Please keep at least one language enabled. || కనీసం ఒక భాషను ఎంచుకోండి.
Question 1
ప్రశ్న 1
Which combination correctly identifies the principal current Indian Standard guideline for concrete mix proportioning and the code whose durability requirements must also be checked?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262:2019 is the current Indian Standard guideline specifically dealing with concrete mix proportioning. IS 456:2000 supplies relevant requirements such as durability-related limits on water-cement ratio, minimum cement content and minimum concrete grade for exposure conditions. Mix proportioning therefore cannot be treated as a strength calculation alone. The proportions must also satisfy workability, durability and other project requirements. The other listed standards concern testing, aggregates or equipment rather than forming this principal mix-proportioning pair.
వివరణ:
Question 2
ప్రశ్న 2
In the context of IS 456, what does the characteristic compressive strength of concrete signify?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Characteristic strength is defined statistically as the strength below which not more than 5 percent of test results are expected to fall. It is therefore not the same as the arithmetic mean strength of production. Because some natural variation is inevitable, a concrete mix is proportioned for a target mean strength higher than the characteristic strength. The statistical margin helps keep the lower tail of the strength distribution within the specified acceptance objective. It is incorrect to interpret the characteristic strength as a value that every individual cube must necessarily exceed.
వివరణ:
Question 3
ప్రశ్న 3
Under IS 10262:2019, which rule is used to determine the target mean compressive strength for mix proportioning?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262:2019 requires the target mean compressive strength to be obtained from two expressions. The first is fck + 1.65S, where S is the applicable standard deviation. The second is fck + X, where X is the grade-dependent margin specified by the standard. The higher of these two values is adopted for proportioning. This prevents the design margin from becoming inadequately small merely because a low standard deviation is assumed or observed.
వివరణ:
Question 4
ప్రశ్న 4
For M25 concrete, assume S = 4.0 N/mm² and X = 5.5 N/mm² as applicable under IS 10262:2019. What target mean compressive strength should be adopted?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For M25 concrete, the characteristic strength fck is 25 N/mm². The statistical expression gives 25 + 1.65 × 4.0 = 31.60 N/mm². The grade-margin expression gives 25 + 5.5 = 30.50 N/mm². IS 10262:2019 requires the higher of the two results to be adopted. Hence the target mean compressive strength is 31.60 N/mm² and Option B is correct.
వివరణ:
Question 5
ప్రశ్న 5
For M40 concrete, the assumed standard deviation for good site control is 5.0 N/mm². If site control is classified as fair so that this assumed value is increased by 1.0 N/mm², and X = 6.5 N/mm², what target mean strength governs?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For fair site control, the assumed standard deviation becomes 5.0 + 1.0 = 6.0 N/mm². The statistical target is therefore 40 + 1.65 × 6.0 = 49.90 N/mm². The alternative grade-margin target is 40 + 6.5 = 46.50 N/mm². The higher value must govern under IS 10262:2019. Therefore 49.90 N/mm² is the required target mean strength.
వివరణ:
Question 6
ప్రశ్న 6
An established production record for M25 concrete justifies using S = 3.2 N/mm², while X = 5.5 N/mm². According to IS 10262:2019, what target mean strength should be used?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Using the established standard deviation, the statistical expression gives 25 + 1.65 × 3.2 = 30.28 N/mm². The grade-based expression gives 25 + 5.5 = 30.50 N/mm². The standard requires the higher of these two values rather than automatically selecting the statistical result. Consequently the target mean strength is 30.50 N/mm². This question illustrates the purpose of the X margin when an established standard deviation is relatively low.
వివరణ:
Question 7
ప్రశ్న 7
A preliminary free water-cement ratio of 0.48 is obtained from the strength relationship, but the applicable durability requirement limits the free water-cement ratio to 0.45. Which value should be adopted for proportioning?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The preliminary water-cement ratio selected for strength must be checked against the durability limit. IS 10262 requires the lower of the strength-based value and the durability-limiting value to be adopted. Here the strength relationship suggests 0.48, whereas durability permits no more than 0.45. The adopted ratio must therefore be 0.45. Averaging the two values would violate the durability requirement and is not an accepted mix-design procedure.
వివరణ:
Question 8
ప్రశ్న 8
For reinforced concrete made with normal-weight 20 mm nominal maximum size aggregate under severe exposure, which set of IS 456 durability requirements is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For severe exposure, IS 456 specifies 320 kg/m³ as the minimum cement content for reinforced concrete with 20 mm nominal maximum size normal-weight aggregate. The corresponding maximum free water-cement ratio is 0.45. The minimum grade of reinforced concrete for this exposure is M30. These requirements address durability and must be checked in addition to the strength-based mix calculations. The higher sets in the other options correspond to more aggressive exposure classifications rather than severe exposure.
వివరణ:
Question 9
ప్రశ్న 9
According to IS 10262:2019, what is the tabulated water content for 20 mm nominal maximum size angular coarse aggregate at 50 mm slump, before other corrections?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262:2019 gives a reference water content of 186 kg/m³ for 20 mm nominal maximum size angular coarse aggregate. The tabulated value corresponds to a slump of 50 mm and saturated-surface-dry aggregate conditions. It serves as a starting estimate for trial proportioning rather than an immutable final quantity. Corrections may be needed for aggregate shape, required slump and the use of chemical admixtures. The values 208 kg/m³ and 165 kg/m³ are the corresponding reference values for 10 mm and 40 mm aggregate respectively.
వివరణ:
Question 10
ప్రశ్న 10
For 20 mm angular coarse aggregate, the reference water content is 186 kg/m³ at 50 mm slump. Using the IS 10262 guideline of about 3 percent change for each 25 mm change in slump, what is the estimated water content for 100 mm slump before admixture correction?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Raising slump from 50 mm to 100 mm is an increase of 50 mm. At about 3 percent for every 25 mm increase, the total increase is about 6 percent. Therefore the estimated water content is 186 × 1.06 = 197.16 kg/m³. This is a preliminary estimate and may subsequently be modified through trial batches or admixture use. Option B is consequently the correct calculated value.
వివరణ:
Question 11
ప్రశ్న 11
For the same workability and 50 mm slump, IS 10262 permits the 20 mm angular-aggregate reference water content of 186 kg/m³ to be reduced by about 20 kg/m³ when rounded gravel is used. What water content does this indicate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The reference water content for 20 mm angular coarse aggregate is 186 kg/m³. For rounded gravel, the guideline permits an approximate reduction of 20 kg/m³ to obtain the same workability. The resulting estimate is therefore 186 − 20 = 166 kg/m³. Rounded particles generally have lower water demand because their shape produces less interparticle resistance than angular crushed aggregate. The value remains a trial-design estimate and should be confirmed using the actual materials.
వివరణ:
Question 12
ప్రశ్న 12
Which statement best reflects the usual water-reduction guidance in IS 10262:2019 for chemical admixtures at appropriate dosages?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262 recognizes that chemical admixtures can significantly modify the water demand for a required workability. Ordinary water-reducing admixtures usually permit a reduction of about 5 to 10 percent at appropriate dosages. Superplasticizing admixtures can commonly permit reductions of about 20 to 30 percent or more. These percentages are guidance values rather than automatic fixed corrections for every product and mixture. The actual reduction must be established with the selected admixture and confirmed through trials.
వివరణ:
Question 13
ప్రశ్న 13
A trial mix uses 180 kg/m³ of free water and an adopted water-cement ratio of 0.45, with no supplementary cementitious material included in the ratio. What cement content is indicated before durability and maximum-content checks?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For a concrete containing only cement as the cementitious binder in this calculation, water-cement ratio equals mass of free water divided by mass of cement. Rearranging gives cement content = water content ÷ water-cement ratio. Substitution gives 180 ÷ 0.45 = 400 kg/m³. This calculated content must still be checked against the applicable minimum cement content for durability and the maximum cement-content provision. Thus Option B is the correct preliminary cement content.
వివరణ:
Question 14
ప్రశ్న 14
A calculated mix requires 470 kg/m³ of cement, excluding fly ash and ground granulated blast-furnace slag. Which statement is most consistent with IS 456?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 states that cement content, excluding fly ash and ground granulated blast-furnace slag, in excess of 450 kg/m³ should not be used unless special consideration is given. A calculated value of 470 kg/m³ therefore crosses that general threshold. High cement contents can increase risks such as drying-shrinkage cracking, early thermal cracking and damage associated with alkali-silica reaction. The provision is not an absolute statement that every value above 450 kg/m³ is forbidden under all circumstances, because the code allows special consideration. Hence Option B accurately reflects the code requirement.
వివరణ:
Question 15
ప్రశ్న 15
For 20 mm nominal maximum size coarse aggregate and Zone II fine aggregate, what coarse-aggregate volume fraction of total aggregate is given by IS 10262:2019 at a water-cement ratio of 0.50?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262:2019 tabulates the coarse-aggregate fraction for a reference water-cement or water-cementitious materials ratio of 0.50. For 20 mm nominal maximum size aggregate with Zone II fine aggregate, the tabulated fraction is 0.62. This means 62 percent of the total aggregate volume is initially assigned to coarse aggregate under the reference conditions. The complementary fine-aggregate fraction is therefore 0.38 before any required adjustments. Changes in water-cement ratio, aggregate shape or placement requirements may justify modifying the reference proportion.
వివరణ:
Question 16
ప్రశ్న 16
A mix uses 20 mm aggregate and Zone II fine aggregate. Starting from a coarse-aggregate fraction of 0.62 at w/c = 0.50, what fraction results at w/c = 0.40 using the IS 10262 adjustment rule?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The water-cement ratio decreases from 0.50 to 0.40, which is a reduction of 0.10. IS 10262 increases the coarse-aggregate fraction by 0.01 for every 0.05 decrease in the ratio. A decrease of 0.10 therefore requires an increase of 0.02. The corrected fraction is 0.62 + 0.02 = 0.64. The corresponding fine-aggregate fraction before any other adjustment would be 1 − 0.64 = 0.36.
వివరణ:
Question 17
ప్రశ్న 17
For a pumpable concrete mix, suppose the otherwise corrected coarse-aggregate fraction is 0.64 and the designer adopts the full permitted 10 percent reduction in that estimated fraction. What coarse- and fine-aggregate fractions result?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262 allows the estimated coarse-aggregate content to be reduced by up to 10 percent for more workable mixes such as pumped concrete, subject to performance requirements. A full 10 percent reduction gives 0.64 × 0.90 = 0.576. Since coarse and fine aggregate fractions together make unity, the fine-aggregate fraction becomes 1 − 0.576 = 0.424. The change increases mortar content and can improve pumpability around congested reinforcement or through pipelines. It must still be confirmed that the resulting workability, water-cement ratio and strength satisfy IS 456 and the project specification.
వివరణ:
Question 18
ప్రశ్న 18
What approximate entrapped-air content is used in IS 10262:2019 for normal non-air-entrained concrete with 20 mm nominal maximum size aggregate when no reliable project-specific air data are available?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For ordinary and standard grades, IS 10262:2019 gives an approximate entrapped-air content of 1.0 percent for 20 mm nominal maximum size aggregate. The corresponding approximate values are 1.5 percent for 10 mm aggregate and 0.8 percent for 40 mm aggregate. Entrapped air occupies part of the unit volume and therefore affects the absolute-volume calculation of aggregate quantities. Where suitable site data for a similar mix are available, actual air-content values may be used as permitted by the guideline. For the stated condition, Option C is the appropriate design value.
వివరణ:
Question 19
ప్రశ్న 19
For 1 m³ of concrete, take cement = 400 kg with specific gravity 3.15, water = 180 kg, chemical admixture = 4 kg with specific gravity 1.20, and entrapped air = 1 percent by volume. Approximately what absolute volume remains for total aggregate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The cement volume is 400/(3.15 × 1000) = about 0.1270 m³. The water volume is 180/1000 = 0.1800 m³, while the admixture volume is 4/(1.20 × 1000) = about 0.0033 m³. Entrapped air occupies 0.01 m³ of the one-cubic-metre total volume. The remaining aggregate volume is therefore 1 − 0.1270 − 0.1800 − 0.0033 − 0.0100 = about 0.6797 m³. Rounded suitably, the available total aggregate volume is about 0.680 m³, so Option C is correct.
వివరణ:
Question 20
ప్రశ్న 20
A mix has 0.680 m³ of total aggregate volume after the absolute-volume calculation. If the coarse-aggregate fraction is 0.64 and the coarse aggregate has a specific gravity of 2.70, what is the coarse-aggregate mass per cubic metre, approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The coarse-aggregate absolute volume is the total aggregate volume multiplied by the coarse-aggregate fraction. Thus the coarse volume is 0.680 × 0.64 = 0.4352 m³. Mass is obtained by multiplying this volume by the specific gravity and by 1000 kg/m³. Therefore the coarse-aggregate mass is 0.4352 × 2.70 × 1000 = 1175.04 kg. The nearest listed value is 1,175 kg, making Option B correct.
వివరణ:
Question 21
ప్రశ్న 21
For reinforced concrete under moderate exposure, IS 456 Table 5 gives 300 kg/m³ as the minimum cement content for 20 mm aggregate. If 10 mm nominal maximum size aggregate is used, what minimum cement content results after the Table 6 aggregate-size adjustment?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 456 Table 5 values for minimum cement content are based on 20 mm nominal maximum size aggregate. Table 6 requires an adjustment of +40 kg/m³ when 10 mm nominal maximum size aggregate is used. Starting from 300 kg/m³ for reinforced concrete under moderate exposure gives 300 + 40 = 340 kg/m³. This adjustment concerns the durability-related minimum cement content and is distinct from the strength-based cement calculation. Consequently Option C is correct.
వివరణ:
Question 22
ప్రశ్న 22
During trial batching, Trial Mix No. 1 gives workability different from the stipulated value. What is the appropriate next step under IS 10262:2019?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Trial Mix No. 1 is used to check the calculated proportions against actual fresh-concrete behavior. Its workability is measured and the mix is also observed for segregation, bleeding and finishing properties. If workability differs from the stipulated value, water and/or admixture content is adjusted suitably. The mix proportions are then recalculated while keeping the preselected free water-cement or water-cementitious materials ratio unchanged. The recalculated mixture constitutes Trial Mix No. 2, so Option B correctly describes the prescribed logic.
వివరణ:
Question 23
ప్రశ్న 23
After Trial Mix No. 2 has achieved the required workability, how are Trial Mixes No. 3 and No. 4 normally prepared under IS 10262:2019?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
IS 10262 uses additional trial mixes to establish how strength varies around the selected water-cement or water-cementitious materials ratio. Trial Mixes No. 3 and No. 4 normally retain the water content used for Trial Mix No. 2. The free w/c or w/cm ratio is then varied by about plus and minus 10 percent of the preselected value while workability requirements are also satisfied. These trials provide useful information for finalizing a mix that meets both strength and durability requirements. Changing aggregate specific gravity or concrete grade designation is not the intended trial variable.
వివరణ:
Question 24
ప్రశ్న 24
When supplementary cementitious materials such as fly ash or GGBS are incorporated in the binder system, which statement is correct for mix proportioning?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
When supplementary cementitious materials are used, the relevant ratio is the water-cementitious materials ratio rather than blindly considering only the Portland cement mass. IS 10262 directs this ratio to be used consistently with the applicable IS 456 durability provisions or the project specification. The calculated cementitious-material content must also be checked against the required minimum content for durability. Mineral additions therefore do not eliminate durability verification or trial batching. Option B correctly reflects the interaction between binder composition and mix-proportioning requirements.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about IS 10262:2019 mix proportioning:
1. For target mean strength, the higher of fck + 1.65S and fck + X is adopted.
2. When w/c decreases below 0.50, the prescribed coarse-aggregate fraction is decreased by 0.01 for every 0.05 decrease.
3. The absolute-volume method accounts for volumes of binder, water, admixture and entrapped air before assigning the remaining volume to aggregates.
4. Trial Mixes No. 3 and No. 4 normally use the water content of Trial Mix No. 2 while varying the free w/c or w/cm ratio by about ±10 percent.
Which statements are correct?
1. For target mean strength, the higher of fck + 1.65S and fck + X is adopted.
2. When w/c decreases below 0.50, the prescribed coarse-aggregate fraction is decreased by 0.01 for every 0.05 decrease.
3. The absolute-volume method accounts for volumes of binder, water, admixture and entrapped air before assigning the remaining volume to aggregates.
4. Trial Mixes No. 3 and No. 4 normally use the water content of Trial Mix No. 2 while varying the free w/c or w/cm ratio by about ±10 percent.
Which statements are correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement 1 is correct because IS 10262:2019 adopts the higher of the statistical margin expression and the grade-based X expression. Statement 2 is incorrect because lowering the water-cement or water-cementitious materials ratio causes the coarse-aggregate fraction to be increased, not decreased, by 0.01 for each 0.05 reduction. Statement 3 is correct because the absolute-volume procedure subtracts the volumes of the non-aggregate constituents and entrapped air from one cubic metre before splitting the balance between coarse and fine aggregate. Statement 4 is also correct because Trial Mixes No. 3 and No. 4 normally retain Trial Mix No. 2 water content while varying the selected ratio by about ±10 percent. Therefore Statements 1, 3 and 4 are correct and Option B is the unique answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
-
Question 1 ప్రశ్న 1Answer: A. IS 10262:2019 together with IS 456:2000 సమాధానం: A.
-
Question 2 ప్రశ్న 2Answer: B. The strength below which not more than 5 percent of test results are expected to fall సమాధానం: B.
-
Question 3 ప్రశ్న 3Answer: C. Use the higher of fck + 1.65S and fck + X సమాధానం: C.
-
Question 4 ప్రశ్న 4Answer: B. 31.60 N/mm² సమాధానం: B.
-
Question 5 ప్రశ్న 5Answer: C. 49.90 N/mm² సమాధానం: C.
-
Question 6 ప్రశ్న 6Answer: B. 30.50 N/mm² సమాధానం: B.
-
Question 7 ప్రశ్న 7Answer: C. 0.45, because the lower limiting value governs సమాధానం: C.
-
Question 8 ప్రశ్న 8Answer: B. Minimum cement 320 kg/m³, maximum free w/c 0.45, minimum grade M30 సమాధానం: B.
-
Question 9 ప్రశ్న 9Answer: B. 186 kg/m³ సమాధానం: B.
-
Question 10 ప్రశ్న 10Answer: B. 197.16 kg/m³ సమాధానం: B.
-
Question 11 ప్రశ్న 11Answer: B. 166 kg/m³ సమాధానం: B.
-
Question 12 ప్రశ్న 12Answer: A. Water-reducing admixtures usually reduce water by 5–10 percent, while superplasticizers usually reduce it by about 20–30 percent or more సమాధానం: A.
-
Question 13 ప్రశ్న 13Answer: B. 400 kg/m³ సమాధానం: B.
-
Question 14 ప్రశ్న 14Answer: B. The value exceeds 450 kg/m³ and should not be used unless special consideration is given to the increased risks associated with high cement content సమాధానం: B.
-
Question 15 ప్రశ్న 15Answer: B. 0.62 సమాధానం: B.
-
Question 16 ప్రశ్న 16Answer: C. 0.64 సమాధానం: C.
-
Question 17 ప్రశ్న 17Answer: A. Coarse 0.576 and fine 0.424 సమాధానం: A.
-
Question 18 ప్రశ్న 18Answer: C. 1.0 percent సమాధానం: C.
-
Question 19 ప్రశ్న 19Answer: C. 0.680 m³ సమాధానం: C.
-
Question 20 ప్రశ్న 20Answer: B. 1,175 kg సమాధానం: B.
-
Question 21 ప్రశ్న 21Answer: C. 340 kg/m³ సమాధానం: C.
-
Question 22 ప్రశ్న 22Answer: B. Adjust water and/or admixture content, recalculate the mix while keeping the preselected free w/c or w/cm ratio, and treat the result as Trial Mix No. 2 సమాధానం: B.
-
Question 23 ప్రశ్న 23Answer: A. Keep the water content equal to Trial Mix No. 2 and vary the free w/c or w/cm ratio by about ±10 percent of the preselected value సమాధానం: A.
-
Question 24 ప్రశ్న 24Answer: B. The water-cementitious materials ratio should be considered as applicable, and the cementitious-material content must still be checked against relevant durability requirements సమాధానం: B.
-
Question 25 ప్రశ్న 25Answer: B. 1, 3 and 4 only సమాధానం: B.