Caltrans non-standard Special Provisions Pervious Concrete. David Akers Feb 28, 2012

Transcription

1 Caltrans non-standard Special Provisions Pervious Concrete David Akers Feb 28, 2012

2 Section Paragraph Content 19 RSS B Changes title of the section B USAGE NOTES FOR PERVIOUS CONCRETE AND PERMEABLE INTERLOCKING BLOCKS Pervious pavement areas are not required to have 95% relative compaction C Areas under pervious pavement required to have 88 to 90% relative compaction May be used as often as needed according to the permeability of the underlying soil as determined during the design investigation. 26 Creates Class 4 Aggregate Base Use Class 4 AB when - A reservoir is required - Pavement will be loaded by any heavy vehicles Class 4 AB probably not required under bike or pedestrian paths for support Where required use - 6 in. over soil with R-value > 25 - otherwise use 8 in. minimum Pervious Concrete Pavement - sets paving requirements; requires that 90-7 also is used in special provisions 40-9 Permeable Interlocking Concrete Pavement - defines materials and placement requirements for PICP. Will normally have Class 4 AB under it.

3 ADD TO SECTION A 1. Use if: 1. Water is scarce 2. Compaction can be obtained without the use of water 3. Excessive compaction effort will not be required to meet the specified compaction Where water is scarce, material to be compacted to at least 90 percent must be compacted without adding water if the specified relative compaction can be obtained. 2. Use for areas paved with pervious concrete, permeable interlocking concrete pavers, or porous asphalt. Insert the minimum relative compaction of either "90" or "95" as recommended by the designer. Where an area is paved with pervious concrete, permeable interlocking concrete pavers, or porous asphalt, sections B and C do not apply. Obtain a relative compaction of at least percent. Obtain this relative compaction for the paved area plus 3 feet on each side. Obtain this relative compaction to a depth of at least 2.5 feet below the finished grade.

4 CHANGES TO B Add to section B: Item 2 of the 1st paragraph does not apply to. Use for areas paved with pervious concrete, permeable interlocking concrete pavers, or porous asphalt. Add to section B: Section B does not apply to areas paved with pervious concrete, permeable interlocking concrete pavers, and porous asphalt.

5 REPLACE SECTION C WITH C Relative Compaction, less than 95 Percent Except for areas paved with pervious concrete pavement or permeable interlocking concrete pavement, obtain a relative compaction of at least 90 percent. For areas paved with pervious concrete pavement or permeable interlocking concrete pavements, obtain a relative compaction of at least 88 percent and not more than 90 percent.

6 PERVIOUS PAVEMENT DESIGN - STRUCTURE Any pavement design program can be used Provided design strength limited to 3,000 psi compressive Lower strength reflects load transfer through aggregate to aggregate contact

7 RECOMMENDED MINIMUM PAVEMENT STRUCTURES Following designs are the minimum needed for structural adequacy and/or constructability. Check designs for hydraulic sufficiency; thicker design prevails. Class 4 AB thicknesses are structural minimums; greater thickness is permissible. Thicker Class 4 AB will be required when Pervious concrete is adjacent to a thick section of nonpermeable pavement, or If there is a high hydraulic storage requirement.

8 PEDESTRIAN AND BIKE PATHWAYS, OCCASIONAL LIGHT VEHICLE PERMITTED SIDEWALK EXCEPT AT DRIVEWAY Option foot pervious concrete on native soil Option 2 Permeable interlocking concrete pavement on native soil with a minimum 0.10 foot thick bedding layer.

9 MAINTENANCE VECHICLE PULL-OUT Option 1 Pervious Concrete 0.45 foot pervious concrete on 0.50 foot Class 4 AB. MVP must be outside shoulder area. If R-value is less than 25 add 0.20 foot base or reinforcing fabric. Grading plane of subgrade should be sloped away from shoulder at 2 percent or more. Option 2 Permeable Interlocking Pavement Permeable interlocking concrete pavement may be an option. Contact Pavement Program, Office of Concrete Pavement and Pavement Foundations for recommendations.

10 RECOVERY ZONE OUTSIDE SHOULDER AREA AND GORE AREA Within 10 feet of edge of shoulder 0.45 foot pervious concrete on 0.50 foot Class 2 or Class 4 AB. Beyond 10 feet from edge of shoulder 0.35 foot pervious concrete on native soil. Grading plane of subgrade and Class 2 AB should be sloped away from shoulder at 2 percent or more. Color treatment for pervious concrete is recommended so the pervious concrete looks like soil to minimize intentional trafficking.

11 SIDEWALK AT DRIVEWAY Option foot pervious concrete on 0.70 foot Class 4 AB Option 2 Permeable interlocking concrete pavement on 0.70 foot Class 4 AB.

12 SHOULDER OF MINOR HIGHWAY OR OFF-RAMP Contact Pavement Program, Office of Concrete Pavement and Pavement Foundation for recommendation.

13 MAINTENANCE ACCESS ROAD Option foot pervious concrete on 0.70 foot Class 4 AB Option 2 Permeable interlocking concrete pavement on 0.70 foot Class 4 AB.

14 PARKING AREA FOR PASSENGER VEHICLES INCLUDING TRAFFICKED AREA Option foot pervious concrete on 0.50 foot Class 4 AB. If R-value is less than 25 add 0.20 foot base or reinforcing fabric. Option 2 Permeable interlocking concrete pavement on 0.50 foot Class 4 AB. If R-value is less than 25 add 0.20 foot base or reinforcing fabric.

15 PARKING AREA FOR HEAVY VEHICLES (e.g. rest area on highway with AADTT > 3000) Option foot pervious concrete on 0.70 foot Class 4 AB on reinforcing fabric. Option 2 Permeable interlocking concrete pavement on 0.70 foot Class 4 AB on reinforcing fabric. Note In trafficked area with ADTT > 2000, use a non-permeable paving material. Water from non permeable area may flow to permeable area. Grading plane of subgrade below Class 4 AB must be below AB of adjacent pavement. Slope of grading plane of subgrade should be zero percent. Place filter fabric on vertical interface between base of non-pervious pavement and pervious structural section.

16 PERVIOUS PAVEMENT DESIGN - HYDRAULIC Based on maximum amount of interconnected voids Concrete not degraded by Placing crew walking through the concrete compressing the voids Balls of cement and aggregate in the placed concrete Given Infiltration rate of soil Storm size Tributary area

17 HYDRAULIC DESIGN Simple calculation 6 thick pervious concrete with 20% voids will hold 1.2 of water for a given area 7 thick aggregate base with 30% voids will hold 2.1 of water Total storm water contained = 3.6 Problems How long to completely drain the system? Is there tributary area draining into the pervious concrete?

18 TIME TO DRAIN THE SYSTEM Depends on the underlying base soil From Hydraulic Design of Pervious Concrete, EB303, PCA, Michael Leming, Rooney Malcolm, and Paul Tennis

19 TRIBUTARY AREA Pervious can accept storm water from hardscape, impervious pavement, or structures Maximize storm water capture with proper sloping of the paved areas

20 Example Parameters Thickness, in Available Storage, cf Results Soil Permeability Pervious Agg Base 24-Hr, % 5-Day, % 5-Day Exfiltration, cf Run-off, cf 5-Day Storage, cf Sandy soil, Loam, clay, silt, Clay, clay loam, Clay, clay loam, Pervious area Total drained area Total storage 48,000 sf 54,000 sf 4,800 cf - pervious only 25,200 cf - 21" of aggregate base 30,000 cf - total storage

21 Stage (inches above bottom of storage) Hourly rainfall (in) Example Exfiltration Rate 0.25 in/hr 0 of Aggregate Base 5-Day Exfiltration 11,200 cf Elapsed time (hr) Precip (in) Stage (in) Top gravel (in) Top Pavement (in) Pond limit (in) 4.0

22 Stage (inches above bottom of storage) Hourly rainfall (in) Example Exfiltration Rate 0.01 in/hr 0 of Aggregate Base 5-Day Exfiltration 11,200 cf Elapsed time (hr) 4.0 Precip (in) Stage (in) Top gravel (in) Top Pavement (in) Pond limit (in)

23 Stage (inches above bottom of storage) Hourly rainfall (in) Example Exfiltration Rate Aggregate Base 5-Day Exfiltration 4760 cf Run-off 5490 cf Storage 1000 cf Elapsed time (hr) 4.0 Precip (in) Stage (in) Top gravel (in) Top Pavement (in) Pond limit (in)

24 Stage (inches above bottom of storage) Hourly rainfall (in) Example Exfiltration Rate 0.01 in/hr 21 Aggregate Base 5-Day Exfiltration 4760 cf Run-off Storage 6490 cf Elapsed time (hr) 4.0 Precip (in) Stage (in) Top gravel (in) Top Pavement (in) Pond limit (in)

25 Example Parameters Thickness, in Available Storage, cf Results Soil Permeability Pervious Agg Base 24-Hr, % 5-Day, % 5-Day Exfiltration, cf Run-off, cf 5-Day Storage, cf Sandy soil, Loam, clay, silt, Clay, clay loam, Clay, clay loam, Pervious area Total drained area Total storage 48,000 sf 54,000 sf 4,800 cf - pervious only 25,200 cf - 21" of aggregate base 30,000 cf - total storage

26 Other Comments Use aggregate base even if hydraulic design does not need it Provides a non-rutting pavement foundation No recompaction required Choker courses are not required 10 to 12 is maximum practical single lift thickness

27 Design Entire Streets

28 Got Slope? Gain useable volume with stone base 40% porosity HDPE section

29 Draft Shoulder Use Design