2013 Session: 694

• Tennessee Stabilized Base Using Substandard Fly Ash and Byproduct Limestone Screenings
  Abstract: Substandard fly ash (high carbon/loss-on-ignition (LOI)) and byproduct limestone screenings are plentiful materials in Tennessee. Utilization of these materials could result in both economic and environmental benefits. The Tennessee Department of Transportation (TDOT) Specification 312 for an Aggregate-Lime-Fly Ash Stabilized Base Course includes hydrated lime, fly ash, and TDOT Grading C limestone. The specification requires an average compressive strength of 950-psi (6.5-MPa) for three specimens, with no individual compressive strength less than 800-psi (5.5-MPa), after 28-days of curing at 100 °F (37.8 °C).The use of substandard fly ash and limestone screenings was compared to the use of standard materials. The control set consisted of the control fly ash with an aggregate blend, while the variable sets consisted of the control and variable fly ashes, respectively, with limestone screenings. The average compressive strength and coefficient of variation were 1,263-psi (8.71-MPa) and 5.8% for the control set, 1,416-psi (9.76-MPa) and 4.9% for the first variable set, and 966-psi (6.65-MPa) and 3.2% for the second variable set, respectively. The average static modulus of elasticity and coefficient of variation were 3,000-ksi (20.68-GPa) and 7.8% for the control set, 2,650-ksi (18.27-GPa) and 5.2% for the first variable set, and 1,400-ksi (9.65-GPa) and 8.7% for the second variable set, respectively.Analysis of these results indicates that a high LOI fly ash can be useful as a stabilizing agent when used in combination with hydrated lime. These results also suggest that byproduct limestone screenings can be used effectively as a significant part of the aggregate.
  Authors: Dillon, Sarah; Crouch, Lewis Keith; Knight, Marcus L.
  Authors: Dillon, Sarah; Crouch, Lewis Keith; Knight, Marcus L.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 694
  Paper Number: 13-0776
  Practice-Ready: Yes
• Kay County Shale Subgrade Stabilization Revisited
  Abstract: This paper presents a re-examination of a research project on US-77 in Kay County, Oklahoma concerning chemical stabilization of an 8-inch compacted shale subbase layer completed in 1983. The primary focus of this paper was to examine the changes in the pavement surface deflection and backcalculated modulus of the stabilized subbase layer within the project test sections over time.The original research project test sections were identified and tested with a trailer mounted Falling Weight Deflectometer (FWD) unit in August 2010. The FWD deflection survey performed in July 2000 and the original Benkelman beam deflection survey performed in June 1985 following the original pavement construction were used in this pavement analysis.The pavement had been overlain with two thin asphalt overlays. The FWD deflection data was normalized by ratio of the new thickness to the original pavement thickness so that the original Benkelman beam deflection data could be used. The pavement analysis uses the two-layer Hogg model and three-layer model in the Modulus 6.0 software to estimate the subgrade modulus and 8-inch stabilized subbase layer subgrade modulus respectively. The conclusions are the following: a) the pavement surface deflections indicate that the stabilized subbase layer sections have relatively stiff subgrade support, b) the three-layer model predicts a higher subbase layer modulus, and c) chemically stabilized subbase layers do not significantly lose strength or degrade with time and can be depended on as part of the structural section.
  Authors: Clarke, Christopher R.
  Authors: Clarke, Christopher R.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 694
  Paper Number: 13-1530
  Practice-Ready: Yes
• Stabilizing Sulfate-Rich Soils Using Traditional Stabilizers: Continuing Case Study of State Highway 289 in Grayson County, Texas
  Abstract: Because of the risk of sulfate induced heave, the Texas Department of Transportation (TxDOT) has limited the use of traditional, calcium-based stabilizers on construction projects where sulfate concentrations exceed 8,000 parts per million (ppm). Beyond that limit non-traditional additives must be evaluated for use, or the material must be removed and replaced with a select material with acceptable sulfate concentrations. Significant sulfate concentrations were encountered on the State Highway (SH) 289 extension project in October, 2008 during the construction of the 8-inches of lime stabilized subgrade. Due to the limited availability of both non-traditional stabilizers and select replacement material, and after extensive laboratory testing, these sulfate-rich subgrade soils were successfully stabilized with lime using alternative construction techniques. These alternative techniques included extended mellowing and additional pulverization of the stabilized subgrade. Performance monitoring was conducted on the SH 289 project in the Spring of 2010. Non-destructive test methods, such as inertial profiler, falling weight deflectometer (FWD), and dynamic cone penetrometer (DCP) were utilized in order to evaluate the overall performance of the pavement. TxDOT assisted in the collection of the non-destructive test data. Additionally, lime treated subgrade samples were collected in order to perform follow-up sulfate testing approximately 14 months after stabilization was completed. With a satisfactory overall pavement performance, the results of this study indicate that the construction methods employed on this project provide a viable alternative to removal and replacement on projects with sulfate-rich soils.
  Authors: Hilbrich, Stacy L.; Scullion, Tom
  Authors: Hilbrich, Stacy L.; Scullion, Tom
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 694
  Paper Number: 13-4781
  Practice-Ready: Yes
• Tennessee Stabilized Base Using Substandard Fly Ash and Byproduct Limestone Screenings
  Authors: Crouch, Lewis
  Authors: Crouch, Lewis
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 694
  Paper Number: 13-0776
• Kay County Shale Subgrade Stabilization Revisited
  Authors: Clarke, Christopher
  Authors: Clarke, Christopher
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 694
  Paper Number: 13-1530
• Stabilizing Sulfate-Rich Soils Using Traditional Stabilizers: Continuing Case Study of State Highway 289 in Grayson County, Texas
  Authors: Hilbrich, Stacy
  Authors: Hilbrich, Stacy
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 694
  Paper Number: 13-4781