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Similar a Pervious Concrete: Getting Down to the Details
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Pervious Concrete: Getting Down to the Details
- 1. Pervious Concrete Getting Down to the Details Sean Van Delist Cement Council of Texas
- 3. Permeable Pavements: Applying the Technology
- 4. Porous Pavements Bruce K. Ferguson
- 11. Tree Protection
- 14. Other Uses
- 15. Other Uses
- 17. Other Uses
- 20. Full Exfiltration Permeable Surface Course Gravel/Stone 40% voids Filter Fabric Curb
- 21. No Exfiltration Permeable Surface Course Gravel/Stone 40% voids Liner Curb
- 22. Partial Exfiltration Permeable Surface Course Gravel/Stone 40% voids Filter Fabric Curb
- 24. Surface Course Types: Choosing the Proper Material for the Specific Application
- 25. Dubai Initiative “ It is a very good initiative as long as it does not consume too much water, and does not need much maintenance,
- 27. Decks
- 28. Mulch
- 35. PICP
- 36. Grid/ Turf Pavers & Grasscrete
- 44. Subgrade Soils
- 51. Rainwater Harvesting- Finley Stadium Chattanooga, Tennessee
- 56. Pervious Concrete: What & Why?
- 61. Surface Texture Comparison 3/8” rock or gravel is most common size due to smoothness and appearance
- 76. Falling Head Permeability Test
- 77. Evaluating the Surface Durability Potential of a Pervious Concrete Mixture
- 82. Load Test
- 83. Pervious Concrete: How? Design & Construction
- 86. Key Tools & Resources
- 92. Balance
- 100. Thickness vs. Modulus of Rupture
- 106. Various Placing Equipment Types
- 107. Concrete Compaction More Compaction = Less Porosity Strength Increases Porosity Decreases More Compaction
- 110. Compaction of pervious concrete material during placement
- 111. Jointing and Cross Rolling
- 112. Edge Thickness & Compaction is Critical
- 113. Stresses are Greatest at Edges & Corners
- 120. Insufficient Curing
- 121. Raveling
- 122. Curing 6 MIL PLASTIC
- 124. Loose Edges
- 125. Gaps
- 126. Crash and Burn
- 129. Tie Bars?
- 134. Effects of Joint Spacing 10.0 ft 3.0 ft 3.0 ft 3.0 ft Ultra-thin Slabs Deflect Concrete in Compression Standard Slabs Bend Concrete in Tension
- 135. Jointing Details
- 140. Sealing Joints? Joints don’t need to be sealed, but sealant can reduce or eliminate raveling at joints
- 146. Panels
- 147. “ Natural” Construction/ Isolation Joints?
- 149. Header Curb
- 150. Where Pervious Concrete Abuts Conventional Pavement or Structures
- 152. Pervious Concrete: Other Considerations
- 153. Striping
- 154. Integral Color
- 155. Stamping
- 156. Stained
- 161. Prevent Runoff
- 162. Prevent Debris from Washing Onto Slab
- 163. Slope Grade Away from Pavement SWALE
- 164. Grade Pavement High
- 165. No Adjacent Dirt Parking
- 166. Islands/Vegetation
- 168. Routine Maintenance- Litter Removal
- 169. Vacuum Sweeping
- 170. Vacuum Sweeping
- 174. Before and After Cleaning
- 175. Repair Work
- 176. Questions? For additional information or assistance, Please call or email: Sean Van Delist 210-883-8060 [email_address]
Notas del editor
- “ Big Three” pollutants in urban runoff Sediment (dirt and debris) Heavy Metals - brake linings Hydrocarbons Hydrocarbon sources Asphalt pavement – Primary source Surface treatments and sealers Middle Tennessee State studies – 90 – 95% of hydrocarbons from binder and sealers Oil that drips onto pavements from vehicles Pervious concrete provides more than 80% reduction of “Big Three”
- Other uses for pervious concrete include erosion protection and greenhouse floors.
- Some of the images used in this presentation shows worker that are not using the proper safety equipment or clothing.
- Outdoor synthetic tracks. Nike Grind
- A pervious concrete pavement in a stormwater management design is a part of a system, and not just a pavement in itself. The pavement supports traffic loading while allowing water to pass through the concrete surface. For better effectiveness water should flow vertically through the pavement runoff from the pavement should be minimized. The base, the material under the pavement, acts as temporary storage while supporting the pavement. Grade or slope in the design will affect the storage capacity of the system. A flat pervious concrete pavement system offers the maximum storage capacity. However site conditions and other project constraints may not allow for a flat pervious concrete pavement system to be an economically viable option.
- Here are examples of a residential street and a roadway through a park.
- As the compaction is increased, the permeability is decreased and a compromise has to be reached. Experience has shown that a compaction of the base/subgrade should be in a range of 92 to 95% of the modified proctor compaction. A uniform compaction of 92% seems to give good results of pavement support and permeability. A value of 95% gives good results for the aggregate base. These values will change depending on the subgrade materials and local codes. The concept is to have sufficient pavement support while maintaining sufficient permeability.
- No standards have been developed for the design of the thickness of base materials below pervious concrete pavements. The design thickness has been based on prior experience of performance. Most base thicknesses, for parking area designs, have been at least a 6-inch section. Some designs may indicate a section greater than 6 inches if required to meet stormwater volume storage. Base thickness requirements may also include considerations as to whether the pavement will be subject to deep frost line conditions. In some cases a separate base material may not be required. The pervious concrete may be placed directly on a uniformly compacted soil. This may be the case if pervious concrete is used in areas around trees where the tree roots should not be disturbed. This is also possible in areas where the native soils are highly permeable, and with minimal compaction make a good base for the pavement.
- The total storage capacity of the pervious concrete system includes the capacity of the pervious concrete pavement, the storage capacity of the aggregate subbase, and the amount of water which leaves the system by infiltration into the underlying subgrade. If the pervious concrete has 20% porosity then every inch of pavement can store 0.20 inches of water. If the subbase, number 67 stone for example, has a porosity of 40% then every inch of pavement can store 0.40 inches of rain. Therefore, a 6 inch pervious concrete pavement on 6 inches of #67 stone can store 3.6 inches of water.
- Texture and Porosity are affected by aggregate size, grading, angularity, and the paving equipment you use.
- 3/8” rock or gravel is most common size due to smoothness and appearance.
- The water content must match two things. One is the equipment being used and the other is the weather. The heavier the equipment the lower the water to cement ratio could be. The hotter the weather the higher the water to cement ratio has to be. You can always add water to the concrete at the jobsite to get the correct water to cement ratio.
- Pervious concrete mixtures are stiff mixtures with low water content, and tend to stiffen up faster than higher slump conventional concrete. Set retarding admixtures are often used. Hydration stabilizing admixtures are also used. Air entraining admixtures are used to increase the resistance to damage from freezing and thawing. Viscosity modifying admixtures are gum-based products that improve the cohesivity (stickiness and bonding potential) of cement paste. Their use in pervious concrete mixtures has been seen to provide benefits to the consistency of the mixture during installation. Integral color can be added to pervious concrete in liquid or powdered form. The type, and color, of the aggregate may also influence the decision of using color. Broadcast, dry-shake color, applied to the surface of concrete flatwork is not recommended.
- A typical pervious concrete mix will have anywhere from 15 to 30 percent voids, depending largely on the size of the aggregate used. Field studies have shown that a pervious concrete made with 3/8” aggregate exhibits an average void content of 20 to 25 percent. Because there is no fine aggregate, the density (unit weight) of pervious concrete is slightly less than conventional concrete, weighing in at about 100 to 120 pcf. Compressive strength of pervious concrete averages from 2,500 to 3,500 psi under typical conditions. For applications where higher strengths are deemed necessary, a small amount of fine aggregate (about 500 lbs per CY) can increase the compressive strength. Realize, however, that this will decrease the percentage of voids in the mix. In most cases, we recommend that compressive strength should not be used as acceptance criteria. Rather, you should use density and void content. For acceptance criteria, the density (unit weight) of the plastic pervious concrete should be within 5 lbs (+/-) of the approved mix design.
- A typical pervious concrete mix will have anywhere from 15 to 30 percent voids, depending largely on the size of the aggregate used. Field studies have shown that a pervious concrete made with 3/8” aggregate exhibits an average void content of 20 to 25 percent. Because there is no fine aggregate, the density (unit weight) of pervious concrete is slightly less than conventional concrete, weighing in at about 100 to 120 pcf. Compressive strength of pervious concrete averages from 2,500 to 3,500 psi under typical conditions. For applications where higher strengths are deemed necessary, a small amount of fine aggregate (about 500 lbs per CY) can increase the compressive strength. Realize, however, that this will decrease the percentage of voids in the mix. In most cases, we recommend that compressive strength should not be used as acceptance criteria. Rather, you should use density and void content. For acceptance criteria, the density (unit weight) of the plastic pervious concrete should be within 5 lbs (+/-) of the approved mix design.
- The concrete producer should perform a density (unit weight) test on the first few loads of concrete each production day to verify the plant is running properly. The unit weight is simply the weight of one cubic foot. It is critical in quality control. The Unit Weight should be +/- 5 pcf of specified.
- For larger projects, the engineer might require core test to check for stab thickness and dry density. If necessary, core samples can be obtained from the pavement in accordance ASTM C 42, Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete, to measure the in-place density and other properties as needed. The density of cores after trimming can be determined by determining the calculated volume of the core from its dimensions or by procedures described in ASTM C 140, Test Methods for Sampling and Testing Concrete Masonry Units and Related Units . ASTM is in the process of standardizing test procedures for pervious concrete.
- History: Nearly 750,000 sq. ft. in Texas (all < 10 years old) Almost 500,000 sq. ft. in Austin area alone No known structural failures Some edge failures Mostly all “failures” due to improper installation Surface sealing Raveling Local History: Nearly 750,000 sq. ft. in Texas (all < 10 years old) Almost 500,000 sq. ft. in Austin area alone No known structural failures Some edge failures Mostly all “failures” due to improper installation Surface sealing Raveling
- For parking lot designs, a 6-inch section has been shown to be successful under automobile traffic, with occasional truck traffic. An 8-inch section is normally used for residential streets and heavier truck traffic areas such as delivery lanes.
- The typical process of finishing pervious concrete has five basic steps. Spreading the concrete means raking it off of the truck. Striking off the pavement a little high. Then compact the concrete down to the right elevation. Jointing and edging occurs next followed immediately by curing.
- The more compaction you have the stronger the concrete the less porosity. With pervious poured out of the truck with not compaction you can get severe raveling of the surface, that is the surface will deteriorate. It has very little strength but a great amount of porosity. The perfect amount of compaction will optimize strength and porosity. If you over compact you can seal the surface. You have great strength but no porosity which mean no drainage and the system will fail.
- Critical issues of construction that can lead to failure if not done properly are subgrade compaction, proper mixing water, sufficient compaction, and preventing evaporation.
- Use 6 mil plastic for curing. A few points when securing with plastic sheeting: do not use dirt; use 2x4s or reinforcing bars. Keep in place for at least 7 days; and make sure it is cut and ready before discharge begins and maybe even before the trucks arrive.
- When joints are placed in pervious concrete pavements, it should be jointed when the pavement dimensions are greater than 20 feet in any direction. In some places a 15-foot joint spacing is standard practice. Drying shrinkage in pervious concrete is not as severe as in conventional concrete, and therefore will have a reduced chance of cracking. Experience should dictate the typical joint spacing in a local region. Joints can be placed closer together if the layout warrants. The panels between the joints should be made as square as possible, and the length to width ratio should not exceed 1.5.
- Here’s an example of the joint perpendicular to the curb.
- You can joint the concrete in two ways. You can tool the joint or cut the joint. Tooled joints are preferred. The use of pavement saws for cutting joints are discouraged because the dust residue from the sawing operation can settle into the pores of the pavement. If care is taken to vacuum the dust during the sawing operation then this method of cutting joints is acceptable. Alternatively, water may be used in the sawing operation to flush the pores of the pavement immediately after sawing.
- There is no need to seal joints.
- Consider isolation joint between pervious and conventional pavement.
- Here’s an example of a pervious concrete driveway.
- When placing a pervious concrete pavement adjacent to an asphalt pavement, for example, curbing could be used to prevent water from seeping into the base of the asphalt pavement. This is called a header curb.
- Here are other examples of Header Curbs.
- 15 mil Stego wrap, wrapped underneath the drain rock 12 -24” in
- Pervious concrete can be striped.
- Here’s an example of how pervious pavement should not be treated.
- Curbs can also be used to prevent unpaved areas from draining onto the pavement by controlling the flow path of storm water during a storm event. These areas, allowed to drain onto the pervious concrete, could bring soil or debris that could impact the performance of the pavement/stormwater system.
- Slope surrounding grade away from pervious pavement to avoid debris from clogging the slab.
- Make sure the pavement is graded higher than the surrounding landscaping.
- Avoid having dirt parking next to a pervious pavement.
- Vegetated swales, as defined in Low Impact Development (LID), can be used as separators between parking areas. These areas are designed to be below the top of pavement, and become a part of the overall stormwater management design. Trees, or shrubs, may also be planted in the vegetated swales.
- No standards have been developed for the design of the thickness of base materials below pervious concrete pavements. The design thickness has been based on prior experience of performance. Most base thicknesses, for parking area designs, have been at least a 6-inch section. Some designs may indicate a section greater than 6 inches if required to meet stormwater volume storage. Base thickness requirements may also include considerations as to whether the pavement will be subject to deep frost line conditions. In some cases a separate base material may not be required. The pervious concrete may be placed directly on a uniformly compacted soil. This may be the case if pervious concrete is used in areas around trees where the tree roots should not be disturbed. This is also possible in areas where the native soils are highly permeable, and with minimal compaction make a good base for the pavement.
- No standards have been developed for the design of the thickness of base materials below pervious concrete pavements. The design thickness has been based on prior experience of performance. Most base thicknesses, for parking area designs, have been at least a 6-inch section. Some designs may indicate a section greater than 6 inches if required to meet stormwater volume storage. Base thickness requirements may also include considerations as to whether the pavement will be subject to deep frost line conditions. In some cases a separate base material may not be required. The pervious concrete may be placed directly on a uniformly compacted soil. This may be the case if pervious concrete is used in areas around trees where the tree roots should not be disturbed. This is also possible in areas where the native soils are highly permeable, and with minimal compaction make a good base for the pavement.
- Removing debris from the surface of the pavement is important in maintaining the porosity of the pervious concrete pavements. Trash, such as leaves or paper, may degrade into small particles that may migrate into the void structure of the pavement and reduce the porosity. Periodic sweeping, or a combination of a vacuuming and sweeping, can help reduce the infiltration of materials into the pavement. Here’s an example of pervious before cleaning and after cleaning.
- You will see color variation if you try to repair a slab. In this case the island was moved and new pervious was placed. Naturally it didn’t match the existing slab.