Asphalt makes an excellent road surface, there is no denying it. However, it is toxic not only to the workers absorbing the fumes, but also to the ground, water and generally the environment it sips into.
Center for Disease Control (CDC) - Research on Asphalt Toxicity
National Park Service, Colorado State University - Environmental Contaminants, Asphalt
Virginia Dept of Transportation - Leaching & Toxicity of Recycled Asphalt Pavement to Aquatic Organisms
Over the last two decades we have had summers so hot, that the temperature retained by asphalt is becoming newsworthy problem in larger metropolitan areas worldwide, especially with the elderly population.
Why do we still use asphalt after 40 years?
For the same reason we still pump gas in cars. We often assume that science and technology will secure the continuous improvement of productivity and quality, all at decreasing expense. While noble in theory, current business practices demonstrate that we rarely maintain this never-ending path of improvements, and even resist fundamental breakthroughs due to carefully protected investments and comfortable profit margins.
What is asphalt? (wiseGeek.com)
Asphalt is a thick brownish or black substance derived from the same crude oil which produces kerosene, gasoline and vinyl. It is literally scraped from the bottom of the barrel after all other petroleum-based products have been refined or processed. The tar from the crude oil is usually mixed with sand or gravel (often called aggregate) to form the finished product we call asphalt. The black tar forms a strong adhesive bond with the aggregate, which makes it durable. When used in road construction, asphalt is usually poured over a bed of heavier aggregate in a heated state, then pressed into place by an extremely heavy steam roller. Asphalt does have some drawbacks as a construction material, however. The sulphur fumes released during the heating process can be hazardous to workers and very unpleasant for passers-by. Traffic and constant exposure to the elements can cause asphalt to wear out faster than anticipated. Because the ground beneath the asphalt can repeatedly freeze and thaw, asphalt roads are susceptible to cracks and pothole formation.
Concrete as an alternative
Concrete has always been a great alternative to asphalt. However, it comes with a drawback. If you don't have top notch equipment and engineering from the first layer of base to the last day of work, any missed step or corner cut will inevitably transform into a costly tragedy of proportions unimagined just a few short years later. Concrete as an alternative is cleaner but costs are about the same. Do concrete properly, and it probably costs much more than asphalt. You do get a long lasting, durable road in return.
Polymer as an alternative
Polymer technology (advances in chemistry which allow us to make long strings of molecules) has gradually entered the paving industry, as it has into many other areas. The first to cross into the paving industry were companies which provided dispersible polymer for dust control.
How does polymer address the strength problem?
A good polymer will bond just like asphalt. Just like with asphalt sourcing for good aggregate will make your road as strong as the rock you are bonding with the polymer. Some projects use crushed rock to gain incredible bond and surface strength.
Elasticity
Polymer molecules are long, allowing a great level of elasticity without compromising road strength. Polymer will remain elastic for many, many years after asphalt starts to crack.
Heat Island Effect
The dark color of asphalt is due to the fact that is is 80% carbon. Dark absorbs heat instead of reflecting it. Polymer when applied looks like milk. After it cures (24-48 hours) it becomes transparent. Your road will take the color of your aggregate rock. Use red rock for a red road, and white rock for a white road. Go to town with this idea, make a rainbow road, use rock color for markers, and with a little maintenance it will stay that way for 20 years!
Polymer 101 - what you need to know before sourcing paving polymer
There are many types of pavement polymer. The ones approved for road application cannot be toxic. You recognize these because they are "water soluble". That is the Achilles' Heel of the polymer industry. Hydrophobicity (resistance to the effects of weathering by water, rain) is an area where every vendor claims stellar results. Since the industry is new there are no standards to live up to, so consequently everyone claims their product is great. However, most of these products have been designed for dust control, so they create a temporary crust only.
Main issue to remember - lack of wet bonding strength
Lack of awareness and lack of understanding (lack of education) in the “polymer on the dirt” industry is an issue that needs to be addressed. The fact is that nearly all of the polymer soil stabilization companies will accept, market, sell and use any and every water-based polymer that they can obtain at low cost regardless of the quality or consistency of the polymer. Despite what these companies may say or portray, the quality control is non-existent in the industry. To remember: the biggest single problem with the vast majority of polymers is high water absorption and/or lack of wet bonding strength.
What are the recommended tests for road surface polymer?
The polymer soil stabilization industry must get film strength testing wet and dry as well as bond strength testing wet and dry to be written into the specifications. The industry also needs to make the end consumer and the spec writers understand the importance of the polymer hydrophobicity standards and polymer wet strength.
All water-based latex polymers have some inherent limitations but some have more limitations than others. As a consumer or client you must incorporate proper testing into your requirements, forcing out all but the vendors of product which makes the cut!
Say that in English please!
When you want to paint your living room, you will use INTERIOR paint (vinyl and copolymer blends of vinyl). When you want to paint your car, you will use EXTERIOR paint (acrylic). Likewise, when you choose a polymer for soil stabilization (an aggregate bonding agent, like asphalt) you would want to use exterior grade, a superior material that was designed to resist the elements, and won't wash away with rain. So you must always choose 100% ACRYLIC.
How can I tell what I'm looking at?
An easy way to determine polymer quality and type is by reviewing the respective product's MSDS. An MSDS that shows a wide range of pH will be inconsistent, will likely be a vinyl copolymer blend, and if the pH is below 7 it will likely be all vinyl. An MSDS that has a range for percent solids will be inconsistent, and so will be your road.
When long-term stabilization is the goal, it is important to check the MSDSs of each potential product to ensure that one is using a product that can stand up to the required task for the time frame necessary with the least possibility of requiring reapplication.
Where to buy the correct polymer for road paving applications?
PolymerPaving.com markets accessory products that enhance the already good characteristics of the DirtGlue polymer exponentially. These accessory products allow DGp to cure faster, to be applied at lower temperatures, to tolerate high plasticity soils such a clays and silts much better, and to enhance overall bond strength. This is the only polymer soil stabilization company that has this new and superior technology.
Additional details are available from projects@polymerpaving.com
![[Valid RSS feed]](http://www.look4articles.com/images/icon_Rss.png "XML Feed For RSS"){kind=icon}
Category Rss Feed
Print This Article
Add To Favorites
![[Valid RSS feed]](http://www.look4articles.com/images/rss.jpg "XML Feed For RSS")