Issuu on Google+

TECHNICAL BULLETIN

Pavement Performance Testing Comparative Test Results NaturalPAVE XL Resin Pavement Vs. Hot Mix Asphalt


NaturalPAVEŽ XL Resin Pavement™

Marshall Stability Pavement Strength And Durabilty

Concrete, with its slab-like behavior and requirement for expansion joints, is classified and tested as a rigid pavement material. Hot mix asphalt pavement and NaturalPAVE XL Resin Pavement, with more elastic behavior and joint-free construction, are classified and tested as flexible pavement materials. The Marshall Stability Test Method (ASTM D 1559) has long been a standard procedure used by materials testing laboratories for evaluation of hot mix asphalt pavement mixtures and other types of flexible pavement materials. The stability of a pavement mixture is tested after the pavement specimen is heated to 140° Fahrenheit temperature, which is representative of hot weather service conditions. Stability is the maximum load resistance that a pavement mix test specimen will develop under compression. Stability translates into the resistance of a paving mixture to distortion, to displacement, to shearing stresses, to rutting and to shoving. Stability is dependent upon both internal friction and cohesion. Internal friction is primarily a combination of the frictional and interlocking resistance of the aggregate in the mix. Cohesion is primarily a measure of the adhesive quality and binding force of the binder material and the efficiency of the specific application rate of the binder in relationship to the specific aggregate material.

8,870 lbs Stability

12,922 lbs Stability

The Marshall Design Criteria provided by the Asphalt Institute requires minimum values for different traffic classifications starting at 750 pounds for light traffic, 1200 pounds for Medium Traffic and 1800 pounds for Heavy Traffic. Cold mix pavement mixtures formulated with NaturalPAVE XL Resin Pavement Binder largely provide far higher stability values due to the unique bonding characteristics of the NaturalPAVE XL product technology. Marshall test results of mixtures using

15,700 lbs Stability

2


Hot Mix Apshalt Pavement a combination of pavement quality dense graded aggregate materials and the NaturalPAVE XL Resin Pavement Binder often approach or exceed 10,000 pound stabilities, which is the top end of the testing capability of the Marshall Test apparatus.* As part of the Marshall Stability test, a “flow” measurement is also taken to evaluate the relative flexibility of different pavement mixtures. A higher stability measure indicates greater bonding strength. A higher flow number indicates greater flexibility and greater resistance to fatigue cracking. The high stability and high flexibility of NaturalPAVE XL Resin Pavement mixtures are visually demonstrated by the condition of the pavement specimens at left following the Marshall Stability test. Hot mix asphalt pavement specimens, as pictured at right, often break apart in pieces at the point where their peak stability is measured. NaturalPAVE XL Resin Pavement specimens, with far higher binding strength and flexibility usually bulge to some small degree, rather than break apart, at the point where peak stability is achieved.

Generally 4,000 - 6,000 lbs. Stability

“Typical Marshall Stability values for hot mix asphalt [are] 4,000 to 6,000 pounds. The NaturalPAVE XL samples tested in our laboratory had Marshall Stability values of 8,000 to 18,000 pounds. NaturalPAVE XL also maintained a higher flow number which, in combination with the stability results, would indicate that the material has good rut resistance, as well as good flexibility for fatigue cracking resistance.” ~ Kleinfelder, Inc. “...it does appear the Resin Pavement (NaturalPAVE XL) can withstand higher loads with a more plastic deformation than the conventional Asphaltic Concrete mixture.” ~ Alpha Geotechnical & Materials, Inc. As indicated in the quotation above, NaturalPAVE XL Resin Pavement mixtures regularly have significantly higher stability and flow test values than the hot mix asphalt pavement mixtures currently in nationwide use.

Marshall Stability Apparatus

*Correction factors are used to compensate for the variations in thickness between different pavement specimens prepared for testing. Once correction factors are calculated the recorded Marshall Stability test results can greatly exceed 10,000 pounds.

3


Resilient Modulus Pavement Strength And Durabilty

Resilient Modulus testing is the method now standardized by the U.S. Department of Transportation’s Federal Highway Administration (FHWA) for the evaluation of pavement materials performance. This is the state of the art test method, recognized both nationally and internationally. In the interest of replicating the dynamic loading conditions that pavement layers experience under automobile and truck traffic, Resilient Modulus testing evaluates the elasticity of the pavement material and its ability to be resilient and return to its original shape and size without any permanent deformation, or damage, after repetitive loading cycles are applied. The comparative resiliency of a pavement material allows pavement design engineers to determine the load bearing capacity of a certain layer thickness of a specific pavement material and to evaluate layer equivalency. In other words, “How many inches of conventional Hot Mix Asphalt Pavement are required to provide the same layer equivalency as a one inch thick layer of a typical NaturalPAVE® XL Resin Pavement™ material?” All pavement materials behave differently at different temperatures and in the Resilient Modulus testing series reported here, which was conducted at the University of Oklahoma pavement materials testing laboratory, the NaturalPAVE specimens were tested at both 77°F (25°C) and 120°F (49°C). The Marshall Stability Test method, which SSPCo mostly uses to evaluate NaturalPAVE XL Resin Pavement mix performance in comparison with Hot Mix Asphalt pavement materials, is conducted at 140°F (60°C), a temperature that is fairly typical of black, heat absorbent Hot Mix Asphalt pavement surfacing in full sun exposure during the summertime. The Marshall Stability Test method measures the bonding strength and the resistance of the pavement material to rutting and shoving under heavy loading conditions. It is well known that Hot Mix Asphalt pavement materials suffer rapid loss of strength and

4


resiliency in hot weather conditions, so it is not surprising that NaturalPAVE mixtures are commonly several times the strength of Hot Mix Asphalt pavement materials in Marshall Stability testing. As indicated in the written report on the University of Oklahoma testing series authored by Terrracon Consultants, Inc., the Reslient Modulus values for NaturalPAVE XL Resin Pavement are far higher than hot mix asphalt in all cases, and NaturalPAVE retained its stability at high temperatures far more effectively. The Hot Mix Asphalt pavement had far lower Reslient Modulus values when tested at 77°F (25°C) and then lost stability at twice the rate as NaturalPAVE Resin Pavement when temperatures were increased. The Resilient Modulus testing demonstrated that a one inch layer of NaturalPAVE XL Resin Pavement is equivalent, at all of the stress levels and temperatures used in the evaluation, to thicker layers of Hot Mix Asphalt pavement. Based upon the Reslient Modulus test values that were recorded at 77°F (25°) temperatures, the one inch thick layer of NaturalPAVE was equivalent to two inches of Hot Mix Asphalt, and on the test values at the 120°F (49°C) temperature, the one inch thick layer of NaturalPAVE was equivalent to more than four inches of Hot Mix Asphalt pavement. Taking all the testing data into account, a layer of NaturalPAVE XL Resin Pavement would be equivalent to a Hot Mix Asphalt pavement material of approximately twice the layer thickness. In hotter climates, the results of both Marshall Stability and Resilient Modulus testing indicate that significantly more than two inches of Hot Mix Asphalt would be required in order to be equivalent to a one inch layer of NaturalPAVE XL Resin Pavement.

NaturalPAVE® XL Resin Pavement™

Specimen #1 Tested at 77° F

Sequence Number

1

Load P (lbs)

899

1784 2674 3561 4432

Deviatoric Stress Sd

45.7

90.6 135.8 180.9 225.1 135.62

Stress Ratio

0.09

0.18

(psi)

(Sd/ST)

Resilient Modulus MR (ksi)

2

3

0.27

4

0.36

5

0.44

AVG 2670

0.268

1932 1821 1712 1514 1458 1687.4*

* A Resilient Modulus test result of 1687.4 KSI equals 1,687,400 PSI

series at University of Oklahoma was previously evaluated for low temperature performance at the University of Nevada Reno pavement materials testing laboratory (see page 7). This NaturalPAVE mix performed without problem down to -30°C (-22°F) temperatures, meeting the low temperature performance requirements for asphalt pavement materials used in colder regions such as the New England states, while a second NaturalPAVE mix tested without problem to below -40°C (-40°F) temperatures.

For additional information on this Resilient Modulus testing series, see our document “Layer Equivalency Between NaturalPAVE XL Resin Pavement and Hot Mix Asphalt” available on our website, www.sspco.com

With the understanding that pavement materials must endure very low temperatures as well as hot temperatures during the annual cycle of the seasons, the same NaturalPAVE mix that was evaluated in the Resilient Modulus testing

5


Solar Reflectance SRI

54.0

The most important aspect of a cool pavement is its ability to reflect rather than absorb solar energy. Among the traditional pavement materials, concrete is the most reflective (high albedo), while black asphalt is the least reflective (low albedo) and most absorbent of solar energy. Typically NaturalPAVE® XL Resin Pavement™ mixtures are formulated with light colored aggregate mixtures and consequently have high solar reflectance similar to concrete pavements. The differences in pavement surface temperatures between heat absorbent asphalt and highly reflective NaturalPAVE XL Resin Pavement can be significant. For example, utilizing an infrared thermometer during mid-August afternoon conditions (98°F air temperatures) and measuring areas of pavement subject to full day sun exposure, the following pavement surface temperatures were recorded at a zoo facility in Washington, D.C.

New Asphalt Pavement. . . . . . . . . . . . . 145°F Weathered Asphalt Pavement. . . . . . . . 139°F NaturalPAVE XL Resin Pavement . . . . 121°F SRI

48.8

SRI

52.7

Cool Pavement

The NaturalPAVE® XL Resin Pavement™ specimens pictured above have solar reflectance measurements that help in meeting or exceeding the minimum Solar Reflectance Index (SRI) of 29 to qualify as high albedo pavement materials. Use of such pavement materials reduces heat absorption and radiance as required for a LEED™ Rating System Point toward “Green Building” Certification from the USGBC as per Credit SS 7.1 (Heat Island Effect) for light-colored/ high albedo pavement.

As part of its educational mission regarding sustainable living practices for the Las Vegas Valley, the Springs Preserve in Las Vegas, Nevada, has an outdoor exhibit displaying the difference in residual heat between objects that reflect solar energy and objects that are nonreflective and absorb solar energy. Using the lizard thermometer sculptures pictured at right, visitors can observe the temperature differences throughout the day between the reflective white lizard and the heat absorbent black lizard. The 119.4°F and 153.5°F temperatures exhibit with temperature sensors to display the difference in displayed were recorded Outdoorresidual heat from reflective and non-reflective objects mid-morning on a summer day while the air temperatures were still under 100°F. They closely parallel the actual temperatures of reflective NaturalPAVE XL Resin Pavement and heat absorbent black asphalt pavement surfaces in these same weather conditions. NaturalPAVE XL Resin Pavement is the ideal surfacing for overlaying existing asphalt, as well as for new pavement installations and paving projects where the relationship of pavement surface temperatures to human health, urban heat island effect and climate change are of concern.

6


Thermal Conductivity NaturalPAVE XL

Portland Concrete

Hot Mix Asphalt Worse

3.0 2.0 1.0 Average Thermal Conductivity

Better

K(W/m. oK)

The thermal conductivity of a pavement material is also relevant to its effectiveness as a cool pavement. A pavement that has high thermal conductivity, such as asphalt, is going to rapidly absorb the solar energy and transmit heat through the pavement into the base course materials and subgrade soils below the pavement. As indicated by testing at the ASU SMART Materials Testing Facility, both asphalt and concrete pavment materials conduct heat more rapidly than NaturalPAVE® XL Resin Pavement™. This means NaturalPAVE XL Resin Pavement has superior insulation value, or thermal resistance. In combination with high solar reflectance, this advantage in thermal resistance makes NaturalPAVE XL Resin Pavement the standard for cool pavement technology.

Thermal Conductivity Arizona State University SMART Materials Testing Facility

Thermal Stress Restrained Specimen Test

Low Temperature Performance

Marshall Stability testing provides impressive high temperature performance measurement for NaturalPAVE XL Resin Pavement mixtures. The NaturalPAVE XL pavement binder technology is equally impressive in low temperature performance. The Thermal Stress Restrained Specimen Test (TSRST) is a standard test for evaluating hot mix asphalt pavement binders. With a requirement of -26° Centigrade performance typical for most of the hot mix asphalt pavement binders used in northern cold climate states, NaturalPAVE XL Resin Pavement mixtures have performed effectively at temperatures as low as -40° Centigrade.

TSRST Apparatus

7


Rotational Penetrometer

The comparative test results that Beneficial Designs, Inc. obtained from field testing pavements with the Rotational Penetrometer closely parallel test results in pavement materials testing laboratories. When NaturalPAVE XL Resin Pavement mixtures are compared with hot mix asphalt mixtures using the Marshall Stability Test, NaturalPAVE XL Resin Pavement specimens regularly exhibit Stability values higher than those typical for asphalt. Stability is a test value that translates into the pavement’s resistance to distortion, displacement, shearing stresses, rutting and shoving. NaturalPAVE XL Resin Pavement, similar to hot mix asphalt, is a surface course pavement material that is reliant on the workmanship of the pavement contractor during placement operations and on the strength and stability of the base course and underlying layers upon which it is constructed. SSPCo is a supplier of pavement materials only and not a contractor, engineer, installer, or construction inspector.

Worse

DISPLACEMENT (IN INCHES)

0.3

NOT FIRM

MODERATELY FIRM

0.17

0.11 0.09

0.21

FIRM

1.5 1.0

Hot Mix Asphalt Worse

NaturalPAVE XL

NOT STABLE

MODERATELY STABLE

0.18 0.17

0.27

0.23

STABLE

Better

Results of Rotational Penetrometer testing conducted by Beneficial Designs, Inc., on installations of NaturalPAVE® XL Resin PavementTM and hot mix asphalt pavement are illustrated at right. Both the asphalt and NaturalPAVE XL Resin Pavement surfaces provided very firm and very stable accessible surfaces in all weather conditions. In both dry and wet testing the NaturalPAVE XL Resin Pavement surface performed slightly better than the asphalt pavement surface in Firmness and Stability.

0.5

Hot Mix Asphalt

Surface Firmness

DISPLACEMENT (IN INCHES)

The US Architectural and Transportation Barriers Compliance Board (the Access Board) is responsible for setting standards for wheelchair accessibility. The Access Board, in conjunction with the National Center for Medical Rehabilitation Research, funded research to establish objective standards for surface characteristics that effect trail accessibility, including the relative “Firmness” and “Stability” of outdoor surfaces. A portable testing device, known as a Rotational Penetrometer, was developed as the basis of a general measurement system. This measurement system is able to evaluate the wet weather performance of various trail surfacing materials as well as dry weather performance. Field testing was conducted by Beneficial Designs, Inc., the firm that developed the Rotational Penetrometer measurement device.

NaturalPAVE XL

Better

Accessibility and ADA Requirements

Surface Stability

In summary, NaturalPAVE XL Resin Pavement is an appropriate all-weather pavement for accessible applications where smooth joint-free running surfaces similar to asphalt pavement are desired, but with more environmentally friendly compositions and appropriate natural aesthetics.

This publication is intended for use by professional personnel who are competent to evaluate the significance and limitations of the information provided. It was reviewed carefully prior to publication. Final determination of the suitability of any information or material for the use contemplated, or for its manner of use, is the sole responsibility of the user.

S O I L S TA B I L I Z AT I O N P R O D U C T S C O M PA N Y, I N C . PO Box 2779, Merced, CA 95344-0779 • Phone: (800)523-9992 or (209)383-3296 • Fax: (209)383-7849 Email: info@sspco.com • Website: www.sspco.com NaturalPAVE and the SSPCo Globe logo are registered trademarks of Soil Stabilization Products Company, Inc. Resin Pavement is a trademark of Soil Stabilization Products Company, Inc. • ©2011 Soil Stabilization Products Company, Inc. - All Rights Reserved


Tech Bulletin