is free from segregation and bleeding, 54. 1 : 1: 2D. 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. [Neither (A) Nor (B)] [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. 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) Any thoughts? Pick up the incorrect statement from the following : a. Tricalcium silicate (C3S) hydrates rapidlyb. Air entrained concrete is found to be more resistant for alkali-aggregate reaction. 30 minutesB. 1 : I: 3c. Reduced bleeding and segregation and reduction of water cement ratio reduces the overall permeability of the concrete. The cement concrete, from which entrained air and excess water are removed after placing it in position, is called________. Terms* According to I.S. [Neither (A) Nor (B)] [BOth (A) and (B).] 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 … 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 air entrained concrete has increased the workability of concrete without increase the water-cement ratio. sodium carbonates and bicarbonatesd. Air entrained concrete is one of the most important development in concrete technology. Define air-entrained concrete. increases strength, 38. Air Entrained Concrete. 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. It meets the requirements of ASTM C 260, AASHTO M 154 and CRD-C 13. 40 minutesC. 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 preliminary test is repeated if the difference of compressive strength of three test specimens, exceeds, 31. 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. 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. 100 cm, 76. 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. between 150 to 500 kg/cm2D. 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. 20 mm to 30 mmb. burning at high-temperaturec. Vibration • Excessive vibration will reduce air content. pressure compaction of the bags on lower layersd. Percentage of pozzolanic material containing clay upto 80% used for the manufacture of pozzolana cement, is. You will receive a link and will create a new password via email. For concreting tunnel linings, tranportation of concrete is done by, 75. Allowance should be made for this so that the correct level of air is obtained in the hardened concrete. Pick up the incorrect statement from the following : a. Admixtures accelerate hydrationb. Tricalcium silicate (C3S) develops early strengthd. Ease with which it can be mixed, transported and placed in position in a homogeneous state. 44. Air pockets, or irregularly sized air voids, are spread throughout the concrete and have negative effects on product appearance, strength and durability. The diameter of the Vicat plunger is 10 mm and its length varies from, a. If 1500 g of water is required to have a cement paste 1875 g of normal consistency, the percentage of water is, 6. (i) and (iv) C. (ii) and (iii) D. (iii) and (iv) Answer: Option A 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. If the compaction factor, 7. Q: How does hard-troweled air-entrainment impact strong concrete? 3. 30% b. 1 : 1 :2, 68. 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) Air entrained concrete consists of microscopic air bubbles in the concrete mixtures. decreases workabilityc. alkalis. 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. It was first used in early 1930 especially in USA. 1: 1: 3d. 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 a) By cellular construction. 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. As for the mix, it should be designed to take account for the increase in air content. Concrete entrained air testing is a must for such concrete. Its unit weight is less than air-entrained concrete. 1. 1 : 1.5 : 3 mix, 1. 60 minutesD. Thin particlesb. An aggregate is known as cyclopean aggregate if its size is more than, 57. 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. A: It’s pretty well known in the concrete industry that hard-troweled surfaces and air-entrained concrete don’t mix. (1) and (2) B. Answer=> c. 54. The air voids again provide relief sites for the buildup of salt concentrations and the pressures that result due to concentration gradients. 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. As a result, the cured concrete is far more durable to freezing temperatures than non-air-entrained concrete. 1 : 3 : 6C. 47. He is now asking that the entire slab be removed and replaced a day later? નો ફાઈન કોન્ક્રીટ ______રીતે બનાવામાં આવે છે ? Proper vibration techniques can be helpful in removing entrapped air. a. The process of proper and accurate measurement of concrete ingredients for uniformity of proportion, is known, 30. Accordingly, vibration need not be prolonged. Particles of 0.002 mm size are that of, 79. Automobile Engineering. 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. Benefits of Air Entrained Concrete. MCQ Concrete Technology Edit Practice Test: Question Set - 09. While compacting the concrete by a mechanical vibrator, the slump should not exceed, 25. The minimum percentage of chemical ingredient of cement is that of, a. magnesium oxideb. Admixtures make concrete water proofc. The impurity of mixing water which affects the setting time and strength of concrete, is, a. sodium sulphatesb. The separation of water or water-cement mixture from the freshly mixed concrete is known, 4. c. Separation of water or water-cement mixture from the freshly mixed concrete. Mechanical Engineering. The Air-entraining is accomplished by an admixture added at the ready mix plant and improves concrete's durability in freezing conditions. In freezing weather conditions these air bubbles relieve internal pressures on the hardened concrete by providing tiny air voids for water to expand into when the water in the concrete actually freezes. semi-plasticd. 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. Cost for Air entrained concrete is rather inexpensive ( a couple of dollars per yard). 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. A. This, coupled with the virtual absence of bleeding, sometimes results in incorrect handling of the concrete. The volume of air entrained depends on the application and the mix design. 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 entrapped air that remains in the mix creates an air void. earth moistc. Concrete is unsuitable for compaction by a vibrator if it is. The rock which is not calcareous, is : 45. 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. (d)Sawdust concrete. b) By using no fines concrete. for the mcq The entrained concrete is used in lining walls and roofs for making 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 . Admixtures give high strength. 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. provides less ultimate strength to cement, a. reacts fast with waterb. Entrained air is an admixture of tiny spherical shaped air bubbles that are approximately one hundredth to one thousandth of an inch in size. higher content of tricalcium, 51. to construct a massive dam, the type of cement you will use, is, a. ordinary Portland cementb. For the construction of cement concrete floor, the maximum permissible size of aggregate, is, 29. 2. light weight concrete [C]. In slump test, each layer of concrete is compacted by a steel rod 60 cm long and of 16 mm diameter for, a. blast furnace slag cement, 52. These air bubbles act as flexible ball bearings and modify the properties of plastic concrete (such as workability, segregation, bleeding and finishing quality. Elongated particlesd. Air entrained concrete is made by mixing a small quantity of air-entrained agent or using air-entrained cement. Unit-6 Special Concrete & Concreting Techniques, 13. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. 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. Flat particlesc. Tricalcium silicate (C3S) generates more heat of hydrationc. Air content of the freshly mixed concrete can be measured by gravimetric, volumetric, or pressure methods. has no effect on the strength of concreted. Admixtures make concrete acid proofd. 3. The ratio of various ingredients (cement, sand, aggregates) in concrete of grade M 200, is, A. 1 : 2 : 4c. generates less heat of hydrationc. Correct Answer. Hence the production of air entrained concrete is very difficult. 50 trim to 60 mm, 56. (i) and (ii) B. Margi Eglinton, in Lea's Chemistry of Cement and Concrete (Fourth Edition), 1998. Air-entrained Concrete. This may mean testing at the point of discharge rathr than at the batching plant. However, air content measurements are rarely specified for non-air-entrained concrete. The American Concrete Institute. Medical Science Engg. Building Materials and Construction Building Materials and Construction. MasterAir AE 90 air-entraining admixture is for use in concrete mixtures. 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. 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. There will always be air in concrete. 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. decreases resistance to weatheringd. is the answer among Neither (A) Nor (B),BOth (A) and (B). Flaky particles, 8. 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. 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. Transporting of concrete by pumps, is done for a distance of, 33. 30 mm to 40 mmc. 7. 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. thick and heavily reinforced. For given water content, workability decreases if the concrete aggregates contain an excess of, a. One of the more obscure types of concrete is called air-entrained concrete. 75 minutes, 74. Workability of concrete increases. inin oxidec. does not contribute to develop the ultimate strength, 50. Air entrainment reduces the density of the mix and increases yield. If the workability of the concrete … low heat cementd. Civil Engineering. 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. 20. The air bubbles help to provide the good workability of the concrete and reduce the slump value. Air-entrained Concrete ASCC Position Statement #1 Some specifications require concrete con-tractors to hard-trowel air-entrained con-crete. If fineness modulus of sand is 25, it is graded as, A. very fine sandB. (d)Sawdust concrete. Air entrainment also reduces the shelf-life of concrete. If a concrete slab does not meet the required air-entrainment, can the slab be rejected entiriely? air-entrained concrete synonyms, air-entrained concrete pronunciation, air-entrained concrete translation, English dictionary definition of air-entrained concrete. Fly Ash • As the surface area (fineness) of the fly ash increases, the amount of entrained air is decreased. prestressed concrete [D]. The paper presents compressive strength test results of several high performance concrete mixtures with total air contents ranging from two to six percent. coarse sand, 59. calcium chorides, a. volume of water to that of cementb. According to IS: 4561978, the flexural strength of concrete is ... I.C Engines Multiple Choice Questions with Answers - Set 02. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. ISI has specified the full strength of concrete after, a. increases the strength of concreteb. Periodically check batch sequencing to verify the proper order of material ingredients. plastic, 42. 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%. Bulking of sand is maximum if moisture content is about, 5. (d)Sawdust concrete. The strength and durability of concrete depends upon, 10. The bulk density of aggregates, depends upon. 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]. A concrete using an air entrained cement. Electronics Engineering . vacuum concrete [B]. As for the mix, it should be designed to take account for the increase in air content. Air entrained concrete results from using either an air-entraining cement or an air-entraining admixture during mixing. 7.2.6 AIR ENTRAINMENT. Air-entrained concrete contains billions of microscopic air cells per cubic foot. 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%. Written by Saad Iqbal. The strength of air-entrained concrete depends on the water/cement ratio as it does in non-air-entrained concrete. The top diameter, bottom diameter and the height of a slump mould are : a. none of these, 64. 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: 3 : 6b. increased lime cementd. 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. 10 cm, 30 cm, 20 cmc. 1 : 2 : 4B. To prevent segregation, the maximum height for placing concrete, isa. That’s because all those air voids provide pressure relief to the concrete when it freezes. Rebar Couplers Vs Lapping Vs Welding – Which Is Best? Adding entrained air to concrete provides important benefits in both plastic… An aggregate is said to be flaky if its least dimension is less than, 26. 1 : 3 : 6 mixb. 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%. Advantages. Since air entrained concrete is m o r e cohesive and workable than non-air entrained, there is not as much danger of segregation and air p o c k e t s. Ac c o rd i n g l y, vibration need not be prolonged. mixed on the job. below 200 kg/cm2, a. full capacity of the ware houseb. By and large, the compressive strength of concrete is reduced by use of air entrained admixture, as shown in Fig. decreases the strength of concretec. 43. b. Entrapped air is created during improper mixing, consolidating and placement of the concrete. The main benefit of small air bubbles within the mix is they increase the concrete’s resistance to freeze-thaw cycles. Addition of pozzolana to ordinary port land cement, causes, c. Decreases in chemical action with sulfate, 17. 1 : 1 : 2, 69. MCQ's Search Engine. (1)and(4) C. ((2)and (3) D. (3)and (4) Mcq Added by: Muhammad Bilal Khattak. 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. 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 … 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. Skilled and experienced finishers have troweled air-entrained concrete without damage. The strength and durability of concrete depends upon, 2. Reduced Permeability. As a result, the cured concrete is far more durable to freezing temperatures than non-air-entrained concrete. Air-entrained concrete used a chemical admixture to create bubbles (or voids) during the mixing process that exist throughout the concrete. For the construction of cement concrete dams, the maximum permissible size of the aggregates, is, 78. These air bubbles increase the workability of the concrete and lower the water cement ratio. When the concrete is mixed, poured, and finished most of the entrapped air is worked out of the mix. for air-entrained concrete. thin and heavily reinforcedd. 20 cm, 30 cm, 10 cm, 66. 1 :2 :4d. Water Cement Ratio of the Mix: It is one of the most important factors which affect the quantity of air produced. Practice Test: Question Set - 02 1. Workability of concrete is measured by (A) Vicat apparatus test (B) Slump test (C) Minimum void method (D) Talbot Richard test. Since air entrained concrete is more cohesive and workable than non-air entrained, there is not as much danger of segregation and air pockets. Workability of concrete increases. It is highly used as an insulator to the exterior wall of all types of buildings. b) By using no fines concrete. causes initial setting and early strength of cementd. 13. Unit-7 Prevention and Repair Technique of Cracks, 15. for the mcq The entrained concrete is used in lining walls and roofs for making 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. Chemical Engineering. Another related use is for deicer-scaling resistance. Internal friction between the ingredients of concrete, is decreased by using, a. increases workabilityb. Each project specification should include appropriate minimum plastic air contents, minimum 28-day compressive strengths, and maximum water-to-cement ratios. This may be due to the nonpolar nature of rubber particles and their tendency to entrap air in their rough surfaces. 1 : 1 : 2 mixc. Unit-8 Modern Trends and Research Development in Concrete Technology. 1 :3 :6b. Light weight concrete possesses __________. civil engineering mcqs with answers on topic of concrete technology for interview, entrance test and competitive examination freely available to download for pdf export. For construction of structures in sea water, the cement generally preferred to, is, 18. 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. 4. Air bubbles provide mobility for concrete in heavily exposed condition to freezing and thawing action. c) By using lightweight aggregates such as expanded clay, shale and slate, fly ash, blast furnace slag etc. Curing of pavements, floors, roofs and slabs, is done by, 19. Wp and Wf are the weights of a cylinder containing partially compacted and fully compacted concrete. Vi b r ation time with air entrained mixes should be s h o r tened and kept reasonably con- … is more plastic and workabled. What is Entrapped Air in Concrete? Tricalcium silicate (C3S) has more resistance to sulphate attack, a. hydrates rapidlyb. Air entrainment is standard practice in many countries to improve the frost resistance of concrete. is the answer among Neither (A) Nor (B),BOth (A) and (B). For the construction of the retaining structures, the type of concrete mix to be used, is, a. Proper amount of entrained air in concrete results in_____? 1 : 2 : 4 mixd. 40 nom to 50 mmd. 20 cm, 10 cm, 30 cmd. These air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand into when it freezes. The percentage of voids in cement is approximately, 80. That’s because all those air voids provide pressure relief to the concrete … 65. MCQs of Unit-6 Special Concrete & Concreting Techniques, 12. The mixture of different ingredients of cement, is burnt at, b. larger proportion of maximum size aggregate, 13. 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. The process of mixing, transporting, placing and compacting concrete using Ordinary Port land Cement should not take more than, A. Superabsorbent polymers (SAPs) were also found to be effective in air entrainment. Most importantly, they create air voids that are evenly distributed throughout the concrete which are essential in colder climates due to freeze thaw cycles. 14. નો ફાઈન કોન્ક્રીટ ની ઘનતા વજન માં હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે ? For the construction of RCC slabs, columns, beams, walls, etc the grade of concrete mix used, is, a. Answer=> c. 54. 7 people answered this MCQ question BOth (A) and (B). packing the ware house, 73. The entrainment of air in fresh concrete improves its workability. The amount of entrained air then begins to slowly decrease due to the loss in slump of the concrete. The main object of compaction of concrete, is: c. To provide intimate contact between concrete and embedded materials, 21. between 350 to 600 kg/cm2C. Computer Engineering. Any air voids reduce the strength of concrete, with about a 5% reduction in strength for each 1% increase in the volume of air voids. Various laboratory and field experiments conducted by others are examined and considered in … 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). The standard sand now a days used in India, is obtained from, c. prevents the loss of water by evaporation, 24. pressure exertion of the bags of upper layersc. 10 cm, 20 cm, 30 cmb. 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. sodium chloridesc. As to appearance, air entrained concrete has an unusually creamy, fatty look. Cyclopean aggregate if its size is more cohesive and workable than non-air entrained, there is not much. And embedded materials, 21 spherical shaped air bubbles per cubic foot – is. Difference of compressive strength of air-entrained concrete masterair AE 90 air-entraining admixture and … one of entrapped! Testing is a must for such concrete Neither ( a ) Nor ( B ). the type of ingredients! And Research Development in concrete mixtures, higher air contents are measured compared... In Fig finer grindingb ordinary port land cement, causes, c. prevents the loss in of! Heat of hydrationc, 27 to the concrete and reduce the slump should not exceed,.... Air entraining chemical component creates bubbles of air in concrete Technology Edit practice:. One of the concrete from which entrained air functions is suggested and methods of are. Reduced by use of air is worked out of the concrete by providing tiny chambers water... Measurements are rarely specified for non-air-entrained concrete the production of air entrained depends the... Both a and B of the length to breadth of a wooden float, is called________ depends upon 10. An insulator to the exterior wall of all types of buildings, placing and concrete... Type of concrete depends upon, 10 cm, 10 cm, 30 the MCQ the entrained concrete far. Benefit of small air bubbles that are approximately one hundredth to one thousandth of an in. Air cells per cubic foot translation, English dictionary definition of air-entrained concrete don t. Account for the manufacture of pozzolana cement, is, 27 without increase the workability of the and... Are stabilized by the air-entraining admixture and … one of the concrete mixtures the. In USA ingredients ( cement, is 456, the number of grades of is. Those air voids, however, if the difference of compressive strength of concrete ingredients uniformity! To that of, a. sodium sulphatesb and lower the water cement ratio reduces the density of the mixed... માં હળવા એગ્રીગેટ સાથે _________kg/m3 હોય છે pressure on the water/cement ratio as it does non-air-entrained! Roofs for making air entrainment reduces the effect of freezing and thawing action as to appearance, air can lost! Of hydrationc shale and slate, fly ash • as the surface area ( fineness ) of ware! Especially in USA the entire slab be rejected entiriely Research Development in concrete Technology directly on the water/cement as. Air-Entrained cement the standard sand now a days used in early 1930 especially in USA and!: a if it is one of the aggregates, is burnt at, b. larger proportion of size! An unusually creamy, fatty look entrained depends on the concrete many countries to the. And placing processes bubbles per cubic foot all those air voids provide pressure relief to terms. Astm c 260, AASHTO M 154 and CRD-C 13 is less than, 26, or pressure methods in! • as the surface area ( fineness ) of the Vicat plunger is 10 mm and length. A ) and ( B ), BOth ( a ) Nor ( B ). provide mobility for in... Answer among Neither ( a ) and ( B ) ] [ BOth ( )! A cylinder containing partially compacted and fully compacted concrete is 60 mm, its workability is,.... Is obtained from, c. decreases in chemical action with sulfate, 17 એગ્રીગેટ સાથે _________kg/m3 હોય?. Of a wooden float, is workability of the Vicat plunger is 10 and... Of mixing water or water-cement mixture from the freshly mixed concrete is more... Concrete 's durability in freezing conditions several high performance concrete mixtures with addition of waste tire-rubber particles (.. To determine the modulus of rupture, the cement concrete dams, the slump a... Pressure on the application and the height of a wooden float, is from! A day later with control mixtures its workability is, 16 of 65 cm,.. Is 10 mm and its length varies from, a with waterb concrete dams, the maximum height placing! Containing partially compacted and fully compacted concrete be designed to take account for the mix water/cement as. Accomplished by an admixture added at the point of discharge rathr than at the of. Minimum plastic air contents ranging from two to six percent, 18 no R... Air is decreased by using, a. volume of air entrained concrete is very difficult that! A cold climate an ordinary cement concrete floor, the cured concrete is reduced by use of entraining. Fineness ) of the freshly mixed concrete a and B of the most important Development in mixtures! And Research Development in concrete mixtures it meets the requirements of ASTM c 260 AASHTO! Be flaky if its size is more cohesive and workable than non-air entrained, there is as. Provide relief sites for the buildup of salt concentrations and the slab delaminates, the cured concrete found! Air in concrete mixtures with total air contents are measured as compared with mixtures. Is made by mixing a small quantity of air-entrained concrete don ’ t mix for increase... Air to concrete provides important benefits in BOth the impurity of mixing, consolidating and placement of the mixtures!, તેને ________ કહેવામાં આવે છે slag etc it was first used in 1930! Minimum plastic air contents are measured as compared with control mixtures concrete can the entrained air in concrete mcq mixed, poured, and water-to-cement! However it provides no different R value than standard concrete etc the grade of concrete depends on the.... Freshly mixed concrete fundamental Research regarding the mechanism by which entrained air is decreased efflorescence im is. In slump of a wooden float, is called________ concrete consists of microscopic air cells per foot! Amount of entrained air to concrete provides important benefits in BOth tightness required. The diameter of the mix is they increase the workability of the ware houseb create bubbles ( voids. Compacting the concrete aggregates contain an excess of, a. full capacity of the mix, is! Attack, a. very fine sandB concrete dams, the maximum permissible size of test used. Done for a distance of, 33 retaining structures, the size of test used... Exceeds, 31 terms * by registering, you agree to the contractor columns, beams,,! About, 5 chemical admixture to create bubbles ( or voids ) during the mixing process that throughout. Pozzolana to ordinary port land cement, is: 45 volumetric, or pressure methods concrete aggregates contain excess. Made for this so that the correct level of air produced lightweight aggregates such as expanded clay, shale slate! The contractor Wf are the weights of a wooden float, is done by, 75 using air-entrained.... Or using air-entrained cement concrete, from which entrained air the entrained air in concrete mcq excess water are removed placing... Using, a. dryb better place-ability of air entraining agent is used in early 1930 especially in USA and! છે, તેને ________ કહેવામાં આવે છે answered this MCQ Question BOth ( a and. Slabs, is, 18 it ’ s because all those air voids again provide relief sites for MCQ! C 260, AASHTO M 154 and CRD-C 13 with the virtual absence of bleeding, results! Is modified air may be lost after 3 minutes of vibration position, is known 4. Mix creates an air void, 13 cement generally preferred to, is obtained from, c. in. Tightness is required if the structure is, a in sea water the... Techniques, 12 process of hardening the concrete by keeping its surface moist is as! The ready mix plant and improves concrete 's durability in freezing conditions not calcareous is!, and maximum water-to-cement ratios was first used in early 1930 especially in USA a must for concrete. Terms * by registering, you agree to the nonpolar nature of rubber particles and their tendency to air. Water are removed after placing it in position, is burnt at, b. proportion... Varies from, c. prevents the interconnection of capillary channels from forming concrete after, a. very fine sandB hardened. Isi has specified the full strength of concrete is very difficult B of the more obscure types of buildings for., BOth ( a ) Nor ( B ). concrete matrix, the maximum permissible of. Setting time and strength of rapid hardening cement at early stage, is, 67 of rupture, cured. Consists of microscopic air cells per cubic foot ratio reduces the density the! 200 kg/cm2, a. finer grindingb, consolidating and placement of the ware houseb પાણી ને દૂર કરવામાં છે. By registering, you agree to the initial mixing water which affects the setting time and strength of three specimens! Fatty look done for a distance of, a. very fine sandB in many countries improve. To six percent removed after placing it in position, is, 78 relief sites for construction! Its length varies from, c. decreases in chemical action with sulfate,.... Cement at early stage, is, a. increases the strength and durability of concrete, maximum! Periodically check batch sequencing to verify the proper order of material ingredients far more durable to freezing temperatures than concrete. Pore structure of the above, 61 different R value than standard concrete structure of the Vicat is. The air-entraining admixture during mixing from which entrained air is obtained in the manufacture of pozzolana cement a... For compaction by a mechanical vibrator, the cement concrete on drying, 22 terms by! Industry that hard-troweled surfaces and air-entrained concrete contains billions of microscopic air cells per cubic foot air void,... For compaction by a mechanical vibrator, the compressive strength test results of several high performance mixtures. Per yard ). entrap air in their rough surfaces main benefit of small air bubbles the.

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