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Soil 1

SOILS 1. Q- How will you prepare sample for proctor if there are soft particles in the sample? A- By preparing 5 individual samples having different moisture content. Discard sample

every each test. 2. Q- What is the minimum surcharge weight place in doing a C.B.R. test ? A- 10 lbs. (4.54 kg). 3. Q- How do you calculate actual surcharge weight for C.B.R ? A- By equation : W = d x v x A

Where : A = AREA OF MOLD. W = Actual surcharge weight d = Density of material, V = Thickness of Layers.

4. Q- What is the difference between a standard proctor test & a modified proctor test ? A- Aside from the compactive energy which is 5 times greater than in the standard test, the

maximum density and optimum water content obtained from the two compaction test is greater in fine-grained that for a coarse-grained soils.

5. Q- What is S.P.T. ? Describe the procedure of this test in detail. A- S.P.T. or Standard Penetration Test:

The standard split-tube sampler, 18 inches in length and 2 inches in diameter is driven into the soil, with a drive weight of 63.5 kg. At 30 inches free falling. The blow count for the first 6 inches is not used, as this is to seat the sampler below the disturbed soil in the bottom of the borehole. The number of blows to drive the final 12 inches is the penetration resistance. If it is not practical to drive the sampler the full 12 inches because of very dense, cemented hardpan, rock, etc., the boring log dense, cemented hardpan, rock, etc., the boring log will indicate the blow count and penetration as ratio i.e. 70:4 for 70 blows and 4 inches in penetration.

6. Q- Define liquid limit and plastic limit. How do you calculate plasticity index ? How many strokes are specified for rolling the thread of soil when determining plastic limit ? and How many revolution per second when determining liquid limit ?

A- Liquid limit is the % water content in which the soil mass has a capacity to flow as a liquid. It is in between the liquid and plastic state. The rate is 2 revolution per second. Plastic limit is the % water content in which the soil mass can be molded without crumbling. It is in between the plastic and semi-solid state. The rate is 80 to 90 strokes per minute.

7. Q- Could we used sand for embankment material ? A- Yes, (by plating) it is a method of covering or confining of unstable fills with a suitable,

stable material. 8. Q- Why is wadi sand preferable to wind blown sand as a construction material ? A- Because wadi sand are free from clay and other organic matters and also meet grading

requirements for fineness modulus. 9. Q- What are the test you run to determine the suitability of a sub grade material ? A- a) Sieve analysis

b) Atterberg test c) Proctor test d) C.B.R. test e) Field Density test.

10. Q- What are the basic test normally carried out to determine soil characteristics and conditions ?

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Soil 2

A- a) C.B.R. test b) Sieve analysis c) Atterberg test.

11. Q- How do you determine the shear strength of a soil ? A- By tri-Axial test: The basic principle is that a cylindrical soil specimen is first encased

in a thin rubber membrane and subjected to fluid pressure around the cylindrical surface. The lateral pressure is held constant while an axial load is applied and increased until failure occurs.

12. Q- Why and when C.B.R. value needs adjustment ? What is the rate of loading ? A- When the curve is concave upward shape because of swell, adjustment is made by

adjusting the point of origin by extending the line of stress-strain curve downward until it intersect the abscissa. Rate of loading is 0.05 inch per minute.

13. Q- How do you take a sand sample from a sand stockpile ? A- Take sample at inner middle of stockpile at random. 14. Q- How would you carry-out in-situ density test on prepared sub grade ? A- By sand cone method. 15. Q- How do you reduce the size of field samples ? A- By splitting or quartering of samples. 16. Q- How will you distinguished A-1 and A-7 soil visually ? A- A-1 materials is a well-graded gravel or sand or a mixture of sand and gravel with or

without non-plastic soil binder. Whereas, A-7 material is a clayey soil. 17. Q- What is C.B.R. ? A- C.B,R, or California Bearing Ratio : It is a ratio of a force required to penetrate a

sample to a certain depth (with a 5 cm. piston) to a force required to penetrate the sample of high quality crushed stone with the same depth and piston.

18. Q- Where will you fix the penetration gauge in C.B.R. test ? A- In a plunger, to determine the accurate relationship between the load and penetration. 19. Q- How do you classify soils ? A- Soils are classified as coarse-grained and fine-grained soils. Materials passing the 3

inches sieve and retained #4 sieve are considered coarse-grained while material passing #4 sieve and retained #200 sieve are fine-grained soils.

20. Q- What is the pressure in pneumatic rollers ? A- 80 psi. 21. Q- How much thickness is allowed for rockfill ? A- Maximum thickness Maximum unit of weight for

Of Free Layer (cm.) Vibrating (kg./unit of width,m.) 40 2,300 2,900 60 2,900 3,600 80 3,600 4,300 100 4,300 5,000 * For multi vibrating, unit of weighing shall be limited in accordance with unit of axial weight.

22. Q- What is the construction procedure for preparing natural ground to receive the

embankment layers ? A- Removal of undesirable materials such as logs, tress, stumps, weeds, heavy grass, etc.

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Soil 3

23. Q- What is the allowable tolerance of the top of sub grade layer and how it can be measured ?

A- Refer to Tolerance Table. 24. Q- What is A-3 soil ? can we used sand in subgrade and embankment ? A- A-3 soil is a fine-beach or desert blown sand without fines or with a small amount of

non-plastic silt. This kind of material cannot be used for subgrade because of the following reasons; a) Poor load sustaining qualities b) Highly permeable c) Compressible under sustained loads d) Subject to changes in strength and volume du to variation in water content, For embankment yes, by method of plating.

25. Q- If water is not available for this kind of job, what will you do ? A- Either by spraying sand stabilizer or by using vibratory roller with high frequency low

amplitude. 26. Q- How will you compact rock-fill ? A- As mentioned above (Q-21) Refer to M.O.C. circular. 27. Q- What do you understand by the material of aggregate base coarse ? A- This materials consist of clean, tough, durable, sharp angle fragments free of soft,

disintegrated or decomposed stone and free from any deleterious matter. Max. size of agg. Is 2, LL = 25 max., P.I = 6 max. (Look Q-55).

28. Q- What types of soil are well suitable for sub grade ? A- A-1-a, A-1-b, A-2-4. 29. Q- What do you mean my type A, AA, AAA in the compaction of soil ? A- Type A

: Compacted density of a soil shall be equal or greater that

90% of Maximum Density or 70% of Relative density. Type AA : Compacted density of a soil shall be equal or greater than

95% of maximum density or 74% of relative density. Type AAA : Compacted density of a soil shall be equal or greater than

100% of maximum density or 78% of relative density. 30. Q- What do you mean by relative density ? What is the formula ? A- It is the state of compactness of a soil with respect to the loosest and densest state at

which it can be placed.

% R.D. = 100xfieldr x min.)rmax.(rmax.r x min.)r field(r

31. Q- What is the maximum allowable percentage of friable particles for aggregate base coarse mix ?

A- 0.25% 32. Q- What is the proportion of natural sand to dunes sand to minimize the phenomena of

rutting ? A- The proportion of natural sand should not exceed 155 of the percentage passing a #4

sieve. The natural sand should not contain more than 50% of the dunes sand, for instance : if per the design mix, the percentage passing a #4 sieve is 50% of all the quantity of aggregates, the allowable percentage of dune sand will be 7.5%, it could also reach 1.2 of this proportion or 4%.

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33. Q- When you are establishing gradation, what is your target ? A- To meet the gradation requirements of the specification and yield a mix design to the

criteria of the design method. The gradation should be made up to the most economical proper aggregates to be found.

34. Q- What is fineness modulus and how to determine it ? A- It is a numerical number, which outlines the grain size of the material by fineness point

of view. It is determined through sieve analysis by adding total percentage retained on sieve , 3/8, #4, #8, #16, #30, #50, #100 and dividing the sum by 100. F.M. = 3.58 is coarser than F.M = 1.63 Limit (2.3 3.1)

35. Q- In sand equivalent why the heavy particles goes down, what is the reason ? A- Those particles whose specific gravity is heavier than water will go down and those

particles whose specific gravity is lighter than water will be in the upper portion due to sedimentation process.

36. Q- What is uniformity coefficient and effective grain size ? A- Uniformity Coefficient, is the ratio of the diameter corresponding to percent finer (P =

60%) and the effective grain size. Effective Grain size, is the diameter of particles corresponding to percent finer ( P = 10%) on the grain size curve.

U.C = 10%atSieve60%atSieve

37. Q- What are the factors affecting density of soil ? A- a) Relative volume of solid and void spaces : The greater the volume of solids or the

less the volume of voids, the greater is the density. b) Specific gravity of soil particles : The greater the specific gravity of solids, the

greater is the density, all other factors being equal. c) Amount of water is void spaces: This factor affect only the wet density. It is obvious

that the amount of water the greater is the wet density. 38. Q- What is permeability and its significance ? A- Is that hydraulic property of a soil which indicates the case with which water will flow

through the soil mass. It is significant on numerous engineering problems such as seepage through dams and irrigation canals, lowering the water table to improve stability of foundations, selecting capacity of pumps for lowering the ground-water level during excavations, and settlement of structures resting on compressible soils.

39. Q- What is a shrinkage limit ? A- A- highest water content at which a soil mass attained a minimum volume but continue

to loose weight. 40. Q- What is consolidation in soil ? A- It is the escape of water and a gradual transfer of stress from the water to solid in a soil

mass. * It is not synonymous with compaction which is artificial compression of a soil by re-

arrangement of its particles aided by lubricating effect of water. 41. Q- What is a proctor test ? A- It is the determination of the amount of mixing water that a soil mass can be compacted

to higher density.

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42. Q- What is scalping ? A- It is the removal of deleterious fines. 43. Q- What is the significance of C.B.R. test ? A- It is useful in evaluating subgrade soils and sub-base & base coarses material containing

a small amount of material retained on 3/4" sieve. * The higher the C.B.R. value, the greater the bearing capacity of the soil and thereby lesser the thickness of the pavement.

44. Q- How many trucks we can allow for grizzly ? A- Only One (1) truck. 45. Q- What are the type of test to determine the strength of subgrade? A- 1. In in-situ:

a) Loading test b) Plate bearing test.

2. In laboratory: a) California Bearing Ratio (C.B.R) b) Tri-axial test c) Hveem Stabilometer test

3. Estimation based on classification of soil. 46. Q- What do you mean by group index and how to it is determine? A- It is an emperical value used to evaluate the kind/type of soil to be use for subgrade

material. It could be determine by equation: G.I. = (F-35) (0.2 0.005 (LL-40)) 0.001 (F-15) (PI 10)

Where : G.I. Group Index F - % passing 0.074mm (#200) sieve. LL Liquid Limit PI Plasticity Index.

47. Q- What are the engineering properties of soils ?

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A- 1. Granular Soils: a) Good load bearing qualities b) Permeable c) Comparatively incompressible when subjected to static loads. d) Not subject to changes in strength or volume due to vibration and water

content, However loose granular materials will undergo considerable reaction in volume when subjected to vibratory loads.

2. Fine-Grain Soils: a) Poor load sustaining quality b) Highly impermeable c) Compressible under sustained loads d) Subject to changes in strength and in volume due to variation in water content.

3. Organic Soils Inferior than fine-grained soils with respect to the properties stated under the latter group.

48. Q- What are the 2 methods for sampling ? A- 1. Disturbed sampling

2. Undisturbed sampling. 49. Q- What is Soil Stabilization ? A- It is the process which improve the properties of materials by additives to improve

strength, plasticity, workability and shrinkage. 50. Q- What do you know about Lime Stabilization ? A- Lime stabilization is the most economic and effective with clay soils, where pH = 12.30

added to soil by about 3% to 7% by weight of dry material. 51. Q- What do you know about compaction of sand ? A- Compaction is performed on sand in cases of;

1. Water content are between dry and saturated state. 2. Completely watered (saturated) 3. Completely dry (Unsaturated) * Compaction in completely dry state give the highest dry density and layer thickness

can be increase by using of dry compaction. Compaction should be made by roller vibratory with Low Amplitude and High

Frequency. 52. Q- What is the relation between modified and standard proctor ? A- The standard and modified proctor test give result nearly closed together for granular

soil, but for plastic clay soil modified gives higher results than standard. 53. Q- What is the energy for compacted test ? A- Energy is equal to the number of layer multiplied by the number of blows, Weight of

Hammer and height divided by the volume of the mold. 54. Q- What are the causes of sub-surface soil ? A- 1. Jaw Hammer

2. Fan Hammer 3. Conical Hammer.

55. Q- Describe the Aggregate Base Course material.

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A- Materials: (Crushed Stone or Crushed Gravel) 1. Hard 2. Durable 3. Free from dirt 4. Shall obtain not more than 85 of flat elongated, soft, disintegrated pieces. 5. 90% by weight of particles with at least two fractured faces and 100% by weight

of particles at least one fractured face. 6. Minimum Abrasion loss is 45%.

7. Soundness loss by sodium sulphate not more than 12% subjected to 5 cycles. 8. Liquid Limit not more than 25 and Plasticity Index not more than 6 for material

passing sieve #40. 9. The amount of material passing sieve #200 not more than one half of the material

passing sieve no. 40. 10. The maximum size of aggregate not more than 2/3 of the thickness of the layer. Plant Mix: 1. Central proportioning and mixing plant. 2. Traveling plant. Placing, Spreading and Compaction: 1. The base aggregate shall be spread by spreader boxes. 2. The layer should not be less than 7 cm. Nor more than 15 cm. Of compacted

thickness. 3. The aggregate shall not be spread more than 2,000 sq.m. in advance of the rolling. 4. After the course has been completely compacted the surface shall be tested for

smoothness and accuracy of grade and crown. 5. The finished surface shall not vary more than 9 mm from a 5 m straightedge when

applied to the surface parallel with and at right angles to the centerline. Thickness: 1. Thickness shall represent not more than 300 m2 getting by cores. 2. When the difference is more than 12 mm, the contractor shall correct such areas

by scarifying, adding base mixture, rolling, reshaping and finishing. 56. Q- Did we can use A6, A7 in embankment ? If yes, How. If No, Why ? A- Yes, we can use A6, A7 in embankment after stabilization by lime and run the tests

required to know the actual required classification. 57. Q- In Sabkh area did we can use rock fill? And if rock fill not available what type of soil

we use ? A- Yes, we can use rock fill or soil type A-1a, A-1b, A-2-4 for the first 1.5 m from the

natural ground. 58. Q- What is the min required No of Passes for rollers in rock fill. A- Min. 5 times. 59. Q- What is the purpose of compaction?

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A- ase the shear strength of soil. ase permeability and water absorption. ase settlement of embankment under repeated loads.

60. Q- What are the factors affect degree of compaction? A- - Optimum moisture content.

- Type of soil. - Compacted effort.

61. Q- State five reasons behind compaction of soil? A- Five reasons behind compaction of soil are:

a) Decrease settlement b) Increase resistance to shear stresses and erosion. c) Decrease swelling and shrinkage of soil when exposed to water. d) Increase soil resistance against seepage of water and absorption of water by

capillarity rise. e) Increase density of soil.

62. Q- State four factors affecting density of soil? A- The factors affecting density of soil are:

a) Water content b) Rate of compaction c) Rate of compaction d) Granular size.

63. Q- Can pure clay be used as an embankment material? If not, why not? If yes, under what conditions?

A- Clay soils are poor soils having higher plasticity index 11 minimum. Shrinkage is likely to take place in such soils. Materials which expands and contracts a great deal such as clay offers an undesirable base for supporting surfaces.

Soils may be fully compacted, but as water penetrates, the materials expand and as the water evaporates, the materials contract, attain the flexibility and damage to the surface area. This is extremely critical on rigid surfaces such as concrete highways or buildings. Such clayey soils are compacted at their OMC which happens to be higher than shrinkage limit. So clayey soils should be avoided to use in the embankment. If any better material is not available than clayey soils can be used provided it is compacted with sheep foot roller. The typical sheep foot roller can be self-propelled or towed, and compacts with a kneading action on the soil. These units generally range in weight from 2 tons to 20 tons and vary in coverage width normally between 30 and 100 inches. The feet or pads can be of various shapes and are normally less than 10 inches in length. The sheep foot compactor is operated on the theory that the feet will compact the lower layers of the soil first and work towards the surface in successive passes.

64. Q- If you find loss material on top of sub grade about 1 cm, what your action? A- Clean the surface by approved equipments. 65. Q- When you stop the contractor? A- 1) If he did not correct unsafe condition for workmen or general public.

2) For failure to carry out provisions of the contract. 3) For failure to carry out orders and directives. 4) Due to unsuitable weathers.

66. Q- How to know during compaction of the materials if the water is more or less by eyes, and by hands?

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A- 1) Rollers will make shoving in layer. 2) Tires trucks will make holls in layer. Sheep roller in case of clay will pick up the materials from layer. By hands: We take mass of soil and press in hand. 1) If water goes out indicate more water. 2) If it is plastic mass indicate proper water. 3) If it is loss in hand indicate less water.

67. Q- What is the R Relative Plasticity Index of soil? A- R = P.I

PLWc or (Liquidity Index). To know degree of softening of soil and consistency. Max R = 1 at liquid limit If near to zero this mean stiff soil. R = Zero at plastic limit. R = (-) solid or semisolid state.

68. Q- If you have different materials ready to use in embankment. How to use it? A- When we have materials such as clay, chalk or sand shall be spread in alternate layers

over the full width of embankment. 69. Q- What is the meaning of reinforcement layer and what are its uses ? A- It is a layer between compacted sand or compacted Rock fill provided every 10 m

height approx. To decrease settlement of layers. 70. Q- What are the advantages of plating? A- 1- Confining A-3 material.

2- Protect A-3 against erosion and scouring. 71. Q- How we can say soil is non plastic? A- 1- When liquid limit can not be determined.

2- When plastic limit is higher than liquid limit. 3- When a soil can not be rolled into threads.

72. Q- What is the time elapse bet. Two embankment layers to get proper compaction? A- Not more than 3 days prior to the application of subsequent layers or prime coat, should

be retested. 73. Q- Define those terms: compression, consolidation, shrinkage, compaction, rebound,

expansion, swelling, loosening or scarifying. A- Compression:

The loss in external volume under sustained load. Consolidation: The loss in volume with time.

Shrinkage: The loss in volume resulting from capillary stresses during drying soil.

Compaction: The loss in volume due to artificial temporary loads as rolling, tamping, vibration.

Rebound: The increase in volume due to remove sustained load. Expansion: The increase in volume with time. Swelling: The increase in volume resulting from increasing of water content. Loosening or scarifying: The increase in volume due to artificial operations.

74. Q- What are the ideal soils for road?

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A- should be dense, free from excessive moisture, high in internal friction and cohesion and possess low compressibility and capillarity.

75. Q- What are the types of soil stabilization? A- Mechanical stabilization.

Soil cements stabilization. Lime stabilization. Chemical stabilization.

Asphalt 1

ASPHALT 1. Q- What is the temperature of water in getting specific gravity of asphalt? A- 25*C 1'C 2. Q- How will you get the specific gravity of molded specimen if voids are present in the

sample ? A- Coat the specimen with paraffin by chilling the specimen in a refrigerating unit to a

temperature of approximately 4.5 'C for 30 minutes and then dipping the specimen in warm paraffin (5.5'C above melting point).

3. Q- What is the rate of application of MC-1 & RC-2 ? A- 0.65 lit./sq.m to 1.75 lit./ sq.m. for NC-1

0.10 lit./sq.m to 0.20 lit./sq.m. for RC-2. 4. Q- What is the method normally used for preparing asphalt mix design ? Describe the

essential steps and procedures. A- Marshall method; The essential steps are;

1. Selection of quality of aggregates. Important properties to be considered are shape, surface texture & wetting

characteristics of aggregate particles. 2. Selection of aggregate gradation. Important properties are workability of mix, surface texture of pavement & over-

all economy. 3. Selection of type & grade of bituminous binders. Important properties are

workability, climatic conditions, aging considerations & gradation of aggregate. 4. Determination of correct amount of bituminous binders. Procedures: 1. Preliminary calculation

a) Calculate surface area of aggregates. b) Calculate percent emulsion.

2. Determine optimum asphalt content by immersion compression stability test. a) Prepare trial mix specimen at different emulsified asphalt content at 1%

increments using the specified compaction method. b) Calculate theoretical maximum density (D) of each specimen from equation,

D, g/cc =

(asp)S.G.asp.%

(agg.)S.G.agg.%

100

c) Determine actual density (d) of each compacted specimen and determine dry stability by unconfined compression test.

d) Calculate percent air voids in total mix from equation,

% V = DdD x 100

e) Determine wet stability to evaluate resistance to water action on duplicate specimens after immersion in water for 4 days. Losing strength is considered measure of water action.

5. Q- How would you adjust the mix if air void and stability is low ? A- Either by increase little asphalt content or by increasing the amount of aggregate

particles. *Air void is kept above 4 to allow film thickness of asphalt to the aggregate particle

Asphalt 2

which give durable and stable asphalt mix. 6. Q- How would you classify cutback asphalt and their respective spraying temperature ? A- a) Slow curing cutback (S.C) - - - - - - 10'C 130'C

b) Medium curing (M.C) - - - - - - 50'C 80'C c) Rapid curing (R.C) - - - - - - 65'C 95'C

7. Q- What are the tests you should run on a compacted asphalt pavement ? A- a) Density & Thickness test

b) Riding quality. 8- Q- What is rutting and its causes ? A- It is the channel-like grooves that occur in the wheel track of a pavement. The main

causes are; a) Poor compaction b) Fine-graded mix c) Excessive asphalt content, Low air voids. d) High temperature e) Excessive wheel and traffic loads f) Natural aggregates g) Dune sand more than 7.5% of fine aggregates h) Low softening point.

9. Q- On the mixing plant, How can you say the hot mix is okey or not okey ? A- a) Required temp. should be uniform

b) Mix should be free from excessive fines c) Mix should be free from free asphalt d) Larger aggregates should not be uncoated e) Appearance should be uniform f) Should not be burned g) Should not be too brown or gray h) Should not be too fat i) Should not steam in truck.

10. Q- When do you put the flow meter to determine the flow of an asphalt mix ? A- Before Marshall testing start. 11. Q- How many blows will you apply on each face of asphalt specimen ? A- *75 blows for heavy loads (Use by M.O.C. in all type of traffic.

50 blows for medium loads 35 blows for light loads.

12. Q- What are the requirements for bituminous coarses in respect of the following; a) Voids in mineral aggregates b) Percent air voids c) Marshall stability d) Hveem stability e) Marshall flow

A- Limits Wearing course Base course

Asphalt 3

a) V.M.A. b) Percent air voids c) Marshall stability (min.) d) Hveem stability (min.) e) Marshall flow (mm)

15 4 7 1000 40

2 3.5

13 5 8 1000 40

2 3.5 13. Q- What is the Marshall mixing and compacting temp. of hot mix? A- Mixing temp. 160'C 5'C

Compacting temp. 145'C 5'C. 14. Q- Where will you get asphalt sample during production and paving operation ? A- During production, samples should be taken from that him, One sample consisting of

four soil samples taken in a small sample units to form a composite sample. During paving, samples should be taken behind the paver, sample units taken from different locations constituting of minimum of four sub-samples to make one composite asphalt samples for grading, Marshall and extraction. * M.O.C. circular 513, section 1.4.3.

15. Q- What is MC-1 and RC-2 ? A- MC-1 or Medium curing cutback is a liquid bituminous material having kerosene as a

solvent. Its purpose is to stabilized and waterproof the absorbent surface and to promote adhesion to the bituminous course to follow. RC-2 or Rapid curing cutback is a liquid bituminous material having gasoline or naphtha as a solvent. Its purpose is to provide bond with a super imposed course.

16. Q- What is raveling and its causes ? A- It is a progressive loosening or separation of aggregate particles in a pavement surface

coarse from the surface downward or from the edge inward. The causes are; a) Lack of compaction b) Construction in thin lift during cold weather c) Dirty or disintegrated aggregates d) Too little asphalt in the mix e) Overheating of asphalt mix f) Mix is very close to coarse g) Action of water h) Sensitive aggregate refuse coating due to special charge (anti-stripping materials must be used)

17. Q- What is softening point and its use ? A- It is an indicative measurement of temperature at which the harden asphalt reach an

arbitrary degree of softening. This is useful in the classification of certain asphalts (bitumens) and tars.

18. Q- What is stripping test and its purpose ? A- It is a test to estimate the coated area as above 95% or below 95% by static-immersion

in water. Its purpose is to determine the retention of a bituminous film on an aggregate surface in the presence of water.

19. Q- What is the reason for some spots appear after every 20 meter behind the paver ?

Asphalt 4

A- a) Dirty lumps of old asphalt from the paver b) Temperature of the mix is low c) Auger is not distributing the mix properly d) Paver operator is folding the hopper sides after each load e) Screed is tilted or uneven f) Screed is not vibrating properly g) Screed is not heated properly h) Stopping of continuity.

20. Q- What is the maximum aggregate size for B.B.C. & B.W.C. ? A- 1 inch, inch. 21. Q- What is the rang eof temperature for bituminous mixture delivered to the paver at site ? A- 140'C 150'C. 22. Q- What is the pressure at the nozzles of the bitumen distributor is equal to ? A- 2.00 3.50 kg/sq.m. 23. Q- What is the maximum variation allowed for asphalt content ? A- 0.30%. 24. Q- What is the minimum capacity of power unit and pump distribution system of a bitumen

distributor ? A- 950 liters/minute. 25. Q- What is the minimum capacity of asphalt distributor ? A- 4,000 liters. 26. Q- What is the max. loss of Marshall stability allowed for asphalt? A- 25% 27. Q- What is the min. temp. required for applying prime coat ? A- 15'C 28. Q- What is the max. plasticity index for combined mineral aggregated of B.B.C. and

B.W.C. ? A- B.B.C. = 6 & B.W.C. = 4 29. Q- How do mineral filler improve properties of mix ? A- When voids is high but stability is satisfactory in the mix, it leads to higher permeability

resulting in premature hardening of the asphalt. To reduced voids, filler is increased which improves the properties of the mix.

30. Q- What will happen if we over-used the filler ? A- Over-used of filler may bring the voids low in the mix, consequently instability or

flushing after the pavement is exposed to traffic. 31. Q- During paving operation if there is much fine particles, what will happen ? A- Excessive fines can cause a mix to have a lean, brown, dull appearance like a mix too

little asphalt. 32. Q- If soundness is higher, stability is equal to 1000 kg. Exactly, would you let the

contractor to proceed ? A- A higher soundness not allowed but it does not help in the longer stability and

durability of the pavement in general. So, it is better to adjust the mix to achieved higher stability than just to trust on soundness of aggregate alone. The contractor should be instructed accordingly.

33. Q- What factors affecting the compaction of asphalt mix ? A- a) Mix properties:

Asphalt 5

1. Aggregate, If maximum aggregate size or percentage of coarse agg. in the mix increases, the workability decreases and greater compactive effort is required to achieve the target density. Natural sand often turns the mixes tender which are easily over-stressed by heavy rollers and too much rolling. Combination of filler and asphalt produces necessary cohesion when the mix cools. But too many fines will make the mix gummy and very difficult to compact.

2. Asphalt, Proper compaction can be achieved only when asphalt is still fluid enough. Consequently, compaction of the mix is extremely difficult once the mix has cooled to 85'C. Grade of asphalt is also important. Higher viscosity asphalt in the mix requires higher compaction, temperature and/or greater compactive effort. If quantity of asphalt in mix increases, film thickness of asphalt on aggregate also increases, which make the mix workable and easy in compaction and vice versa.

3. Mix temp., Up to a certain point, the hotter the mix, the more fluid the asphalt and less resistant to compaction and vice versa if it cools.

b) Environmental conditions: Ambient temperature, humidity, wind and the temp. of the surface under the mix also affects the compaction. c) Layer (lift) thickness: Generally, it is easier to achieved target density in thicker layers of asphalt concrete than in thinner ones, because of the difference in rate of cooling.

34. Q- What produces a workable mix and non-workable mix ? Do you have to adjust bitumen content or agg. ?

A- Basic causes of workability are; 1. Larger maximum sizes of particle 2. Excessive coarse aggregate 3. Too low a mix temperature 4. Too much medium-sized sand 5. Low mineral filler content 6. High mineral filler content So, instead of adjusting bitumen content, the aggregate should be adjusted.

35. Q- What do you check, when you go to the mixing plant ? A- a) Inspection of truck beds

b) Mixing of aggregate is enough-mixing time c) Weighing of ingredients i.e., aggregate, filler & bitumen d) Temperature of the mixture is uniform e) Appearance of mix f) Rate of mixing should coordinate with paving requirements.

36. Q- During production of aggregate what do you look for the stockpiled materials ? A- a) Do aggregate meet quality specifications

b) Are proper sizes being produced c) Satisfactory storage d) Separation of stockpiles e) No segregation allowed f) Mineral filler kept dry g) No deleterious materials to acceptable limits

37. Q- As asphalt inspector, what important properties you are looking for and what is your target on site ?

Asphalt 6

A- a) Asphalt content should check job-mix formula b) Aggregate gradation should check job-mix formula c) Required temperature should be uniform d) Mix should be free from excessive fines e) " " " " " free asphalt f) " " not be burned g) " " not be too brown or gray h) " " not be too fat i) " " not steam in truck j) " " smoke on discharge from hopper k) Larger agg should not be uncoated, etc.

38. Q- What do you watch during pavement ? A- a) Temperature of the paving mixtures

b) Appearance of the paving mixtures c) Alignment and thickness of the pavement d) Rolling at correct time and temperature e) Sufficient rolling f) Surface irregularities and its repairs g) Quantity paved during the day h) Stations/Locations paved in each shift i) Coordination with the mixing plant to maintain the rate of mixing and rate of paving j) Weather conditions of the day, etc.

39. Q- What is Marshall stability tests ? A- It is the method that covers the measurement of the resistance to plastic flow of

cylindrical specimens of bituminous paving mixtures loaded on the lateral surface by means of Marshall apparatus. The method outlines are as follows; a) Bulk specific gravity determination b) Stability and flow test c) Density and voids analysis d) Loss of stability

40. Q- What is the rate of loading of test machine in the Marshall stability test ? A- 2 inches (51 mm) per minute 41. Q- What are the test involved for liquid asphalt ? A- a) Penetration

b) Viscosity c) Flashpoint d) Thin-film oven test e) Rolling thin-film oven test f) Ductility g) Solubility h) Specific gravity, etc.

42. Q- If asphalt sample in laboratory is cooled then reheated for 2 or 3 times (for a breakdown in equipment), what will heating do to the sample ?

A- Re-heating of asphalt sample in laboratory is not permissible because by this process the asphalt looses its viscous properties which will not yield the stability, voids in the mix, and flow etc., and aside re-heated samples will no longer be a representative of the in-situ pavement.

43. Q- Why not to use high penetration asphalt say 100 120, Do air voids affected ?

Asphalt 7

A- Harder asphalt cements are recommended for heavy duty pavements and for hot weather construction. Generally asphalt of penetration grade 60 70 is used in medium to heavy types of pavements. Higher penetration grade like 100 120 will not produce a thick film of coating around the particles. This will turn the mix instable, indurable and low in voids. This will filled the air voids more comparatively, making the mix more brittle and easily disintegrated when exposed to traffic.

44. Q- If stability is low say 400 which is less than the specification, what is the problem ? A- Stability of asphalt pavement is its ability to resist shoving and rutting under loads

(traffic). Stability depends on internal friction and cohesion. Inter-practical friction is related to shape and surface texture of the aggregate. Following are the possible causes and their effects for the instability of pavement:

Causes Effects 1. Excessive asphalt in mix. Wash hoarding, rutting and flushing or

bleeding. 2. Excessive medium size sand in mixture. Tenderness during rolling and for period

after construction, difficult in compaction. 3. Rounded aggregate, little or no crushed

surfaces. Rutting and channeling.

45. Q- What is the maximum variation in specific gravity of marshall mold ? A- 0.02. 46. Q- What are the type of asphalt mix ? A- a) Dense graded type : Aggregate is well-graded from coarse to fine, and

contains an appreciable amount of material passing #200 sieve.

b) Open graded type : Have a poor grading or it may differ from the dense graded only in the amount of material passing #200 sieve.

47. Q- How to improve filler ? A- By adding certain amount of :

a) Portland Cement b) Crusher powder c) Caolina clay d) Earth fillers e) Asbestos powder f) Limestone powder.

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48. Q- How to determine the mixing time of asphalt ? A- Mixing time in second = second/kilosinoutputPugmill

kilosincapacitydeadPugmill 49. Q- How to determine the maximum theoretical specific gravity without using rice method ? A- By equation:

Gmm = abbsb VVV

W

Where: W- Weight of compacted mix (grans) Vsb Vol. Of agg. (by bulk sp. gr., g/cc) Vb Volume of bitumen, cc. Vab Volume of absorbed bitumen, cc.

50. Q- What is the formula in determining Percent Index of Retained Strength ? A- % (IRS) = 100xstabilityDry

stabilityWet (loss of stability) % IRS - - - - - - 70% minimum.

51. Q- What is the Job-mix formula ? A- a) Definite grading of aggregate

b) Definite percentage of asphalt c) Delivery temperature

52. Q- What do you mean by effective asphalt content ? A- It is the asphalt content that serve as a binder. 53. Q- What do you mean by Voids of Mineral Aggregate (VNA) ? A- It is an intergranular space between the mineral aggregate particles. 54. Q- Did asphalt affect by acids, alkalis, and salts ? A- No 55. Q- Why was that material called a thermoplastic material ? A- Because it softens as it is heated and hardens as it is cooled. 56. Q- Tell us about the difference of the following materials;

a) Cutting back asphalt b) Cutback asphalt

c) Emulsified asphalt d) Emulsion breaks or sets e) Liquid asphalt

A- a) Dissolving the asphalt in selected petroleum solvents. b) The diluted asphalt. c) By emulsifying the asphalt with water. d) When the asphalt and water separate. e) Combination of cutback asphalt and emulsified asphalt.

57. Q- What is the percentage of aggregate in asphalt mix ? A- Normally from 90% to 95%. 58. Q- How to classify crude oil ?

Asphalt 9

A- 1. Asphaltic base crude 2. Paraffin base crude 3. Mixed base crude

59. Q- What is the desired properties of asphalt cement ? A- 1. Consistency: Is the term used to describe the degree of plasticity of asphalt

at any particular temperature specified and measured by penetration test or a viscosity test.

2. Purity: Refined asphalts are almost pure bitumen and are usually more than 99.5% soluble in carbon disulfide (Solubility test).

3. Safety: Asphalt not foam at temperature up to 175'C and flash point of asphalt should be known.

60. Q- Why you added filler to mix ? A- a) To improve resistance to weathering.

b) To improve strength. c) To increase stability. d) To close the space between coarse and fine aggregate, etc.

61. Q- What are the test for asphalt and its definition ? A- 1) Penetration - Measures the distance that a standard needle will penetrate a

sample at a specified temperature and at a given time. Standard Needle - - - 100 grams

Specified temp. - - - 25'C Time - - - - - - - - - - - 5 seconds

2) Viscosity: a) Saybolt Furol - Number of seconds required for 60 cc of liquid

asphalt to flow thru an orifice of standard size (0.124 cm) at a specified temperature.

NC 30 - - - - - 25'C 70 - - - - - 50'C 250 - - - - - 60'C E.A - - - - - - 25'C Viscosity - - - 60 seconds

b) Kinematic Kinematic =

Time measured for a fixed volume of the liquid to flow through a calibrated capillary glass viscometer under accurately reproducible head at a controlled temperature (60'C). Approx. time (Sec.) x Viscometer Calibration.

3) Ductility - Ability of the asphalt to stretch before breaking. Distance (cm.) that a standard briquette of asphalt cement will stretch before breaking.

4) Flash point - Indicates the temperature at which the asphalt can be heated without the danger of spontaneous flask in the presence of an open flame.

5) Loss on Heating - Determine the loss of volatile oils and change in penetration cause by excessive heating.

6) Distillation (E.A & Cutback) -

Determine the amount of diluents that distills off at specified temperature denoting its evaporation characteristics. It also determine the proportion of asphalt present in the mixture.

7) Specific Gravity - See definition of terms. 8) Spot test - Dissolving the sample to xyleneheptane, If result is;

Negative ( - ), asphalt is okey Positive ( + ), asphalt is not okey (burned)

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9) solubility - Determine the bitumen content of the asphalt. Bitumen Content - - - - 99% Solvent used - - - - Trichlorothylene

10) Cement Mixing (E.A) - By mixing 100 cc of E.A. with 50 gram Portland cement. (passing #14) sieve.

11) Sieve Test (E.A) - Determine the amount of asphalt that is present in emulsion in relatively large globule. *Passing #20 sieve the amount retained is the large globule which is 0.1%

12) Storage Stability - To detect the tendency of asphalt globule to settle during storage.

13) Softening Point - Indicates the temperature at which the harden asphalt reach an arbitrary degree of softening.

62. Q- What are the grades of asphalt cement ? A- a) 40 50 penetration grade

b) 60 70 " " c) 85 - 100 " " d) 120 - 150 " " e) 200 300 " "

63. Q- How to determine the grade of asphalt ? A- a) By Penetration Test : Old Method

b) By Viscosity Test : Modern Method 0 temp. of 60'C to 135'C. 64. Q- What are the uses of blown asphalt ? A- 1. Application for roofing

2. Pipe coating 3. Fill cavities of concrete pavement 4. Use as water proofing membrane, etc. * Very rare to use in asphalt aggregate mixtures.

65 Q- What do you understand about artificial aggregate ? A- Blast-furnace slag is the most commonly used artificial aggregate, have unusual

resistance to wear and use in bridge deck & roof deck. 66. Q- What is the suitability of aggregate for use in asphalt construction ? 1. Size and Grading

a) Dense-graded b) open-graded c) One size

d) Coarse graded e) Fine graded f) Gap graded 2. Cleanliness 3. Toughness 4. Soundness 5. Particle shape Affect workability & strength. 6. Surface texture

7. Absorption - A certain degree of porosity is desirable as it permits aggregate to absorb asphalt which then forms a mechanical linkage between the asphalt film and the stone particle.

8. Affinity for asphalt:

Asphalt 11

Stripping - -

Separation of the asphalt film from the aggregate through the action of water, such material is referred to as (Water Loving) such as siliceous aggregates (quartzite & some granites). Aggregates that exhibit a high degree of resistance to film stripping in the presence of water are usually most suitable in asphalt paving mixes, such material is referred to as (water hating) such as limestone, and dolomite usually high resistance to asphalt film stripping.

67. Q- What is the desired properties of asphalt mix ? A- a) Stability - Resistance to displacement and shearing stress caused by

stationary and moving loads. b) Durability - Resistance to disintegration due to the effects of traffic, water,

and temperature change. c) Flexibility - Ability of the pavement to adjust to the settlement of the base

without cracking. d) Skid Resistance - The frictional resistance between the surface of the

pavement and the vehicle tire to resist motion. e) Workability - Is the ease by which the material can be placed to its

desired form and compacted to required density. f) Fatigue Resistance - Resistance to wear and aging. g) Impermeability - Resistance to the penetration of water.

Asphalt 12

68. Q- What are the factors affecting the stability ? A- a) Gradation of aggregate

b) Hardness c) Shape and surface texture of aggregate d) Quantity of asphalt e) Degree of compaction : at least 95% compacted

69. Q- What are the factors affecting durability ? A- a) Density of the compacted pavement

b) Properties of the aggregate c) Quality of the asphalt

70. Q- What are the factors affecting flexibility ? A- a) Quality of the asphalt

b) Quality of the mineral filler * The more viscose the asphalt the more flexible.

71. Q- What are the factors affecting skid resistance ? A- a) Quality of asphalt

b) Surface texture of the aggregate 72. Q- What are the factors affecting workability ? A- a) Graduation of aggregate

b) Consistency of the asphalt c) Temperature of the mix

73. Q- What is the effect of hydrated lime on asphalt ? A- Hydrated Lime which is highly alkaline starts a chemical reaction to change the

character of the aggregate surface and neutralized any acidic properties present in asphalt. It improves the coatability and bonding process of asphalt without reveling or bleeding with durable surface. It is usually added to aggregate at the pugmill.

74. Q- What is the chemical composition of asphalt ? A- 1. Carbon : 70% - 85%

2. Hydrogen : 7% - 12% 3. Nitrogen : 0% - 1% 4. Sulphur : 1% - 7% 5. Oxygen : 0% - 5%

75. Q- What are the test recommended on fillers ? A- 1. Particle size analysis by hydrometer (Mineral Filler)

2. Plasticity Index (Mineral Filler) 3. Immersion Compression test (Joint Filler)

76. Q- What will be you recommendation to minimize rutting ? A- 1. Gravel should be scalped on at least 1.5" screen before feed to the crusher.

2. Natural sand limited to 15% from fine aggregate and should not contain more than 50% dune sand.

3. Trial section should be made to determine the maximum density in the field and air voids in the mix at that density.

4. Filler to asphalt cement ratio should be between 1.3 to 1.5 to get softening point of 85'C to 95'C maximum.

5. Use asphalt 40/50 instead of 60/70 penetration in the desert areas. 6. Follow the M.O.C Circular 2401 & 2403.

Asphalt 13

7. The total thickness of the asphalt layers shall not exceed 15 cm. Or as shown on the drawings not more than 20 cm.`

77. Q- What are the types of asphalt cracks ? A- 1. Alligator Cracks: These are inter-connected cracks forming a series of

small blocks resembling an alligators skin or chicken wire.

Causes: Excessive deflection of the surface over unstable subgrade or lower course of the pavement. The unstable support usually is the result of saturated granular bases of subgrade.

Repair: Deep patch, skin patch, agg. seal coat patch, slurry seal patch. 2. Edge Cracks: Longitudinal cracks, 1/3 meter from the edge of

pavement with or without transverse cracks branching towards the shoulders.

Causes: 1. Due to lack of lateral (shoulder) support. 2. Settlement or yielding of the material underlying the cracked

area due to result of poor drainage, frost heave or shrinkage from drying out of the surrounding earth.

Repair: 1. Fill as for reflection cracks. 2. Fill with asphalt emulsion slurry or emulsified or cutback

asphalt mixed with sand. 3. Edge Joint Cracks: Is really a Seam; It is the separation of the Joint

between the pavement and the shoulder. Causes: Alternate wetting and drying beneath the shoulder surface.

Shoulder settlement, mix shrinkage, and trucks straddling the joint. Repair: Improve the drainage by getting rid of the condition that traps

water. Same as reflection cracks.

4. Lane Joint Cracks: Are longitudinal separations along the seam between two paving lanes.

Causes: A weak seam between adjoining spreads in the courses of the pavement.

Repair: See reflection cracks. 5. Reflection Cracks: In asphalt overlays which reflect the crack pattern

in the pavement structure underneath. Causes: 1. Vertical or horizontal movements in the pavement beneath the

overlay, brought on by expansion and contraction with temperature or moisture changes.

2. Traffic or earth movement. 3. Loss of moisture in sub-grades with high clay contents.

Repair: Fill with asphalt emulsion slurry or light grade of emulsified asphalt mixed with fine sand. Also, special asphalt compounds or heavier bodied asphalt material may be used to fill large cracks.

6. Shrinkage Cracks: Are interconnected crack forming a series of large blocks usually with sharp corners or angles.

Causes: 1. Volume change in the asphalt mix or in the base of subgrade. 2. Volume change of fine aggregate asphalt mix that have a high

content of low penetration asphalt. Repair: Fill cracks with asphalt emulsion slurry followed by a surface

treatment or a slurry seal over the entire surface.

Asphalt 14

7. Slippage Cracks: Crescent-shape cracks that point in the direction of the thrust of wheels on the pavement surface.

Causes: 1. Lack of a good bond between the surface layer beneath, may be due to dust, oil, rubber, dirt, water, or other non-adhesive material between the two courses.

2. Mixture having a high sand content. 3. Can occur whether the sand is sharp or rounded. 4. Improper compaction during construction causes the bond layers to

be broken. Repair: Remove the surface layer from around the crack to the point where

good bond between the layers is found, then fill the area with plant mixed asphalt material.

8. Widening Cracks: Are longitudinal reflection cracks that show up in the asphalt overlay above the joint between the old and new sections of a pavement widening.

Causes: See reflection cracks Repair: See reflection cracks 78. Q- What are the causes of distortion in asphalt ? A- 1. Too little compaction of the pavement courses.

2. Too many fines in surface mixture. 3. Too much asphalt 4. Swelling of underlying courses or settlement.

79. Q- What are the different forms of distortion ? A- 1. Grooves or ruts

2. Shoving 3. Corrugations 4. Depressions 5. Upheaval

Rutting:

These are channelized depressions which may develop in the wheel tracks of an asphalt pavement.

Causes:

(Mentioned before)

Repair: Level the pavement by filling the channels with hot plant mixed asphalt material, followed with a thin asphalt plant-mix overlay.

Corrugations & Shoving: Is a form of plastic movement typified by ripples across the asphalt pavement surface. SHOVING is a form of plastic movement resulting in localized bulging of the pavement surface. These occur usually at points where traffic starts and stops, on hills where vehicles brake on the downgrade, on sharp curves, or where vehicles hit a bump and bounce up and down.

Asphalt 15

Causes:

Lack of stability which is caused by: 1. Too much asphalt in the mix 2. Too high a proportion of fine aggregate. 3. Too smooth texture or too round soft coarse or fine agg. 4. Too soft asphalt cement. 5. Excessive moisture.

Repair: Shoved areas must be removed and patched. (Thick asphalt surface)

To repair corrugations in a thin surface treatment; 1. Scarify and break up the surface with a rotary tiller. 2. Mix the broken-up surface material with the base material to a depth

of 10 cm (4 in.) 3. Compact and reshape the base. 4. Prime the base. 5. Apply a new surface treatment.

Grade Depressions:

They dip several centimeter or more below grade and water will collect in them. These birdbaths make deterioration in pavement and give hazards to motorists.

Causes:

1. Poor construction method 2. Settlement of lower pavement layers.

Repair: Depressions should be filled with hot plant-mixed asphalt material and compacted to bring them up to the same grade as the surrounding pavement.

Upheaval: Is the localized upward displacement of a pavement due to swelling of the subgrade or some portion of the pavement structure.

Causes:

1. Expansion of ice in the lower courses of the pavement or the subgrade.

2. Swelling effect of moisture on expansive soils. Repair: See alligator cracks Deep patched. 80. Q- What is disintegration in asphalt pavement ? A- Disintegration is the breaking up of a pavement into small loose fragments.

Two (2) common types are; 1. Potholes 2. Raveling

Potholes: These are bowl-shaped holes of various sizes in the pavement resulting from localized disintegration.

Causes:

Weakness in the pavement resulting from: 1. Little asphalt 2. Too thin an asphalt surface 3. Too much fines 4. Too few fines 5. Poor drainage

Asphalt 16

Repair: (Temporary) Filling with a pre-mixed asphalt patching material. (Permanent) By cutting out the hole to solid material on both sides and bottom and filling it with new base and surface material.

Raveling: This is the progressive separation of aggregate particles in the pavement from the surface downward or from the edges inward. Usually fine aggregate comes off first and leaves little pock marks on the pavement surface. As the erosion continues, large and large particles are broken free and the pavement soon has the rough and jagged appearance typical of surface erosion.

Causes: 1. Lack of compaction during construction. 2. Construction during wet or cold weather. 3. Dirty or disintegrating aggregate. 4. Too little asphalt in the mix. 5. Overheating of the asphalt mix.

Repair: Surface treatment (Slurry seal, Sand seal, Aggregate seal, Plant-mixed surface treatment).

81. Q- What are the causes of skid hazard or slipping ? A- 1. A thin film of water on a smooth or slipping ?

2. A thick film of water which at high speeds, causes the vehicle to leave the pavement surface and skim over the water like an aquaplane.

3. May also develop from surface contamination, such as from oil spillage or certain types of clay.

Treatment: Cleaning the surface of contamination to removal of excess asphalt and resurfacing to improve surface drainage.

82. Q- What is bleeding in asphalt ? A- Bleeding or flushing is the upward movement of asphalt in an asphalt pavement

resulting in the formation of a film of asphalt on the surface. Causes

: 1. Too much asphalt in one or more of the pavement courses. 2. Too heavy a prime or tack coat 3. Overweight traffic.

Repair: 1. Repeated applications of hot sand 2. Hot slag screening 3. Hot rock screening to blot up the excess asphalt.

83. Q- What is polished aggregate ? A- These are aggregate particles in the surface of a pavement that have been polished

smooth. This includes both naturally smooth uncrushed gravels and crushed rock that wears down quickly under the action of traffic.

Causes: 1. Some aggregates, particularly some types of limestone will become polished rather quickly under traffic.

2. Some types of gravel are naturally polished and if they are used in a pavement surface without crushing they will be a skid hazard. These polished aggregate are quite slippery when wet.

Repair: 1. Cover the surface with a skid resistance treatment. 2. Application of a hot plant mixed surface treatment and sand seal.

84. Q- What is Loss of cover aggregate ? A- The whipping-off of aggregate under traffic from a surface-treatment pavement, leaving

the asphalt.

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Causes: 1. Cold mix 2. Too dusty aggregate 3. too wet aggregate 4. Poor compaction 5. When steel-wheeled roller alone is used for compaction, aggregate

may be lost from low spots that are bridged over by the roller. 6. Too cool the weather 7. Too soon of fast traffic 8. Surface which absorbs part of the asphalt leaving too little to hold the

aggregate. Repair: Hot coarse sand, spread over the affected areas. 85. Q- What is a longitudinal streaking in asphalt ? A- Alternating lean and heavy lines of asphalt running parallel to the centerline of the

road. Causes: 1. Spray bar on the asphalt distributor not set at the correct height for the

spray fans to overlap properly. 2. Spray bar rising as load in distributor lightens.

86. Q- What are the classification of asphalt treatment ? A- 1) Sprayed asphalt treatment:

a. Dust laying b. Road oiling c. Prime coating d. Tack coating e. Fog sealing. 2) Sprayed asphalt and cover aggregate treatment: a. Single surface treatment b. Multiple surface treatment c. Sand seal. 3) Asphalt aggregate mixtures: a. Emulsion slurry seal b. Road mix c. Plant mix

87. Q- What are the advantages of pneumatic roller in asphalt paving? A- 1. They provide a more uniform degree of compaction than steel wheel roller.

2. They improve the seal near the surface thus decrease the permeability of layer. 3. They orient the aggregate particles for greatest stability, as high pressure truck tires

do after using the asphalt surface for some time. 4. Pneumatic rollers not increase density but increase stability which assures minimum

distortion under heavy traffic. 88. Q- What is the case or appearance of subgrade before applying prime coat ? A- Clean surface shall be given a light application of water and allowed to dry to a surface-

dry condition. 89. Q- How will you determine the defficiences of asphalt mixtures ? A- 1. Too Hot: Blue smoke rising from the mix indicates an overheated batch. 2. Too Cold: a) Stiff appearance

b) Improper coating of the larger aggregate particles. 3. Too much asphalt: Mix in truck appears lying flat.

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4. Too little asphalt: a) It has a lean b) Granular appearance c) Improper coating d) Brown appearance.

5. Non-uniform mixing : a) Spots of lean b) Brown dull appearance.

6. Excessive Coarse Agg.: a) Poor workability b) Coarse appearance

7. Excessive fine Agg. : a) Different texture from a properly graded mix after it has been rolled.

8. Excessive moisture : a) The mix may also foam so that it appears to have too much asphalt.

9. Segregation: a) Improper handling b) Loads have become contaminated.

90. Q- What are the rolling procedures ? A- 1. Transverse joints rolling

2. Longitudinal joints rolling 3. Outside edge rolling 4. Initial or breaking rolling 5. Second or intermediate rolling 6. Finish rolling.

91. Q- Why the contractor start the rolling operation on the low side of spread ? A- The reason for these is that the asphalt mixture when hot, tend to migrate towards

the low side of the spread under the action of the roller. 92. Q- What are the stops in rolling paving mixtures ? A- 1. Rolling shall begin as soon as the mixture will bear the roller without undue

displacement. 2. Rolling shall be longitudinally, beginning at the low side of the spread of material

and proceeding toward the high side. 3. Slow and uniform speed, 3 mph for steel rollers and 5mph for pneumatic rollers. 4. Roller wheels should kept moist with only enough water to avoid picking-up the

material. 93. Q- What are the types of roller required for compacting hot mix asphalt ? A- Function Types Weight

In tons Number of

passes Breakdown

Intermediate Finishing

Steel Pneumatic Steel

10 12 10

5 8

4 8- 12

4 94.

Q-

What are the reasons for drainage in asphalt pavement ?

A- 1. To collect and drain surface and sub-surface water. 2. To prevent or retard embankment erosion.

3. To intercept water from surrounding area and carry it out from the area. 4. To lower the ground water table.

95. Q- Which requires more prime coat, A-1-a or A- 2-4 material ?

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A- A2-4 material because it absorbs more prime coat due to more surface area. 96. Q- If while performing the test of coating and stripping of bitumen aggregate mixture,

it is observed that the estimated coated area is below 95%. What to do ? A- Antistripping agent to be used to promote coating and adhesion. Additives are used

to aid the coating of aggregates, particularly when in a damp or wet condition. They are also used to increase the resistance of asphalt film to stripping by the action of water.

97. Q- What is the use of silicones in hot mix ? A- Silicones are added to asphalt under certain conditions to reduce the effects of

moisture or other conditions. For example, silicones may be added to hot asphalt to prevent foaming while in storage. Silicones in asphalt mixes have been used to prevent hardening of asphalt concrete in storage, to prevent slumping and segregation of the mixture during transportation, and tearing of the mix during lay down.

98. Q- What is the use of hydrated lime in hot mix ? A- Hydrated lime is added to some low grade aggregates to render them suitable for

use in asphalt mixture in highway construction. Sometimes it is difficult to coat certain aggregates with asphalt because of their siliceous or acidic surfaces. Hydrated lime, which is highly alkaline, starts a chemical reaction that changes the character of aggregate surfaces and neutralizes any acidic properties present in asphalt. Adding hydrated lime often improves the coatability and bonding properties of asphalt to these aggregates. Hydrated lime may serve as a filler in the aggregate material. With the addition of hydrated lime, up to (1) percent additional asphalt over the normal asphalt content can be used in the mix without raveling or bleeding of the finished pavement. This produces a firmer, denser pavement with a more durable surface.

99. Q- What is the use of rubber in asphalt ? A- Natural synthetic and reclaimed rubber in the form of powder, crumbs, pellets and

latex has been used in asphalt to alter certain properties. Studies have shown that adding rubber in amounts as little as 0.1 percent but usually in amounts ranging from 1 to 5 percent, materially changes the properties of asphalt. The purpose of using rubberized asphalt has been to obtain a material possessing improved elasticity, increased adhesion and greater resistance to fracture at low temperature.

100. Q- Where you add anti-stripping material ? A- At Bug mill, Asphalt storage. 101. Q- How you get softening point of asphalt after paving ? A- By ABESON method. (A.A.S.H.T.O T-170-82). 102. Q- What are the forms of filler Bit. Ratio ? A- (Filler/Bit.) for getting highest softening point are zero:1, 1:1, 1.5.1, 2.3:1

(Zero/100%, 50/50%, 60/40%, 70/30%) 103. Q- What is the initial compaction acting by paver ? A- 80% of required compaction. 104. Q- What is the Asphalt macadam ? A- Asphalt macadam is compacted crushed rock affect as base construction.

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105. Q- How you express penetration and ductility ? A- Penetration by mm/10

Ductility by cm. 106. Q- What do you mean by dense graded mix in asphalting work ? How it differs from

open graded mix ? When it is used ? A- Open graded asphalt mix differ from dense graded ones in that they (1) Contain much little no fine aggregates/dust (2) Asphalt content of open graded mixes

generally is set as high as possible. (3) Open graded mixes are often applied in a thin inch. Overlay over old pavements (4) Open graded mixes better resist the reflection of cracks from the old pavement upward to the surface.

Definitions: a) Open Graded Mix A well graded asphalt mix containing little or no fines with a high percentage of aggregate

voids. b) Dense Graded Mix: Continuously graded mix from a specified max. size of aggregate to dust, so as to have a

low aggregate voidage. 107. Q- What is value Engineering ? A- Value Engineering : An organized effort directed at analyzing the function or highway components with the purpose of achieving the required function at the

lowest possible cost. 108. Q- What precautionary measures are adopted in case of high loss of stability? A- Stripping value lest of asphalt should be rechecked. Less coating of asphalt (below 95%) can give the more loss.

Checking of asphalt batching plant and proportion of natural and crushed sand is necessary, as the higher quantity of natural sand gives the more loss.

It is necessary to check the plasticity index of fine aggregates as more plasticity in premix reflects the swelling properties of clay.

Check the bitumen content % of hot mix as little asphalt content % gives more loss. Therefore it is necessary to determine the optimum asphalt content of asphalt with care.

Rechecking of Sand Equivalent test is also necessary as less value of Sand Equivalent also gives the indication of more plasticity in material.

It is also necessary to recheck the compaction temperature of Marshall molds.

The temperature of the bot water in which the Marshall molds are being kept to know the stability and loss of stability may be carefully checked.

109. Q- What is the precautionary measure taken if a hot mix results in excessive voids? A- The percentage of air voids can be decreased by increasing asphalt content. Voids can

also be reduced by increasing the mineral filler contents. Care should be taken that asphalt content may be increased upto a certain limit to avoid further problems of rutting and bleeding.

110. Q- What is the meaning of open Graded and Gap Graded? A- The same meaning, Gap Graded means some sizes are deleted we have only more fine

and more coarse, it will be harsh mix.

Asphalt 21

111. Q- What are the types of protections in road construction? A- Slope protection.

Irish crossing. Grouted and loss rip rap. Borrow ditch. Culverts and Bridges. Guard rails. Gabons. Dykes. New jersey Barrier.

112. Q- What is the difference between sand equivalent and material passing No 200 sieve? A- Sand equivalent gives the proportion of clay and dust percentage by volume, while

gradation determines the same percentage by weight. 113. Q- Who gives more sand equivalent and fineness modules natural sand or crushed sand?

Why? A- Natural sand gives more sand equivalent and fineness modulus because less filler and

clay. 114. Q- What is the function of loss of stability? A- To know the durability of asphalt. 115. Q- What is the relation between Gmm and asphalt content? A- As asphalt content increase Gmm decrease. 116. Q- What is the relation between (V.M.A) and Asphalt content? A- (V.M.A) increase as asphalt content increase. 117. Q- What is the relation between air voids and Asphalt content? A- Voids are more at low asphalt content. 118. Q- What is the relation between Asphalt content and stability? A- As per curve. 119. Q- What is the relation between ac and loss of stability? A- More Ac the low the loss of stability. 120. Q- Can bitumen absorption be higher than the water absorption in asphalt mix design? A- Bitumen absorption can not be higher or even equal to water absorption in

any case. As Bitumen is more viscous and has high molecular volume as copared to water.

Bitumen penetrates less in agg. compared to water. 121. Q- In case bitumen absorption is higher than the water absorption in your asphalt mix

design? What does it mean?

A- It means either Gse is abnormally higher or Gsb Is lower in case Gse is higher value of Gmm is also. So both G.s.e. and G.s.b need to be rechecked. This is all due to the experimental error.

Asphalt 22

( G.S.a > G.s.e. > G.s.b > apparent effective Bulk.

122. Q- what is the rigidity or stiffness how it is caused in asphalt mix and what does it harm? A- Rigidity or stiffness is caused in hot mixes where low penetration asphalt is used.

Cause the volume changes making the pavement ridge and give higher value of marshal stability and low flow values. Pavement of such hot mix is cracked under heavy volume of traffic.

m(kg/mflowstabilityRigidity )

123. Q- What causes of high loss of stability? A- Stripping more than 5%.

Natural sand is more. Plasticity index is more. (more clay) More asphalt content. Less value of Sand equivalent. (more clay) Temperature of marshal mold. and water temperature. & of filler asphalt ratio.

124. Q- How to clean Trucks during Asphalt production? A- By thin film of paraffin oil or calcium hydroxide solution. 125. Q- What is the tolerance of marshal stability? A- + 200 from the design value. 126. Q-

What are the limits of ( flatthin ) and elongated pieces?

A- The flat w

t = 1/3, the elongated L

w1= 1/3

Where 2w 1w (width) L (Length) T (thickness)

127. Q- What is the riding quality? A- Special equipment to measure the tolerance of surface. 128. Q- What is the difference in temperature allowed bet. aggregate and asphalt cement. A- Asphalt temperature not less than 14oc from the aggregate temperature at Time of

entrance to bug mill. 129. Q- What is asphalt plank? A- Asphalt plank consists of asphalt, finder and mineral aggregate to produce uniformly

dense mass. 130. Q- What is the plasticity index for mineral filler? A- Not more than 4 except hydrated lime and hydraulic cement.

Interview with Highway Construction

Concrete 1

CONCRETE 1. Q. In construction, what are the main problems we can face in Saudi Arabia? A- Cracks on concrete due to hot whether condition. 2- Q. In slab, the drawing shows certain bars and their spacing, suppose that particular bar size is

not available at site, what will you do? A- Calculate the areas of steel bars available at site against the area of steel bars on the

drawing by equation; A1 = D2 ; N1 = N2

4Dx2N4

DxN22

21

1

N1 (D1)2 = N2 (D2)2

N2 22

211)D(

)D(N Where:

D1 : Diameter of steel bar on the drawing D2 : Diameter of steel available on site N1 : No. of bars required on the drawing N2 : Calculated No. of bars using steel bars available at site.

3. Q- What is the maximum spacing of bars for slab? A- Max. Spacing = 20cm. (5 bars in one meter) 4- Q- How to make a dense concrete? A- a) Proper proportion of water-cement ratio.

b) Aggregate must be well-graded. c) Concrete should be air-entrained. d) Good vibration, etc. e) Use plasticizer.

5- Q- What is tremie in concrete? A- It is a method of placing concrete underwater. A tube called tremie about 10" 12" in

diameter, rigid and watertight are held vertically in water during pouring operation to avoid washing-out of concrete mix.

6- Q- What is the use of plasticizer and super plasticizer in concrete? A- Plasticizer: Primary Action Practical Effect Reduction of the force of attraction between

the cement particles and/or reduction of the surface tension of the water. Reduce W/C ratio

Increasing plasticity; reduction of w/c ratio by up to 10%; resultant 15% increase in strength; possibility for reduction of cement content.

Super Plasticizer: Primary Action Practical Effect Extreme lowering of the force of attraction

between the cement particles. Extreme increases in workability or reduction of water content by 20-30%; strength can increase by 50% owing to lesser water demand.

Q- What is the function of calcium chloride in hot weather concreting?

Interview with Highway Construction

Concrete 2

A- When added to concrete mixtures impart as an accelerating agent. Increasing the rate of hydration; speeding up the setting, and early strength development. (Never use in Hot Weather).

8- Q- What is the effect of chloride and sulfate in concrete? Chloride attack:

a) When the lime in cement react with carbon dioxide (CO2) it will produce calcium carbonate.

b) The presence of calcium carbonate in water, increases the amount of alkalinity up to 11%, thereby the water will attack the reinforcement which lead to corrosion.

c) While rust increases, the volume of the bars also increases leading to produce cracks in concrete.

Sulfate attack:

a) When tricalcium aluminate (C3A) in cement react with sulfate due to the presence of moisture, it produces gel expansion in concrete and the volume will also increases leading to cracks in concrete.

b) Also contribute to disintegration of the aggregates. 9- Q- What type of cement are you going to use in sulfate area? A- Type V or sulfate resisting cement. 10- Q- What are the methods for curing concrete? A- a) Water curing method

b) Membrane curing method c) Steam curing method d) Cold weather curing method

11- Q- When do you start curing concrete? A- Right after the final placement of concrete mix, when the water sheen or mixing water just

begun to disappear. 12- Q- What is the rate of application of curing membrane? A- One (1) liter /5 sq. m. ; If applied by hand spray.

One (1) liter /3 sq. m. ; If mechanically applied. 13- Q- What is the initial and final setting time of concrete? A- 45 minutes ; 8 hours 14- Q- What are the types of admixtures? A- a) Plasticizer

b) Retarder c) Accelerator

d) Plasticizer with retarding agent Type D e) Plasticizer with accelerating agent f) Superplasticizer

g) Superplasticizer with retarding agent 15- Q- What is the effect of retarded in concrete mix? A- To delay the setting time of about 1 4 hours over normal setting time and reduces the

mixing water by about 3-9 kg/cu.m. and increased the compressive strength by about 10-15%. The common chemical used is Lignosulfic acid.

16- Q- What are the precautionary measures during cold weather concreting? A- a) Avoid overheating of fresh concrete

Interview with Highway Construction

Concrete 3

b) Appropriate equipment should be available for heating the concrete materials. c) Maintaining favorable temperature after concrete is place, etc.

17- Q- At what time concrete should be placed after mixing water? A- As soon as possible; not more than 30 minutes if truck mixer is used or not more than one

hour if truck agitator is used 60. 18- Q- What are the precautions during hot weather concreting? A- 1- During mix production:

a) Lower the fresh concrete temperature by using cool aggregates and cool mixing water.

b) Dampen the aggregate if they are dry and absorptive. c) Under shed.

2- During Construction: a) Dampen the sub grade and forms. b) Erect windbreaks to reduce wind velocity over the concrete surface. c) Erect sunshades to reduce concrete surface temperature. d) Protect the concrete with covering during any appreciable delay between

placing and finishing. e) reduce time between placing and start of curing by improved construction

procedures. f) Protect the concrete during the first few hours after placing and finishing to

minimize evaporation, by application of moisture to the surface, using a light fog of spray.

19. Q- Describe procedures in performing slump test. A- Damper the slump cone and base plate. Take fresh flowing concrete by scoop or pail. Mix

thoroughly if necessary to have uniform paste. Placed it in a cone in 3 equal layer rodding each layer with 25 blows. Lift the cone vertically in 5 seconds, completing the test in 2.5 minutes, then measure and record the sag.

20- Q- What is the allowable tolerance for slump test? A- 15 mm; if slump (0 75mm) & 25mm : If more than 75mm slump. 21- Q- Which aggregate will have less mixing water, natural or crushed aggregate? Why? A- Natural aggregate, because has less surface area. 22- Q- What is the rate of loading in crushing concrete cylinders? What will happen if rate was

increased? A- The rate of loading is 20 50 Psi/ second. If the rate of loading was increased, result of

concrete strength will also increased due to the sudden impact of force, thereby leading to inaccurate strength result.

23- Q- Approximately how many kilograms of concrete mix in one cubic meter? A- About 2,500 kg. 24- Q- What are the test you should run for the aggregates to check suitability for concrete and for

asphalt before preparing a mix design? A- a) Sieve analysis

b) specific gravity and absorption c) Unit weight d) Abrasion test e) Soundness test f) Sand equivalent g) Organic impurities h) Thin & Elongated pieces i) Fineness modulus j) Friable particles, etc.

Interview with Highway Construction

Concrete 4

25- Q- Why the sand equivalent are being made? A- To determine the proportion of fine dust or claylike material in the soil or in the aggregate. 26- Q- Why do you crushed cylinders after 7 days, why not after 27 days or after 30 days? And

why the cylinders are crushes after 28 days for ultimate strength? A- After 7 days to determine the strength-gain or development of concrete, results should not

be lesser than 75% of the specified strength at 28 days. Then it is tested after 28 days because this is the estimated 100% strength development of the concrete.

27- Q- Which one gives more concrete strength, standard cubes or standard cylinders? Why? A- Standard cubes, because of the ratio L/D is equal to 1 and also the test load applied is

parallel to layers. 28- Q- What is the purpose of curing concrete? A- a) To maintain the moist environment and to prevent the escape of mixing water

required for hydration processes and helps in the development of strength. b) To prevent cracks. c) To increase strength.

29- Q- What is bleeding in concrete? A- It is the upward movement of mixing water due to settlement of aggregates in concrete

mix. 30- Q- What are the methods used for concrete mix design?

Which do you prefer and why? A- The methods are: ACI method and CP 110 method.

ACI method are more preferable because the specific gravity of individual materials are included in the computation.

31- Q- How to adjust the amount of water for batching concrete? A- By equation: ADJUSTED WT. OF WATER Design wt. Of water

wt. Of C.A. x 100moisture%absorption%

wt. of F.A. x 100moisture%absorption%

32- Q- How will you calculate the Saturn Survey Drag aggregate with 1.5% absorption? A- By equation:

CORRECTED WT. OF AGG. = Uncorrected wt.

100%1 absorption

33- Q- How do you reduce water content in a mix design and what are the advantages of reducing

water in a concrete mix? A- By using water reducing admixture. The advantage are less cracking, possibilities and

increase compressive strength. 34- Q- What is alkali reactivity? What type of cement are you going to use if aggregate is

susceptible? A- It is the reaction of certain aggregate containing silica or silica alumina which react alkali

is cement producing "gel" which lead to cracking due to osmatic pressure. The type of cement to be used are; a) Low alkali cement; having less than 0.6% alkali by weight of cement. b) Pozzolanic cement

35- Q- What are the different types of cement?

Interview with Highway Construction

Concrete 5

A- Type I or Ordinary Portland Cement Type II or Moderate Sulfate Resisting Cement

Type III or High Early Strength Cement Type IV or Low Heat Resisting Cement Type V or High Sulfate Resisting Cement

36- Q- What is pre-tensioning and post-tensioning? A- Pre-tensioning:

The tendons or cables are held in a stretched condition during placing of plastic concrete until the concrete has hardened. Then as the tension of the reinforcing steel is released, it compresses the concrete.

Post-tensioning The pre-stressing tendons or cables are placed in ducts before concrete is casts, after

the concrete has hardened, the tendons or cables are stretched to a predetermined tension by jacking and are wedged in its position. The tubes may also be pressure grouted.

37- Q- What is the effect of humidity on creep and shrinkage? A- It contribute losses of water in concrete thereby causing cracks due to volume change. 38- Q- What could be the maximum depth of a structure you can cast in one (1) lift? A- 1.5 meters 39- Q- What is the required slump for class "A" vibrated concrete? A- 25mm 75mm (1 3 inches) 40- Q- In the grouted riprap, what is the proportion for the mortar to be used for grouting? A- 1 part cement and 2 part sand. 41- Q- What is the limiting temperature for concreting? A- Not less than 5oC during cold weather, and

not more than 33oC during hot weather. 42- Q- What is the effect of aluminum pipe during pumping of concrete mix? A- It will exhibit decreased strength due to chemical reaction of abraded aluminum particles

with the alkalies in the portland cement, resulting in the formation of hydrogen gas and thereby increasing in volume of fresh concrete.

43- Q- What are the Non-Destructive test to determine strength and other properties of concrete? A- a) Indentation Rebound test (Schmidt Rebound Hammer)

b) Sonic test c) Pulse-transmission at sonic & ultra-sonic frequencies d) Radioactive test e) Penetration Probe test

44- Q- What are the curing procedures? A- a) By maintaining a moist environment by the application of water through pounding,

sprays, steam or saturated cover materials such as earth, sawdust, have or burlap. Care should be taken to insure that saturated cover materials do not dry out and absorb water from the concrete.

b) By prevention of loss of mixing water from the concrete by means of sealing materials such as impervious sheets of paper or plastic or by application of a membrane forming curing compound to the freshly placed concrete.

45- Q- How shrinkage cracks and honey-combing are repaired? A- By guniting or shot-concreting. 46- Q- What is the max. storage period of cement before you request test for its quality?

Interview with Highway Construction

Concrete 6

A- a) Every 3 months ; if cement stored in bags. b) Every 6 months ; if cement stored in bulk.

47- Q- What are the types of cracks before hardening of concrete? A- a) Plastic settlement cracks

b) Plastic Shrinkage cracks c) Early Frost Damage cracks d) Constructional Movement cracks

48- Q- What is pH? A- a) A scale of numbers 0-14 which indicate the acidity or alkalinity of a solution.

Numbers below 7 indicate acidity and numbers above 7 indicate alkalinity. b) The pH value of the solution is the logarithm of the hydrogen ion concentration (H)

in moles per liter

pH = log H1

For example a solution of 4.5 pH has an hydrogen ion concentration of (10-4.5). 49. Q- What is the causes of plastic shrinkage and plastic settlement? A- The primary causes of plastic shrinkage are; a) Rapid early drying

b) Reinforcing steel are very near the surface of the pavement. c) Low rate of bleeding and fast surface evaporation.

The primary causes of plastic settlement are: a) Excessive bleeding b) Rapid early drying condition

50- Q- What is the main problem in bridges in the Kingdom? A- Cracks 51- Q- What are the kinds of bearing? A- 1- Single "roller" bearing

2- Multiple roller bearing 3- Linear rocker bearing\ 4- Point rocker bearing 5- Knuckle pin bearing 6- Knuckle cylindrincal bearing

7- Knuckle spherical bearing 8- Knuckle leaf bearing 9- Plate sliding bearing

10- Elastomeric laminated bearing 52- Q- What is construction joints and cold joints? A- Construction joints:

It is merely a stopping places of construction. They separate the areas of concrete placed at different times and should bond new concrete to existing concrete and not permit neither horizontal nor vertical movement. A good quality construction joint should provide complete water-tightness.

Interview with Highway Construction

Concrete 7

Cold joints: When the placement of concrete is delayed for any reason and the concrete takes it initial set, a cold joint is said to be occurred. When this happens, the contractor shall have to removed the previously partially placed-concrete from the forms immediately.

53- Q- Where to provide metal beam guardrail? A- a- In the sharp curve.

b- In the hilly area. c- In the steeper slopes d- To structural location

54- Q- What are the necessary precautions to be taken while applying thermoplastic paint? A- a- Pavement shall be free from foreign matters and dust.

b- Should dry and clean. c- Should have good weather condition.

d- Barricades should be installed, etc. 55- Q- What is to be done if shifting of box culvert is required? A- a- Select the low lying areas.

b- Locate catch main area. c- Determine the level of water. d- Calculate actual vent dimension.

e- Calculate velocity or discharge of water by equation: Q = VA where :

Q : is the discharge, m3/hr. V : is the velocity, km/hr. A : cross-sectional area, m2

56- Q- Cores are taken for what purpose? A- a- If the samples failed from the required strength. b- To determine the actual thickness of the structure.

c- To determine the formation of harden concrete, etc. 57- Q- What criteria as to spacing of stirrups be followed in a beam? A- 1- Put the maximum spacing in the center of the beam.

2- Put the minimum spacing at both ends, to resist the maximum shear, using equation;

qst =

bxenxfxA ss

where : qst = Allowable stresses carried by stirrups.

AS = Cross-sectional area of bar. fS = Steel stresses (working stress) n = Number of legs e = Spacing between stirrups b = Width of concrete section

58- Q- How many times do you apply curing membrane? A- Two (2) times, first application is parallel to the pavement, and the second application is

perpendicular to the first application or vice versa. 59- Q- What is the minimum and maximum slope of chutes during pouring concrete?

Interview with Highway Construction

Concrete 8

A- Minimum slope is 1: 3 Maximum slope is 1 : 2 Maximu