Advancements in Permeable Pavements

Transcription

1 Advancements in Permeable Pavements Engineers Workshop Saint Vincent College March 14 &

2 Permeable Pavements There are several different words that are used to describe a pavement that water drains through and is used to create a Stormwater Management System Permeable Porous Pervious

3 Definition of Permeable Pavement in the DEP s Best Management Practice Manual A Permeable surface course, underlain by a uniformly-graded stone bed which provides temporary storage for peak rate control and promotes infiltration. The surface course may consist of porous asphalt, porous concrete, or various porous pavers laid on uncompacted soil

4 Advantages in using Permeable Pavements Valuable, usable land is no longer taken for retention or detention ponds Less expensive than underground detention systems. Recharge the aquifiers Remove polution through microbial filtration Control the first flush of a storm. Create a Safer environment

5 DEP Best Practice Manual Porous Asphalt National Asphalt Paving Association Porous or Pervious Concrete National Ready Mix Concrete Association Porous or Permeable Pavers International Interlocking Concrete Pavement Association

6 Permeable Systems Porous Asphalt and Pervious Concrete are very similar products by design. Porous asphalt is a flexible pavement and uses liquid asphalt to bind aggregates together Pervious Concrete is a rigid pavement and uses Portland cement to bind aggregates together. The mixtures of ingredients are critical to the success of the product and the system as well as the installation. Both by design are to have completely porous surfaces

7 Permeable Paving Systems Pervious Concrete Porous Asphalt

8 Permeable Interlocking pavers Interlocking Pavers create infiltration through different size void spaces filled with small aggregate, where the pavers butt together.

9 Infiltration Rates If all the systems are properly installed. Pervious Concrete generally has the highest infiltration rate when initially installed. The rigidity of the product will maintain the void structure. Porous Asphalt will have a good initial infiltration rate as long as it isn t over compacted during installation. Interlocking Paver have the lowest infiltration and that is due to the design. Infiltration only through the voids.

10 Maintaining the Infiltration Rate ASTM C1701 is specific to the Pervious Concrete Industry. The Asphalt or Paver industry does not currently have a test procedure for infiltration rates.

11 Concrete Industry Recommendation Perform the ASTM C1701, 7 Days after the installation when the plastic curing is removed. Create a Baseline for the project that can be used as a comparison for periodic maintenance. Test every six months and compare to the baseline to determine what the maintenance schedule should be for your particular project

12 ASTM C1701 There has been talk within the 1701 committee to have an acceptance number that must be achieved but the number has not been determined. The test is used just to monitor the infiltration rate.

13 Regular Cleaning/ Maintenance The Asphalt and Concrete Industries have share similar viewpoints that periodic vacuuming will keep the pore structure open and water will infiltrate. Paver Industry looks at removing some or all of their gravel to clean

14 Completely Neglected System What can you do if a Pervious Concrete system has been neglected and never cleaned and is to the point of system failure. Specialized Cleaning equipment and evaluate with ASTM C1701

15 Pervious Concrete Advancements Concrete Mix Designs

16 Changes in the mix Cement Optimum Type I lbs./yard lbs Some mixes have incorporated fly ash or slag---100lb Silica Fume -4% Aggregates CLEAN 3/8 stone lbs./yard Fine Aggregates Sand lbs./yard lbs Water Potable W/C Ratio Admixtures Accelerators/retarders have been used Air entrainment Viscosity Modifier Hydration Stabilizer

17 Changing the Mix Ease in unloading trucks The older dry, zero slump pervious mixes were very difficult to get out of the truck. If a contractor or concrete truck driver added water to help get it out of the truck, then the mix had too much paste and sealed the surface.

18 Too Dry vs Wetter mix Dry Wet-Homogenous

19 Better Mix allows for Better Finish Older Pervious mixes with an excessive amount of cement would seal the surface if steel finish tools were used. Lowering the cement content allows for a steel pan finish better, more durable finish.

20 Changes to the mix The use of a Hydration Stabilizer very potent chemical admix that slows the set of the concrete, allows more work time to be able to do decorative work like stamping pervious concrete.

21 Changes to Mix The use of Hydration Stabilizer extends work time to allow for Stenciling.

22 How these changes affect Specifications ACI 522 is the standard Specification for Pervious Concrete. A very active committee with too many changes to even keep up with. The latest draft specification has more changes in any single version than any other ACI document

23 Latest ACI 522 changes Previous version stated no steel finishing equipment was to be used. Suggestion for a good specification would be: Steel finishing tools are permitted as long as the surface does not become sealed off

24 Latest ACI 522 changes Contractor and Technicians from testing lab qualifications. NRMCA Pervious Contractor Certification Requirements Technicians Installer Craftsman Higher Qualifications / Higher Quality

25 Pervious Contractor Certification A Pervious Concrete Technician is a person who demonstrated knowledge by successful completion of a written exam (passing grade of 75%) about proper procedures to place, compact, finish, edge, joint, cure and protect pervious concrete pavements, but who lacks the requisite field experience to qualify as a pervious concrete Installer or Craftsman.

26 Pervious Contractor Certification A Pervious Concrete Installer is a person who has demonstrated the ability to place, compact, finish, edge, joint, cure and protect pervious concrete pavements and has documented a limited project-based field experience in placing pervious concrete. Documentation of at least 3 projects totaling a minimum of 10,000 square feet

27 Pervious Contractor Certification A Pervious Concrete Craftsman is a person who has demonstrated the ability to place, compact, finish, edge, joint, cure and protect pervious concrete pavements and has documented a higher level of field time-based experience in placing pervious concrete. The Craftsman level is intended for contractor personnel who have achieved this highest level of certification by completing the work experience as indicated by the certification criteria. Craftsman are expected to lead an installing crew, work with the concrete supplier to ensure the mixture is appropriate for the installation, designate duties and assignments to the crew, evaluate site and placement conditions and make decisions when the pour needs to be stopped or re-scheduled.

28 Pervious Contractor Certification Craftsman Work Experience: OPTION A: Complete a Performance Evaluation administered by a Local Sponsoring Group approved by NRMCA and document work experience constructing pervious concrete pavement exceeding 1500 hours OR OPTION B: Provide documentation of work experience constructing pervious concrete pavements exceeding 3000 hours

29 Upgrading the Contractor Qualifications Previous ACI522 spec 5 Technicians or 3 Installers or 1 Craftsman Latest Draft ACI Installers or 1 Craftsman

30 Testing Lab Field Technicians Previous versions of ACI 522 did not require Testing Lab Field Technicians to have any qualifications or experience with Pervious Concrete. The latest version has a requirement of Pervious Technician. The main function that field techs have is checking density. If not done properly concrete can be rejected. The procedure is different than used for standard concrete.

31 ACI 522 Requirements ACI522 requires a contractor to provide x 10 mock up pads. Cores will taken from the test panels and used for hardened density comparisons to the actual project placements. Fresh (plastic) Density for the concrete used in the mock up should be +or- 5lbs from the design weigh used in the ASTM1688 process. Once that is accepted then it will be used as acceptance in the job placement.

32 Best Practices in Pervious Spec Writing Always include Contractor Qualification requirements. Require the Ready Mix Concrete Supplier for the pervious concrete to have documentation that he has supplied Pervious Concrete successfully. Require testing lab techs to be Pervious technicians

33 Best Practices in Pervious Spec Writing Do not provide perscriptive proportions for Pervious Concrete Mix designs. Cement content, W/C ratio, admixtures to be used Require that ASTM C1701 be performed 7 days after completion of a project. Contractor installation should require contractor to install and strike-off with a motorized roller screed. It should allow finishing with steel tools provided the surface does not seal.

34 Best Practices in Pervious Spec Writing Curing Pervious Concrete Generally the specification is 7 days covered with 6 mil plastic. If the project was installed in cold temperatures, below 50 degrees, 7 Days may NOT be sufficient. 6 mil plastic, with thermal blankets for 30 days may be necessary in late fall when there will be extended cold temperatures slowing the curing process.

35 Cost of a Pervious Concrete System vs A Complete Underground Detention System

36 Cost of Pervious Concrete

37 Comparing Systems Catch basins Water quality units Manholes 4 and 5 Storm Chambers and piping Gravel excavation and exporting material Labor Asphalt Paving Total cost of case study project $113,445

38 Comparing Systems Pervious Concrete Geo textile fabric 12 Gravel 6 Pervious Concrete Total $91,201 A cost savings of $22,244 over the underground retention system.

39 Pervious Concrete Education NRMCA Pervious Concrete Contractor Certification Class April 11 th Greensburg, Private Industry Council 8:00 12:00 Classroom. Lunch Review and Certification test Hands on Demo at 2:30 Stone and Co. Greensburg Full Certification Engineers Classroom portion without test 75.00

40 The saying in the industry is when it rains, it drains. This video is proof that it will.

41 Questions Bruce Cody PA Aggregates and Concrete Association