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EMC SQUARED®
TESTING

Dynamic Modulus

Suction and Dielectric Testing

Resilient Modulus

Falling Weight Deflectometer

 

DYNAMIC MODULUS

AGGREGATE MATERIALS TREATED WITH EMC SQUARED STABILIZER AVERAGE
1.7 TIMES STRONGER THAN TYPICAL HOT MIX ASPHALT AT 70°F

...changes in loading frequency and temperature, from below freezing to 130 OF temperature, had minimal impact on the modulus of the EMC SQUARED Stabilized Aggregate...

Dynamic modulus is the main input required for design of Hot Mix Asphalt (HMA) pavements using the nationally recognized AASHTO Mechanistic-Emperical Pavement Design Guide (MEPDG). HMA pavement materials are viscoelastic in nature and their dynamic modulus values vary dramatically in response to changes in loading rate and temperature. For example, HMA materials exhibit much lower dynamic modulus values (significant strength loss) as pavement temperatures increase. In contrast, dynamic modulus testing shows that EMC SQUARED Stabilized Aggregate materials retain a relatively consistent dynamic modulus (consistent strength) through the full range of loading rates and temperature changes, indicating elastic rather than viscoelastic behavior.

TYPICAL DYNAMIC MODULUS DATA FOR HMA MIXTURE

DYNAMIC MODULUS OF EMC SQUARED STABILIZED AGGREGATE CURED FOR 168 HOURS @ 104OF

This laboratory evaluation under the direction of Dr. Sebaaly included both Dynamic Modulus (E*) and Repeated Load Triaxial (RLT) testing, the state of the art test methods for evaluating Hot Mix Asphalt (HMA) materials and providing input for AASHTO MEPDG pavement designs. EMC SQUARED Stabilized Aggregate materials exhibit flexible, or elastic behavior, and modulus values most similar to HMA materials. Consequently, those test methods are equally appropriate for evaluation of these stabilized aggregate materials and for pavement design purposes. The study found that the Dynamic Modulus property of the stabilized aggregate after one week of curing was in the range of 450,000 to 500,000 psi and that it was a very stable material that could be expected to resist permanent deformation very effectively and without excessive stiffening and risk of shrinkage cracking. Dr. Sebaaly states “The combination of the elastic behavior of the EMC SQUARED stabilized aggregate material with its good level of long-term modulus makes it an appropriate choice for pavements serving heavy loads at slower speeds (worst case conditions) as well as for pavements subjected to standard loading conditions.” Unlike HMA materials, which are weakened by increasing temperatures and slower loading conditions due to their highly viscoelastic nature, the study found that changes in loading frequency and temperature, from below freezing to 130°F temperature, had minimal impact on the modulus of the EMC SQUARED Stabilized Aggregate, and that the EMC SQUARED Stabilized Aggregate can therefore be represented by an average constant Dynamic Modulus property of 475,000 psi (versus the Master Curve required for HMA).

COMPARISON OF TYPICAL PERMANENT DEFORMATION CHARACTERISTICS
TYPICAL HOT MIX ASPHALT COMPARED WITH EMC SQUARED STABILIZED AGGREGATE
CURED FOR 72 HRS AT 104°F.

The Typical Deformation Curve for HMA Mix and the Permanent Deformation Characteristics of the EMC SQUARED Stabilized Aggregate, as shown above, are developed from the results of Repeated Load Triaxial (RLT) testing. RLT testing measures the resistance of a material to rutting and permanent deformation. In comparison to the HMA Mix, the EMC SQUARED Stabilized Aggregate Mix showed only 0.1% permanent axial strain. The report on the testing indicates that the deformation characteristics of the stabilized aggregate are expected to remain constant at all temperatures used in the related Dynamic Modulus testing and that the stabilized aggregate is not anticipated to generate any permanent deformation under a wide range of loading conditions.

 

SUCTION AND DIELECTRIC TESTING

The tendency of a soil or aggregate material to attract sufficient quantities of water to cause changes in its physical properties indicates that it is moisture susceptible. Clay, silt and glacial till are all typically classified as highly moisture susceptible, and the presence of these materials as constituents in a soil or aggregate mixture, even in small quantities, will likely have such strong influence that the soil or aggregate mixture will also be moisture susceptible. The selection of aggregate base materials with adequate strength and resistance to damage under traffic loading and changing climatic conditions is important to maximizing the life of pavements. Changes in moisture content can significantly alter the engineering properties of aggregate materials, and moisture susceptibility consequently has major impact on field performance.

According to research conducted by the Texas Transportation Institute (TTI) and the Finnish National Road Administration (FNRA), electrical properties can be used to classify the strength properties of base course aggregates. The studies by TTI were funded by the Texas Department of Transportation (TxDOT) and the US Department of Transportation, Federal Highway Administration (FHWA). The studies showed that the dielectric value and electrical conductivity relate to both the strength and deformation properties, and the moisture and frost susceptibility of base course aggregates. The dielectric value correlates well with the California Bearing Ratio (CBR) value of compacted base materials. The testing methodology, known as Suction and Dielectric Testing, can be utilized to identify aggregate base course materials (also described as flexible base or granular base materials) that are moisture sensitive and frost susceptible and consequently prone to significant reduction in resilient modulus, shear strength and flexural strength in the actual service environment (see description of categories in box at right). The dielectric values of highway base layers can also be measured in the field using Ground Penetrating Radar (GPR) technology. GPR measurement permits nondestructive assessment of the quality of in-place pavement structural sections and for prediction of performance and diagnosis of observed problems.

Suction and Dielectric Testing has also been incorporated in the National Cooperative Highway Research Program (NCHRP) study “Performance Related Tests of Aggregates for Use in Unbound Pavement Layers.” For further background and technical papers on Suction and Dielectric Testing, see Texas Transportation Institute. The Suction and Dielectric Testing methodology was developed by FNRA to address major highway pavement failures attributable to poor performance of the aggregate base course materials. TxDOT was interested in this electrical properties measurement system due to a series of highway pavement failures attributable to moisture susceptible base course materials in West Texas and the Panhandle region of Texas, where pavements experience substantial freeze-thaw cycling. Failures occurred in both bound and unbound bases. Heavily cement-treated “bound” base mixtures (5 to 6 percent cement by weight) were found to be permeable and moisture susceptible in laboratory Suction and Dielectric Testing conducted as part of the forensic study subsequent to the pavement failures. The cement-treated bases had disintegrated under traffic, and field core studies indicated that the stabilization process had been reversed by leaching.

Three aggregate materials evaluated in this laboratory research study conducted at the Texas Transportation Institute (see test results to the left) were obtained from original supply sources for three road construction projects in Alaska, New Mexico and Nevada. Each project was located in a cold climate area with severe winter conditions where aggregate materials are subjected to freeze-thaw cycling as well as seasonal fluctuations in temperature and moisture conditions. In previous field installations of each of the three aggregate materials (in the absence of stabilization treatment), it was evident that they were moisture susceptible and subject to loss of stability in wet weather and freeze-thaw conditions. On each of the three road construction projects, the aggregates were treated with EMC SQUARED® Stabilizer (1000), and placed into service as aggregate surface courses, providing running surfaces for vehicles and heavy trucks. During this time, over six months in one case and years in the others, the stabilized aggregates provided excellent running surfaces, requiring little to no maintenance and with no evidence of moisture penetration or frost damage. The Alaska aggregate sample was obtained from the stockpile used to supply a 1991 FHWA Experimental Feature Project where the EMC SQUARED treated aggregate surface course serviced the haul truck traffic (approximately 17,000 truckloads a year) to Prudhoe Bay and the adjacent oilfields for a period of over four years before this section of “the Haul Road,” known as Elliott Highway, was further upgraded. The stabilized aggregate surface courses on the three projects, having first proven effective while directly subjected to the full range of environmental conditions, to heavy truck traffic and to winter snow plowing operations, were eventually utilized as stabilized or “bound” bases for three different asphalt based surface courses. The Alaska project was surfaced with aggregate base rock treated with “high float” asphalt emulsion, the New Mexico project was surfaced with reclaimed asphalt pavement millings (RAP) treated with the EMC SQUARED Stabilizer, and the Nevada project was paved with hot mix asphalt.

Given the field performance history of these three aggregates from three different regions (as untreated and as stabilized materials), the group of aggregates provided a unique opportunity to demonstrate the effectiveness of Suction and Dielectric laboratory procedures as a performance based test methodology for identification of moisture susceptible aggregate materials and for evaluation of a designated stabilization product in treatment of a specific aggregate material. In the case of these three aggregate materials, the Suction and Dielectric testing provided excellent correlation with the field performance history. Testing of the untreated aggregates predicted accurately that they were moisture sensitive and highly frost susceptible. Testing of the aggregates stabilized by the EMC SQUARED Stabilizer treatment indicated that they were non-moisture sensitive and non-frost susceptible in service for road and highway base applications.

The field performance of each of these three heavily trafficked stabilized aggregate installations is impressive and worth further study. For additional background, review “TREATMENT OF MOISTURE AND FROST SUSCEPTIBILITY - Field and Laboratory Studies”. While all three field projects in this study were stabilized with highly successful applications of the EMC SQUARED Stabilizer (1000) product formulation, which fully met project requirements, the laboratory series also included treatment of an additional specimen of the Nevada aggregate material in demonstration that further reduction of moisture and frost susceptibility available with use of the EMC SQUARED System. The research was conducted under the direction of Dr. Tom Scullion, who has done pioneering research in Suction and Dielectric Testing, Ground Penetrating Radar (GPR) and stabilization of aggregate and soil materials.

For sake of reference, typical dielectric constant values for highway materials are tabulated below:

Material Dielectric Value
Dry Aggregates 4-6
Asphaltic Concrete 5-7
Portland Cement Concrete 7-9
Aggregate Base 6-20*
Subgrades 0-25*

*(depends on Moisture Content)

When Less Is Better

A Dielectric Value of greater than 15 indicates hat the aggreagate is wet or water saturated and extremely moisture and frost susceptible
A Dielectric Value of 10 to 15 indicates that a significant amount of free water has accumulated within the aggregate during the testing period and is a warning signal that the material is moisture sensitive and frost susceptible
Aggregate materials with a Dielectric Value of less than 10 are considered non-moisture sensitive and non-frost susceptible in service for road and highway base applications

*(depends on Moisture Content)

Sample Data
Aggregate Samples Untreated EMC SQUARED
1 Alaska 17.5 8.0
2 New Mexico 35.0 7.1
3 Nevada 17.3 7.7
* Nevada 17.3 5.7

* Treated with EMC SQUARED and EMS Earth Materials Sealant

The Suction and Dielectric Testing results of three aggregate materials (see above) treated with EMC SQUARED Stabilizer (1000), are summarized in the table above. Note that all three untreated aggregates were classified as non-moisture sensitive and frost susceptible. A separate specimen* of the Nevada aggregate was treated with EMC SQUARED 2000 and EMS Earth Materials Sealant, The Dual Component Treatment, which effectively further reduced moisture and frost susceptibility. The Dielectric Values of the aggregates stabilized by EMC SQUARED System treatments are very similar to the values described above for Asphaltic Concrete (hot mix asphalt, or HMA), Portland Cement Concrete and Dry Aggregates.

Wider use of the Suction and Dielectric Test method as a performance indicator should do much to demonstrate that moisture sensitivity and frost susceptibility are far more common to aggregate base materials than generally recognized, and that these problems can be economically treated with advanced concentrated liquid stabilizer technology. Electrical properties are now also being utilized by the Texas Transportation Institute and other organizations for the classification of strength properties and the moisture and frost susceptibility of both untreated soils and stabilized materials.

RESILIENT MODULUS

THE STABILIZED BASE COURSE

The aggregate base course material was treated with SSPCo’s EMC SQUARED® Stabilizer, an economical concentrated liquid stabilizer treatment for base course materials that increases stability without the excessive rigidity (cracking) typical of cement treated base (CTB) materials. In testing conducted at University of Nevada Reno (UNR), the EMC SQUARED System treatment improved the resilient modulus of base course material by a factor of more than 5 times. Materials engineering consultants Professional Service Industries (PSI) provided the following layer equivalency factors and commented that the treated base course had a layer equivalency factor and load carrying capacity approximately equivalent to that of typical hot mix asphalt pavement.

THE PAVEMENT SURFACE COURSE

The access roads, trail system, parking areas and work areas at the Las Vegas Springs Preserve are surfaced with a NaturalPAVE® XL Resin Pavement mixture that blends with the tannish white local soil and rock materials and provides “cool pavements” for a site where 115°F summertime temperatures are common. The NaturalPAVE XL Resin Pavement was tested throughout the design and construction process. Using test procedures standardized for flexible pavements such as hot mix asphalt, materials engineers verified that the NaturalPAVE XL Resin Pavement demonstrated significantly higher stability values (resistance to rutting) than typical hot mix asphalt.

THE STRUCTURAL SECTION

Resilient Modulus testing evaluates the response of a pavement or base course material to dynamic loading. This test method is regarded by AASHTO (American Association of State Highway and Transportation Officials) as the primary factor in characterizing materials for highway pavement applications.

Resilient Modulus Results and Layer Equivalency Factors
Sample ID Average Resilient
Modulus (psi)*
Layer Equivalency
Factor**
Aggregate base with EMC SQUARED 272,500 0.35***
Untreated Aggregate Base 51,000 0.10

As indicated in the Resilient Modulus test results and the layer equivalency factor provided above for the aggregate base course treated with EMC SQUARED, the structural section on this project is more representative of “full depth asphalt”, rather than the typical flexible pavement layer on top of a weaker base course with distinctly different engineering characteristics. Given the low cost of the EMC SQUARED Stabilizer treatment, the pavement life-like performance of the stabilized base provides a highly economical method of “thickening” the effective pavement layer.

 

DOCUMENTING HIGH STRENGTH OF STABILIZED LAYERS WITH FALLING WEIGHT DEFLECTOMETER TESTING

Pictured here is a Falling Weight Deflectometer (FWD) testing appartus* evaluating the strength of a stabilized heavy haul road at Fort Bliss after several months in service under heavy haul trucks and tracked military equipment. The FWD equipment is capable of simultaneously providing Resilient Modulus measurement of both the Stabilized Aggregate Surface Course layer and the Stabilized Soil Subgrade layer below in a non-destructive manner while testing the performance of many miles of road in a single day. The FWD produces a force impulse through the layers that closely simulates a moving wheel load, and it provides a means to determine the equivalency of various materials in relation to their ability to support dynamic or repetitive loading.

Regarding the stabilized heavy haul road structural section at Fort Bliss, the average layer moduli for the stabilized soil subgrade layer was 40,000 psi and the average layer moduli for the stabilized aggregate surface course layer was 165,000 psi.** Using the comparative chart provided by the American Association of State Highway Transportation Officials (AASHTO) for correlation with other standard index tests for additional perspective, the FWD testing demonstrated that the stabilized subgrade soil was significantly stronger than 30,000 psi, the Resilient Modulus value that correlates with a CBR of 100, an R-Value of 85, and a Texas Triaxial of 2.0. The measurements from this group of four test values are representative of high quality crushed aggregate base materials (and some aggregate base materials treated with conventional stabilizer products), so the higher moduli of the native soil material stabilized with the EMC SQUARED System stabilizer treatment (40,000 psi) and the far higher moduli of the aggregate materials stabilized with the same EMC SQUARED System treatment (165,000 psi, or 5.5 times the referenced 30,000 psi strength) demonstrate in materials engineering measurements how this advanced, broad spectrum stabilization technology is producing an entirely new level of field performance and solving problems previously unaddressed. The stabilized heavy haul road system at Fort Bliss provides an excellent example.

* FWD field testing conducted April 7, 2011 by Fugro Consultants, Inc., Austin Texas.

** FWD data analysis by Peter Sebaaly, Ph.D., P.E., Director of the Western Regional Superpave Center, Director of the Nevada Technology Transfer Center, Professor, Civil and Environmental Engineering Department, University of Nevada, Reno.

 

Soil Stabilization Products, Inc.
PO Box 2779
Merced, CA 95344

Toll Free: (800) 523-9992
Phone:     (209) 383-3296

Fax: (209) 383-7849

Email: INFO@SSPCO.COM

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