FIELD MONITORING AND LABORATORY STUDIES GIVE WINDOW INTO EXCEPTIONAL PERMANENCE

ABSTRACT

Our most recent newsletter featured a case study about a segment of Interstate Highway pavement in New Mexico, designed with its base course and subgrade treated with the innovative EMC SQUARED System liquid stabilizer products. As of 2024 the extended service life of this pavement will be eight times beyond the lifespan of the conventionally designed pavement that it replaced.

https://stabilizationproducts.net/newsletters_buriedtreasure.html The previous pavement failed and required full depth replacement within three years of its construction, in spite of being designed with a thick layer of asphalt pavement placed on top of a cement treated base (CTB) course. Also of note, highway pavements constructed in Texas that used these same liquid stabilizer products for treatment of subgrade soils remain smooth running and in excellent condition over this same extended time, remaining far smoother-running than nearby highways built on subgrade soils that were treated with cement, fly ash and lime, three calcium-based chemicals. In all cases, the exceptional performance of the pavements designed with base courses and subgrades treated with EMC SQUARED System stabilizer products is even more noteworthy because these highways were constructed on top of the most highly problematic soils and worst-case ground conditions. Compared to the calcium-based chemical stabilizers and the geosynthetic products that the Federal Highway Administration (FHWA) promotes online and in the training courses they provide regarding soil stabilization and base reinforcement, more innovative product technology is now delivering superior results in prolonging the smooth-running behavior of asphalt and concrete pavements. The monitoring and measurement of pavement smoothness according to the International Roughness Index (IRI) is internationally recognized as the most important measure of highway pavement performance. It provides a means to evaluate and compare the performance of different reinforcement and stabilization products in prolonging the lifespan of pavements. While the EMC SQUARED System products produced exceptional results in the field and in materials testing laboratories, proponents of the old calcium-based chemical treatments dismissed the impressive performance of the newer generation products on the basis that they hadn’t yet withstood the test of time by demonstrating the permanence of their benefits in major highway applications. Now that the tables have turned, with highways constructed on EMC SQUARED treated materials maintaining superior smoothness and pavement condition for well over two decades, the opportunity is here to review the engineering basis behind the exceptional performance record of these advanced stabilizer products. This report will summarize materials testing conducted by the State of New Mexico and the New Mexico office of an internationally prominent geotechnical and materials testing firm, as well as the results from three research studies conducted by two of the most highly regarded university-based highway engineering organizations in the United States.

LABORATORY TESTS PROVIDE THE ENGINEERING BASIS FOR DESIGNING HIGHWAYS WITH BASE COURSE AND SUBGRADE STABILIZED WITH EMC SQUARED SYSTEM STABILIZATION TREATMENTS

Presented here is an assortment of laboratory test results from independent third-party studies conducted by highway research and materials engineers in the interest of helping reviewers better understand why these newer generation stabilizer products are so successful in the most important of all performance categories: Prolonging Pavement Smoothness and Extending Pavement Service Life. In regard to the Interstate Highway success story in New Mexico that is referenced above, constructed as a Federal Highway Administration (FHWA) Demonstration Project under the direction of the New Mexico Department of Transportation (NMDOT), only limited testing took place in the state’s materials testing laboratories prior to or during construction. Unconfined Compressive Strength (UCS) tests were conducted with soil materials sampled from the Interstate 40 MP 93– MP 97 project and treated with EMC SQUARED System liquid stabilizer products. As illustrated in the state’s UCS test results shown below, the subgrade soils treated with the EMC SQUARED System stabilizer treatment easily exceeded the 200 psi minimum after 7 days curing that the state had set as their standard for stabilized soils used in highway subgrade construction.

NEW MEXICO DEPARTMENT OF TRANSPORTATION UCS TEST RESULTS

In the interest of serving reviewers with a wider range of engineering test data regarding the performance benefits yielded by this stabilizer treatment, the Albuquerque office of AMEC Earth & Environmental (now Wood Group) was contracted to conduct additional tests with soils sampled from the Interstate 40 project. This laboratory study included Resistance Value (R-value) testing of both the untreated soil and soil treated with EMC SQUARED System stabilizer products. By testing soils treated with the stabilizers, as well as testing the same soils without the addition of the stabilizer treatment, reviewers are given the ability to compare performance values both before and after the application of the stabilizer treatment, and ascertain the extent of improvement. UCS testing measures shear strength, while the R-value is a stiffness test measuring the resistance of compacted aggregate and soil materials to deformation. AMEC staff also sampled soils from two other NMDOT highway locations and subjected those soils to both UCS and R-value tests to afford reviewers with the additional perspective on the performance of the stabilizer products in treatment of three different soil materials. In the case of each of the three soil materials, the EMC SQUARED System treatment proved notably effective, an example being the Unconfined Compressive Strength test results from the state materials laboratory graphed below.

This laboratory testing series measured the increasing strength of the stabilized material over time and evaluated the gain in strength achieved by using the level of compaction energy specified for application of the EMC SQUARED Stabilizer products. https://stabilizationproducts.net/docs/18846.pdf

The performance of the Interstate 40 pavement (Eastbound MP 94–MP 96) constructed over worst case native ground conditions with its subgrade and base course layers stabilized with EMC SQUARED System treatments has proven exceptional for more than two decades. Referencing the White Paper available via the hyperlink above, the results of the R-value laboratory tests associated with the EMC SQUARED Stabilized Subgrade for this segment of interstate highway reveal in laboratory language just how major the improvement EMC SQUARED Stabilizer treatment made in increasing the resistance of the stabilized soil to deformation. For reviewers not versed in the R-value test index, an aggregate material must test at R-value 78 or higher to meet specifications for highway base course applications (Caltrans). An R-value of 10 is considered the equivalent of CBR 1, the very lowest number value on the CBR index and representative of a soil with extremely poor load bearing capacity. As the R-value test results graphed in the White Paper illustrate, we can see that the untreated soil sampled from the I-40 subgrade was improved by the application of the EMC SQUARED System treatment from a very low R-value of 11 up to an R-value of 71, nearly meeting the specification requirements to qualify as an aggregate base course material. Another clayey soil sampled from the subgrade of US 550, a highway project similarly located in northwestern region of New Mexico, was improved to an even higher R-value by the same stabilization treatment.

RESEARCH STUDY #1 – MOISTURE-RESISTANT STABILIZED AGGREGATE MATERIALS

The pavement design of the Eastbound MP 94–MP 96 segment of the I-40 Demonstration Project incorporated the installation of an EMC SQUARED Stabilized Aggregate base course layer in combination with the EMC SQUARED Stabilized Subgrade, further increasing the stiffness of the pavement structural section and reducing the moisture and frost susceptibility of the critically important foundation layers under the asphalt pavement. While no testing was conducted by the State of New Mexico at that time to evaluate the performance of the EMC SQUARED Stabilized Aggregate material or the aggregate material prior to application of the stabilizer treatment, it is fortunate that testing was later conducted at two nationally recognized materials testing laboratories on EMC SQUARED Stabilized Aggregate mixtures formulated with the same and similar aggregate materials sampled from another project in New Mexico. The same aggregate material treated with the EMC SQUARED Stabilizer that was used in construction of the base course for Eastbound MP 94–MP 96 segment of the Demonstration Project, was evaluated in a Tube Suction Testing study conducted at the Texas Transportation Institute (TTI) at Texas A&M University. Tube Suction Testing uses dielectric values and electrical conductivity, two electrical property measurements, to determine which aggregate base course materials are appropriate for use in road construction and to identify those that are prone to failure as a result of their moisture and frost susceptibility. The aggregate base material identified in the study as New Mexico was sourced from the supplier that produced the crushed aggregate base materials used in the construction of the previously referenced Demonstration Project on Interstate 40. As illustrated in the graph of the Tube Suction Test results shown below, this New Mexico aggregate was a highly moisture and frost susceptible material and it was used extensively, without the application of the stabilizer treatment, for many other I-40 reconstruction projects in this same area of New Mexico. The extremely poor performance of this aggregate source in the Tube Suction Test conducted at TTI is one important clue as to why this length of Interstate 40 has been so highly prone to premature pavement failures. As is evident in reviewing the graphed test results and the Research Report referenced in the hyperlink below, this same problematic aggregate material after treatment with the EMC SQUARED Stabilizer, performed similarly to asphalt and concrete pavement materials in resistance to damage by moisture and frost effects.
https://stabilizationproducts.net/docs/18587.pdf

New Mexico Aggregate Tube Suction Test Results

RESEARCH STUDY #2 – NEW APPROACH TO STABILIZATION OF SUBGRADE SOILS

The research study summarized above was conducted at the Texas Transportation Institute (TTI) using electrical property measurements to evaluate the moisture and frost susceptibility of aggregate materials, both before and after treatment with the EMC SQUARED Stabilizer. A second study conducted at TTI under the direction of Dr. Robert Lytton, an internationally recognized authority on the engineering behavior of expansive clay soils, was focused on stabilization of soils rather than aggregate materials. This second study also included the use of electrical property measurements to determine if a stabilized soil mixture has an acceptably low level moisture susceptibility to be considered for use in highway construction. Of important note, the study was focused on stabilizing soils in a manner not previously considered by highway engineers schooled in the belief that the chemical soil stabilization process is exclusively the realm of the calcium-based stabilizers, cement, fly ash and lime. Dr. Lytton defined the goal of the study as identifying a product technology that would do something more than what can be achieved with the application of bulk chemical products, such as lime. In addition to effectively increasing the strength and stiffness of the soil so as to provide a stable working platform for construction traffic, he also wanted to identify a chemical treatment that would provide two additional benefits, the first being “decrease the permeability of the treated soil to reduce the amount of water penetrating into the natural subgrade from the surface,” and secondly to “decrease suction of the treated soil below that of the natural soil so the treated layer will not attract water from below.” Dr. Lytton envisioned an entirely new approach to defining the goal of subgrade stabilization. As a result, we now have full scale highway demonstration projects that have been in service for over two decades, proving the wisdom of Dr. Lytton’s insight into extending pavement service life by using stabilizer products that improve the engineering behavior of soils in radically different manner than calcium-based chemicals. As he predicted, keeping water out of the subgrade under pavements is the key to extending smooth-running behavior and service life. The FHWA Demonstration Project on I-40 featured in the previous Newsletter is an outstanding example of this new design concept at work.

This second research study at TTI was conducted for the purpose of identifying an alternative to the use of lime stabilizer products and consequently evaluated lime treatment as well as the EMC SQUARED System stabilizer treatment for sake of comparison. The study found the EMC SQUARED System stabilizers to be “Superior to lime treatment in terms of strength, stiffness, permeability and swell resistance” and specifically recommended their use for an interstate highway project and a turnpike project that were subsequently constructed on subgrades treated with EMC SQUARED System stabilizer products. The final report recommended the use of EMC SQUARED System stabilizer products as alternatives to lime treatment and made special mention of the suitability of water tight subgrades for construction of highway pavements running across worst case ground conditions and deep deposits of expansive clay soils.
https://stabilizationproducts.net/docs/18588.pdf

In regard to the suitability of stabilized soils for subgrade construction, this study set the upper limit for Electrical Conductivity at 100 milliSiemens per centimeter. As documented below, the soil stabilized with the EMC SQUARED System treatment easily passed this test requirement, and then tested even more impressively four months after being continually subjected to moisture conditioning treatment.

This study measured the Dielectric Constant of an EMC SQUARED stabilized soil material, setting the upper limit as a Dielectric Value of 12, just below the Dielectric Value of 16, which is the point at which plastic deformation of the pavement is predicted as the result of the physical property changes in the soil driven by moisture infiltration and fluctuations in moisture content. Dielectric constants below 11 indicate that the treated soil can adequately resist plastic deformation and can maintain sufficient water tightness. This study also evaluated the untreated or “raw” soil, as well as the same soil treated with lime chemical. As indicated below, the soil treated with the EMC SQUARED System application was highly resistant to moisture infiltration, while the raw soil and the lime treated soil were both highly moisture susceptible and unacceptable for subgrade construction.

RESEARCH STUDY #3 – PERFORMANCE OF EMC SQUARED STABILIZED AGGREGATE IN PAVEMENT MATERIALS TESTING LABORATORY EVALUATION

The third research study relevant to the performance of the EMC SQUARED Stabilized Aggregate base course layer within the pavement structural section of the I-40 Demonstration Project was conducted in the asphalt pavement materials testing laboratory at the Western Regional Superpave Center (WRSC) at the University of Nevada Reno. The source of the untreated aggregate material used in the Second Research Study was located in south central New Mexico and was similar to the aggregate source for the I-40 projects in gradation and plasticity. This second project involved the construction of over 116 miles of military supply roads designed with a base course layer constructed with locally available soils treated with applications of EMC SQUARED Stabilizer and a running surface constructed with EMC SQUARED Stabilized Aggregate materials. Given the pavement-like performance of the stabilized aggregate running surface, state-of-the-art Dynamic Modulus and Repeated Load Triaxial (RLT) test methods typically used to evaluate Hot Mix Asphalt pavement materials were used to evaluate the stabilized aggregate mixture and compare its performance with that of typical hot mix asphalt mixtures. Hot Mix Asphalt (HMA) is a viscoelastic material, meaning it loses its modulus, or stiffness, as temperatures warm or as load weights are increased. Responsive to the viscoelastic nature of HMA materials, the Dynamic Modulus test method evaluates the structural response of HMA materials under various combinations of traffic loads, speed and environmental conditions, including temperature variations ranging from below freezing to 130°F. To make an “apples versus apples” comparison between a typical viscoelastic HMA mixture and an elastic EMC SQUARED Stabilized Aggregate pavement, the Dynamic Modulus and RLT were the test methods that could provide a sophisticated and meaningful comparison between these two different kinds of flexible materials.

Interestingly, the EMC SQUARED Stabilized Aggregate maintained elastic behavior and consistently good modulus value regardless of changes in temperature and loading frequency. The stabilized aggregate, in fact, had a higher modulus than the asphalt pavement in testing at all temperatures ranging from below 70°F to 130°F (21.11°C to 54.44°C). Thirty thousand pounds per square inch (30,000 psi) is typically assumed in design as the modulus value for aggregate base course materials. As graphed in the technical summary report available in the hyperlink below, the stabilized aggregate mixture had a modulus of over 250,000 psi within 24 hours of curing and 475,000 psi after 7 days of curing. This is approximately the same modulus as a typical asphalt mixture exhibits when it is tested in Dynamic Modulus at a temperature of 55°F (12.78°C). Much like concrete pavement mixtures, EMC SQUARED Stabilized Aggregate mixtures go on to cure and improve over time, but they are ready to support traffic almost immediately upon placement.

Based upon the results of the Repeated Load Triaxial testing that was also conducted in the WRSC pavement testing laboratory, the conclusion of the study was that the stabilized aggregate material “..is not anticipated to generate any permanent deformation under a wide range of loading conditions.” (Dr. Peter Sebaaly)
https://stabilizationproducts.net/docs/18828.pdf

SUMMARY

The presence of a stabilized base course layer with such exceptional engineering test values supporting the asphalt pavement on the Eastbound MP 94 – MP 96 segment of Interstate 40 helps explain why this particular segment of heavily trafficked highway pavement is going on 24 years of trouble-free service when the previous conventionally designed pavement that it replaced had completely failed after just 3 years. As evident in this summary review of material testing studies, there is a solid engineering basis behind this demonstration of the permanence of EMC SQUARED System stabilizer treatments on the Interstate Highway System.

IMPLEMENTATION PLAN

No one chemical or mechanical stabilization product is going to solve every problem, or turn every soil or aggregate material into a high-stability, moisture-resistant layer. While field testing is recommended whenever feasible, modern performance-based laboratory test methods can be used to design road and highway projects that fully realize the cost benefits of including stabilized base courses and subgrades constructed with EMC SQUARED System stabilizer treatments. The economic advantages of this process, typically a third the cost of cement or lime treatment, and a small fraction of the cost of importing crushed aggregate materials, are so great that investment in state-of-the-art laboratory testing and design services is cost justified. Paralleling the old saying “You have to spend money to make money,” in order to save big money on construction costs and extend pavement service life, a fraction of one percent of the potential savings will need to be invested in laboratory testing preliminary to project design phase. Contact our office for technical assistance.