Caminos de papa
Potawot Health Village está ubicado en 40 acres de tierra en Arcata, CA. Se han construido aproximadamente una milla y media de caminos para el disfrute comunitario de la tierra de conservación que rodea la instalación principal. En lugar de aplicar asfalto convencional para crear pasarelas, Potawot optó por implementar un pavimento de resina de pino para aliviar el impacto potencial en la tierra. Eric Johnson de Potawot dijo que eligieron el material porque "es semiimpermeable y no está compuesto de... contaminantes a base de petróleo (combustible fósil) [que] se derramarán en nuestros humedales y dañarán a los invertebrados y otros organismos y al agua subterránea".
Descripción del material: Pavimento de resina de pino
- El material
Los caminos de resina de pino en Potowat, como se muestra en la figura. 1, se componen de una combinación de agregado regular o roca triturada, sellada con resina de pino y brea de pino (Product Review, 1999).
- Cómo se procesa
Esta alternativa natural al asfalto no se mezcla ni se vierte en caliente como se hace con el asfalto normal, sino que se mezcla mediante un proceso en frío. El agua y la emulsión de pino se mezclan y luego se colocan donde se necesita. Luego, la mezcla se compacta y fragua utilizando métodos convencionales, como apisonadoras en áreas más grandes. La instalación en Potawot se realizó mediante la contratación de una empresa de construcción local, "Hooven and Co., que luego subcontrató a Mercer Frasier para colocar el pavimento" (Eric, 2008). En lugar de que el producto fragüe por enfriamiento, fragua por evaporación del agua que sale de la mezcla (Product Review, 1999).
- El producto final
Gran parte de la energía requerida para colocar asfalto normal se evita porque la mezcla no tiene que calentarse, lo que ahorra recursos de combustibles fósiles. Además, debido a que el material adhesivo está hecho de resina de árbol en lugar de asfalto normal a base de petróleo, el pavimento no contiene ningún químico volátil a base de petróleo (Product Review 1999). El producto final es similar en apariencia al asfalto en textura y espesor, pero puede variar en color. La resina de pino es transparente y toma el color del árido.
Durabilidad
La resistencia del pavimento de resina de pino varía según la calidad de la aplicación, la ubicación del sitio y el producto de resina de pino real utilizado. NaturalPave XL, un distribuidor de resina de pino, utiliza la prueba de estabilidad de Marshall para cuantificar la calidad del producto. Esta prueba calienta el pavimento a 140 F y luego observa cómo responde el pavimento cuando se aplica un peso pesado. NaturalPAVE XL soportó "8,000 a 18,000 libras" (NaturalPAVE XL, 2008). Los resultados típicos de Estabilidad Marshall para asfalto convencional son generalmente de 4,000 a 6,000 libras.
Other studies have claimed that resin pavement has three times the compressive strength (Product Review, 1999). yet there are still issues with any pavement you place on unstable soil. The Potawot paths are constructed on unstable wetland soil which as you can see in Fig. 2 have produced slight cracks in the pavement that had to be fixed.
Cost
According to the EPA, Resin Pavements cost $3/sq. foot for the material and installation.The project at Potawot total cost was $6/sq. foot. Eric Johnson reported the material itself costed $3/sq. foot and installation of the pavement by a local company resulted in another $3/sq. foot.
Comparison to Conventional Asphalt
Asphalt is the most conventional pavement material in our current society and may be cheaper and easier in the short run. Asphalt paving costs $1-5/ sq. foot including installation (Costhelper.com). Many asphalt paving companies exist and it is convienant to schedule a project.
Asphalt may be cost effective in the short term but it also has negative externalities associated with it as well. Since it is a hot mix, it takes energy from fossil fuels to heat it up. Once it is heated it emits harmful air pollutants into the air, such as formaldehyde (EPA, 2003). Asphalt is a impervious material, meaning it does not let water filter through. This diverts rainwater directly into storm drains which lead to runoff of petrochemicals from the pavement to bodies of water, polluting water as well.
Pine resin pavement is an appropriate alternative for asphalt. Pine resin also has benifits and shortcomings and they are listed in the table below.
| Advantages | Disadvantages |
|---|---|
| High solar reflectivity: it reflects more sunlight so the pavement absorbs less heat. | Product is difficult to find |
| Not composed of petroleum products | Higher cost |
| Materials are natural and renewable | Labor intensive |
| Application is not as energy intensive as conventional asphalt | Certain outdoor temperatures are needed for proper finishing |
| Emits less air pollution | Limited amount of information is available |
Links to pine resin producers
References
- Johnson, Eric. Email. Dec. 2, 2008.
- Dooley, Erin E. "New Default for Asphalt?" Environmental Health Perspectives vol.116, no 9, pg 379, 2008.
- "Paving Without Asphalt or Concrete"Product Review: Environmental Building News. Nov. 1, 1999.
- NaturalPAVE® XL "Technical Bulletin-Pavement Preformance Testing." Soil Stabilization Products Company, Inc.
- NaturalPAVE® XL "An aesthetic, environmentally friendly alternative to asphalt". Soil Stabilization Products Company, Inc.
- "Resin Pavement: Cool Pavement Product Information" Environmental Protection Agency, US Government.Oct. 2008. [1]
- "National Emission Standards for Hazardous Air Pollutants: Asphalt Processing and Asphalt Roof Manufacturing" Environmental Protection Agency, US Government Federal Register. May 17, 2003 [2]
- "Pavement Pricing" www.costhelper.com [3]
Update October 2014
The pine resin pavement has held up well, it is very impressive and durable. There are some cracks and vegetation growing through the walkway, along with a few small sink holes and one big one. Overall, the pavement is like that of other materials, it does it's job well but can get rundown.
Pine resin pavement
Wider view of pine resin pavement
Cracks and vegetation in pavement
Vegetation in pavement
Part of the pine resin pavement is sinking
Update October 2017
Much of the remaining pine resin paths are still functional and easily accessible as a result of routine maintenance. Some previous cracks were repaired in the past and currently remain intact. Cement was used to replace one section of the trail. A couple new potholes were observed and large amounts of invasive grass vegetation was found breaching a stretch of the pathway adjacent to gardening area's fence line. To prepare damaged areas, a saltwater mixture is applied during Summer as a soil-friendly herbicide, along with manual weed removal. Holes and cracks are then refilled with an Eco-friendly glue similar to trail materials. During our brief interview, it was mentioned that the saltwater herbicide technique is not as successful as hoped for. One major issue mentioned by staff was that the trail becomes very slippery during Winter/ wet seasons. This hazard, along with routine upkeep, etc. has called for reassessment of the trail's materials. Possible future replacement is being planned with different Eco materials.
Trail damage
Pine resin trail entrance
Pothole
Update September 2018
Since October 2017 other sections of the trail have been replaced by traditional pavement. In certain parts of the remaining trail, cracks, splits, grass, pot holes and dips that are a few inches deep have taken over. The outer edges of the old pavement are crumbling, jagged, fragile and falling apart. Despite some of the trail being in bad shape, other parts of the trail look to be doing great. The portions that seem to be doing great are free of grass sprouting from the middle of the pavement and seem to be the portions closest to where the old pavement meet the new pavement. While speaking to Alme from Potawot community center mentioned that the issues with the pine resin pavement are from the unstable soil.
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