Staff Memo: Results of Mineralogical Analysis of Taconite Aggregate

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Date Created
2005-05
Description
Mineralogical analyses were performed on the Mesabi Select aggregate taken from a stockpile (-1 inch size) at MnROAD comprised of crushed material obtained from the top 25 feet of the 'Lower Cherty' member, or LC-8 bed (LC-6 bed in NRRI study), of the United Taconite mine near Eveleth. The material was utilized in asphalt (cell 32) and concrete pavement (cell 54) constructed at MnROAD's low volume loop.

Use of Material Delivery Management System (MDMS) for Asphalt Paving Applications

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Date Created
2021
Report Number
2021-10
Description
Each year, the Minnesota Department of Transportation (MnDOT) is affected by the large volume of data produced each day on highway construction projects. Significant time and resources are spent toward proper documentation, organization, mining, and review and use of this information. Intelligent construction technologies (ICT) are continuously being developed by the industry to assist agencies with simplifying and improving these processes along with other heavy construction activities. Efforts toward electronic construction are one of the many ICT initiatives that are moving forward for use nationally and internationally - electronic ticketing being one of them. The Material Delivery Management System (MDMS), formerly called the E-Ticketing system, was piloted on approximately 40 projects. This report summarizes the lessons learned, future recommendations, and the American Association of State Highway and Transportation Officials (AASHTO) provisional practice created as a result of these efforts. Additionally, this report details the workflow that was created to guide a user through pre-construction activities, the source process, delivery of material, data export, and end-of-day activities such as reconciling of quantities and labor compliance reviews as related to the MDMS. Future enhancements are recommended to establish a standardized platform for the viewing of MDMS by the agency (Veta MDMS) and for standardization of data for import into AASHTOWare Project, using Representational State Transfer Application Programming Interface (REST API) and JavaScript Notation (JSON), along with enhancements to the Veta software.

Use of Relative Surface Technology for Creation of Relative Milling Surface Models and During the Automated Machine Guidance Milling Operation

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Date Created
2021
Report Number
2021-09
Description
The Minnesota Department of Transportation needed to correct the existing profiles of the eastbound and westbound lanes of TH2. This roadway was reconstructed 9 years ago, and since then, it has experienced significant pavement movement due to the presence of silt seams in the subgrade material. The movement of the roadway had stabilized and was still considered to be in good structural condition. Consequently, it was decided to move forward with correcting the profile to remove the significant irregularities that were present within the roadway profile. After evaluation of the project constraints, it was decided that the most cost-effective solution was to use a relative system (with respect to the existing surface) for creation of the existing surface and milling-depth models, in lieu of conventional survey and milling methods that later require use of robotic total stations during the milling operation. The project team selected the Topcon SmoothRide Resurfacing solution for both creation of the 3D model and use during the milling operation. The accuracy of the relative surface LiDAR scan was within 3 to 5 mm in the vertical direction and only required approximately 8 hours to collect, clean and review the relative surface measurements, while conventional methods would had required several days, or more. It was found that the relative surface measurements adequately identified and documented the magnitude of the vertical roadway movement and could be used to assist with the correction of irregular profiles of roadways. Consequently, the Topcon SmoothRide Resurfacing solution was also used during the milling operation and was considered successful.

Assessment of the Trimble MX7 for Use in Creation of Alignment Files for the Intelligent Compaction and Paver Mounted Thermal Profile Methods

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Date Created
2019
Report Number
2019-20
Description
The objective of the work was to validate the Trimble MX7 system for use in collecting infrastructure information for creation of in-place alignment files for use with intelligent compaction and paver mounted thermal profiling technologies and also to provide the capability to collect other asset information along the roadway. One project per district; where conventional survey methods were already used to capture the in-place center alignment; was selected for verification of the Trimble MX7. Additionally; a project with photo targets was also used for more accurate verification of the system with highly accurate known points on the roadway. From these verification runs; the average position error of the Trimble MX7 trajectory in the X; Y; and Z direction was found to be 2; 2 and 3 cm; respectively. Forward intersection and reference plane extractions methods were used to extract the centerline feature. It was found that the forward intersection method provided more accurate feature extractions. On average; the difference between the MX7 and photo targets using the forward intersection extraction method was 0.26 ft (3.1 inches); while the 95 percent confidence interval was between 0.2 ft (2.9 inches) and 0.3 ft (3.2 inches). Similar position error results were also found when comparing the MX7 positions to alignment files created using conventional survey methods. It was concluded that the MX7 has the needed horizontal accuracy to capture the in-place centerline for use in creation of alignment files for the IC and PMTP methods.

Duration of Spring-Thaw Recovery for Aggregate-Surfaced Roads

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Date Created
2006
Report Number
2006-12
Description
Low-volume roads constructed in regions susceptible to freezing and thawing periods are often at risk of load-related damage during the spring-thaw period. The reduced support capacity during the thawing period is a result of excess melt water that becomes trapped above the underlying frozen layers. Many agencies place spring load restrictions (SLR) during the thaw period to reduce unnecessary damage to the roadways. The period of SLR set forth by the Minnesota Department of Transportation is effective for all flexible pavements; however, experience suggests that many aggregate-surfaced roads require additional time relative to flexible pavements to recover strength sufficient to carry unrestricted loads. An investigation was performed to improve local agencies' ability to evaluate the duration of SLR on aggregate-surfaced roadways. This was accomplished through seasonal measurements of in situ shear strengths, measured using the dynamic cone penetrometer (DCP), on various Minnesota county routes. In situ strength tests were conducted on selected county gravel roads over the course of three years. Strength levels recorded during the spring-thaw weakened period were compared to fully recovered periods that typically occur in late spring/summer. The results indicate that aggregate-surfaced roads generally require 1 to 3 additional weeks, over that of flexible pavements, to reach recovered bearing capacity. Additionally, a strong correlation was found between duration required to attain given strength recovery values and climatic and grading inputs.

Refinement and Validation of the Hydraulic Fracture Test

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Date Created
2003
Report Number
2003-28
Description
The Washington Hydraulic Fracture test was developed under the Strategic Highway Research Program to address the need for a rapid, inexpensive test for concrete aggregate freeze-thaw durability. The original test and analysis procedures were not sufficiently reliable and accurate to merit widespread adoption and implementation. Several follow-up research efforts have been performed and each has resulted in improvements to the test. This report describes the results of recent research efforts to improve the test. The "hydraulic fracture index" has been replaced by a model that predicts freeze-thaw test dilation as a function of the distribution of particle mass retained on various sieves after testing. This model was developed using data obtained from freeze-thaw and hydraulic fracture testing of 18 quarried carbonate and gravel aggregate sources, and the resulting correlation is exceptional (r-squared = 0.98). In addition, a large test chamber was developed to allow testing of aggregate samples five times larger than the original small chamber, thereby allowing aggregate durability characterization with a single test run. It is believed that the hydraulic fracture test is now ready for more broad-based validation testing and eventual widespread acceptance and implementation as an accurate screening tool for concrete aggregate freeze-thaw durability.

Condition and Durability of Segmental Concrete Block Retaining Walls Along Roadways in Minnesota

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Date Created
2001
Report Number
2001-16
Description
This research project assesses the nature and extent of premature deterioration of segmental concrete block retaining walls (SCBRWs) along roadways in the Minneapolis-St. Paul area. Researchers conducted a two-stage condition survey on 104 SCBRWs. The first stage, a general distress survey, focused on determining the type, severity, and extent of distresses present. The second stage, a peak winter survey, assessed the extent of snow/ice cover and exposure to winter sun. According to research results, only 7% of the SCBRWs surveyed were in poor or very poor condition. But researchers observed many distress types in 50% or more of the walls surveyed, including freeze-thaw damage, scaling, manufacturing flaws, and efflorescence. Freeze-thaw damage and scaling were most highly associated with decreases in overall wall condition. Efflorescence and freeze-thaw damage were found to be at least partly dependent upon SCBRW age and block manufacturer. Durability problems appear to be directly related to the lack of durability of the block units, which suggests problems with the use of inadequate mix designs, non-durable aggregate, and/or inadequate curing procedures. The report includes recommendations to address possible deficiencies in manufacturing processes and quality.

Minne-ALF Project Overview and Retro-Fit Dowel Study Results

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Date Created
1999
Report Number
2000-02
Description
A laboratory-based linear loading pavement test stand, the Minnesota Accelerated Loading Facility (Minne-ALF) simulates the passage of heavy traffic loads moving at speeds up to 65 kph (40 mph) over small, full-scale pavement test slabs. Hydraulic actuators control a rocker beam, which simulates loads. Researchers simulated the passage of 40-kN (9-kip) single-wheel loads at a rate of 172,000 per day, although wheel loads up to 100 kN (22 kip) can be simulated at varying speeds. Full-axle simulations are possible with frame modifications. Concrete slabs were cast and dowels were installed in slots across cracks/joints. Test variables included joint face texture, repair backfill material, and dowel material and length. Test outputs included measurements of load transfer efficiency and differential deflection across the joint/crack. The effect of joint/crack face texture was great when the joint/crack remained tight. Load carrying performance was improved using Speed Crete 2028 in place of 3U18 concrete backfill with similar joint and dowel bars. Load transfer was unaffected by the use of stainless steel-clad dowel bars in lieu of epoxy-coated dowel bars. Researchers recommend additional testing to examine the effects of dowel length and dowel materials.