Test 25 - Aggregate Shape, Texture and Shape Indices

Question 1 ప్రశ్న 1

Which combination correctly distinguishes particle shape from surface texture of aggregate?

A Angular and rounded describe shape, while rough and smooth describe surface texture. B Angular and rough both describe only particle size. C Rounded and smooth both mean exactly the same physical property. D Flaky describes surface texture, while rough describes particle size.

Question 2 ప్రశ్న 2

Which description most appropriately characterizes a rounded aggregate particle?

A A particle substantially shaped by attrition or water action so that sharp edges have largely been removed B A particle whose least dimension is less than 0.6 times its mean sieve size C A particle having well-defined sharp edges formed by crushing D A particle whose greatest dimension exceeds 1.8 times its mean sieve size

Question 3 ప్రశ్న 3

Compared with rounded aggregate of otherwise similar grading, angular aggregate generally has which combination of effects in concrete?

A Greater inter-particle friction and interlock, generally lower workability at the same paste content B Lower inter-particle friction and necessarily lower bond with cement paste C No influence on workability or particle interlock D Automatic conversion of coarse aggregate into fine aggregate

Question 4 ప్రశ్న 4

Which pair consists entirely of surface-texture descriptions rather than particle-shape classifications?

A Rough and smooth B Angular and rounded C Flaky and elongated D Rounded and elongated

Question 5 ప్రశ్న 5

Under IS 2386 (Part 1), a coarse aggregate particle is considered flaky when:

A Its least dimension is less than 0.6 times its mean sieve size. B Its greatest dimension is greater than 0.6 times its mean sieve size. C Its least dimension is greater than 1.8 times its mean sieve size. D Its mass is less than 60 percent of the average particle mass.

Question 6 ప్రశ్న 6

An aggregate particle belongs to a size fraction having a mean sieve size of 18 mm. Its least dimension is 10.5 mm. How is it classified under the flakiness criterion?

A Flaky, because the limiting thickness is 10.8 mm and the particle is thinner than this. B Not flaky, because the limiting thickness is 9.0 mm. C Elongated, solely because its thickness is 10.5 mm. D Rounded, because its mean sieve size exceeds its thickness.

Question 7 ప్రశ్న 7

A coarse aggregate test sample weighs 2000 g. The total mass of particles identified as flaky by the prescribed thickness gauges is 360 g. What is the flakiness index?

A 9 percent B 18 percent C 36 percent D 55.6 percent

Question 8 ప్రశ్న 8

Under IS 2386 (Part 1), an aggregate particle is considered elongated when:

A Its greatest dimension exceeds 1.8 times its mean sieve size. B Its least dimension is less than 1.8 times its mean sieve size. C Its greatest dimension is less than 0.6 times its mean sieve size. D Its surface is rougher than a standard reference particle.

Question 9 ప్రశ్న 9

A particle has a mean sieve size of 18 mm and a greatest dimension of 33 mm. What is its classification under the elongation criterion?

A Elongated, because 33 mm exceeds 1.8 × 18 mm. B Not elongated, because the limiting dimension is 36 mm. C Flaky solely because its greatest dimension is 33 mm. D Fine aggregate because it is shorter than 40 mm.

Question 10 ప్రశ్న 10

An aggregate sample weighs 1500 g, of which 270 g is classified as elongated using the applicable length gauges. What is the elongation index?

A 9 percent B 15 percent C 18 percent D 27 percent

Question 11 ప్రశ్న 11

What is the applicability limitation of the standard flakiness-index and elongation-index gauge procedures under IS 2386 (Part 1)?

A They are not applied to aggregate sizes smaller than 6.3 mm. B They apply only to material passing the 150 micrometre sieve. C They are restricted to fine aggregate below 4.75 mm. D They can be performed only on aggregate larger than 80 mm.

Question 12 ప్రశ్న 12

Which apparatus pairing is correct for the determination of aggregate shape indices?

A Thickness gauge for flakiness and length gauge for elongation B Length gauge for flakiness and Vicat plunger for elongation C Le Chatelier mould for flakiness and Blaine apparatus for elongation D Los Angeles machine for flakiness and pycnometer for elongation

Question 13 ప్రశ్న 13

How does IS 383:2016 require combined flakiness and elongation to be determined for coarse aggregate?

A Determine flakiness first, remove the flaky particles, determine elongation on the remaining portion, and add the two indices numerically. B Determine elongation first and classify every elongated particle automatically as flaky. C Determine both indices independently on two unrelated samples and multiply them. D Estimate the combined index visually without using gauges.

Question 14 ప్రశ్న 14

A 2000 g coarse aggregate sample contains 360 g of flaky particles. After removing them, the remaining 1640 g contains 328 g classified as elongated. What is the combined flakiness and elongation index according to the sequential IS 383 procedure?

A 20 percent B 28 percent C 38 percent D 44 percent

Question 15 ప్రశ్న 15

A crushed coarse aggregate has a combined flakiness and elongation index of 43 percent. What is the normal conformity assessment under IS 383:2016 if no discretionary relaxation has been granted?

A It satisfies the requirement because any value below 50 percent is acceptable. B It does not satisfy the normal 40 percent maximum. C It automatically becomes fine aggregate. D It satisfies the requirement provided its angularity number exceeds 10.

Question 16 ప్రశ్న 16

Which statement best describes the engineering meaning of angularity number under IS 2386 (Part 1)?

A It is an indirect measure of coarse-aggregate angularity based on the excess void content of a compacted single-size aggregate over that associated with ideally rounded particles. B It is the percentage of particles passing a thickness gauge. C It is the ratio of the longest particle dimension to the shortest dimension. D It is a direct measurement of aggregate surface roughness using a microscope.

Question 17 ప్రశ్న 17

A compacted single-size coarse aggregate has 42 percent voids. Using the angularity-number concept in which 33 percent voids represents ideally rounded aggregate, what is the angularity number?

A 5 B 9 C 33 D 42

Question 18 ప్రశ్న 18

In an angularity-number test, the mean mass W of aggregate filling the cylinder is 4650 g, the mass C of water required to fill the cylinder is 3000 g, and the aggregate specific gravity G is 2.50. Using Angularity Number = 67 − 100W/(CG), what is the angularity number?

A 3 B 5 C 8 D 12

Question 19 ప్రశ్న 19

If Aggregate X has a substantially higher angularity number than Aggregate Y, while grading and other properties are comparable, which interpretation is generally appropriate?

A Aggregate X is more angular, tends to produce greater inter-particle friction and may require more paste or water for equal workability. B Aggregate X is necessarily smoother and more rounded. C Aggregate X must have a smaller maximum size. D Aggregate Y must be flaky.

Question 20 ప్రశ్న 20

Why does IS 2386 (Part 1) state that the angularity-number test is unsuitable for aggregate that breaks down significantly during the prescribed compaction?

A Particle breakdown changes the grading and packing during the test, so the measured void condition no longer represents the original particle angularity reliably. B Broken aggregate automatically becomes cement. C Angularity can be determined only from aggregate colour. D The test requires aggregate to dissolve completely in water.

Question 21 ప్రశ్న 21

For otherwise similar aggregate size and grading, which surface texture generally gives the lower water or paste demand for a specified concrete workability?

A Smooth texture B Very rough texture C Highly porous texture in every case D Surface texture has no influence on workability

Question 22 ప్రశ్న 22

Which statement best describes the usual trade-off associated with a rough-textured aggregate surface?

A It can enhance mechanical bond with cement paste but generally increases surface-related paste demand and reduces workability compared with a smoother aggregate. B It always increases workability and eliminates the need for cement paste. C It necessarily reduces bond because roughness prevents paste contact. D It changes coarse aggregate into fine aggregate.

Question 23 ప్రశ్న 23

Two aggregates have the same grading and maximum size. Aggregate R is predominantly rounded and smooth, while Aggregate A is angular and rough. For a highly workable pumped concrete mixture, which statement is most appropriate?

A Aggregate R will generally favour workability and pumping, while Aggregate A may require additional paste or mixture adjustment. B Aggregate A must always require less paste because angular particles slide more easily. C Both must produce identical fresh-concrete behaviour because their grading is equal. D Aggregate R is prohibited from use in structural concrete.

Question 24 ప్రశ్న 24

A pavement concrete requires good aggregate interlock, but the available crushed aggregate contains a large proportion of flaky and elongated particles. Which engineering decision is most appropriate?

A Angular and reasonably cubical aggregate is desirable for interlock, but excessive flaky and elongated particles should still be controlled because they can impair packing and compaction. B All flaky particles should be preferred because thin particles always provide the greatest concrete strength. C Particle shape can be ignored whenever the aggregate is crushed. D Rounded aggregate and flaky aggregate are identical classifications.

Question 25 ప్రశ్న 25

Why is it incorrect to conclude that 'the more angular the aggregate, the better the concrete' without qualification?

A Increasing angularity may improve interlock, but excessive angularity can increase voids, internal friction and paste demand and reduce workability. B Angular particles can never bond with cement paste. C Only rounded aggregate can develop concrete strength. D Angularity affects only aggregate colour.

Question 26 ప్రశ్న 26

Consider the following statements about aggregate shape and texture:
1. Flakiness is based on the least particle dimension relative to mean sieve size.
2. Elongation is based on the greatest particle dimension relative to mean sieve size.
3. Angularity number is an indirect packing-based measure of angularity of coarse aggregate.
4. Surface roughness and flakiness are identical properties and are measured by the same definition.

Which statements are correct?

A 1 and 2 only B 1, 2 and 3 only C 2, 3 and 4 only D 1, 2, 3 and 4

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