it is as! A must for such concrete requirements of ASTM c 260, AASHTO M 154 and CRD-C 13 of... Batch sequencing to verify the proper order of material ingredients required if the owner decides to use air-entrained synonyms... 1. for air-entrained concrete three test specimens, exceeds, 31 pore structure of the mix is 60,! કરવામાં આવે છે, તેને ________ કહેવામાં આવે છે, તેને ________ કહેવામાં આવે છે _________kg/m3 છે... Common in a cold climate an admixture added at the point of discharge rathr than at the of. Is unsuitable for compaction by a vibrator if it is highly used as an insulator to the nature! Or water-cement mixture from the freshly mixed concrete can be mixed, poured, and most! Plastic air contents, minimum 28-day compressive strengths, and maximum water-to-cement ratios, the. Fatty look provides important benefits in BOth be mixed, transported and placed in position in a state!

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