LRRB Local Operational Research Assistance Program (OPERA) for

Local Transportation Groups Field Report

Date: 18th April 2013 Project Title: Sustainable Pavement Rehabilitation using Thin Bonded Overlay Constructed with High Taconite Mix Project Number: 2010-13 Agency: City of Duluth Person Completing Report: Eshan V. Dave, University of Minnesota Duluth Project Leader: Cindy Voigt, City of Duluth Phone Number: 218-730-5071 Problem: Large quantities of taconite tailings are available from the Minnesota Mesabi Iron Range mining operation; these could be utilized to substitute the new mineral aggregate in hot-mix asphalt. Such replacement leads to great reduction in environmental impacts of hot-mix asphalt manufacture. Thin overlay systems have become popular options for pavement preservation and rehabilitation. In addition to functional improvements, these systems ensure a high degree of waterproofing benefits while reducing the economic and environmental burden. Significant research and implementation thrusts have been made by public agencies, universities and private companies in the United States as well as overseas to study fine graded (typically 4.75 mm nominal maximum aggregate sized asphalt mixtures) thin asphalt overlay techniques as a means for pavement preventive maintenance, rehabilitation and renewal. The City of Duluth has several streets that require functional and structural rehabilitation and thin bonded overlays may be a viable alternative to traditional overlays. The main problem is that standard thin overlay mixes that utilize the mining byproduct of taconite tailings have not been developed nor have the field performance of such overlays been documented. Solution:

A set of three test sections were constructed on Yosemite Avenue located in the North Western portion of Duluth. The test sections include: (1) Traditional overlay; (2) Thin bonded overlay constructed using spray-paver and fine graded mix with taconite tailings; and (3) Same as section two except thinner overlay and constructed with greater amount of engineered emulsion tack coat application. Each section is at least 1000 feet in length, the cross-section of various test sections are shown in Figure 1. These test sections will allow for conducting a field evaluation of the following variables:

Performance of thin wearing course as compared to traditional lift;

Use of fine graded asphalt mixture with significant amount of taconite tailings as replacement to traditional mineral aggregates;

Effectiveness of bonded wearing course constructed using spray paver equipment and engineered emulsions as tack coat.

(a) Section-1: Traditional Overlay

(b) Section-2: Overlay with Thin Wearing Course

(c) Section-3: Overlay with Thin Bonded Wearing Course

Figure 1: Schematic of the Test Sections (Wearing courses for Section 2 and 3 utilize fine graded asphalt mixture containing high amounts of taconite tailings; Section 2 is constructed with tack coat application rate of

0.08 gal./sq. yd and Section 3 with 0.20 gal./sq. yd.) Procedure:

A majority of the research thrust from this project was on developing the design of a fine graded asphalt concrete mixture with taconite tailings. The primary objective was to develop a mix that satisfies the requirements of Superpave volumetric mix design procedure. Various types of aggregate samples were procured form local contractors

Traditional Wearing Course (1.5 inch)

Binder Course (2 inch)

Reclaimed Base (~ 6 inch)

Subgrade

Thin Bonded Wearing Course (1 inch)

Binder Course (2.5 inch)

Reclaimed Base (~ 6 inch)

Subgrade

Thin Bonded Wearing Course (0.75 inch)

Binder Course (2.75 inch)

Reclaimed Base (~ 6 inch)

Subgrade

and a number of tests were conducted to ensure compliance with Superpave consensus properties and to get inputs for conducting mix designs. These include:

(1) Aggregate Gradations (AASHTO T-27) (2) Fine Aggregate Angularity (AASHTO T-304) (3) Specific Gravity and Absorption (AAHSTO T-84)

A total of six different aggregate blends were evaluated, each were manufactured to include between 31 and 63% taconite tailings. A total of 26 mixes were tested and three final mix alternatives were developed (see Table 1). Details for various mixes tested during this study are shown in Table 1 of the Appendix. All mixing, compaction and gravimetric testing was conducted according to the requirements of Superpave procedure, that is:

(1) Superpave Volumetric Design for Hot Mix Asphalt (HMA) (AASHTO R-35) (2) Bulk Specific Gravity of Compacted Hot Mix Asphalt (HMA) Using Saturated

Surface-Dry Specimens (AASHTO T-166) (3) Theoretical Maximum Specific Gravity and Density of Hot Mix Asphalt (HMA)

(AASHTO T-209) (4) Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by

Means of the Superpave Gyratory Compactor (AASHTO T-312)

Table 1. Recommended Mix Alternatives

Mix Alternative

Aggregate Percentages Design Asphalt Content

(%)

New Added Asphalt

(%)

Taconite Tailing

Washed Sand

BA Sand

Crusher Fines

Dust RAS

Mix-1 47.1 46.1 -- -- 6.8 -- 7.8 --

Mix-2 40.5 -- 54.0 -- 5.5 -- 7.8 --

Mix-3 45.5 -- 24.5 25.0 1.0 5.0 7.7 7.1

Comparisons were made between different mix alternatives in terms of cost and measured volumetric properties; the third alternative (Mix-3) was selected as the final mix. Cost evaluations were also conducted to determine the suitability for use of recycled asphalt shingles (RAS) in the mixture. The motivation behind use of RAS was to lower the cost of the mix by reducing the required virgin binder amount. Preliminary characterization of RAS was conducted as part of this study. This included gradation analysis, asphalt content determination and gradation analysis for residue aggregates. The final mix design for thin wearing course mix was developed. The final gradation for the mix is shown in Figure 2. The original plan was to construct the test sections during late summer or early fall of 2011. Due to the shut-down of Minnesota State agencies in July, the spray paving equipment became unavailable. Thus, actual construction of the wearing course occurred during September 2012. Immediately following the construction, field samples were obtained from all test sections to conduct additional laboratory characterization tests and verify the in place material properties. The test sections were also revisited in February 2013 for a visual survey, follow-up visits on a routine basis (every 6 months to 1 year) for evaluation of field performance is planned.

Figure 2: Gradation of the Mix (Blue line) along with recommended Superpave Control Points (Black line)

Results:

The primary finding from this research effort is that use of taconite tailings in fine graded asphalt concrete mixture is a viable option. A mixture design that meets the Superpave volumetric and aggregate gradation requirements can be produced using the mining by-product material. A review of previous research projects also indicated that combining thin wearing course with bonded paving approaches that utilized engineered asphalt emulsions as tack coat and spray paver equipment for paving operations can significantly enhance the performance of the pavement. This project utilized coarse taconite tailings (No. 4) with minimal amount of dust. Additional material with particles smaller than 75 microns (passing # 200 sieve) was needed to meet the gradation and volumetric requirements. For this project, bag-house fines collected at the hot-mix plant were used for that purpose. Future projects may include finer fractions of the mining by-product to further reduce the mineral aggregate requirements. The construction of the thin bonded overlays was completed on September 19th 2012.Since the project required manufacture of a specialty mix in relatively small quantities, the hot-mix supplier opted for late season manufacture near the end of the hotmix production season. The construction of thin overlays required significant coordination as three agencies/companies were involved: (1) Ulland Brothers produced the mix; (2) City of Duluth hauled and compacted the mix; and (3) Hall Brothers Paving laid the mix using spraybar-paver. The weather on the day of construction was sub-par for purposes of hot-mix pavement construction, however due to small size of the project and necessary coordination of various agencies and companies, the construction was continued instead of rescheduling. On the day of construction, there was a hail storm in the afternoon which was followed by rain of varying intensities during the actual construction. Figures 3 shows a picture during the construction of thin bonded overlay as well as the final finished project on the next day.

(a) Construction of Thin-Bonded Overlay

(b) Finished Thin Overlay Section

Figure 3: Construction of Thin Bonded Overlay and the Finished Pavement The materials used in this project included significant amounts of taconite tailings and recycled asphalt shingles. Both of these products help lower the necessary energy demands as well as the carbon dioxide (CO2) emissions associated with the manufacture of new construction materials, primarily aggregates and asphalt binder. Comprehensive evaluation of energy demands and CO2 emissions were conducted using the PaLATE (Santero et al., 2011) system to compare traditional hot-mix asphalt (with 30% recycled asphalt pavement) with the taconite mix used in the current study.

The comparisons of material production as well as transportation and construction related energy demands and CO2 emissions are presented in Table 2. Details on the calculations can be found elsewhere (Hanson and Dave 2013). The results show significant energy savings and reduction in CO2 emissions for the taconite mix in the material production category. The greater transportation energy demand and CO2 emissions are a result of hauling both the taconite tailings from the Iron Range and the RAS from Wisconsin. While transportation and construction activities for the taconite mix have environmental costs, the overall environmental costs for traditional mix is still significantly greater. Through use of taconite tailings, approximately 45 tons of mineral aggregates were substituted with by-product material from the Iron mining operations. Please note that the test sections in this study are only 1000 feet and the limited length does not represent a typical rehabilitation scenario. Annually 1.2 billion tons of mineral aggregates are used in the United States for manufacture of asphalt concrete; even at small replacement percentages, use of mining by-products to replace mineral aggregates will have significant positive environmental impacts. The expected prolonged performance and environmental benefit outweigh the additional construction costs.

Table 2. Environmental Cost Comparison (Energy Demands and CO2 Emissions)

Energy Demand (MJ/inch-mile placed)

Mix Type Material

Production Transportation &

Construction Total

Traditional Mix 744,577 20,598 765,175

Taconite Mix (used in this study)

599,820 34,608 634,428

CO2 Emissions (kg/inch-mile placed)

Mix Type Material

Production Transportation &

Construction Total

Traditional Mix 32,373 1,540 33,913

Taconite Mix (used in this study)

30,230 2,587 32,817

A set of laboratory tests were conducted on the asphalt mix sampled during the construction as well as on the cored samples obtained from the pavement one day after construction.. The mix and cored samples were tested by Golder Associates to determine the mix volumetrics as part of the standard Quality Control and Quality Assurance (QC/QA) test suite for asphalt materials. The final report from Golder Associates is attached as an appendix to this report, the key volumetrics testing results are as following:

As constructed air void level (from testing of cores) = 4.3%

Total asphalt content of the mix = 7.7%

Total asphalt content of cored samples (mix and tack coat) = 7.9%

Percent crushed aggregates = 95%

Marshall Stability = 11,972 N (Required minimum for heavy traffic = 8,000 N)

Marshall Flow = 11.6 (Required limit for heavy traffic 8 – 14) From the volumetric testing it can be observed that the plant produced mixture matched very well with the lab produced design. It can also be observed that due to excellent

Marshall stability and flow results, the mix is not anticipated to have any rutting associated problems. This could be a concern for traditional hot mix when a large amount of asphalt binder is present (as in this case). The asphalt mix sample was also tested to measure the fracture energy of the mix. Fracture energy of asphalt mix has shown to give an indication of cracking performance of the pavement, especially in cold climatic regions (Dave and Koktan, 2011). The fracture energy testing was conducted as per the ASTM D7313 test procedures using the disk shaped compact tension (DCT) test. A recent study by Marasteanu et al. (2012) provided the recommendations for the fracture energy based performance specifications that can be used to minimize the potential for low temperature cracking in asphalt pavements. For the pavement constructed through this project, the minimum recommended fracture energy threshold is 400 J/m2

. The fracture energy results for all three replicate test specimens are shown in Figure 4. The results show that all replicate samples meet the minimum recommended fracture energy of 400 J/m2 and thus the taconite mix used in the current project is anticipated to have very good thermal cracking performance.

Figure 4: Fracture Energy Results (Recommended Minimum = 400 J/m2)

The project is relatively recent and thus it is not possible to provide detailed account on the long term performance results for the three test sections. During the latest visual survey of the project during February 2013 the following key observations were made:

There are a few cracks in all three test sections due to base settlement

No thermal cracks are present in any of the three test sections

The longitudinal joint in the control section has started to crack Figure 5 shows a few pictures from the project from the visual survey.

(a) Longitudinal Cracking at the Construction Joint in Control Section

(b) Cracking Associated with Base Settlement through Section 2 and 3

Figure 5: Pictures from Visual Survey for Cracking Evaluation of the Project While this study only looked at the preliminary performance of the thin bonded wearing course based pavements that use taconite tailings in the mix, the University of Minnesota Duluth and the City of Duluth will continue to monitor this project for several subsequent years.

Implementation:

The asphalt mixture developed through the research efforts from OPERA funding were utilized to construct two 1000 foot long test sections and one control section. Based on the performance of thin overlay sections versus the control section, future street improvement and rehabilitation projects may be considered using taconite tailings and/or spraybar paver. Status:

The design and construction phase has been completed for the project. The asphalt mix developed through this study was tested in laboratory for performance prediction and showed very promising results. The feasibility of using high taconite mix in conjunction with spraybae paver was tested through this project with successful results. Early performance has been promising and continued monitoring of the test sections is planned. Total Duration of Project: 12 Months Project End Date: 1st August 2012 Approximate Cost of Entire Project: $37,000* (*Excludes control section, binder course and City staff time) Total OPERA Funds used for project: $10,000

References

Dave, E.V. and Koktan, P.D., “Synthesis of Performance Testing of Asphalt Concrete.” Report no. MnDOT 2011-22, Minnesota Department of Transportation, St Paul, MN, 2011. Hanson, C.E., and Dave, E.V., “Sustainability Evaluation of Asphalt Pavements Constructed using Recycled Materials and Mining By-Product.” Proceedings of the European Asphalt Technology Association Conference (EATA2013), Braunschwaig, Germany. (in-press) Marasteanu, M, Moon, K.H., Teshale, E.Z., Falchetto, A.C., Turos, M., Buttlar, W., Dave, E., Paulino, G., Ahmed, S., Leon, S., Bahia, H., Arshadi, A., Tabatabaee, H., Ojo, J., Velasquez, R., Mangiafico, S., Williams, C., Buss, A., “Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study -Phase II”, Report No. MN/RC 2012-23, Minnesota Department of Transportation, St. Paul MN, 2012. Santero, N., Masanet E., and Horvath, A., “Life-cycle Assessment of Pavements, Part I: Critical Review.” Resources, Conservation and Recycling, Vol. 55(9-10), pp. 801-809, 2011.

Appendix: Details on Testing of Asphalt Mixtures

Aggregate Percentages Asphalt Content

(%)

Taconite Tailing

Washed Sand

BA Sand

Crusher Fines

Dust Notes

63 31

6 6.72

31 63

6 6.78

47.1 47.1

5.8 6.75

60

35

5 6.69

45.5

50

4.5 6.7

35

60

5 6.72

63 31

6 6.2

63 31

6 6.7

63 31

6 7.2

63 31

6 7.7

63 31

6 7.7 75 Gyrations

47.1 47.1

5.8 6.3

47.1 47.1

5.8 6.8

47.1 47.1

5.8 7.3

47.1 47.1

5.8 7.8

47.1 46.1

6.8 7.8

47.1 46.1

6.8 8.3

47.1 46.1

6.8 8.6

40.5

54

5.5 7.3

40.5

54

5.5 7.8

40.5

54

5.5 8.3

40.5

54

5.5 8.3 Verification Mix

40.5

54

5.5 7.5

40.5

54

5.5 7.5 Verification Mix

40.5

54

5.5 7.5 100 Gyrations

45.5

24.5 29 1 7.7

Project Pictures Prior to Rehabilitation Send and Email a completed report with pictures to: Mindy Carlson, CTS - 200 TSB, 511 Washington Ave. SE, Mpls. MN 55455, email carlson@umn.edu. For

questions about this report please contact Mindy Carlson at 612-625-1813.

Golder Associates Inc. 4438 Haines Road Duluth, MN USA 55811 Telephone (218) 724-0088 Fax (218) 724-0089

OFFICES ACROSS AFRICA, ASIA, AUSTRALIA, EUROPE, NORTH AMERICA, SOUTH AMERICA

January 11, 2013 City of Duluth Engineering Department 411 West 1st Street Duluth, MN 55802 Attention: Cindy Voigt RE: REPORT OF BITUMINOUS PAVEMENT TESTING CITY OF DULUTH YOSEMITE AVENUE GOLDER PROJECT NO. 113-81053 Dear Cindy, Introduction This report presents the results of the bituminous pavement testing performed by Golder Associates Inc. (Golder) for the above referenced project. We understand that paving was performed by Ulland Brothers on September 19th, 2012. Background Information The current phase of construction consists of a single wear course placement on two 1000 foot sections of Yosemite Avenue. The City of Duluth previously paved this street in 2011 but left one of the two 1000 foot sections slightly thinner for placement of wear course in 2012 using an experimental polymer modified tack coat. Section 1 (East lane) was planned to be ¾ inch thick wear course placed using specialized paver in conjunction with the new highly polymer modified tack coat. Section 2 (West lane) was planned be 1 inch thick wear without specialized tack coat. The base and binder courses of the control sections were already paved by the City last summer along with the remainder of the Yosmite Avenue project. Scope of Services Golder’s scope of services requested by the City of Duluth included laboratory of testing of the hot mix samples taken and split by the University of MN Duluth (UMD), nuclear density tests of pavement surfaces in the control section before and after adding the topping wear course, obtaining core samples from the control section of the pavement, performing laboratory testing of companion core samples for density and thickness, and providing additional core samples to UMD for their testing.    

January 11, 2013 -2- Golder Project #113-81053

Golder Associates

Test Methods and Test Results The following sections summarize the test methods and results of testing performed by Golder. Nuclear Density Testing Golder Associates Inc. (Golder) preformed nuclear density testing of the asphalt surface in the control section on September 18, 2012, before the topping wear course placement and again on September 21, 2012, follow topping placement . Testing was performed in accordance with ASTM D2590-11, Standard Test Method for Density of Bituminous Concrete in Place by Nuclear Methods. The field density tests were taken with a Troxler model 3440, averaging 5 tests in Nomograph Asphalt Mode for thin layer density determination. The density of the underlying base is incorporated in the thin layer density calculation. The results of nuclear density testing are included on the attached table titled “Field Density and Core Density Test Summary Table”. Hot Mix Testing During placement three hot mix samples were obtained by the University of Minnesota, Duluth (UMD) and Golder received split samples of each. The location of the samples was not identified and sample weights were small, between 16 – 16.5 pounds each. Since the mix was the same, Golder combined the three samples, and tested a composite on behalf of the owner for quality assurance (QA) purposes. Laboratory testing included the following tests:

ASTM D2172/D2172M-11 Standard Test Methods for Quantitative Extraction of Bitumen From Bituminous Paving Mixtures

ASTM C136-06 Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates ASTM D2041/D2041M-11 Standard Test Method for Theoretical Maximum Specific

Gravity and Density of Bituminous Paving Mixtures ASTM D6926-10 Standard Practice for Preparation of Bituminous Specimens Using

Marshall Apparatus ASTM D6927-06 Standard Test Method for Marshall Stability and Flow of Bituminous

Mixtures ASTM D2726-11 Standard Test Method for Bulk Specific Gravity and Density of Non-

Absorptive Compacted Bituminous Mixtures

The results of bituminous mixture testing performed by Golder are included on the attached reports titled “Golder Hot Mix Asphalt Test Report” and “Determination of Percent Crushed Particles in Course Aggregate Report”. Core Density Testing Three core locations were selected and marked by UMD, with each of the three locations including five core samples (four - 6 inch cores samples for UMD testing and one – 4 inch companion core sample for Golder testing). Coring was performed by Golder on August 20, 2012 and the 6 inc cores were delivered to the UMD Civil Laboratory. Core density testing was performed on all three companion cores by Golder. Sampling and testing methods included the following:

January 11, 2013 -3- Golder Project #113-81053

Golder Associates

ASTM D5361-11 Standard Test Method for Sampling Compacted Bituminous

Mixtures for Laboratory Testing ASTM D2726-11 Standard Test Method for Bulk Specific Gravity and Density of Non-

Absorptive Compacted Bituminous Mixtures Density and thickness of Golder’s three core samples are included on the attached table titled “Field Density and Core Density Test Summary Table”. Closing We trust that this report provides you with the information required at this time. Please contact us at (218) 724-0088 if you have any questions or require further information. We are available to discuss any of the test results with the City of Duluth and UMD at your convenience. Sincerely, GOLDER ASSOCIATES INC.

Amy Thorson, P.E. Robert C. Christen, S.E.T Project Engineer Senior Materials Specialist Attachments: Field Density and Core Density Test Summary Table Golder Hot Mix Asphalt Test Report Determination of Percent Crushed Particles in Course Aggregate Report

Table 1

Troxler and Core Density Test Results

Yosemite Avenue

Duluth, Minnesota

Golder Project  No. 113‐81053

Test # (Note #1)

Date Location CourseAverage Dry Density (pcf)

(Note #2)

% - MTD 1" Topping

(Note #3)

% - MTD 3/4"

Topping (Note #3)

Core Thickness (inches) (Note #4)

T-1A 9/18/20121001' N. of Page St.,

5' W of C/LBase (Non-Wear) 137.9 --- --- ---

T-1B 9/21/2012 " 1" Topping (Wear) 141.5 91.1 --- ---

T-2A 9/18/20121001' N. of Page St.,

4' E of C/LBase (Non-Wear) 137.7 --- --- ---

T-2B 9/21/2012 " 3/4" Topping (Wear) 142.8 --- 92.0 ---

T-3A 9/18/2012756' N. of Page St.,

6' W of C/LBase (Non-Wear) 141.2 --- --- ---

T-3B 9/18/2012 " 1" Topping (Wear) 138.4 89.1 --- ---

T-4A 9/18/2012756' N. of Page St.,

5.5' E of C/LBase (Non-Wear) 142.0 --- --- ---

T-4B 9/21/2012 " 3/4" Topping (Wear) 140.0 --- 90.1 ---

T-5A 9/18/2012304' N. of Page St.,

3.5' W of C/LBase (Non-Wear) 137.2 --- --- ---

T-5B 9/21/2012 " 1" Topping (Wear) 142.2 91.6 --- ---

T-6A 9/18/2012304' N. of Page St.,

7.5' E of C/LBase (Non-Wear) 137.7 --- --- ---

T-6B 9/21/2012 " 3/4" Topping (Wear) 138.4 --- 89.1 ---

Average of Troxler Densities

90.6 90.4

C-1A901' N. of Page St., E.

Lane3/4" Topping (Wear) 136.2 --- 87.1 0.7

C-5A931' N. of Page St., E.

Lane3/4" Topping (Wear) 138.9 --- 89.4 0.8

C-9A811' N. of Page St., W.

Lane1" Topping (Wear) 135.2 87.1 --- 1.4

Average of Core Densities

87.1 88.3 ---

Notes:

#3: The above field density and core density test results were compared to the maximum theoretical density (MTD) of 155.3 pcf, obtained from Golder’s laboratory testing on the composite bulk sample of hot mix.

#4: Core thickness was determined in general accordance with ASTM D3549.

Test Identification Test Results

#1: For test locations, T=Troxler, C=Core, A = Base (Non-Wear) Course, and B = Topping (Wear) Course.

#2: The field density tests (identified with T in test location) were taken with a Troxler model 3440, averaging 5 tests in NomographAsphalt Mode for thin layer density determination. The density of the underlying base is incorporated in the thin layer densitycalculation. The laboratory density tests (identified with C in test location) were tested in accordance with ASTM D2726, on coresamples of the in-place pavement obtained in general accordance with ASTM D5362.

Golder Associates Inc. Review by: A. Thorson

Date Reported:  1/10/2012