pavement design

1. Material characterization
Course Instructor : Prof. Hana Naghawi
:Prepared by
Mohammad AL Hiary

2. Resilient Modulus
• The Resilient Modulus (MR): is a measure of subgrade material
stiffness.
• A material’s resilient modulus is actually an estimate of its modulus of
elasticity (E). While the modulus of elasticity is stress divided by strain
for a slowly applied load, resilient modulus is stress divided by strain
for rapidly applied loads.

3. Resilient Modulus
• Resilient modulus is determined using the triaxial test. The test
applies a repeated axial cyclic stress of fixed magnitude, load duration
and cycle duration to a cylindrical test specimen. While the specimen
is subjected to this dynamic cyclic stress, it is also subjected to a static
confining stress provided by a triaxial pressure chamber. It is
essentially a cyclic version of a triaxial compression test; the cyclic
load application is thought to more accurately simulate actual traffic
loading.

4. Triaxial cell test

5. MR for Granular materials
The resilient modulus test for granular materials and fine-grained soils
is specified by AASHTO (1989) Sample conditioning can be
accomplished by applying various combinations of confining pressures
and deviator stresses

6. Transducer arrangement for indirect tensile test

7. procedures
Set the confining pressure to 5 psi (35 kPa), and apply a deviator stress of 5 psI and
then 10 psi, each for 200 repetitions .
2. Set the confining pressure to 10 psi , and apply a deviator stress of 10 psi
and then 15 psi, each for 200 repetitions .
3. Set the confining pressure to 15 psi, and apply a deviator stress of 15 psi
and then 20 psi , each for 200 repetitions .
After sample conditioning, the following constant confining pressure increasing
deviator stress sequence is applied, and the results are recorded at the 200th
repetition
of each deviator stress :

8. procedures
1. Set the confining pressure to 20 psi, and apply deviator stresses of 1, 2 ,5, 10, 15,
and 20 psi
2. Reduce the confining pressure to 15 psi , and apply deviator stresses of1, 2, 5,
10, 15, and 20 psi .
3 . Reduce the confining pressure to 10 psi , and apply deviator stresses of 1 ,2, 5,
10, and 15 psi.
4. Reduce the confining pressure to 5 psi, and apply deviator stresses of 1 ,2, 5, 10,
and 15 psi.
5. Reduce the confining pressure to 1 psi, and apply deviator stresses of 1 ,2, 5, 7 .5,
and 10 psi .
Stop the test after 200 repetitions of the last deviator stress level or when the
specimen fails .

9. The results of resilient modulus tests on a
granular material

10. Resilient modulus
Invariant stress Resilient modulus

11. MR for fine –Grained soils
Sample conditioning for fine-grained soils is not as extensive as that for
granular materials. AASHTO recommends the use of a confining
pressure of 6 psi followed by 200 repetitions each of deviator stresses
of 1, 2, 4, 8, and 10 psi .

12. The results of resilient modulus tests on a
fined grained soil

13. Correlations with Other Testes
Most of tests measure the strength of the material and are not a true
representation of the resilient modulus
The correlation is not valid if the actual conditions are different from
those under which the correlation is established .

14. Correlations chart for estimating MR of
subgrade soil

15. Correlations for estimating MR of subgrade
soil
R Value: The R value is the resistance value of a soil determined by a
stabilometer
*Pv : the applied vertical pressure of 160 psi
*D2 : is the displacement of stabilometer fluid necessary to increase horizontal
pressure from 5 to 100 psi
*ph :is the transmitted horizontal pressure at pv of 160 psi
R value ranges from 0 to 100
.

16. Correlations for estimating MR of subgrade
soil
CBR The California Bearing Ratio test (CBR) is a penetration test,
wherein a standard piston, having an area of 3 in^2,
`
CBR value ranges from 0 to 100 .

17. Correlations for estimating MR of subgrade
soil

18. Correlations for estimating MR of HMA

19. Correlations for estimating MR of HMA
Depend on :
1. Structural Layer Coefficient
2. Marshall stability
3. Cohesiometer at 140 c
C is the cohesiometer value in grams per inch
L is the weight of lead shot in grams
W is the diameter or width of specimen in inch
t is the thickness of the specimen in inches

20. Correlations for estimating MR of Bases and
Subbases

21. Correlations for estimating MR of Bases and
Subbases
• The resilient modulus of untreated bases is correlated with
CBR
R value
Texas triaxial classification
• the resilient modulus of bituminous-treated bases is correlated with
the Marshal stability
• the correlation chart for estimating the resilient modulusof granular
subbases from CBR, R values, and Texas triaxial classification . For the
sameuntreated granular materials,

22. DYNAMIC MODULUS OF BITUMINOUS
MIXTURES
• The dynamic modulus represents the stiffness of the asphalt material
when tested in a compressive-type, repeated load test
• The dynamic modulus is one of the key parameters used to evaluate
both rutting and fatigue cracking distress

23. Asphalt Institute Formulas

24. Asphalt Institute Formulas
• F is the load frequency in Hz
• T isthe temperature in °F
• P200 is the percentage by weight of aggregate passing through a No.
200 sieve
• Vv is the volume of air void in %
• A is the asphalt viscosity at 70°F in106 poise
• Vb is the volume of bitumen in %

25. Asphalt Institute Formulas
If sufficient viscosity data are not available to estimate A at 70°F, one
may use the equation
P77°F is the penetration at 77°F

26. FATIGUE CHARACTERISTICS
• Fatigue of bituminous mixtures and Portland cement concrete under
repeated flexure is an important factor of pavement design.
• The fatigue tests are expensive and require a large number of
specimens so nomographs and equations for predicting fatigue life
can be use.

27. Two types of controlled loading
for fatigue testing .

28. Nomographs and Equations

29. Nomographs and Equations
For constant stress tests
For constant strain tests

30. Nomographs and Equations
• et is the tensile strain
• PI is the penetration index
• Vb is the percentage of bitumen volume in the mix
• Sm is the stiffness modulus of the mix
• N f is the number of repetitions to failure

31. Fatigue test of Portland cement concrete
• the concrete will not fail by fatigue when the stress ratio is smaller
than 0 .5
Sc is the modulus of rupture of concrete

32. PERMANENT DEFORMATION PARAMETERS
• Permanent deformation is an important factor in flexible pavement
design
• The most of the permanent deformation occurs in the upper layers
rather than in the subgrade.
• To estimate the rut depth, it is necessary to determine the permanent
deformation parameters of the material for each layer.

33. Types of Tests
1. Incremental Static Test
2. Dynamic Test
3. Creep Test : it can be used to estimate the rut depth due the
permanent deformation of bituminous layer
Cm is a correction factor for dynamic effect with values ranging from 1 to 2
h 1 is the thickness of the asphalt layer,
o-av is the average vertical stress in the asphalt layer
S mix is the stiffness modulus of the mix.

34. Elastic Modulus
Approximate relationship between k values and other soil properties
can be determine by the following :

35. Elastic Modulus

36. Approximate relationship between k values and other soil properties

37. Poisson Ratio
• The Poisson ratio v is defined as the ratio of the lateral strain to the
axial strain.
• Poisson ratio has a relatively small effect on pavement responses

38. Poisson Ratio

39. Modulus of rupture for Portland cement
concrete
• The compressive strength is a universal measure of concrete quality
and durability.
• A general relationship between the modulus of rupture and the
compressive strength is :
Sc is the modulus of rupture in psi
f ‘c is the compressive strength in psi .

40. The relationship between the modulus
of elasticity and the modulus of rupture