Presentation on theme: "Pervious Concrete: Unique Benefits Liv Haselbach Associate Professor Civil and Environmental Engineering Washington State University"— Presentation transcript:
Pervious Concrete: Unique Benefits Liv Haselbach Associate Professor Civil and Environmental Engineering Washington State University Associate Director: CESTiCC Center for Environmentally Sustainable Transportation in Cold Climates
What is Low Impact Development? Land development that mimics the natural hydrological and other natural cycles…. Typical practices include: Vegetated ‘green’ roofs Bio-retention cells (raingardens) Permeable pavements Permeable pavements include: Porous asphalt Permeable pavers Pervious concrete Grid and other surface techniques
Permeable Pavement Systems! Surface Infiltration Underground Storage Pollutant Removal: - on top- in ground - in reservoir- to air?
What are Permeable Pavements? Porous asphaltPermeable pavers Pervious concreteAlso overlays
What is Pervious Concrete? Mixture of : Coarse aggregate, Cementitious material, Admixtures, and Water. Carefully controlled amounts of water & cementitious materials are used to create a paste that forms a thick coating around aggregate particles without flowing off during mixing & placing.
How is pervious concrete placed? ConcreteConPC Cement11 Aggregate34 Water1/2~1/3 Fines2~0 Mixed Compacted & Covered Cured 7 days
Porosity of Pervious Concrete Total Porosity Ranges: ~13%-40% Recommended: ~20-25% Tortuousity (vertical and horizontal flow)
Reduces Runoff Reduces Pollutants Improves Safety Mitigates Heat Island Effect May Decrease Erosion Reduces Road Noise Some Benefits
Heat Island Effect Metal Removal pH Recap of Some Studies from WSU
Placements in Pullman Valley Playfield Walks Vetmed Circle Sloan Sidewalk
Work from Other Locations Placement at Iowa State University Placements in Greenville, SC Laboratory and Modeling Work Placement near Salem, OR Placement in Kent, WA
Mitigates Heat Island Effect Source (EPA, 1992)
Heat Island Mitigation Based on work by Liv Haselbach, Michelle Boyer and Bill Cofer and data from Iowa State University led by Vernon Schaefer and John Kevern of UMKC. Portions of this material are based upon work supported by the National Science Foundation grant # The opinions, findings and conclusions presented here are those of the authors and do not necessarily reflect those of the research sponsors. The authors are grateful to the Department of Public Works for the City of Greenville, South Carolina and to Allen Gaither for their assistance in the previous study which provided the field data.
Heat Island Mitigation According to LEED: Heat Island Mitigation for Pavements can come from: - Shading - Naturally with trees or other vegetation - Artificially with: - Roofs (but should be ‘cool’ roofs) - Appurtenances such as solar cells - Under buildings - Open graded pavements with at least 50% open and vegetated - Highly reflective pavements (Most concretes are highly reflective, but pervious is not)
Heat Island Mitigation Permeable pavements may have other characteristics beneficial in mitigating the heat island effect, such as: The insulating capabilities of the extensive pore structure Or evaporative cooling from the water stored in the systems. Unique Structure of Pervious Concrete Vertical Porosity Distribution (Denser on Top) More Porous with Depth Therefore heat will transfer more rapidly through top than through middle and even slower through bottom.
Surface Temperatures Hot Summer Day Surface Temperatures: Greenville SC Courtesy: Haselbach, L.M.: Pervious Concrete and Mitigation of the Urban Heat Island Effect, Proceedings, Proceedings TRB Annual Meeting, Wash. DC, Jan. 2009
Undersurface Temperatures! Greenville SC Measured Temperatures at the Bottom of the Pavement Layers on a HOT Day in July
Iowa State Study Pavement Cross Section and Sensor Placement Kevern, J., Haselbach, L. and Schaefer, V.R., Hot Weather Comparative Heat Balances in Pervious Concrete and Impervious Concrete Pavement Systems, 2 nd International Conference on Countermeasures to Urban Heat Island, September 2009, Berkeley, CA
Less Heat Gain After Heat Waves Where: ΔE pcc =heat gain for traditional concrete system ΔE pcpc,corr =heat gain for pervious concrete system Orange filled triangles indicate daytime precipitation Haselbach, L., Boyer, M., Kevern, J., and Schaefer, V. (2011), Cyclic Heat Island Impacts on Traditional versus Pervious Concrete Pavement Systems, Transportation Research Record Journal of the Transportation Research Board (TRB), No. 2240, TRB of the National Academies. Wash, DC, pp
Metal Removal REMOVAL OF HIGH LEVELS OF DISSOLVED ZINC AND COPPER BY PERVIOUS CONCRETE Acknowledgments Funding from Washington State Ferries WSU contributions: Cara Poor, Jerin Tilson, Marc Beutel, Charles Knack, David Yonge, Michael Wolcott and Kirsti McDaniel
Where does the zinc and copper come from? 21
Research Project Objectives “Average” Levels for roadways +100 µg/L for zinc +20 µg/L for copper We tested for “Hot Spot” concentrations of 5x +500 µg/L for zinc +100 µg/L for copper Why? These are places of concern such as parking areas, congested expressways, queuing areas, etc., where the concentrations are about five times typical. 22
Dissolved Metal Capture Dissolved zinc and copper love concrete! Chemistry Speak – Zinc and copper complexation to hydroxide and carbonate ions. Initially a rapid surface phenomenon in “channels, nooks and crannies” of pervious paving. Then potential diffusion into concrete matrix. 23
Experimental Setup and Test Method Dripped contaminated “rainwater” on pervious concrete cylinders, simulating a ½” rain event. Fairly fast flow rate, about 3 inch per hour!!!! 24
Zinc Results for Hot Spot Tests 25 >95% Average Reduction Haselbach, L., Poor, C., and Tilson, J., Dissolved Zinc and Copper Retention from Stormwater Runoff in Ordinary Portland Cement Pervious Concrete, Construction and Building Materials, 53C..
Copper Results for Hot Spot Tests 26 >90% Average Reduction Haselbach, L., Poor, C., and Tilson, J., Dissolved Zinc and Copper Retention from Stormwater Runoff in Ordinary Portland Cement Pervious Concrete, Construction and Building Materials, 53C..
Accelerated Aging Events –Zinc (OPC) 27 Haselbach, L., Poor, C., and Tilson, J., Dissolved Zinc and Copper Retention from Stormwater Runoff in Ordinary Portland Cement Pervious Concrete, Construction and Building Materials, 53C..
Accelerated Aging Events –Copper (OPC) 28 Haselbach, L., Poor, C., and Tilson, J., Dissolved Zinc and Copper Retention from Stormwater Runoff in Ordinary Portland Cement Pervious Concrete, Construction and Building Materials, 53C.
Smaller Carbon Footprint: pH Absorbs CO 2 from atmosphere Carbonation Process CO 2 (g) + H 2 O(l) = H 2 CO 3 (aq) H 2 CO 3 (aq) = H + (aq) + HCO 3 - HCO 3 - (aq) = H + (aq) + CO 3 2- (aq) Ca(OH) 2 (s) = Ca 2+ (aq) + 2OH - (aq) H + (aq) + OH - (aq) = H 2 O(l) Ca 2+ (aq) + CO 3 2- (aq) = CaCO 3 (s) Simplified Equilibrium Equation CO 2 (g) + Ca(OH) 2 (s) = H 2 O(l) + CaCO 3 (s) Work with Jon Thomle with help from Rob Borden ➜
pH Methods of Testing Three levels of ambient air restrictions TBC BC NC Control Little CO2 Exposure If Used as an Overlay Typical Pervious Concrete System
Decline in Exfiltrate pH Levels Deionized Water. Reference: Thomle, J. and Haselbach, L. (2011), The Declining pH of Waters Exfiltrated through Pervious Concrete, ACI SP-282, The Leading Edge of Pervious Concrete, American Concrete Institute
pH in Exfiltrate Most applications pH not a concern after 0.5 years. (Plus, in pervious concrete systems pH buffered by contact with soil and dissolved minerals.) Also performed tests with cylinders immersed in water with varying levels of carbonates as in natural waters (rivers, lakes, marine.)
Accelerated Carbonation Reference: Haselbach, L. and Thomle, J. (2014), An Alternative Mechanism for Accelerated Carbon Sequestration in Concrete, Sustainable Cities and Society, 12, 25–30.
Summary Pervious concrete provides treatment for dissolved zinc and copper (full system or overlay only) Pervious concrete systems provide mitigation for the heat island effect Pervious concrete can have pH benefits…with time. GO COUGS!!!!!!!!!!!!!!!!!!!!!!