Transcript Slide 1
Pervious Concrete Pavement 4825 Butler Road, Glyndon Maryland 1 Demonstration Panel October 12, 2007 Pervious Concrete Pavement 4825 Butler Road, Glyndon Maryland 3 Pervious Concrete Pavement 4825 Butler Road, Glyndon Maryland 4 Pervious Pavement Section Underdrains Inlet Detail Observation Wells Pervious Concrete Pavement 4825 Butler Road, Glyndon Maryland Work In Progress 9 Specifications and Testing for Pervious Concrete • Rod Meyers, P.E., CDT, BASF • Matt Cockerham, North Star Specifications and Testing for Pervious Concrete • Desired Plastic Properties • Desired In Place Properties • Common Specification Provisions Desired Plastic Properties Batching Consistency ASTM C 143, Slump Test, does not apply Too little water Proper Amount of Water Too much water (1) Tennis, P.D., Leming, M.L., Akers, D.J., Pervious Concrete Pavements, Portland Cement Association, PCA Serial No. 2828, 2004, page 8 • Improves permeability • Improves abrasion resistance • Improves cold weather durability Void content, % by vol. Desired Plastic Properties Stable Paste 45 40 35 30 25 20 15 10 5 0 Best Fit Equation Data 0 5 10 15 20 25 30 Paste content, percent by volume 35 Desired Plastic Properties Workability • Maintains w/cm • Permits timely unloading, placement, finishing, and curing Desired In Place Properties Percolation 3 to 5 gal/ft2/min = 288 in./hr to 480 in./hr = 4.8 in./min to 3.2 in/min Desired In Place Properties Percolation • ASTM developing test method to measure percolation • Constant head method Percolation, in/min Percolation as a Function of Void Content 100 Best Fit Line 80 Data 60 40 20 0 0 5 10 15 20 25 30 35 Void Content, percent by volume Figure A7.5.1, ACI 211.3, Minimum void content for percolation based on NAA-NRMCA tests and test methods Percolation, in/min = 5.684*10-7*(void content,%)5.3034 Measuring Voids Testing Fresh Density • Sample in accordance with ASTM C 172 • Sample every 100 cubic yards • Within +/- 5 lb/ft3 of specified density Testing Fresh Density ASTM C1688 Density and Void Content of Freshly Mixed Pervious Concrete • 0.25 ft3 measure (standard air pot) • Standard Proctor Hammer • Fill in two lifts • Drop hammer 20 times/lift Testing Fresh Density Alternate Methods • ASTM C29 Jigging Procedure • ASTM C138 Rodding Procedure • Filling an empty unit weight bucket Testing Fresh Density Comparing Methods Standard Deviation 6 5 4 3 2 1 0 Proctor - 20 Blows C 29 Jigging C 138 Rodding Usable Voids vrs. Gravimetric Voids Effective Porosity vrs. Total Voids Usable Voids, % = 0.898 * (Gravimetric Voids, %) – 3.1 Usable Voids vrs. Gravimetric Voids Gravimetric Voids % Usable Voids % 10.0 15.0 20.0 25.0 30.0 5.9 10.4 14.9 19.3 23.8 Gravimetric Voids /Usable Voids % 58.8 69.1 74.3 77.4 79.4 A 4 inch thick pervious pavement with 15% usable (effective) voids will store 0.60 inches of rainwater (4” * 0.15 = 0.60”) Desired In Place Properties Mechanical Strength • Rigid Pavement • Flexural Strength 6000 5000 4000 3000 2000 1000 0 28-day Compressive Strength, psi 28-day Compressive Strength, psi Compressive Strength vrs. Void Content Best Fit Line Data 0 5 10 15 20 25 30 Void Content, percent by volume 35 6000 5000 4000 3000 2000 Best Fit Line Data 1000 0 0 5 10 15 20 25 30 Void Content, percent by volume No. 8 Coarse Aggregate No. 67 Coarse Aggregate Figure A7.5.2, ACI 211.3, Relationship between void content and 28-day compressive strengths for No. 8 and No. 67 coarse aggregates No. 8 Coarse Aggregate fc = 6,526 - 193.7 * (void content, %) No. 67 Coarse Aggregate fc = 5,657 - 170.7 * (void content, %) psi psi 35 28-day Flexural Strength, psi Flexural Strength vrs. Void Content 700 600 500 400 300 200 100 0 Best Fit Line Data 0 5 10 15 20 25 30 35 Void Content, percent by volume Flexural Strength, Fmr = 832.8 – 20.3 * (void content, %), psi Pavement Serviceability AASHTO Road Test Relationship between serviceability and load repetitions Designing Pavements to Account for Fatigue Estimating Flexural Stress ACI 330 Guide for The Design and Construction of Concrete Parking Lots Desired In Place Properties Abrasion Resistance • Strong, dense surface • Good curing Desired In Place Properties Cold Weather Durability • Freezethaw Durability • Frost Heave Frost Heave Frost Penetration Depth in MD = 30” FAA recommends 65% of the frost depth contain non-frost-susceptible material For 30” FPD, depth of pervious material (concrete plus base) shall be 20 inches Cold Weather Durability ASTM C 666 testing has indicated low durability Field service says otherwise Mix Design Development for Pervious Concrete in Cold Weather Sponsored by: Iowa Department of Transportation National Concrete Technology Pavement Technology Center Iowa Concrete Paving Association Conclusions • Failure due to freeze-thaw cycles are the result of aggregate deterioration or cement paste matrix failure • Sand, latex and air entrainment admixture improved freeze-thaw durability The Effect of Coarse Aggregate on the Freeze-Thaw Durability of Pervious Concrete John T Kevern, University of Missouri-Kansas City Kejin Wang, Iowa State University Vernon R Schaefer, Iowa State University Conclusion and Recommendations Aggregate absorption has the greatest effect on freeze-thaw durability Review of Maryland Aggregates Suggested Methods to Improve Cold Weather Durability Use 8” to 24” of Open Graded Base Use Sound Aggregates Use Air Entraining Admixture Use 5 to 10% Fine Aggregate Place perforated PVC pipe in base to capture and remove water Specifications Common Provisions Contractor Qualifications Options – On Site • 1 NRMCA Certified Pervious Concrete Craftsman • 3 NRMCA Certified Pervious Concrete Installers • 5 NRMCA Certified Pervious Concrete Technicians Pre-paving Conference • Within two weeks of first placement • In attendance: Owner’s Representative Contractor Concrete Supplier Concrete Foreman Testing Agency Test Panel • Minimum 225 ft2 • Use proposed mix design and materials • Use proposed placement equipment • Include at least one typical joint Test Panel • Fresh density: with +/- 5.0 lb/ft3 • Three cores: average thickness not more than ¼” less or 1.5” more than specified thickness • Single core: not more than ½” less than specified thickness Testing Thickness • Average of three cores more than 1-1/2” greater than specified thickness • No single core more than ½” less than specified thickness Testing Thickness • Three cores per 5,000 ft2 • Average of three cores not more than ¼” less than specified thickness Testing In Place Density • Three cores per 5,000 ft2 • Minimum nominal diameter of 4 inches • Measure density in accordance with ASTM C140 • Hardened density shall be within +/- 5% of approved hardened density from test panels Subgrade Preparation • Maintain final subgrade elevation • Permeability testing: Portland Cement Association recommends: Soils with a percolation rates of ½ in/hr. ASTM D 3385, Double-ring Infiltrometer testing • Subgrade support: minimum density of 92% maximum dry density • Subgrade in moist condition within 3% of optimum moisture content Base Materials • Open graded aggregate • 30% to 40% void content • Elevation of base shall be maintained during placement of concrete. Concrete Materials • Comply with ASTM C 94 • Aggregates – Max. size 1/3” thickness • Aggregates – Use 3/8” maximum size • Admixtures for controlling hydration may be used and facilitate handling of plastic concrete Isolation Joint Materials • ASTM D994, D1751, D1752 Curing Material • Clear 6 mil or thicker polyethylene • Not acceptable: Woven materials, such as burlap and geotextile fabric Wax-based curing compounds Forms • Height equal to the thickness of the pavement • Held in place by stakes and braced to prohibit movement from pressure of concrete and thrust of machinery Setting Formwork • Utilize form release agent • May use previously placed pavement • Limit placement width to 20 feet Batching and Mixing • Comply with ASTM C 94 • Discharge completed within 60 minutes of introduction of water to cement. Placing and Finishing • Deposit concrete on prewetted material • Spread using comealong, squareended tools, rakes. • Water may be added to obtain required consistency. Minimum 30 mixer revolutions. Placing and Finishing Strike off with vibrating screed. Placing and Finishing Strike off with paving machine Placing and Finishing • Compactive effort: 10 psi, minimum • Do not use steel trowels, power finishing equipment Final Surface Texture Cross-roll to compact concrete to dense, pervious surface Final Surface Texture • Compact slab edges with hand tools • Compact concrete to dense, pervious surface • Edging – radius of not less than 1/4 “ Tolerances • Elevation: +3/4”, -0” • Thickness: + 1-1/2” , - ¼” • Contraction joint depth: +1/4”, - 0” Contraction Joints • Joints as shown on plans or as approved • ¼ to 1/3 pavement thickness • Early-entry dry-cut saw: 1” minimum Contraction Joints • Spacing not exceed 20 feet • Aspect ratio: 125% maximum Contraction Joints • Angle at intersections: 80o to 100o • Intersect free edges at 90o, 1.5’ lap Contraction Joints • Align with curb joints within ¼” Curing • Begin curing with 20 minutes of concrete discharge • Cover surface with 6 mil minimum polyethylene • Cover exposed edges • Cure for uninterrupted 7 days minimum Good References • ACI 522.1-08 Specification for Pervious Concrete Pavement • County of Fairfax, Letter 08-01 • Ohio Ready Mixed Concrete Association • Carolinas Ready Mixed Concrete Association • Tennessee Ready Mixed Concrete Association • Georgia Concrete Promotion Association Thank you