Recent Developments in Porous Concrete Paving Materials

Transcription

1 School of Civil Engineering Purdue University, West Lafayette, Indiana Recent Developments in Porous Concrete Paving Materials Narayanan Neithalath, Rolando Garcia, Will Thornton Jason Weiss, Jan Olek, Bob Bernhard or Purdue Road School - March 25, 2003

2 The Need for Pavements The Time When Cursing Was Louder than Pavement-Tire Interaction

3 Reducing Noise Through Enhanced Porosity Concrete Increasing the porosity of the non-aggregate component of the material Why do we think that this will work 1. Dissipate Energy Through Friction 2. Reduces Surface Area and Resulting Slapping Sound 3. Reduces Horn Effect Driving Direction Block Air Pumping Impact Contact Length Tread Block Slip Highest Slip Velocities Blocks Snap-Out Pavement

4 Other Benefits of Enhanced Porosity Concrete Work for tire and drive train noise as well Rapid drainage of water through interconnected voids Minimizes spray Minimizes glare In the south this is being used for permeable parking lots

5 Influence of Porous Pavements 104 Rolling Noise Measured Using Trailer-Method (db) Test Speed (km/hr) Dense Asphalt Fine Agg. Concrete Porous Asphalt Porous Concrete Caestecker 1997

6 Research Objective Sound Determine whether porous pavements can reduce the total noise level while avoiding potential problem associated with highporosity pavements such as reduced durability Balance Safety, Mechanical, Durability, and Sound Performance Determine Optimal Porosity Determine Proportioning Procedures Mechanical Safety Porosity Durability Cost Hans Arrino (mid 19th Century)

7 Specimen Geometries and Test Procedures For Each Mixture Cast 6 in x 6 in x 28 in Beam Load Casting Direction Casting Direction Span Flexural Strength #1 Sectioning For Sound and Porosity Measurement Casting Direction Span Flexural Strength #2 Sound Measurement Porosity Measurement

8 Mixtures Investigated Influence of Gap Grading and Aggregate Size (#8, #4, 3/8 ) Influence of Blending Aggregates (#8/#4, #8/3/8, #4/3/8 ) Influence of Silica Fume Influence of Sand Content Influence of W/C (To Come) Influence of Fibers (To Come) Micro-particulate (To Come) Mixture I.D. 3/8" Aggregate #4 Aggregate #8 Aggregate Fine Aggregate (Sand) Water-to-Cement Ratio Silica Fume Addition by Cement Weight % % % % ~ % Influence of Gap Grading and Aggregate Size PC-100-3/ PC-100-# PC-100-# Influence of Blending #8 and #4 Aggregates PC-100-# PC-75#8-25# PC-50#8-50# PC-25#8-75# PC-100-# Influence of Blending #8 and 3/8" Aggregates PC-100-# PC-75#8-25-3/ PC-50#8-50-3/ PC-25#8-75-3/ PC-100-3/ Influence of Blending #4 and 3/8" Aggregates PC-100-# PC-75#4-25-3/ PC-50#4-503/ PC-25#4-753/ PC-100-3/ Influence of Sand Content PC-100-# PC-95#4-5Sand PC-97.5#4-2.5Sand PC-92.5#4-7.5Sand Influence of Silica Fume PC-100-# PC-100-#4-06SF PC-100-#4-12SF

9 Using A Simple Method for Screening Mixtures Incoming Sound Hollow Cylinder Sound Waves Loudspeaker Microphone #1 Microphone #2 Sample Reflected Sound Test Specimen Impedance Tube

10 Absorption in 150 mm Thick Specimens (Typ. Conc. 0.05) Absorption Coefficient % #8, 75% #4 25% #8, 75% 3/8" 100% 3/8" Frequency (Hz)

11 Typical Impedance Tube Results Absorption Coefficient % #8, 0% 3/8" 75% #8, 25% 3/8" 50% #8, 50% 3/8" 25% #8, 75 % 3/8" 0% #8, 100% 3/8" Absorption Coefficient % 3/8" 100% #4 100% # Frequency (Hz) Frequency (Hz) Absorption Coefficient % #4 100% #4, 6% SF 100% #4, 12% SF Absorption Coefficient % #4, 0% Sand 100% #4, 2.5% Sand 100% #4, 5.0% Sand 100% #4, 7.5% Sand Frequency (Hz) Frequency (Hz)

12 Influence of Specimen Length Absorption Coefficient (%) c 2l 75 mm Specimen 150 mm Specimen f peak n c = 4 l Frequency (Hz)

13 How Do We Gain an Idea of What the Internal Porosity Looks Like Goal: Separate Porosity Into Total and Accessible Porosity Steps: Cut At Various Depths and Image Seal Sides and Add Low Viscosity Epoxy 12.5 mm 25 mm 25 mm 25 mm 25 mm 37.5 mm

14 Image Processing Sample Preparation Epoxy Added and Specimen Sectioned Using Diamond Bladed Saw Scanning Using a Flatbed Scanner Scanned Image Cropped to a Diameter of 2.75 in (550 Pixels)

15 Image Processing Determine Total Porosity Aggregate Porosity Porosity is White Scanned Image Cropped to a Diameter of 2.75 in (550 Pixels) Color Intensity Threshold Established (~ 150) To Separate Total Porosity (i.e., air and Epoxy Filled Space) Image Cleaned White Pixels (Porosity) Counted = 72,641 Divide By Total Pixels 72,641/ = 30.6%

16 Image Processing Determine Inaccessible Porosity Epoxy Filled Space Epoxy Filled Space Air Filled Void Air Filled Void Air Filled Void Scanned Image Cropped to a Diameter of 2.75 in (550 Pixels) Color the Surface of the Scanned Image Cropped to a Diameter of 2.75 in (550 Pixels) Separate Total Porosity into Accessible Porosity and Inaccessible Porosity

17 Image Processing Determine Inaccessible Porosity Saw Scratches Air Filled Void Color the Surface of the Scanned Image Cropped to a Diameter of 2.75 in (550 Pixels) Color Intensity Threshold Established (~ 70) To Separate Inaccessible Porosity (i.e., Air Filled Space) Image Cleaned Black Pixels (Porosity +Background) and Subtract Background Counted = 225,087 12,376/ = 5.2% 30.6%-5.2% = 25.4% AP

18 Aggregate Size and Pore Size Characteristic Pore Size (mm) /8" & #4 (SR 2) #4 & #8 (SR 2) 3/8" & #8 (SR 4) Percentage of Larger Aggregates

19 Flexural Strength Flexural Strength (MPa) Flexural strength (MPa) Total Porosity (%) Characteristic pore size(mm)

20 Examples of Basic Trends Flexural Strength (MPa) #4 and #8 Aggregate Blend Flexural Strength (MPa) % 3/8" (9.5 mm) 100% #4 (6.4 mm) 100% #8 (3.2 mm) Percent Aggregate #4 (%) Aggregate Size (mm) Flexural Strength (MPa) % #4 Aggregate % Silica Fume By Weight of Cement Flexural Strength (MPa) #4 and Fine Aggregate Blend Percent Silica Fume Addition (%) Percent Fine Aggregate (%)

21 Inspiration for Trying Multi-Layer Systems Series AB - 75% #8's, 25% #4 - Tested 2/2/01 S1R1 - Abs_Coeff_% S1R2 - Abs_Coeff_% S2R1 - Abs_Coeff_% S2R2 - Abs_Coeff_% Average_Abs_Coeff_% Absorption Coefficient Frequency (Hz) Interesting Trend Increasing Absorption At Higher Frequencies

22 Multi-Layer Pavements 0 #8 s Specimen Depth (mm) Accessible Total #4 s Porosity (%) 75% #8 and 25% #4

23 Modeling Sound Absorption and Porosity Z n = z o + 1 Z D Z n 1 α = (1 + R ρ c o 4R ρ c o ) o 2 o + ( M ρ c o o ) 2

24 Using the Model to Determine the Optimal Pore Geometries Maximum absorption coefficient (α) Dp = 2 mm Dp = 3 mm Dp = 5 mm Dp/Da Optimal D p /D a value for each D p where α is max. High Dp/Da: small aperture size, more energy reflected Small Dp/Da: large aperture size, air trapped in pores Aperture Pore

25 Water Permeability mm Intrinsic Permeability (m2) mm 150 mm Graduated Cylinder Specimen Porosity

26 Characterizing the Pore Structure Electrical Impedance Spectroscopy Characterization of pore connectivity and tortuosity

27 Permeability and Conductivity σ β σ 0 φ = σ σ 0 φ Normalized conductivity Porosity Intrinsic permeability (m2) Normalized conductivity (S/m)

28 Controlled Testing Simulated Suspension Speeds of up to 30 mph Tire Testing Frame Road Surface feet 24 in 8-16 in Measure Sound Generated By Tire/Pavement Interaction

29 Summary and Conclusions Porous Concrete May Have Benefits Sound Absorption and Drainage The Structure of these Materials Influence Performance (Impedance Tube, Porosity, Strength, Permeability) Blended Systems Appear to Show Optimal Performance Modeling Appears to Have A Promise to Help Us Optimize the Properties We Want Durability Testing is Beginning for F-T Climates