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 CEAT Brown Bag Lunch Seminar OMP Chicago, IL – May 5, 2005

Concrete Pavement Cracking

Concrete Pavement Joint Deterioration

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

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

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

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

JOINT SHEAR TESTING EXPERIMENTAL SETUP

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

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

CONCRETE MATERIAL COMPOSITION

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

Aggregate Composition

CONCRETE MATERIALS Mix Number 25GRG38GRG25DRG25DTR38GTR25DLS Type I Cement (kg/m 3 ) Fine/Sand (kg/m 3 ) Coarse aggregate (kg / m 3 ) Water Content (kg / m 3 ) W/C ratio Aggregate Type River Gravel River Gravel River Gravel Trap Rock Trap Rock Limestone Max. Size25mm38mm25mm 38mm25mm Agg.GradationGap Dense GapDense

Mix Number 25GRG38GRG25DRG25DTR38GTR25DLS f’c at hrs (MPa) f’c at 28 days (MPa) CONCRETE COMPRESSIVE STRENGTH

JOINT SHEAR STIFFNESS (Wattar-2001) Mix ID Crack Opening (mm) AVG. Joint Stiffness (MPa/mm) 25GRG GRG DRG DTR GTR DLS

EXPERIMENTAL SETUP OF CRACK SURFACE CHARACTERIZATION

CONCRETE CRACK SURFACES

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

Concrete Surface Re-creation Actual surfaceScanned surface 50mm Trap Rock Surface

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

Surface Roughness Parameter

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

 FRACTAL DIMENSION Mix IDFractal Dimension 25GRG GRG DRG DTR GTR DLS2.255 SENSITIVITY INDEX = 1.33%

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

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

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

Power Spectral Area Parameter (PSAP) Determination 2D Fourier Transform

PSAP Calculation 2D Mean Spectral density (mm 3 /cycles) Radial Wave Number (cycles/mm)

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

 PSAP Results and Correlation with Joint Stiffness Radial wave number Number of Component * 25GRG38GRG25DRG25DTR38GTR25DLS R 2 -VALUE * The PSAP does not include the zero radial wave number component PSAP DETERMINATION

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

PSAP predicts load transfer ability across cracks/joints

Roughness Parameter Summary Surface Parameter Correlation with Joint Stiffness Unique Sensitivity Index % Rs0.437No5.0 VSTR0.128No27.7 DfDf 0.476Yes1.3 PSAP0.875Yes23

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

Beam Fracture Testing a0a0 D P S t

WEDGE SPLITTING TEST (WST) (Linbauer and Tschegg-1986)

Fracture Energy (G F ) Definition ftft G F = Area or Work of Fracture Cracked Area

G F determination from WST test

Fracture Energy Results Mix ID G F at 12 hrs G F at 28 days 38GTR GRG DTR GRG DRG DLS AVG. Joint Stiffness (MPa/mm)

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

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

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

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

 AGGREGATE SIZE LARGE BETTER THAN SMALL (38MM) (25MM)

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

CONCLUSIONS  Power Spectral Area Parameter (PSAP) indicates surface roughness and predicts shear stiffness across crack/joint.  G F 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 (G F ).

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 (G F ).  Maintain small crack widths (<1.5 mm)

Concrete Mix Design Update

Concrete Strength Results

QUESTIONS /COMMENTS