1. University of Illinois at Urbana-Champaign
Coarse Aggregate Selection for Improved Rigid Pavement Joint and Cracking Performance
Jeffery R. Roesler, Ph.D., P.E. and Punya Chupanit, Ph.D.
University of Illinois at Urbana-Champaign
Motivation is to characterize our concrete materials into the design instead of MOR or F’c.
How can we eliminate dowels, improve crack resistance? If you wanted high quality materials on job site how could you specify it?
Selecting concrete constituents to improve cracking and joint performance – coarse aggregate

2. Concrete Pavement Cracking

3. Concrete Pavement Joint Deterioration

4. RESEARCH OBJECTIVES
Improve concrete material’s mechanical properties for rigid pavements by selecting the appropriate concrete constituents
> Maintain high shear load transfer across joints
> Increase concrete slab cracking resistance / ductility
Airfield and CRCP applications along with Low volume roads – Shear
All PCC needs more ductility
Idea of using fracture properties can give more insight until material failure mechanisms and factors that really do affect failure.

5. Joint Load Transfer Efficiency (LTE)
Good Load Transfer L
= 1 U
= 0
Poor Load Transfer
LTE =

6. LOAD TRANSFER ABILITY FACTORS AFFECTING THE LOAD TRANSFER CRACK WIDTH
AGGREGATE TYPE
AGGREGATE SIZE
AGGREGATE SHAPE
AGGREGATE GRADATION
CONCRETE STRENGTH
METHOD & TIMING OF CONCRETE FRACTURE

7. CONCRETE JOINT PERFORMANCE
GOOD BAD
Strong Aggregate × Weak Aggregate
(Nowlen-1968; Colley and Humphrey-1967; Abdel-Maksoud-1999; Wattar-2001; Jensen and Hansen-2001)
Large Aggregate × Small Aggregate
(White and Holley-1972; Walraven-1980; Laible et al-1977; Sutherland and Cashell-1945; Abdel-Maksoud-1999; Jensen and Hansen-2001)
Gap Gradation × Dense Gradation
(Bruinsma et al-1995; Abdel-Maksoud-1999; Wattar-2001)
Rough and Strong Surface × Smooth and Weak Surface

8. JOINT SHEAR TESTING EXPERIMENTAL SETUP

9. PREVIOUS JOINT SHEAR TESTING RESEARCH AT UIUC
CONCRETE TEST SPECIMENS BY ABDEL-MAKSOUD(1999) AND WATTAR(2001)

10. JOINT SHEAR STIFFNESS (Abdel-Maksoud-1999;Wattar-2001)

11. CONCRETE MATERIAL COMPOSITION

12. Concrete Mix Design Nomenclature (25GRG)
Aggregate Size, e.g., 25 or 38 mm
Gap Graded = G
Dense Graded = D
River Gravel = RG
Limestone = LS
Trap Rock = TR

13. Aggregate Composition

14. CONCRETE MATERIALS 25GRG 38GRG 25DRG 25DTR 38GTR 25DLS Aggregate Type
Mix
Number
25GRG
38GRG
25DRG
25DTR
38GTR
25DLS
Type I Cement
(kg/m3)
335.4
Fine/Sand (kg/m3)
741.1
Coarse aggregate
(kg / m3)
1198.0
Water Content
165.2
177.0
171.6
W/C ratio
0.49
0.53
0.51
Aggregate
Type
River
Gravel
Trap
Rock
Limestone
Max. Size
25mm
38mm
Agg.Gradation
Gap
Dense
Gap means standard or regular gradation from the pile but dense gradation was created.

15. CONCRETE COMPRESSIVE STRENGTH
Mix
Number
25GRG
38GRG
25DRG
25DTR
38GTR
25DLS
f’c at hrs
(MPa)
4.0
3.9
4.1
3.8
4.2
f’c at 28 days
33.8
31.7
33.6
32.2
38.1

16. JOINT SHEAR STIFFNESS (Wattar-2001)
Mix ID
Crack Opening (mm)
AVG. Joint Stiffness (MPa/mm)
25GRG
2.0
0.793
38GRG
1.187
25DRG
0.708
25DTR
0.825
38GTR
1.094
25DLS
0.616

17. EXPERIMENTAL SETUP OF CRACK SURFACE CHARACTERIZATION

18. CONCRETE CRACK SURFACES

19. NON-CONTACT LASER PROFILOMETER
SYSTEM FRAME
STEPPING MOTOR
LASER SENSOR
SCANNED SURFACE
STEPPING MOTOR

20. Concrete Surface Re-creation
Actual surface
Scanned surface
50mm Trap Rock Surface

21. Concrete Surface Characterization
Roughness
Surface Roughness
Volumetric roughness
Fractals or degree of irregularity
Power Spectral Area Parameter (PSAP)

22. Surface Roughness Parameter

23. Volumetric Surface Texture Ratio (VSTR)
(Vandenbossche-1999)

24. FRACTAL DIMENSION SENSITIVITY INDEX = 1.33% Mix ID Fractal Dimension
25GRG
2.247
38GRG
2.245
25DRG
2.267
25DTR
2.264
38GTR
2.233
25DLS
2.255
SENSITIVITY INDEX = 1.33%

25. Fractal Dimension to Characterize Crack Surfaces
Can’t predict joint stiffness

26. SURFACE ROUGHNESS PARAMETERS
FRACTAL DIMENSION
(Carpinteri et al-1999)
POWER SPECTRAL AREA PARAMETER (PSAP)
BASED ON 2D FOURIER TRANSFORM
DEFINED AS AREA UNDER POWER SPECTRUM

27. POWER SPECTRAL AREA PARAMETER (PSAP)
BASED ON 2D FOURIER TRANSFORM
DEFINED AS AREA UNDER POWER SPECTRUM
Power Spectrum

28. Power Spectral Area Parameter (PSAP) Determination
Hp,q is array of complex coefficients (real and imaginary part
2D Fourier Transform

29. PSAP Calculation Radial Wave Number (cycles/mm)
Kj = cycles / mm
Spectral density = mm^3/cycle
PSAP = mm^2
Radial Wave Number (cycles/mm)
2D Mean Spectral density (mm3/cycles)

30. PSAP DETERMINATION
PSAP is defined as the area under the 2D mean power spectrum from non-zero wave number up to cycles/mm.
The cut-off wave number separates the large amplitude surface components from the small amplitude surface components

31. PSAP DETERMINATION PSAP Results and Correlation with Joint Stiffness
Radial wave
number
Number of
Component *
25GRG
38GRG
25DRG
25DTR
38GTR
25DLS
R2-VALUE
0.067 3
16.22
20.39
17.04
17.29
20.96
16.14
0.875
0.111 5
20.27
25.22
21.47
21.56
26.32
20.23
0.843
0.178 8
24.13
28.94
25.33
25.48
30.37
23.73
0.839
0.222 10
25.63
26.91
27.01
32.08
25.14
0.823
0.289 13
27.22
31.85
28.69
28.73
33.84
26.68
0.797
0.333 15
27.99
32.57
29.58
29.57
34.69
27.43
0.782
0.400 18
28.85
33.45
30.59
30.51
35.69
28.33
0.766
0.555 25
30.21
34.89
32.23
32.03
37.30
29.74
0.742
0.666 30
30.89
35.62
33.05
32.78
38.12
30.45
0.730
1.066 48
31.04
35.13
32.99
32.39
38.40
31.00
0.655
* The PSAP does not include the zero radial wave number component

32. PSAP Results
Scale Independent, Better Predict Shear Load Transfer, Valid with Different Aggregates.

33. PSAP predicts load transfer ability across cracks/joints

34. Roughness Parameter Summary
Surface Parameter
Correlation with Joint Stiffness
Unique
Sensitivity Index % Rs
0.437 No
5.0
VSTR
0.128
27.7 Df
0.476
Yes
1.3
PSAP
0.875 23

35. How can we characterize concrete surface roughness / shear stiffness
How can we characterize concrete surface roughness / shear stiffness? CONCRETE FRACTURE ENERGY

36. Beam Fracture Testing a0 D P S t

37. WEDGE SPLITTING TEST (WST)
(Linbauer and Tschegg-1986)
Wedge angle = 5 degrees
Advantages= smaller specimen size

38. Fracture Energy (GF) Definitionft
GF = Area or Work of Fracture
Cracked Area

39. GF determination from WST test

40. Fracture Energy Results
Mix ID GF
at 12 hrs
at 28 days
38GTR
194.5
566.2
38GRG
145.8
573.3
25DTR
114.4
384.9
25GRG
89.1
252.3
25DRG
87.8
208.8
25DLS
52.7
93.7
AVG. Joint Stiffness (MPa/mm)
1.094
1.187
0.825
0.793
0.708
0.616

41. Effect of Concrete Material Properties on Surface Roughness, Crack Resistance and Shear Load Transfer

42. GF and Shear Load Transfer
Shear load transfer depends on GF at 28 days.
Concrete with high GF at 28 days provides good shear load transfer across cracks/joints.

43. AGGREGATE TYPE (25mm)
1) TRAP ROCK
2) RIVER GRAVEL
3) LIMESTONE

44. AGGREGATE GRADATION
Aggregate gradation doesn’t have much impact.

45. AGGREGATE SIZE LARGE BETTER THAN SMALL (38MM) (25MM)
Fracture energy can give a good indication of surface roughness and fracture resistance
LARGE BETTER THAN SMALL
(38MM) (25MM)

46. Other significance of GF
GF better characterize the effect of Coarse Aggregate on concrete cracking performance.
f’c (12 hrs) = 3.8 – 4.2 MPa
GF (12 hrs) = 52.7 – N/m
f’c (28 days) = 31.7 – 38.1 MPa
GF (28 days) = 93.7 – N/m

47. CONCLUSIONS
Power Spectral Area Parameter (PSAP) indicates surface roughness and predicts shear stiffness across crack/joint.
GF at 12 hours and 28 days can represent the concrete cracking resistance at early and mature ages
Aggregate type and size primarily influence joint shear stiffness (PSAP) and concrete cracking resistance (GF).
Gradation is a minor effect for the materials we studied.

48. CONCLUSIONS
Concrete with large, strong aggregates perform better than concrete with small, weak aggregates.
Design of concrete materials should use more than flexural/compressive strength to quantify material behavior (GF).
Maintain small crack widths (<1.5 mm)
Gf represents a better means to quantify cracking and surface roughness/shear stiffness. Select highest Gf such that ductility is maintained.

49. Concrete Mix Design Update

50. Concrete Strength Results

51. QUESTIONS /COMMENTS