Please keep at least one language enabled. || కనీసం ఒక భాషను ఎంచుకోండి.
Question 1
ప్రశ్న 1
Which combination correctly matches current Indian Standards with hardened-concrete properties?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The IS 516 series now contains separate parts for different hardened-concrete properties. IS 516 (Part 8/Sec 1):2020 covers static modulus of elasticity and Poisson's ratio in compression. IS 516 (Part 6):2020 covers drying shrinkage and moisture movement of concrete specimens. Slump is a fresh-concrete consistency property and aggregate crushing value belongs to aggregate testing. Therefore Option A correctly matches the standards.
వివరణ:
Question 2
ప్రశ్న 2
Which statement best represents the stress-strain behaviour of ordinary hardened concrete in compression?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Concrete is not an ideally linear-elastic material over its entire compressive stress range. Microcracking and the heterogeneous nature of paste, aggregate and interfaces cause increasing nonlinearity as stress rises. Consequently, a clearly defined modulus over a specified stress range is more meaningful than assuming one constant tangent modulus to failure. Standard static-modulus testing therefore uses a defined stress-strain interval. Hence Option B is correct.
వివరణ:
Question 3
ప్రశ్న 3
According to IS 456, which expression may be used to estimate the short-term static modulus of elasticity Ec of normal concrete when experimental data are unavailable?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 gives an empirical expression for estimating the short-term static modulus of elasticity. The expression is Ec = 5000 times the square root of fck, with both quantities expressed in N/mm². The equation is an estimate rather than a universal measured value for every concrete. Actual modulus is influenced strongly by aggregate stiffness and also by age, curing, mixture proportions and cement type. Therefore Option B is correct.
వివరణ:
Question 4
ప్రశ్న 4
Using the IS 456 expression Ec = 5000√fck, what is the estimated short-term modulus of elasticity of M25 concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For M25 concrete, fck equals 25 N/mm². The square root of 25 is 5. Therefore Ec = 5000 × 5 = 25000 N/mm². Since 1000 N/mm² equals 1 GPa, this corresponds to 25 GPa. Hence Option C is correct.
వివరణ:
Question 5
ప్రశ్న 5
Using Ec = 5000√fck, what is the approximate estimated modulus of elasticity of M40 concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For M40 concrete, fck is 40 N/mm². The square root of 40 is approximately 6.325. Multiplying by 5000 gives approximately 31623 N/mm². This equals approximately 31.6 GPa. Therefore Option C is correct.
వివరణ:
Question 6
ప్రశ్న 6
A laboratory-measured modulus differs noticeably from the value predicted by Ec = 5000√fck. Which explanation is most appropriate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The IS 456 equation is an approximate empirical design relationship. Concrete is a composite material, and the stiffness of its coarse aggregate has a major influence on overall elastic modulus. Curing conditions, age, cementitious system and mix proportions can also affect the measured value. Different concretes having the same compressive strength can therefore possess different elastic moduli. Hence Option B is correct.
వివరణ:
Question 7
ప్రశ్న 7
Poisson's ratio of hardened concrete in compression is fundamentally the ratio of:
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A specimen shortens longitudinally when subjected to axial compression and generally expands laterally. Poisson's ratio relates the lateral or transverse strain to the associated longitudinal strain within the relevant loading range. It is therefore a deformation property rather than a strength ratio. IS 516 (Part 8/Sec 1) provides for determination of Poisson's ratio together with static modulus in compression. Therefore Option B is correct.
వివరణ:
Question 8
ప్రశ్న 8
Which statement most accurately defines creep of hardened concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Creep is the progressive time-dependent deformation that develops when concrete remains under sustained stress. An initial elastic strain occurs when the load is first applied, and additional creep strain subsequently develops with time. Creep should not be confused with drying shrinkage, which can occur without external sustained load. It can significantly influence long-term structural deflections and stress redistribution. Therefore Option B is correct.
వివరణ:
Question 9
ప్రశ్న 9
Under the IS 456 creep provisions, as long as concrete stress does not exceed approximately one-third of its characteristic compressive strength, creep may be assumed to be:
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 recognizes that creep depends on several variables, including the magnitude of sustained stress. For stresses not exceeding approximately one-third of characteristic compressive strength, creep may be taken as proportional to stress. This assumption greatly simplifies normal structural calculations. At higher sustained stresses, nonlinear creep behaviour becomes increasingly significant and the simple proportional assumption is less appropriate. Therefore Option B is correct.
వివరణ:
Question 10
ప్రశ్న 10
What is the creep coefficient used in the IS 456 simplified approach?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The creep coefficient expresses the magnitude of long-term creep relative to the initial elastic deformation. IS 456 defines it as ultimate creep strain divided by the elastic strain at the age of loading. A coefficient of 1.6 therefore means ultimate creep strain is estimated as 1.6 times the initial elastic strain. The ultimate creep strain quoted using this definition does not include the initial elastic strain itself. Therefore Option A is correct.
వివరణ:
Question 11
ప్రశ్న 11
In the absence of experimental data, which set of creep coefficients is specified in IS 456 for concrete loaded at 7 days, 28 days and 1 year respectively?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 provides simplified creep coefficients where experimental data and detailed information are unavailable. Concrete loaded at 7 days is assigned a coefficient of 2.2. For loading at 28 days the value is 1.6, while for loading at one year it is 1.1. The decreasing values reflect the generally smaller creep susceptibility of more mature concrete at the time loading begins. Therefore Option B is correct.
వివరణ:
Question 12
ప్రశ్న 12
Concrete is first subjected to sustained load at 28 days and its immediate elastic strain is 400 microstrain. Using the IS 456 creep coefficient of 1.6, what are the estimated ultimate creep strain and total strain due to elastic plus creep deformation?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The creep coefficient is the ratio of ultimate creep strain to elastic strain. Therefore ultimate creep strain is 1.6 × 400 = 640 microstrain. The initial elastic strain remains an additional component of deformation. Total elastic-plus-creep strain is consequently 400 + 640 = 1040 microstrain. Hence Option B is correct.
వివరణ:
Question 13
ప్రశ్న 13
All other relevant conditions being comparable, which concrete would generally be expected to exhibit the larger ultimate creep relative to its initial elastic strain?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Concrete becomes progressively more mature and its internal structure develops with age. Loading a relatively young concrete therefore generally produces greater subsequent creep than applying the same type of sustained stress to older concrete. This behaviour is reflected directly in the IS 456 coefficients of 2.2 at 7 days, 1.6 at 28 days and 1.1 at one year. Actual creep is also affected by humidity, member dimensions, mixture characteristics and stress level. Therefore Option A is correct.
వివరణ:
Question 14
ప్రశ్న 14
Which statement best describes shrinkage of hardened concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Shrinkage is a reduction in concrete dimensions that does not require a sustained external mechanical load. Drying shrinkage develops as moisture is lost from hardened concrete, while other forms of shrinkage can occur because of cementitious reactions and internal moisture changes. If shrinkage is restrained, tensile stress and cracking may develop. Creep, in contrast, specifically refers to time-dependent deformation under sustained stress. Therefore Option B is correct.
వివరణ:
Question 15
ప్రశ్న 15
In the absence of test data, what approximate total shrinkage strain may be used for design according to IS 456?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 permits an approximate total shrinkage strain of 0.0003 when test data are unavailable. This value is intended as a simplified design assumption rather than a universal measured shrinkage of every concrete. Actual shrinkage depends on constituent materials, water content, ambient humidity, member size and curing history. Special structures may therefore require more detailed assessment or measured values. Hence Option B is correct.
వివరణ:
Question 16
ప్రశ్న 16
If a freely shrinking 10 m long concrete member develops a uniform shrinkage strain of 0.0003, what is the approximate unconstrained shortening?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Strain is change in length divided by original length. A length of 10 m equals 10000 mm. The shortening is therefore 0.0003 × 10000 = 3 mm. This calculation represents free shrinkage without structural restraint. If restraint exists, part of the free shortening can instead develop tensile stress and possibly cracking, so Option B is correct.
వివరణ:
Question 17
ప్రశ్న 17
Which set of factors is most relevant to the magnitude and rate of drying shrinkage in concrete?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Drying shrinkage results from moisture-related dimensional changes within the cementitious system. Environmental relative humidity and the distance through which moisture must migrate strongly influence its rate. Aggregate restrains paste shrinkage, so aggregate volume and stiffness also matter. Water content and mixture proportions influence the amount and nature of shrinkable paste. Therefore Option B identifies the relevant group of variables.
వివరణ:
Question 18
ప్రశ్న 18
Which current test-method provision is specifically intended to determine drying shrinkage and moisture movement of hardened concrete specimens?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 516 (Part 6):2020 is dedicated to determination of drying shrinkage and moisture movement of concrete samples. The method assesses dimensional change associated with changes in moisture condition. IS 1199 Part 2 covers consistency of fresh concrete rather than hardened shrinkage. IS 2386 Part 4 concerns aggregate mechanical properties and IS 4031 Part 5 concerns cement setting times. Therefore Option B is correct.
వివరణ:
Question 19
ప్రశ్న 19
A reinforced-concrete beam shows increasing deflection for several years under nearly constant sustained loading, while an unloaded companion specimen stored in the same environment shortens because of moisture loss. Which interpretation is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Creep requires sustained stress and results in additional deformation with time under that stress. The beam's continuing deflection under sustained loading therefore contains a creep component. Shrinkage can occur even in an unloaded specimen because it is associated with moisture and other volume-change mechanisms. The companion specimen's shortening is therefore shrinkage rather than creep. Hence Option B is correct.
వివరణ:
Question 20
ప్రశ్న 20
A long concrete member is strongly restrained against thermal movement. Why can a substantial temperature change be structurally important?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Concrete expands as temperature rises and contracts as temperature falls. If the member is free to move, much of this change appears simply as dimensional movement. If movement is restrained, however, thermal strain can generate internal stress. IS 456 also recognizes that the thermal expansion coefficient depends on factors including aggregate type, cement, humidity and member characteristics. Therefore Option A is correct.
వివరణ:
Question 21
ప్రశ్న 21
Why is low permeability of concrete important for durability?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Many deterioration processes require aggressive substances to penetrate into concrete. Water and oxygen are involved in reinforcement corrosion, while chlorides can destroy passivity of reinforcing steel. Carbon dioxide can cause carbonation and sulphates can attack susceptible cementitious systems. Lower transport properties therefore generally improve resistance to such exposure mechanisms. Hence Option A is correct.
వివరణ:
Question 22
ప్రశ్న 22
According to the durability principles of IS 456, which combination is most effective in producing concrete of suitably low permeability with normal-weight aggregates?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Concrete permeability is governed both by the selected constituents and by workmanship. A suitably low free water-cement ratio reduces the potential capillary pore system. Adequate binder content, proper compaction and effective curing help produce a continuous dense matrix with fewer connected defects. Poor compaction or inadequate curing can negate the advantages of an otherwise well-proportioned mixture. Therefore Option B is correct.
వివరణ:
Question 23
ప్రశ్న 23
Which current IS 516 provision includes determination of depth of water penetration into hardened concrete under pressure?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 516 (Part 2/Sec 1):2018 covers density of hardened concrete and depth of water penetration under pressure. Water penetration provides information related to the resistance of the concrete pore system to pressurized water ingress. Part 6 covers drying shrinkage and moisture movement. Part 8/Sec 1 covers elastic modulus and Poisson's ratio, while IS 1199 Part 4 concerns air content of fresh concrete. Therefore Option A is correct.
వివరణ:
Question 24
ప్రశ్న 24
What property is directly assessed by IS 516 (Part 2/Sec 3):2022?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 516 (Part 2/Sec 3):2022 deals with the oxygen permeability index of hardened concrete. Oxygen transport through concrete is relevant to characterization of its pore connectivity and durability-related quality. It is fundamentally different from fresh-concrete consistency testing or aggregate mechanical testing. The method forms part of the IS 516 family dealing with properties of hardened concrete other than strength. Therefore Option A is correct.
వివరణ:
Question 25
ప్రశ్న 25
Carbonation of reinforced concrete can be durability-significant principally because it:
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Fresh and uncarbonated concrete normally provides a highly alkaline environment that supports passivation of embedded reinforcing steel. Carbon dioxide can penetrate concrete and react with alkaline constituents, lowering the pH of the carbonated region. If the carbonation front reaches reinforcement under suitable moisture and oxygen conditions, the protective passive condition can be lost. Adequate concrete quality and cover therefore play important roles in carbonation-related durability. Hence Option B is correct.
వివరణ:
Question 26
ప్రశ్న 26
Consider the following statements about hardened-concrete properties:
1. The IS 456 expression Ec = 5000√fck is an approximate modulus estimate rather than an exact value for every concrete.
2. Creep is time-dependent deformation associated with sustained stress, whereas shrinkage can occur without sustained external load.
3. Low permeability is generally favoured by a sufficiently low free water-cement ratio, proper compaction and adequate curing.
4. Concrete durability is governed solely by its 28-day compressive strength and is independent of exposure and transport properties.
Which statements are correct?
1. The IS 456 expression Ec = 5000√fck is an approximate modulus estimate rather than an exact value for every concrete.
2. Creep is time-dependent deformation associated with sustained stress, whereas shrinkage can occur without sustained external load.
3. Low permeability is generally favoured by a sufficiently low free water-cement ratio, proper compaction and adequate curing.
4. Concrete durability is governed solely by its 28-day compressive strength and is independent of exposure and transport properties.
Which statements are correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement 1 is correct because the modulus equation is an empirical design estimate and actual stiffness also depends strongly on aggregate and other variables. Statement 2 correctly distinguishes sustained-load creep from shrinkage-related volume change. Statement 3 is consistent with IS 456 durability principles for producing suitably low-permeability concrete. Statement 4 is incorrect because durability also depends on exposure, permeability, cover, constituent quality, workmanship and curing. Therefore Statements 1, 2 and 3 are correct and Option B is the unique answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
-
Question 1 ప్రశ్న 1Answer: A. IS 516 (Part 8/Sec 1):2020 – static modulus of elasticity and Poisson's ratio; IS 516 (Part 6):2020 – drying shrinkage and moisture movement సమాధానం: A.
-
Question 2 ప్రశ్న 2Answer: B. It is generally nonlinear, particularly as stress increases, so a specified secant or chord modulus is used to characterize stiffness. సమాధానం: B.
-
Question 3 ప్రశ్న 3Answer: B. Ec = 5000√fck సమాధానం: B.
-
Question 4 ప్రశ్న 4Answer: C. 25 GPa సమాధానం: C.
-
Question 5 ప్రశ్న 5Answer: C. 31.6 GPa సమాధానం: C.
-
Question 6 ప్రశ్న 6Answer: B. Such a difference can occur because actual modulus depends strongly on aggregate elastic properties and also on age, curing, cement and mixture proportions. సమాధానం: B.
-
Question 7 ప్రశ్న 7Answer: B. Transverse strain to corresponding longitudinal strain సమాధానం: B.
-
Question 8 ప్రశ్న 8Answer: B. Time-dependent additional deformation under sustained stress సమాధానం: B.
-
Question 9 ప్రశ్న 9Answer: B. Proportional to stress సమాధానం: B.
-
Question 10 ప్రశ్న 10Answer: A. Ultimate creep strain divided by elastic strain at the age of loading సమాధానం: A.
-
Question 11 ప్రశ్న 11Answer: B. 2.2, 1.6, 1.1 సమాధానం: B.
-
Question 12 ప్రశ్న 12Answer: B. 640 microstrain creep and 1040 microstrain total సమాధానం: B.
-
Question 13 ప్రశ్న 13Answer: A. Concrete first loaded at 7 days సమాధానం: A.
-
Question 14 ప్రశ్న 14Answer: B. It is a time-dependent volume reduction that can occur without sustained external load, particularly because of moisture-related and hydration-related mechanisms. సమాధానం: B.
-
Question 15 ప్రశ్న 15Answer: B. 0.0003 సమాధానం: B.
-
Question 16 ప్రశ్న 16Answer: B. 3 mm సమాధానం: B.
-
Question 17 ప్రశ్న 17Answer: B. Moisture content, ambient relative humidity, member size, aggregate content and characteristics, and mixture proportions సమాధానం: B.
-
Question 18 ప్రశ్న 18Answer: B. IS 516 (Part 6):2020 సమాధానం: B.
-
Question 19 ప్రశ్న 19Answer: B. The loaded beam's additional sustained-load deformation involves creep, while the unloaded specimen's moisture-related shortening is shrinkage. సమాధానం: B.
-
Question 20 ప్రశ్న 20Answer: A. Because restrained thermal expansion or contraction can generate stresses and possibly cracking even without a change in mechanical load. సమాధానం: A.
-
Question 21 ప్రశ్న 21Answer: A. It helps limit the ingress or movement of water, oxygen, carbon dioxide, chlorides, sulphates and other potentially harmful substances. సమాధానం: A.
-
Question 22 ప్రశ్న 22Answer: B. Adequate cementitious content, sufficiently low free water-cement ratio, complete compaction and adequate curing సమాధానం: B.
-
Question 23 ప్రశ్న 23Answer: A. IS 516 (Part 2/Sec 1):2018 సమాధానం: A.
-
Question 24 ప్రశ్న 24Answer: A. Oxygen permeability index of hardened concrete సమాధానం: A.
-
Question 25 ప్రశ్న 25Answer: B. Can reduce the alkalinity of concrete surrounding reinforcement and thereby increase corrosion risk when carbonation reaches the steel. సమాధానం: B.
-
Question 26 ప్రశ్న 26Answer: B. 1, 2 and 3 only సమాధానం: B.