Typical Dynamic Modulus Data for HMA Mixture and EMC SQUARED Stabilized Aggregate Mixture

Transcription

1 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 modulus values (significant strength loss) as pavement temperatures increase. In contrast, dynamic modulus testing shows that 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. Cold-mixed Stabilized Aggregate materials have the further advantage of gaining strength with additional curing time. Typical Dynamic Modulus Data for HMA Mixture and Stabilized Aggregate Mixture Stronger K 2K Average Dynamic Modulus for All Temperatures after 2 Hours 29 psi 29 ksi Average Dynamic Modulus for All Temperatures after 68 Hours 45,000 psi 45 ksi 30 F F Hotter 28.4 F Results after 24 Hours of curing Results after 2 Hours of curing Results after 68 Hours of curing The above chart references data from a report by Peter Sebaaly, Ph.D., P.E. University of Nevada, Reno, Director of the Western Regional Superpave Center. The original charts are provided on the following pages of this document. SOIL STABILIZATION PRODUCTS COMPANY, INC.

2 Figure The viscoelastic 5. Stabilized behavior Aggregate of Hot Mix Sample Asphalt in (HMA) Dynamic pavement Modulus materials testing is Set-up. again illustrated in the two Figures below, as the modulus of the HMA material drops from a strength of over,000 psi when evaluated at a temperature 0. just below freezing to a modulus value of less 0 than psi when tested under slow loading conditions at a temperature of 30 O F. For the purpose Frequency, of pavement Hz design using the AASHTO (MEPDG) method, the variations in Dynamic the behavior Modulus of a Set-Up Applied Stress & Measured Strain 28.4 F viscoelastic pavement material related to various F combinations of 30 F loading frequency and temperature are presented as a Dynamic Modulus (E*) Master Curve. Figure. Dynamic Modulus of Stabilized Aggregate Cured for 24 hrs at 40 o F. Typical Dynamic Modulus Data for HMA Stress Mixture Figure F Dynamic 0 Modulus Frequency, E* Hz F 30 F 0 Figure 6. Dynamic Modulus of Stabilized Aggregate Cured for 2 hrs at 28.4 F F 30 F 04 o F. Dynamic Modulus E* Master Curve for HMA Typical Mixture *ksi = psi E* Master Curve Figure 8. Typical Dynamic Modulus Data for HMA Mixture. Dynamic Modulus E* at 0 F, ksi 0 Strain time shift = φ = sin(ωt) 0. 0.E-06.E-05.E-04.E-03.E-02 Frequency,.E-0.E+00 Hz.E+0.E+02.E+03.E+04.E+05 Figure F F 30 F The above Figure figures 6. are Dynamic from 4 F a report by Modulus Peter Sebaaly, of Ph.D., EMC P.E. University SQUARED of Nevada, F Stabilized 30 F Aggregate Cured Predicted for E* 2 hrs at 04 o Reno, Director of the Western Regional Superpave Center. SOIL STABILIZATION PRODUCTS COMPANY, INC. F. Ph: (800) Figure or (209) , *ksi 4. Components Fax: (209) , = psi of the Dynamic info@sspco.com Modulus Test and a Typical E* Master Curve for a HMA The SSPCo Globe and are registered trademarks mix. of Soil Stabilization Products Company, Inc. = sin(ωt-φ) Figure 5. Stabilized Aggregate Sample in Dynamic Modulus testing Set-up. COMPARISON OF TYPICAL DYNAMIC MODULUS

3 Figure 5. Stabilized Aggregate Sample in Dynamic Modulus testing Set-up. Dynamic Modulus of Stabilized Aggregate Cured for O F Figure F F 30 F 28.4 F F 30 F Figure 6. Dynamic Modulus of Stabilized Aggregate Cured for 2 hrs at Figure 350. Dynamic Modulus of 04 o F. Stabilized Aggregate Cured for 24 hrs at *ksi = psi 40 o F. Dynamic Modulus, E* (ksi) Figure 0 Frequency (Hz) The above figures are from a report by Peter Sebaaly, Ph.D., P.E. University of Nevada, Reno, Director of the Western Regional Superpave Center. Figure 9. Dynamic 0. Modulus Property of EMC SQUARED Stabilized Aggregate 0 Cured for 2 hrs SOIL STABILIZATION PRODUCTS COMPANY, INC. at 04 o F F F 30 F

4 Figure Figure 5. Stabilized 5. Stabilized Aggregate Sample in in Dynamic Modulus testing Set-up. Dynamic Modulus of Stabilized Aggregate Cured for 2 04 O F Figure Figure 5. Stabilized Aggregate Sample Frequency, in Dynamic Hz Modulus 0 testing Set-up. Hz 28.4 F F 30 F Figure 28.4 F 6. Dynamic Modulus of Stabilized Aggregate F Cured for 30 F 2 hrs at Figure Dynamic Modulus of 04 o F. Stabilized Aggregate Cured for 2 hrs at *ksi = psi 04 o F. *ksi = 300 psi Dynamic Modulus, E* (ksi) Figure F F 30 F The above Figure figures are Dynamic from a report by Modulus Peter Sebaaly, Property of Ph.D., EMC P.E. University of of Nevada, Reno, SQUARED Stabilized Director of the Aggregate Western Regional Cured Superpave for Center. for 2 2 hrs hrs at SOIL STABILIZATION PRODUCTS COMPANY, INC. at 04 o F. *ksi = psi F Frequency, 5 Hz 0 25 Frequency (Hz) F 30 F

5 Figure 5. Stabilized Aggregate Sample in Dynamic Modulus testing Set-up. Dynamic Figure Modulus 6. Dynamic of EMC 0.0 Modulus SQUARED of Stabilized Stabilized Aggregate Aggregate Cured for Cured 68 for Hours 2 at F O F F 0 30 F Figure. Dynamic Modulus of Frequency, Stabilized Hz Aggregate Cured for 68 hrs at Figure 28.4 F 04 o F. F 30 F Figure 6. Dynamic Modulus of EMC SQUARED Stabilized F Aggregate Cured 30 F for 2 hrs at Figure Dynamic Modulus of o F. Stabilized Aggregate Cured for 68 hrs at *ksi = psi 04 o F. Figure 2 Dynamic Modulus, E* (ksi) Dynamic Modulus, E* (ksi) 250 F 30 F F F Frequency (Hz) The above figures are from a report by Peter Sebaaly, Ph.D., P.E. University of Nevada, Reno, Director of the Western Regional Superpave Center. SOIL STABILIZATION Figure 2. Dynamic PRODUCTS Modulus Property COMPANY, of EMC INC. SQUARED Stabilized Aggregate Cured for hrs at 04 o F Soil Stabilization Products Company, Inc. - All 5Rights Reserved 0 25

6 Repeated COMPARISON Load Triaxial Set-Up OF TYPICAL Loading DYNAMIC and Response MODULUS The Typical Deformation Curve for HMA Mix and the Permanent Deformation Characteristics of the Stabilized Aggregate, as shown below, 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 Stabilized Aggregate Mix showed only 0.% 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. Typical Permanent Deformation Curve for HMA Mix 3.0% 2.5% Permanent Axial Strain 2.0%.5%.0% 0.5% Figure 4 0.0% 0,500 3,000 4,500 6,000,500 9,000 0,500 2,000 Load Cycles Figure 5. Stabilized Aggregate Sample in Repeated Load Triaxial testing Set-up. Permanent Deformation Figure Characteristics 4. Components of the of the EMC Repeated SQUARED Load Triaxial Stabilized Test and Aggregate a Typical Cured Permanent for 2 04 O F Deformation Curve for a HMA Mix. Figure 6 Permanent Axial Srain at 04 F (Microstrain),000 0 Figure 6. Permanent Deformation Characteristics of the Stabilized Aggregate SOIL STABILIZATION PRODUCTS COMPANY, Cured for INC. 2 hrs at 04 o F ,000 Loading Cycles The above figures are from a report by Peter Sebaaly, Ph.D., P.E. University of Nevada, Reno, Director of the Western Regional Superpave Center.

7 Evaluation of Stabilized Aggregate in Pavements/Materials Laboratory The 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. 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. The combination of the elastic behavior of the 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 30 O F temperature, had minimal impact on the modulus of the Stabilized Aggregate, and that the Stabilized Aggregate can therefore be represented by an average constant Dynamic Modulus property of 45,000 psi (versus the Master Curve required for HMA). The resistance of the Stabilized Aggregate material to permanent deformation was evaluated in RLT testing with a finding that under a wide range of loading conditions no permanent deformation is anticipated. Furthermore, even in the worst case conditions for a flexible pavement layer, which are slow moving loads in hot environments, the behavior of the stabilized aggregate makes it a good candidate for pavements loaded under such severe conditions. As an example of a severe service application, it should be noted that the EMC SQUARED Stabilized Aggregate materials for this laboratory evaluation were sampled during the construction of military heavy haul road projects designed by the U.S. Army Corps of Engineers (USACE). This high-strength stabilized aggregate material was plant-mixed and placed by asphalt paving machines as a surface course, or running surface, to be used by convoys of military battle tanks and other tracked military equipment as well as heavy haul trucks weighing over 20 tons when fully loaded. The Stabilizer product, manufactured by Soil Stabilization Products Company, Inc. (SSPCo), was specified by USACE for stabilization of subgrade soils as well as stabilization of aggregate surface course materials for over miles of heavy haul road construction projects. Of additional interest, the stabilization of subgrade soils eliminated the need to manufacture and transport over million tons of crushed aggregate subbase material that otherwise would have been required for these projects. The engineering evaluation of the stabilized aggregate materials was conducted under the direction of Peter Sebaaly, Ph.D., P.E., Director of the Western Regional Superpave Center, one of five centers established by the Federal Highway Administration (FHWA) to support the implementation of the Superpave Technology for hot mix asphalt materials. Dr. Sebaaly is also the Director of the Nevada Technology Transfer Center (funded by FHWA and Nevada DOT), and Professor of Civil Engineering in the Civil and Environmental Engineering Department at University of Nevada Reno where the Pavement/Materials Program and materials testing laboratory are located. SOIL STABILIZATION PRODUCTS COMPANY, INC.

8 Dynamic Dynamic Modulus Modulus Setup Set-Up COMPARISON OF TYPICAL DYNAMIC MODULUS Dynamic Modulus Set-Up Applied Stress & Measured Strain Applied Applied Stress Stress and & Measured Strain Stress = sin(ωt) Stress = sin(ωt) Strain time shift = φ Strain time shift = φ = sin(ωt-φ) = sin(ωt-φ) Repeated Load Triaxial Set-Up Loading and Response Repeated Load Triaxial Setup Loading and Response Repeated Load Triaxial Set-Up 0 Dynamic Modulus E* Loading and Response 0 Dynamic Modulus E* 0 Dynamic Modulus E* at 0 F, ksi 0 Dynamic Modulus E* at 0 F, ksi Typical E* Master Curve Typical E* Master Curve 0 SOIL STABILIZATION PRODUCTS COMPANY, INC. 3.0% Soil Stabilization Products.E-06Company,.E-05.E-04.E-06.E-03.E-05.E-02.E-04.E-0.E+00.E-03.E+0.E-02.E+02.E-0.E+03.E+00.E+04.E+0.E+05.E+02.E+03.E+04.E % Inc. (SSPCo) is entering our fourth decade as the leading edge stabilization product technology company, setting the standard for economic improvement of soil, aggregate and recycled pavement materials in construction applications. 2.5% SSPCo has pioneered the implementation of green products in the highway industry. We have 2.5% proven that clean technology 4 F can provide 4 F far more sophisticated, F effective 30 F and environmentally F Predicted 30 F appropriate E* answers Predicted than E* bulk application of asphalt, 2.0% cement, fly ash and lime products. As former general engineering contractors and suppliers of aggregate and pavement Figure materials, 4. Components SSPCo s Figure of 4. the staff 2.0% Components Dynamic are conversant Modulus of the with Test Dynamic the and engineers a Modulus Typical who E* Test specify Master and our a Curve Typical products, for E* a HMA the Master installing Curve contractors, for a HMA and the quality control personnel responsible for monitoring mix. the essential engineering.5% mix. controls during construction processes. Our industry background and technical.5% support services are essential to the success of a product technology that is reliant upon construction processes that must be conducted according to rigorous engineering quality controls. The cost-savings and performance advantages.0% of the System are contingent upon thorough preliminary engineering reviews, competent.0% designs and specifications, and proper installation. Contact us for assistance on your next design or construction project. 6 6 Permanent Axial Strain 0.5% Permanent Axial Strain 0.5% 0