COMPARISON OF TWO FDR ROAD PROJECTS USING EMC SQUARED STABILIZER WITH A MILL AND OVERLAY PROJECT Mescalero Apache Reservation

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1 COMPARISON OF TWO FDR ROAD PROJECTS USING EMC SQUARED STABILIZER WITH A MILL AND OVERLAY PROJECT Mescalero Apache Reservation Beginning in the Fall of 2010, the first of three road reconstruction projects were completed on the Mescalero Apache Reservation in New Mexico. The Mescalero reservation is situated midway between Tularosa and Ruidoso, New Mexico. Funding for all three projects was provided by the Bureau of Indian Affairs (BIA). With project elevations ranging from about 6,500 feet to 7,500 feet these locations are all subject to annual winter snow and frequent freeze-thaw cycles. All three projects were originally specified for Full Depth Reclamation (FDR) with the EMC SQUARED Stabilizer product. In an FDR road reconstruction process, the existing asphalt pavement section and a predetermined amount of underlying aggregate base course materials are pulverized and treated with a stabilizer product to produce a stabilized base course in preparation for placement of a new Hot Mix Asphalt pavement or a chip seal surface treatment. THE PROJECTS MESCALERO BOULEVARD PROJECT. The road passes by the tribe s administration building and then up a hill into a residential area. At its northern terminus, the reconstruction project links to State Highway 70. While the construction specifications called for application of the EMC SQUARED stabilization treatment to the recycled pavement mixture, the FDR approach was not used on this first project. Instead, on recommendation of the project contractor, the distressed asphalt was milled to restore smoothness and damaged areas of pavement were patched with hot mix asphalt. The road was then resurfaced with a 2.5 thick hot mix asphalt overlay. According to the Project Engineer for the BIA, Mr. Ray Pederson, the original FDR design called for application of the stabilization treatment to a 10 depth of recycled pavement and base materials. This deviation from the original FDR project design allows observers to make a performance comparison between this project and the two that followed, both using the EMC SQUARED Base Stabilization treatment. Mescalero Boulevard Mill and Fill approach showing full depth pavement repair. Fall

2 Mescalero Boulevard Mill and Fill approach showing accelerated pavement cracking and rutting. Fall

3 PENN SCOTT DRIVE AND PALMER LOOP DRIVE PROJECTS. At an average elevation of 7,450 feet, the Penn Scott Drive FDR road project is situated at the highest elevation of the three projects. The Palmer Loop Drive FDR project is at an average project elevation of 7,300 feet. These two projects are located off State Highway 70, some 10 miles north east of the Mescalero Boulevard project. These two FDR projects utilized EMC SQUARED Stabilizer to treat a 6 depth of recycled asphalt and base materials. The recycled base and asphalt materials were pulverized and then treated with the EMC SQUARED Stabilizer (1000) solution. A disc plow equipped with depth control gage wheels was used for mixing operations. After the stabilizer solution was applied, the treated materials were shaped to grade and compacted. Both projects were completed with placement of 2 depth hot mix asphalt surface course pavements. Penn Scott Drive Full Depth Reclamation 6 deep, stabilized with EMC SQUARED (1000) Stabilizer 3

4 Palmer Loop Drive - Full Depth Reclamation 6 deep, stabilized with EMC SQUARED (1000) Stabilizer Mill and Overlay versus Full Depth Reclamation with the EMC SQUARED Stabilizer. The Mescalero Boulevard project turned into what is commonly referred to as a Mill and Fill project, which is a top down approach focusing only on repairing the existing asphalt pavement and ignoring the problems of the base course underneath. The other two projects were built from the bottom up, deriving their strength and moisture resistance benefits from use of the EMC SQUARED stabilizer technology. Most premature failures of asphalt pavements are caused by failure of the base course materials underneath the pavement. Given that fact, it could be anticipated that the first project, Mescalero Boulevard, would perform poorly, which has turned out to be the case. In contrast, field reports on the asphalt pavements placed on top of the EMC SQUARED Stabilized Base courses indicate that they remain in excellent condition. Two types of road reconstruction projects are on exhibit. The Mescalero Boulevard project is based on a top down approach that upgrades the upper asphalt layer with no investment made to improve the base layer, while the other two projects were built from the bottom up, with improvement of the foundational layers under the new pavement as the first priority. 4

5 Based on more than twenty-five years of project histories (please see we can reasonably predict the following project outcomes: 1. Lacking a moisture resistant stabilized base, the Mescalero Boulevard pavement project will continue to deteriorate at an accelerated pace. 2. In spite of their location at a higher elevation, the two projects constructed with stabilized base layers will exhibit superior resistance to freeze-thaw and environmental impacts. This will result in more years of maintenance-free performance and extended service life. 3. The ride quality of the two projects with the stabilized base layers will remain smooth, while the ride quality the first project will become progressively rougher. 4. The long term economics of the projects with the stabilized base layers will be superior to the first project. THE ENGINEERING BASIS BEHIND EMC SQUARED STABILIZED BASE MATERIALS Pavements constructed with hot mix asphalt materials are classified as flexible pavements, a type of road surface course pavement that retains some measure of elasticity. Flexible pavement mixtures can be placed as a continuous sheet of pavement, uninterrupted by the construction joints which are typical of rigid concrete pavements. Resilient Modulus and Dynamic Modulus are the state-of-the-art laboratory test methods for measuring the performance of flexible pavement materials. These tests can also be used to evaluate the performance of both stabilized and untreated base course materials, and their compatibility with the asphalt pavement surface course layer. The base course will be expected to provide firm and stable support for the anticipated service life of the constructed road, so the better the base course performs, the longer the asphalt pavement can provide low or maintenance-free service. A strong, waterresistant base course is the ideal foundation in any environment. EMC SQUARED Stabilized Base materials evaluated by Resilient Modulus and Dynamic Modulus test methods have been documented as having the modulus values as much as 5 to 10 times stronger than those of the untreated base materials, providing equivalency in structural section value similar to that of hot mix asphalt pavement materials While maintaining superior elastic behavior, the EMC SQUARED Stabilized Base demonstrated far less susceptibility to permanent deformation than typical hot mix asphalt. If you have further interest in the subject of the layer equivalency of EMC SQUARED Stabilized Aggregate materials, please contact SSPCo for additional information. THE FUTURE IS HERE The Dynamic Modulus testing referenced above was conducted in one of the most highly regarded asphalt pavement materials testing facilities in the United States. The testing documented the cost effective performance of the advanced EMC SQUARED System, a product technology that offers a package of benefits unmatched by any conventional chemical stabilizer product. The availability of this unique stabilizer, proven in laboratory testing and field service for almost three decades, is a game changer at a time when more advanced laboratory test methods (Resilient Modulus and Dynamic Modulus) are in the process of being implemented by road designers and public road agencies across the Unites States. More extensive data developed by these newer test methods is being inserted into state-of-the-art Mechanistic Empirical design (M-E Design) approaches that offer far more sophisticated tools to the design engineer. The new test and design methods represent a valuable tool to design engineers by providing more in-depth understanding of the competency of the native subgrade soils that will underlie the road project, as well as strength values that can be assigned to stabilized soils and stabilized base course materials, while taking into account other variables such as the range of local climatic conditions that will influence the performance of the road during its anticipated service life. With these test methods and M-E Design, designers can now directly apply these engineering values in developing their structural section design for the road construction project, taking advantage of advanced pavement technologies such as the EMC SQUARED stabilizer products. 5

6 Rather than using outmoded top down design methods which rely upon thick asphalt pavement layers for the majority of the strength of the road structural section, design engineers now have the option to more economically improve the stability of their subgrade soils and the strength of their base course materials. The use of low cost stabilizer treatments enable subgrade and base layers to support the traffic loading independent of any asphalt pavement. If the road can be constructed with very stiff and stable subgrade and base course layers, then a much thinner layer of expensive asphalt pavement is going to be needed to provide the wearing surface. These same advancements can also apply to building smoother running and more durable chip seal roads. Since the majority of the expense of building a road is allotted to the hot mix asphalt product used to construct the pavement surface course, the biggest possible cost savings come from designs that reduce the layer thickness of the asphalt pavement and the volume of hot mix asphalt product needed. Bottom up road designs that first explore all options for improving the foundational layers of the road at low cost before determining the required design thickness of the pavement layer will be far more cost effective and efficient. Increased use of modern testing and design methods permits engineers to take advantage of the EMC SQUARED System stabilizer products to include economical stabilized base and subgrade layers in their asphalt pavement designs, thus designing and building longer lasting roads at lower cost. Soil Stabilization Products Company, Inc. PO Box 2779, Merced, CA Ph: (209) or (800) Fax (209) info@sspco.com Website: EMC SQUARED is a registered trademark of Soil Stabilization Products Company, Inc 6