MODULE 5: ppt

Question 1

The costliest items associated with highway construction and maintenance

Answer 1

PAVEMENT

Question 2

True or false:
About 70% of roads are not paved, either composed of either gravel or stabilized
materials (aggregate bound with cementing agent – Portland cement, lime fly ash
or asphaltic cement)

Answer 2

True

Question 3

True or false:
Highways carrying higher volumes of traffic with heavy axle loads requires
surfaces with asphalt concrete or Portland concrete to provide for all-weather
operations and prevent permanent deformation of surface

Answer 3

True

Question 4

PAVEMENT provides two (2) basic functions:

Answer 4

• helps guide driver and delineate roadway by giving visual perspective of horizontal and vertical alignment of path.
  Gives information about driving task and steering control of vehicle
• Support vehicle loads

Question 5

PAVEMENT types

Answer 5

• FLEXIBLE PAVEMENTS
• RIGID PAVEMENTS
• OTHER TYPES:
  COMPOSITE PAVEMENTS – COMBINATION OF FLEXIBLE AND RIGID LAYERS
  -CONTINUOUSLY REINFORCED PAVEMENTS
  -POST – TENSIONED PAVEMENTS

Question 6

Constructed with asphaltic cement and
aggregates
Consists of several layers

Answer 6

Flexible PAVEMENT

Question 7

Flexible PAVEMENT layers:

Answer 7

SUBGRADE
SUBBASE
BASE
WEARING SURFACE

Question 8

Lowest layer; the existing soil
The upper 6 – 8 inches is usually scarified and blended to provide
uniform material before compaction to maximum density

Answer 8

SUBGRADE

Question 9

Usually consist of crushed aggregates
Has better engineering properties (higher moduli) than subgrade in terms
of bearing capacity

Answer 9

SUBBASE

Question 10

Often made of crushed aggregates of higher strength than those used in
the subbase

Either unstabilized or stabilized with cementing material

Cementing materials used are Portland cement, lime fly ash or asphaltic
cement

4-10 inches

Answer 10

BASE

Question 11

Usually made of asphaltic concrete- a mixture of asphalt cement and
aggregates

2-4 inches

Answer 11

WEARING SURFACE

Question 12

Protect the base layer from wheel abrasion and to waterproof the entire
pavement structure

Provides skid-resistance for safe vehicle stops

Answer 12

PURPOSE OF WEARING SURFACE

Question 13

vary with the type of axle loading, available
materials and expected pavement design life (years expected to provide adequate service before it undergoes MAJOR rehabilitation)

Answer 13

THICKNESS OF LAYERS

Question 14

Constructed with Portland cement concrete (PCC) and aggregates

The subgrade is also scarified, blended and compacted to maximum density

Answer 14

rigid PAVEMENT

Question 15

The base layer is OPTIONAL – depends on engineering property of subgrade

Answer 15

rigid PAVEMENT

Question 16

The wearing surface is of Portland cement concrete slab

Slab length caries from 10 to 13 ft for a spacing of 40ft or more

Answer 16

rigid PAVEMENT

Question 17

Built into pavement to control cracking due to shrinkage of concrete during curing process

Answer 17

Transverse contraction joints

Question 18

Load transfer devices

Placed in the joints to minimize deflection and reduce stresses near slab
edges

Answer 18

Dowel bars

Question 19

Slab thickness for PCC highway pavements vary from ________ inches

Answer 19

8-12

Question 20

true or false:
Pavement reduces and distributes surface (contact) pressure on acceptable level at subgrade

Answer 20

true

Question 21

FLEXIBLE PAVEMENTS:
accepted design procedures

Answer 21

ASPHALT INSTITUTE METHOD

NATIONAL STONE ASSOCIATION PROCEDURE

SHELL PROCEDURE

AASHTO FLEXIBLE PAVEMENT DESIGN PROCEDURE

Question 22

Aashto flexible pavement design procedure

Answer 22

SERVICEABILITY CONCEPT

Question 23

Pavement Failure:

Answer 23

Engineering Perception:
Cracking
Rutting
Visible surface distress

Question 24

AASHTO Road Test : combined the two definitions

Answer 24

SERVICEABILITY CONCEPT

Question 25

Concept was developed by Carey and Irick

Answer 25

PAVEMENT SERVICEABILITY - PERFORMANCE

Question 26

-pavement performance at any point in time

Answer 26

Present Serviceability Index (PSI)

Question 27

-pavement already needs rehabilitation; serviceability rating drops

Answer 27

Terminal Serviceability Index (TSI)

Question 28

PSI values: for new pavements:

Answer 28

4.2 – 4.5

Question 29

TSI values: varies by type of highway for highway facilities: local roads:

Answer 29

2.5 or 3.0 2.0

Question 30

Determines the structural number (thickness index) necessary to carry designated traffic loading

Answer 30

FLEXIBLE PAVEMENT DESIGN EQUATION

Question 31

reliability (z-statistic from standard normal curve)

Answer 31

Zr

Question 32

18kip equivalent single-axle load (ESAL) impact of any axle load in terms of the equivalent amount an 18 kip single axle load would have

Answer 32

W18

Question 33

represents the probability of serviceability is maintained at adequate levels from user’s point of view throughout design life = estimates the pavement will perform at or above TSI design life = typical for interstate highways are 90% or higher; local roads are at 50%

Answer 33

Zr

Question 34

overall standard deviation = takes into account the designer’s inability to accurately estimate the variation in future 18kip ESAL = typical values are on order of 0.30 – 0.50

Answer 34

So

Question 35

structural number = represents overall structural requirement needed to sustain design traffic loading

Answer 35

SN

Question 36

serviceability loss = caused by pavement roughness, cracking, patching and rutting = as pavement distress increases, serviceability decreases = for heavy traffic loads, loss may only be 1.2 = for low volume roads, possible loss at 2.7

Answer 36

ΔPSI

Question 37

soil resilient modulus of subgrade, lb/in2 = reflect engineering properties of subgrade = not all agencies uses MR, but instead uses CBR ( California Bearing Ratio) which is the ratio of load-bearing capacity of soil to the load-bearing capacity of high quality aggregate multiplied by 100 MR = 1500 x CBR *1500 is used for CBR values less than 10

Answer 37

MR

Question 38

structural layer coefficients of wearing surface, base and subbase layer

Answer 38

a1, a2, a3

Question 39

thickness layer of wearing surface, base, and subbase layers in inches

Answer 39

D1, D2, D3

Question 40

drainage coefficients for base and subbase

Answer 40

M2, M3

Question 41

Aashto rigid pavement design procedure is based on selected reduction in _____________ and is similar to the procedure for flexible pavements

Answer 41

serviceability

Question 42

Measure of strength:

Answer 42

For flexible pavements: structural number, For rigid pavements: thickness of PCC slab