PREVIOUS YEAR SOLVED QUESTIONS PAVEMENT MATERIALS & CONSTRUCTION. Unit - 1

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1 PREVIOUS YEAR SOLVED QUESTIONS PAVEMENT MATERIALS & CONSTRUCTION Unit What are the desirable properties of Aggregates? Following are the desirable properties of aggregates

2 2. What are the various tests on aggregates & explain the crushing strength test on aggregates?

3 3. Explain the Los Angeles Test on aggregates?

4 4. Explain the Impact Test on aggregates?

5 1. What are the requirements of Bitumen? Unit 2 2. What are the tests on Bitumen? Explain the penetration test on bitumen? 3. Explain the Softening point test on bitumen?

6 4. Explain the Flash & Fire point test on Bitumen? 5. Differentiate between Bitumen & Tar? The following are the differences between bitumen and tars. The weathering properties of bitumen are superior to those of tars. Generally greater deterioration is produced in tar than in bitumen when exposed to equal weather conditions. Bitumen have a better durability and resistance to weathering than tars. Tars are more susceptible to temperature changes than bitumen. Hot weather will soften a tar surface more than a surface made with bitumen of the same viscosity, and it will become more brittle at low temperatures than bitumen. In other words tar becomes brittle in cold weather and the surface treated with tar is apt to bleed in hot weather if a little extra quantity has been used. Tar is therefore considered unsuitable for locations with wide temperature changes. Gritting or surface dressing can be delayed a little where bitumen has been used but not with tar. Surface dressings with bitumen are more prone to failure by water displacement than those made with tar. Tars generally adhere better than bitumen on wet aggregate. Tars can be brought to a spraying condition at lower temperatures than those needed for bitumen; stones need not be heated to high temperatures. Setting time for tars is more than that of bitumen and this property is useful in the production of pre-coated aggregate which can be transported to large distances or kept for some time before spreading. Tars harden much quicker than bitumen. Tars have higher specific gravity than bitumen and lower viscosity and these properties give them greater penetrating power and which are more marked during summers. Higher viscosities can generally be used with tars than with bitumen. Tars produce a less slippery surface than bitumen. Bitumen have a tendency to stay at or just near the surface resulting in a rich and fat surface. Roads built of bitumen need constant traffic to be maintained in good order; otherwise the surface will crack and reduce the life of the road. Tars make harder surfaces (but such surfaces are brittle) than bitumen and should be preferred for roads in areas where bullock carts or other hard tyred traffic predominates. Bitumen make

7 more elastic surfaces and are better suited for pneumatic traffic. Hardening of bitumen is very gradual. Tar is more suitable for dense fine grained surfaces and bitumen for more open surfaces. Volume of tar required is about 10 percent less than that of bitumen for the same type of road work. Tar is cheaper than bitumen. A primer is not generally needed with tar. Road tars do not dissolve in a petroleum distillate such as petrol, kerosene, diesel oil. As such tar carpets have proved to be good material for parking sites as it remains unaffected by spillage of oil and petrol from automobiles.

8 Unit-3 1. What are Bituminous Emulsions? Explain the preparation of Emulsions?

9 2. What are Cutbacks? Give a classification of cutbacks?

10 3. Explain the mechanism of stripping in bitumen?

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12 Unit-4 1. What are the different types of bituminous mixes? Explain the mechanical properties of bituminous mixes? The different types of bituminous mixes are as explained below Well-graded mix: - Dense mix, bituminous concrete has good proportion of all constituents and are called dense bituminous macadam, offers good compressive strength and some tensile strength Gap-graded mix: - Some large coarse aggregates are missing and has good fatigue and tensile strength. Open-graded mix: - Fine aggregate and filler are missing, it is porous and offers good friction, low strength and for high speed. Unbounded: - Binder is absent and behaves under loads as if its components were not linked together, though good interlocking exists. Very low tensile strength and needs kerb protection. Mechanical properties of bituminous mixes Stability Stability is defined as the resistance of the paving mix to deformation under traffic load. Two examples of failure are (i) shoving - a transverse rigid deformation which occurs at areas subject to severe acceleration and (ii) grooving - longitudinal ridging due to channelization of traffic. Stability depends on the inter-particle friction, primarily of the aggregates and the cohesion offered by the bitumen. Sufficient binder must be available to coat all the particles at the same time should offer enough liquid friction. However, the stability decreases when the binder content is high and when the particles are kept apart. Durability Durability is defined as the resistance of the mix against weathering and abrasive actions. Weathering causes hardening due to loss of volatiles in the bitumen. Abrasion is due to wheel loads which causes tensile strains. Typical examples of failure are (i) pot-holes, - deterioration of pavements locally and (ii) stripping, loss of binder from the aggregates and aggregates are exposed. Disintegration is minimized by high binder content since they cause the mix to be air and waterproof and the bitumen lm is more resistant to hardening. Flexibility Flexibility is a measure of the level of bending strength needed to counteract traffic load and prevent cracking of surface. Fracture is the cracks formed on the surface (hairline-cracks, alligator cracks), main reasons are shrinkage and brittleness of the binder. Shrinkage cracks are due to volume change in the binder due to aging. Brittleness is due to repeated bending of the surface due to traffic loads. Higher bitumen content will give better flexibility and less fracture.

13 Skid resistance It is the resistance of the finished pavement against skidding which depends on the surface texture and bitumen content. It is an important factor in high speed traffic. Normally an open graded coarse surface texture is desirable. Workability Workability is the ease with which the mix can be laid and compacted, and formed to the required condition and shape. This depends on the gradation of aggregates, their shape and texture, bitumen content and its type. Angular, flaky, and elongated aggregates workability. On the other hand, rounded aggregates improve workability. 2. Write a note on mix design method for dry bituminous mix?

14 3. Explain the Marshall Mix Design method for bituminous mix?

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16 Unit-5 1. List out the various equipments used in the construction of bituminous pavements? Explain each of them?

17 2. What are the different methods of soil stabilization? Explain?

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19 3. List out various equipments used in the construction of cement concrete pavements?

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21 Unit-6 1. Explain the factors affecting the Subgrade soil strength? Following are the factors affecting the strength of subgrade soil

22 2. What are the steps involved in the construction of Embankment? Following are the steps involved in the construction of Embankment

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24 3. What are the steps involved in the construction of Subgrade? Explain? Following are the steps involved in the construction of Subgrade

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26 Unit-7 1. Write a note on construction procedure for gravel roads?

27 2. Explain the construction procedure for water bound macadam?

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29 3. Write a note on specification of materials for bituminous concrete pavement?

30 4. Write a note on specification of materials for cement concrete pavement slab?

31 5. Write a note on specification of materials for bituminous macadam?

32 Unit-8 1. Explain the construction steps for cement concrete pavement slab?

33 2. With a neat sketch, explain the expansion & contraction joint in cement concrete pavements?

34 3. What are the differences between Flexible & Rigid Pavement?