Test 28 - Aggregate Soundness, Deleterious Materials and Durability

Question 1 ప్రశ్న 1

Which combination correctly matches the aggregate property with the relevant IS 2386 test part?

A Deleterious materials and organic impurities – Part 2; soundness – Part 5; alkali-aggregate reactivity – Part 7; petrographic examination – Part 8 B Deleterious materials – Part 5; soundness – Part 7; alkali-aggregate reactivity – Part 2; petrographic examination – Part 4 C Deleterious materials – Part 3; soundness – Part 1; alkali-aggregate reactivity – Part 5; petrographic examination – Part 6 D All four properties are determined only under IS 2386 Part 4

Question 2 ప్రశ్న 2

Which statement best distinguishes aggregate soundness from aggregate crushing strength?

A Soundness concerns resistance to weathering-related disintegration, whereas crushing value concerns resistance to gradually applied compressive loading. B Soundness and crushing value are two names for exactly the same mechanical test. C Soundness measures only aggregate specific gravity, while crushing value measures grading. D Soundness concerns cement setting time, whereas crushing value concerns concrete slump.

Question 3 ప్రశ్న 3

For concrete liable to exposure to frost, why is the aggregate soundness test particularly relevant?

A It provides an accelerated indication of the aggregate's resistance to repeated weathering and disruptive crystallization effects. B It determines the characteristic compressive strength of the finished concrete. C It directly measures the chloride content of reinforcement. D It determines the fineness modulus of cement.

Question 4 ప్రశ్న 4

Which description most appropriately summarizes the sulphate soundness test of aggregate under IS 2386 (Part 5)?

A Prepared aggregate fractions are subjected to repeated sodium sulphate or magnesium sulphate solution and drying cycles, and the resulting weighted mass loss is assessed. B Aggregate is subjected to a single static compressive load of 40 tonnes. C Aggregate is rotated with steel balls and the loss through a 1.70 mm sieve is measured. D Aggregate is immersed once in water and its specific gravity is reported as soundness.

Question 5 ప్రశ్న 5

For fine aggregate exposed to frost, what general-guide average mass-loss values does IS 383:2016 give after five soundness cycles with sodium sulphate and magnesium sulphate respectively?

A 10 percent and 15 percent B 12 percent and 18 percent C 5 percent and 10 percent D 15 percent and 25 percent

Question 6 ప్రశ్న 6

For coarse aggregate exposed to frost, what general-guide average mass-loss values does IS 383:2016 give after five soundness cycles with sodium sulphate and magnesium sulphate respectively?

A 8 percent and 12 percent B 10 percent and 15 percent C 12 percent and 18 percent D 15 percent and 20 percent

Question 7 ప్రశ్న 7

A fine aggregate for frost-exposed concrete gives an average mass loss of 8.5 percent after five sodium sulphate soundness cycles. If the project adopts the IS 383 general-guide value, what is the correct assessment?

A It satisfies the 10 percent guide value. B It fails because the maximum guide value is 5 percent. C It fails because any measurable loss is prohibited. D Soundness cannot be evaluated from mass loss.

Question 8 ప్రశ్న 8

A coarse aggregate for frost-exposed concrete gives a magnesium sulphate soundness loss of 19.2 percent after five cycles. If the project adopts the IS 383 general-guide value, which conclusion is correct?

A It complies because the guide value is 20 percent. B It does not comply with the adopted 18 percent guide value. C It automatically complies if its crushing value is below 30 percent. D Magnesium sulphate soundness is assessed by concrete slump rather than mass loss.

Question 9 ప్రశ్న 9

A soundness sample contains three aggregate fractions representing 40, 35 and 25 percent of the original grading. Their respective mass losses after the prescribed cycles are 5, 8 and 12 percent. What is the weighted average soundness loss?

A 7.0 percent B 7.8 percent C 8.3 percent D 10.0 percent

Question 10 ప్రశ్న 10

Under IS 383:2016, what is the maximum coal and lignite content specified individually for the fine- and coarse-aggregate categories listed in the deleterious-material table?

A 0.5 percent by mass B 1.0 percent by mass C 3.0 percent by mass D 5.0 percent by mass

Question 11 ప్రశ్న 11

What maximum clay-lump content is specified by IS 383:2016 for the listed fine- and coarse-aggregate categories?

A 1.0 percent by mass B 2.0 percent by mass C 3.0 percent by mass D 5.0 percent by mass

Question 12 ప్రశ్న 12

For uncrushed natural fine aggregate, what is the IS 383:2016 maximum for material finer than the 75 micrometre IS sieve?

A 1 percent B 3 percent C 10 percent D 15 percent

Question 13 ప్రశ్న 13

Which combination correctly gives the IS 383:2016 maximum material finer than 75 micrometres for crushed stone sand, mixed sand and manufactured fine aggregate respectively?

A 15 percent, 12 percent and 10 percent B 10 percent, 12 percent and 15 percent C 3 percent, 5 percent and 10 percent D 1 percent, 3 percent and 5 percent

Question 14 ప్రశ్న 14

What maximum quantity of material finer than the 75 micrometre IS sieve is specified in IS 383:2016 for the listed coarse-aggregate categories?

A 1 percent by mass B 3 percent by mass C 5 percent by mass D 10 percent by mass

Question 15 ప్రశ్న 15

Under IS 383:2016, what are the normal maximum total deleterious-material contents, excluding mica, for uncrushed coarse aggregate and crushed coarse aggregate respectively?

A 5 percent and 2 percent B 2 percent and 5 percent C 3 percent and 3 percent D 10 percent and 5 percent

Question 16 ప్రశ్న 16

Where no specific strength and durability tests have been conducted to justify a higher value, what limit does IS 383 indicate may be applied to mica in fine aggregate?

A 0.25 percent by mass B 1.0 percent by mass C 5.0 percent by mass D 10 percent by mass

Question 17 ప్రశ్న 17

In the IS 2386 (Part 2) organic-impurity colour test on fine aggregate, what does a liquid colour darker than the standard solution primarily indicate?

A The sand must always be rejected immediately without further investigation. B Potentially harmful organic matter may be present and further performance assessment may be required. C The aggregate necessarily contains excessive clay lumps. D The aggregate has automatically passed the durability requirements.

Question 18 ప్రశ్న 18

A fine aggregate fails the organic-impurity screening test. Under IS 383:2016, when may the aggregate nevertheless be accepted on the basis of mortar-strength testing?

A When its relative mortar strength at both 7 and 28 days is not less than 95 percent B When its 28-day relative strength alone exceeds 80 percent C Whenever its fineness modulus exceeds 2.5 D Whenever its water absorption is below 5 percent

Question 19 ప్రశ్న 19

A sand that failed the organic-impurity screening test gives 7-day mortar strengths of 29.2 MPa with the test sand and 30.0 MPa for the control, and 28-day strengths of 39.5 MPa and 42.0 MPa respectively. What is the correct conclusion under the 95 percent relative-strength requirement?

A It satisfies the requirement at both ages. B It fails because the 7-day relative strength is below 95 percent. C It fails because the 28-day relative strength is below 95 percent. D It automatically passes because the 28-day strength exceeds the 7-day strength.

Question 20 ప్రశ్న 20

Why can excessive clay, dust or other very fine deleterious material in aggregate adversely affect concrete?

A It can increase water demand, coat aggregate surfaces, interfere with bond and contribute to undesirable strength or durability behaviour. B It always increases aggregate strength and reduces concrete water demand. C It chemically converts aggregate into cement clinker. D It has no possible influence once cement is added.

Question 21 ప్రశ్న 21

Why are soft fragments and other weak deleterious particles undesirable even when the sound mineral aggregate itself has adequate crushing strength?

A They can break down preferentially during mixing or service and create local weak zones or poor wearing durability. B They necessarily improve abrasion resistance. C They increase the cement grade of the concrete. D They eliminate the possibility of moisture penetration.

Question 22 ప్రశ్న 22

Which combination of conditions is normally necessary for damaging alkali-aggregate reaction to develop in concrete according to IS 383?

A Sufficient internal moisture, a source of alkali and aggregate containing a reactive constituent B Dry concrete, aggregate free from reactive minerals and no alkali source C Only a high cement strength grade D Only high aggregate crushing value

Question 23 ప్రశ్న 23

For the IS 383 mortar-bar assessment using the 38°C temperature regime, which pair gives the permissible expansion limits at 90 days and 180 days respectively?

A 0.05 percent and 0.10 percent B 0.10 percent and 0.20 percent C 0.05 percent and 0.06 percent D 0.20 percent and 0.30 percent

Question 24 ప్రశ్న 24

Which statement correctly describes the IS 383 treatment of slowly reactive aggregate and the accelerated mortar-bar test?

A Slowly reactive aggregate is assessed using the 60°C regime with limits of 0.05 percent at 90 days and 0.06 percent at 180 days; in the 80°C accelerated test using 1 N NaOH, expansion greater than 0.20 percent at 16 days indicates potentially deleterious behaviour. B Slowly reactive aggregate requires no testing if its crushing value is below 30 percent. C The 60°C limits are 1 percent at 7 days and 5 percent at 28 days, and the accelerated test uses pure water. D The accelerated mortar-bar test measures only aggregate water absorption.

Question 25 ప్రశ్న 25

An aggregate source satisfies the specified crushing and impact requirements but fails an applicable soundness requirement and is also suspected of deleterious alkali reactivity. What is the most appropriate engineering conclusion?

A Accept it because mechanical strength automatically proves durability. B Do not establish acceptance from mechanical strength alone; the applicable durability, deleterious-material and alkali-reactivity requirements must also be satisfied. C Ignore the soundness result whenever the aggregate is angular. D Increase the cement content until the aggregate automatically becomes non-reactive.

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