what is a choker course

by Dr. Dwight Leannon PhD Published 2 years ago Updated 1 year ago 5 min read

A stabilizing course or "choker course” consisting of a clean single-size crushed stone smaller than the stone in the recharge bed to stabilize the surface for paving equipment. An open-graded asphalt surface with interconnected voids that allow stormwater to flow through the pavement into the stone recharge bed.

What is a good size for a choker course?

Apr 08, 2016 · Choker Course for Asphalt Pavement. RW11 (Civil/Environmental) (OP) 8 Apr 16 18:05. I have an existing pervious concrete parking lot project that the client is asking to replace with conventional asphalt. I need to utilize the stone base (ASTM #4) for storm water management. I am looking for some ideas as to if a choker course is needed for the ...

What is the difference between Reservoir aggregate and choker course?

Many porous pavements have been constructed since the late 1970s. ... n A stabilizing course or "choker course" consisting of a clean single-size crushed stone smaller than the stone in the recharge bed to stabilize the surface for paving equipment. n An open-graded asphalt surface

What is a choker layer in bioretention systems?

The choker course should be a well graded material that inter-locks the surface of the under lying permeable base and provides a working surface for construction of the bituminous layers. The permeable base layer is typically 200mm/250mm deep. All materials used as permeable aggregates comply with the More › More Courses ›› View Course

How do you reduce drain down potential on a choker?

In bioretention systems a choker layer of ≥ 100 mm depth is the recommended method to prevent migration of finer filter media into the underlying storage reservoir aggregate . These same mid-sized granular materials are recommended for use in Stormwater planter underdrains and may be useful in the fine grading of foundations courses for permeable pavements .

What is the purpose of porous pavement?

Porous pavement is a water-permeable structural groundcover that infiltrates precipitation, attenuates stormwater runoff flows and volumes, and reduces temperatures. Porous pavement provides a stable load-bearing surface without increasing a project's total impervious area.

What is porous asphalt made of?

Porous asphalt consists of standard bituminous asphalt in which the fines have been screened and reduced, creating void space to make it highly permeable to water. The void space of porous asphalt is approximately 16%, as opposed to two to three percent for conventional asphalt.

What is the difference between pervious and permeable?

is that permeable is of or relating to substance, substrate, membrane or material that absorbs or allows the passage of fluids while pervious is admitting passage; capable of being penetrated by another body or substance; permeable.

How do you make porous pavement?

Part of a video titled How To Make Pervious Concrete - YouTube

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Product in your area you can make a basic mix yourself with three parts Rock one part cement powder.MoreProduct in your area you can make a basic mix yourself with three parts Rock one part cement powder. And just enough water to hydrate the cement. Almost any rock will do round.

Is porous asphalt expensive?

Porous asphalt ranges from $10 to $15 per square foot, including installation. While more expensive than traditional asphalt, some studies show that porous pavement can last twice as long. However, porous needs more maintenance and upkeep to extend its life.

Can water pass through asphalt?

When cracks develop in asphalt pavement, they let water penetrate under the surface, deteriorating the ground below. Water can penetrate an asphalt pavement through cracks any time it rains, snows, or becomes damp, causing significant damage.Feb 21, 2021

Do permeable pavers count as impervious?

Does Pervious Paving Count as Impervious Surface? Pervious paving, including pavers with permeable openings and seams, is not considered impervious if it is underlain with pervious soil or pervious storage material, such as a gravel layer that is sized to hold 80 percent of the average annual runoff.Aug 28, 2012

Is block paving considered permeable?

Permeable block paving prevents puddles and slippages as the porous material allows water to soak into your driveway blocks. A safer kerbside solution to standard block paving, you don't need to wait for planning permission to start laying your permeable block paving, either.

Do pavers prevent erosion?

Permeable pavers can be used to stabilize erosion-prone soils, especially in sensitive areas like slopes or along roadways. The permeable pavers can be laid over existing soil and filled with either soil or a fill material, like gravel, to weigh down the underlying soil and prevent erosion.

What is considered porous pavement?

Description. Porous pavement is a paved surface with a higher than normal percentage of air voids to allow water to pass through it and infiltrate into the subsoil.

Is concrete more porous than asphalt?

Each product shines in various areas. Despite its higher installation cost, pervious concrete's greater durability makes it a better long-term option than porous asphalt. Durability: Studies show that concrete typically lasts a decade or longer than asphalt before repairs are needed.Jun 15, 2016

Can you seal permeable concrete?

As for sealers, Riggs says, they'll work as long as you have a good open mix that drains well. “It's important you only apply a light coat and use a sealer that breathes and can handle vapor transmission.”

What is a choker course?

A stabilizing course or “ choker course” consisting of a clean single-size crushed stone smaller than the stone in the recharge bed to stabilize the surface for paving equipment. An open-graded asphalt surface with interconnected voids that allow stormwater to flow through the pavement into the stone recharge bed. n n . DESIGN

Do you need a choker course for polyethylene?

A choker course is not necessary for polyethylene molded block products, since they ride on the surface of the open graded base course. It is necessary for brick pavers, pervious concrete and porous asphalt. You should select choker course materials carefully so as not to have them migrate into the base and create settlement problems.

What is a slideshare?

slideshare.netImage: slideshare.netn A stabilizing course or “choker course” consisting of a clean single-size crushed stone smaller than the stone in the recharge bed to stabilize the surface for paving equipment. n An open-graded asphalt surface with interconnected voids that allow stormwater to flow through the pavement into the stone recharge bed. DESIGN The design of a porous pavement

What is OGFC in engineering?

Open-graded friction courses (OGFC) are now designed using the Superpave or Marshall method with requirements for minimum air voids. The use of a choker course over the stone recharge bed is now considered an optional step. When using a choker course, it is important that the aggregate be sized for the stone recharge aggregate.

What is porous asphalt pavement?

Porous asphalt pavements with stone reservoirs are a multifunctional, low impact development technology that ... placed on top; this is called the stabilizing course or choker course. The last layer consists of one or more layers of porous asphalt mixes with interconnected voids that allow water to

Why is porous asphalt used?

Porous asphalt pavements have been used for more than 30 years around the United States to minimize the environmental impact of pave ments. ... followed by an optional "choker" course of single ...

How deep is a WSDOT permeable ballast?

WSDOT Permeable Ballast (9-03.9 (2) ¾ to 2.5 inches) with a 1- to 2-inch deep choker course consisting of the same aggregate gradation that is use for the pavement wearing course (see below). ¾- to 1½-inch, clean coarse, crushed rock aggregate with 0 to 2 percent passing the 200 sieve.

What is OGFC in construction?

These can be constructed as full-depth porous pavements, where water drains through the pavement to the soil; or they can be constructed as an open-graded friction course (OGFC), which helps move water to the side of a pavement, improving friction while reducing both road spray and noise.

How to design a porous pavement?

The general guidelines for the porous asphalt pavement design are: 1 Consider the location for porous pavements early in the site design process. 2 Soil infiltration rates of 0.1 to 10 inches/hour work best. 3 Minimum depth to bedrock or seasonal high water should be greater than two feet. 4 The bottom of the infiltration bed should be flat to maximize the infiltration area. 5 Limit the maximum slope of porous pavement surface to 5 percent. For parking areas on steeper slopes, terrace the parking areas with berms between parking areas. 6 Look for opportunities to route runoff from nearby impervious areas to the infiltration bed to minimize stormwater structures. Pretreatment may be required. 7 Spread out the infiltration. The maximum ratio of impervious to pervious area should be 5:1. For carbonate soils where there is a risk of sinkholes, the maximum ratio should be 3:1. Do not place porous pavements over known sinkhole areas. 8 The design should provide for an alternate path for stormwater to enter the stone recharge bed in the event that the pavement surface becomes plugged or experiences extreme storm events. 9 An overflow system should be included to prevent water in the stone bed from rising into the pavement surface during extreme storm events. 10 The stone recharge bed should be able to drain within 12 and 72 hours.

What is recharge bed?

A geotextile fabric that allows water to pass through, but prevents migration of fine material from the subgrade into the stone re charge bed. A stone recharge bed consisting of clean single-size crushed large stone with about 40 percent voids.