The Natural Alternative

By Sara Hubbs, Stabilizer Solutions, Inc.

1. After pre-blending the stabilizer thoroughly and uniformly ?EUR??,,????'??? bucket blending, or blending with a shovel or rake will not work ?EUR??,,????'??? place the mix on a prepared sub-grade.

What is Stabilizer?

Stabilizer is a plant derivative that acts as a binder for aggregate fines. The term ?EUR??,,????'??stabilized decomposed granite?EUR??,,????'?? or ?EUR??,,????'??stabilized crushed stone?EUR??,,????'?? refers to the blending of the stabilizer with either decomposed granite and/or a crushed aggregate to create a natural surface for pathways, driveways and parking lots.

The result is a hardened surface that has a natural appearance and is still porous. Testing has shown that the material reduces the heat island effect and also, when installed correctly, is ADA accessible. In order to maintain product consistency, strict QA/QC policies are followed to ensure standards of purity. These standards, proper aggregate selection, and thorough installation are necessary for a successful application.

2. Level the stabilizer to the desired grade and cross section. The depth of most pathways is 3-inches for heavy foot traffic and light vehicles.

Material Selection

The first step is selecting a crushed stone, aggregate, decomposed granite, or shell (specifically the coquina shell), that is of good quality and meets local engineering parameters. We require 1/4-inch to 3/8-inch minus for pathways and 1/2-inch minus for an application with vehicular use. Failure to meet required specifications can result in a material that is unsatisfactory in terms of engineering qualities, especially in structural strength, which will become evident during periods of rain or heavy usage. Local dealers will be able to educate the specifier and end user about availability of approved materials or pre-blended mixes. Material specifications and terminology will vary throughout the country so always contact the local dealer or manufacturer directly to verify local aggregate specifications. Keep in mind that materials that are acceptable for pathways or similar installations, may not be adequate for areas of vehicular use such as fire lanes or parking lots.

3. Water heavily to achieve full depth moisture penetration of the pathway. Water activates the stabilizer. During the water application, randomly test to ensure complete saturation by using a probing device.

Blending of Stabilized Crushed Aggregate

The second step is proper blending of stabilizer with the chosen material. The most accurate way to blend stabilizer is with a computerized plant that uses a weigh belt feeder in conjunction with a pug mill. We have found that this is the best way to maintain and uniformly blend the proper proportions of stabilizer to aggregate. Attempting to ?EUR??,,????'??bucket blend?EUR??,,????'?? is inaccurate and not acceptable. It is highly unlikely that bucket blending with a front-end loader will blend a uniform mix. Most dealers now have approved blending plants and the manufacturer can provide you with contacts in your area who will provide you with pre-blended material. Proportions of stabilizer to aggregate will vary throughout the country however, in general the rate of 12 to 15 pounds of stabilizer per ton of aggregate is the standard. The higher rates are for installations with vehicular traffic. Ensuring that the stabilizer is thoroughly incorporated into the entire blend is of utmost importance seeing that stabilizer is what will bind each particle of the aggregate.

On-site blending and installation can be achieved by using an 8 to 12 yard cement mixer. Smaller projects can be blended in a 9 to 12 cubic foot mixer. The material should always be blended dry, as water is what causes the stabilizer to harden. Other tools you may need for installation or blending may include shovels, rakes, wheelbarrows, a roller to compact, a watering device and for larger projects a loader and water truck.

4. When the stabilizer has been thoroughly saturated with water, compact aggregate screenings to 85 percent relative compaction by using compaction equipment such as a two to four-ton double drum roller or a 1,000-pound single drum roller with vibratory plate tamp. Do not begin compaction for a minimum of six hours after placement.

Installation

The third step is proper installation. As in any application the sub-grade preparation should not be ignored. The sub-grade should be uniform, free of debris and compacted to a minimum of 90 percent. If done correctly the sub-grade should be close to a mirror image of the surface. For most pathway applications the placement of stabilized crushed aggregate after compaction of the sub-base should be three-inches thick. On areas of vehicular use, stabilized crushed aggregate should be placed at a six-inch compacted depth over a six-inch layer of DOT approved base. To encourage drainage, all trails should have a +/- one percent cross slope with larger applications such as parking lots graded with a +/- one percent slope from around the center of the lot. This will prevent direct water flow across the entire parking lot. Stabilized crushed aggregate is erosion resistant, but may wear in areas of direct and constant flow as water is nature?EUR??,,????'???s solvent.

Another important point to highlight is that when installing stabilized crushed aggregate, the material needs to be completely hydrated with water to a moisture content of +/- 15 percent (after it is leveled as it should be blended and laid down dry). This is the step that contractors often underestimate. Stabilizer requires hydration for activation and therefore it is recommended to install the material in lifts to ensure that complete water penetration has been achieved. Simply probing the material with your finger will indicate if the water has penetrated the profile. After the material has been watered and graded, the next step is compaction. The material should be allowed to sit for a minimum period of six to 48 hours prior to compacting (depending on the area of the country and your weather conditions. Stabilized decomposed granite cannot be installed during rainfall). Attempting to compact too soon may create fissures and an uneven surface. Use a static drum roller that weighs in the range of two to eight tons. Vibratory plates or tamps are not recommended as they will crack the surface. The curing period will vary and depends on the weather, but in general the curing phase is three to six days. When the aforementioned steps are followed your application should be successful. Most job failures that we have seen are a result of improper installation.

Stabilized crushed aggregate is a natural paving alternative - it is not concrete and should not be expected to wear as such. After a successful installation the maintenance is quite simple. Remove debris, such as paper, grass clippings, leaves or other organic material by mechanically blowing or hand raking the surface as needed.

Stabilized crushed aggregate is a natural paving alternative. It is not concrete and should not be expected to wear as such. Minor maintenance of the material may be required even though the material is very forgiving and is easy to repair. Should excess dust occur, re-water the surface and the material will harden. The material is easily patched should you encounter areas of uncommon wear and tear. Simply moisten the area of concern and pre-blend a sufficient amount of stabilizer with the proper amount of aggregate in a concrete mixer. Add water to this mixture (10 percent moisture content) and apply moistened pre-blended aggregate to excavated area to finish grade. Finally, compact with an 8 to 10-inch hand tamp or 250 to 300-pound roller (for high traffic applications such as, cart paths, driveways, or parking lots use a larger 1,000-lb roller). Keep traffic off area for 12 to 48 hours after repair has been completed.