Field Evaluation of Thin 4.75-mm Hot Mix Asphalt Dense-Graded

RMAC 40th Annual Conference, February 27-March 1, 2013, Denver, Colorado

Hot Mix Asphalt Dense-Graded Overlay: Surface Characteristics

Disclaimer: This presentation reflects the views of the authors, who are responsible for the facts and the accuracy of the data contained herein. This presentation does not necessarily represent the official views or policies of the Indiana Department of Transportation, the Joint Transportation Research Program or Federal Highway Administration. This report does not constitute a standard, specification or regulation. Neither the authors nor any their employers, nor any agency thereof endorses products or manufacturers.

Shuo Li, Yanna Sun, Yi Jiang, Samy Noureldin, and Todd Shields

Acknowledgements

This project was sponsored by INDOT in cooperation with FHWAthrough the Joint Transportation Research Program (JTRP). Theauthors would like to thank David Andrewski, Mike Prather, JeffreyJames, Jewell Stone, Shakeel Baig, and Tom Duncan for theirguidance. The assistance from Tony Johnson, Kyle Long, BrittneyGick, Patrick Weaver and Ayesha Shah is also acknowledged.Gick, Patrick Weaver and Ayesha Shah is also acknowledged.

INTRODUCTION

INDOT started to experiment with 4.75-mm HMA pavement on I-465 in 2006

Friction testing conducted after 12 months of service indicated that this pavement experienced low friction

INDOT revised the 4.75-mm mix specifications and laid INDOT revised the 4.75-mm mix specifications and laid three more test sections on three different conventional highway

A study was initiated in 2008 to evaluate the field friction performance of conventional 4.75-mm mixes

This paper presents the firsthand and vital information for successful use of 4.75-mm t dense-graded mixes

THE TEST SECTIONS

Site Description Old pavements profile milled and overlaid with ¾” 4.75-mm

dense-graded HMA mixes The mixes on US-27 and SR-227 produced with same JMF AADT in 2007

Road # of Lanes

Length AADT Trucks ESAL Category

Construction Time

I-465 6 4 mi. 104593 19475 5 08/2006US-27 2 4 mi. 7735 741 3 09/2009SR-227 2 3 mi. 1964 77 1 09/2009SR-29 2 9 mi. 5552 1,215 3 08/2010

TABLE 1 Information on 4.75-mm HMA Pavement Test Sections

Materials and Mixes For the 1st 4.75-mm pavement on I-465, no experience

available and the mix design relied on the practice with coarse aggregate size mixes

Binder selection: PG system (temperature, ESAL category) Recycled materials, such as RAP and ARS might be used Aggregate selection: ESAL category Aggregate selection: ESAL category

Natural: sandstone, dolomite, crushed stone, crushed gravel,and natural sand

Synthetic: blast furnace slag (BFS) and steel furnace slag (SF)INDOT polish resistant aggregates (PRA)

For other sections, specifications were revised (aggregate type, gradation)

ESALBinder

Recycled MaterialsAggregate TypeCategory Numbers (106) RAP ARS

1 <0.3 PG 64-22 ≤25% ≤5% BFS, SF, sandstone, dolomite, PRA, crushed stone, crushed gravel, natural sand

2 0.3 to <3 PG 64-22 ≤25% ≤5%

TABLE 2 Summaries of Material Selection for 4.75-mm HMA Mixes

natural sand3 3 to <10 PG 64-22,

70-22≤15% ≤3% BFS, SF, sandstone,

dolomite, PRA4 10 to <30 PG 70-22,

76-22≤15% ≤3% BFS, SF, sandstone,

dolomite1, PRA1

5 ≥30 PG 76-22 ≤15% ≤3%1Dolomite and PRA may be used but cannot exceed 50% of the aggregate by weight when blended with BFS or sandstone, and 40% of the aggregate when blended with SF.

Test Section Aggregate Components Binder RAP

I-465BFS sand (39%), #24 dolomite sand (39%), #24 sand (20%), and Baghouse PG 70-22 0%

TABLE 3 Summaries of Materials, Gradations and Mixes for Experimental Pavements

(a) Mix Materials

I-465 (39%), #24 sand (20%), and Baghousefines (2%)

PG 70-22 0%

US-27/SR-227#12 dolomite (34%), #24 dolomite sand (34%), dolomite sand (30%), and Baghouse fines (2%)

PG 64-22 0%

SR-29#12 dolomite (27%), #24 QA sand (48%), QA fine sand (23%), and Baghouse fines (2%)

PG 64-22 0%

Test Section % Passing through Sieve Sizes (sieve size unit: mm)9.5 4.75 2.36 1.18 0.60 0.30 0.15 0.075

I-465 100 96.1 78.6 52.3 34.8 17.5 9.6 6.3US-27/SR-227 100 90.1 67.2 47.8 32.7 22.6 14.7 7.8SR-29 100 90.0 68.4 42.4 25.4 15.8 11.0 6.7

(b) Aggregate Gradations

Test Section FAA SE AC Va (%) VMA (%) VFA (%) DBRTotal Eff.I-465 45.9 92.1 7.8 5.9 4 17.7 76.9 1.0US-27/SR-227 47.0 80.0 6.9 5.2 4 16.0 75.0 1.5SR-29 47.1 88.3 6.8 5.7 4 17.3 76.9 1.2

(c) Aggregate and Mix Volumetric Properties

TEST AND RESULTS

The Test Section on I-465

FIGURE 1 Friction test results in the test section on I-465

Test Section MPD (mm)Friction

DFT20 FN (smooth tire) FN (Rib tire)I-465 0.24 0.43 16.7 44.4

TABLE 4 Summary of Surface Characteristics in I-465 Test Section

Friction testing with ASTM E 274 trailer started 2007 DF-Tester and CTM testing in 2009 Poor friction numbers varied between 8 and 20 Friction variations in both directions followed a similar trend Friction numbers fluctuated significantly over time FN by rib tire much greater than FN by smooth tire Poor macrotexture MPD: 0.24 mm

The Test Sections on US-27 and SR-227

FIGURE 2 Friction test results in the test sections on US-27/SR-227

TABLE 5 Summaries of Surface Characteristics in US-27 and SR-227 Test Sections

Items US-27 SR-227SB NB SB NB

MPD (mm), 18 months 0.24 0.30 0.18 0.20DFT20, 18 months 0.25 0.27 0.30 0.27FN (smooth tire), 18 months 19.7 28.6 20.1 19.8

Fresh 4.75-mm surfaces might produce good friction performance

Dramatic friction reduction overt time, 47% on US-27 and 36% on SR-227 after 12 months in service

Macrotexture MPD range: 0.18-0.30 mm Good correlation between FN and MPD

The Test Section on SR-29

Items LocationSB NB

FN (smooth tire), fresh surface 32.9 36.6FN (smooth tire), 6 months 21.6 27.6MPD (mm), 6 months 0.21 (Scanner) 0.22 (CTM)DFT , 6 months 0.23

TABLE 6 Summary of Surface Characteristics in SR-29 Test Section

DFT20, 6 months 0.23

Due to site conditions, MPD measured with CTM and Scanner, respectively

Observations similar to those from the test sections on US-27 and SR-227

MPD: 0.21mm (SB), 0.22mm (NB) FN: 21.6 (SB), 27.6 (NB)

HMA SURFACE FRICTION PERFORMANCE

Mix Type and Surface Characteristics

TABLE 7 Frictional Characteristics of Various Pavement Surfaces

Surface Type Friction MPD (mm)4.75-mm HMA on I-465, 36 months 16.7, smooth tire 0.24, CTM4.75-mm HMA on US-27, 18 months 19.7/28.6, smooth tire 0.24/0.30, CTM4.75-mm HMA on US-27, 18 months 19.7/28.6, smooth tire 0.24/0.30, CTM4.75-mm HMA on SR-227, 18 months 20.1/19.8, smooth tire 0.18/0.20, CTM4.75-mm HMA on SR-29, 6 months 21.6/27.6, smooth tire 0.21/0.22, CTM4.75-mm HMA, new (1) 62.5, rib tire 0.21, CTM4.75-mm HMA, 15 months (1) 63.8, rib tire 0.26, CTM12.5-mm HMA, new (1) 65.5, rib tire 0.39, CTM12.5-mm HMA, 15 months (1) 45.9, rib tire 0.39, CTM4.75-mm HMA, new, MODOT (2) - 0.17-0.22, CTM4.75-mm HMA, new, TNDOT (virgin mix) (2) 0.25-0.35, DFT20 0.16-0.33, CTM4.75-mm HMA, new, TNDOT (15% RAP) (2) 0.28-0.33, DFT20 0.19-0.33, CTM4.75-mm HMA, new, MNDOT (2) 0.34-0.49, DFT20 0.13-0.18, CTM

TABLE 7 (continued)

Surface Type Friction MPD (mm)9.5-mm HMA (3) 42.5, smooth tire 0.59, CTM9.5-mm Dense-Graded HMA (4) - 0.53, CTM12.5-mm SMA (4) - 1.07, CTM19.0-mm SMA (4) - 1.11, CTM12.5-mm OGFC (4) - 2.31, CTMDense-graded HMA to OGFC (5) 32.5, smooth tire 1.63, sand patch (24)

27.4, smooth tire 0.53, sand patch27.4, smooth tire 0.53, sand patch41.4, smooth tire 1.57, sand patch33.4, smooth tire 2.19, sand patch37.8, smooth tire 2.97, sand patch

9.5-mm HMA (6) 61.9/64.3, BPN (25) 0.62/0.78, sand patchPolymer modified 9.5-mm HMA (6) 56.6/65.6, BPN 0.76/0.82, sand patchRubber modified 9.5-mm HMA (6) 60.6/64.5, BPN 0.78/0.73, sand patchPolymer modified 12.5-mm SMA (6) 58.4/67.6, BPN 0.89/0.94, sand patch12.5-mm SMA with fibers (6) 60.5/67.8, BPN 0.89/1.07, sand patch19.0-mm HMA (6) 60.9/62.9, BPN 0.73/0.82, sand patch

TABLE 7 (continued)Surface Type Friction MPD (mm)

9.5-mm PFC, new (7) 0.51, DFT20 1.37, CTM9.5-mm PFC, 36 months (7) 0.52, DFT20 1.37, CTM9.5-mm PFC, 60 months (7) 0.42, DFT20 1.48, CTM9.5-mm SMA, newly constructed (7) 0.37, DFT20 1.17, CTM9.5-mm SMA, 36 months (7) 0.61, DFT20 1.03, CTM9.5-mm SMA, 60 months (7) 0.69, DFT20 0.93, CTM9.5-mm HMA, newly constructed (7) 0.52, DFT20 0.30, CTM9.5-mm HMA, 36 months (7) 0.39, DFT20 0.55, CTM9.5-mm HMA, 60 months (7) 0.41, DFT 0.63, CTM9.5-mm HMA, 60 months (7) 0.41, DFT20 0.63, CTM

4.75-mm mixes demonstrated the smallest MPD, 0.20mm-0.35 mm Surface friction and MPD increased as NMAS increased Surface friction increased as MPD increased SMA, OGFC and PFC showed better friction than conventional mixes Modified asphalt binders might improve friction performance Poor friction might be the inherent nature of 4.75-mm HMA mixes

Surface Characteristics of 4.75-mm Mixes

FIGURE 3 Friction variations in all test sections

FIGURE 3 (continued)

It took 12 to 18 months for fresh 4.75-mm mixes to provide stable surface with the following friction characteristics

MPD: 0.20-0.25 mm FN: around 20

EFFECT OF AGGREGATE PROPERTIES

Gradation Limits Superpave gradation limits:

Control points: Max. size, NMAS, PCS, 2.36-mm sieve and 0.075-mm sieve

PCS sieve: 1.18-mmPCS sieve: 1.18-mmRestricted zone: between 0.30-mm sieve and 2.36-mm sieve

Removed by NCHRP Report 4642.36-mm sieve: 53.4%1.18-mm sieve: 36.1%-42.1%0.60-mm sieve: 26.8%-30.8%0.30-mm sieve: 21.1%

FIGURE 4 Aggregate gradation properties of the three 4.75-mm mixes

(a) Aggregate Gradations

(b) Gradation LimitsFIGURE 4 (continued)

Aggregate gradations all lying far above the MDL on 0.6-mm and larger sieves, few coarse particles

Aggregate gradations all passing above the PCS control point, all fined-graded mixesGradations on I-465 and SR-29: CRZGradations on US-27 and SR-227: ARZ

All 4.75-mm mixes contained too much fine sand All 4.75-mm mixes contained too much fine sandPoor macrotexture properties, leading to low frictionWeak skeleton/poor stabilities: significant friction fluctuation

To improve surface frictionProvide a BRZ aggregate gradationProvide a aggregate gradation passing below the PCS control point (more realistic when restricted zone removed)

Packing Properties

Experimental Section I-465 US-27/SR-227 SR-29% Half Sieve (2.36-mm) 78.6 67.2 68.4% Primary control sieve (1.18-mm) 52.3 47.8 42.4% Secondary Control Sieve (0.3-mm) 17.5 22.6 15.8% Tertiary Control Sieve (0.075-mm) 6.3 7.8 6.7

TABLE 8 Fractions of Coarse and Fine Aggregates

% Tertiary Control Sieve (0.075-mm) 6.3 7.8 6.7Coarse aggregate (CA) ratio 1.23 0.59 0.82Fine aggregate coarse (FAc) ratio 0.33 0.47 0.37Fine aggregate fine (FAf) ratio 0.36 0.35 0.42MPD (mm) 0.24 0.21-0.30/0.18-0.20 0.21-0.22

When computed in terms of fine-graded mixes, the new CA ratios areI-465: 0.27 US-27/SR-227: 0.15 SR-29: 0.13

FAc and FAf all inside the desired range (0.35-0.50) CA ratios for all mixes outside the desired range (0.30-0.45)

CA=1.23 (>1.0) on I-465: coarse aggregates no control on aggregate skeleton, difficult to compact and tendency to move under traffic application

If computed in terms of fine-graded mixes, new CA ratios still outside the desired rangeoutside the desired rangeI-465: 0.27 US-27/SR-227: 0.15 SR-29: 0.13

For 4.75-mm mixes, difficult to provide CA inside the desired range

Larger CA may create greater texture, but unbalanced coarse aggregate structure, a CA approaching 1.0 sound reasonable

Possible ways to improve friction: larger %HS, non-continuous gradation between 0.60-mm and 2.36-mm sieves

Aggregate Type, FAA and SE Aggregate type affects friction significantly polishing resistance,

surface feature (particularly microtexture) For 4.75-mm mixes, microtexture important for long-term friction Aggregate type important for 4.75-mm HMA surface friction As FAA increases, rutting resistance increases, better rutting

performance exhibiting better friction performance A larger SE favorable to surface friction

Experimental Section FAA (%) SE (%) MPD (mm)I-465 45.9 92.1 0.24US-27/SR-227 47.0 80.0 0.21-0.30/0.18-0.20SR-29 47.1 88.3 0.21-0.22MODOT project (18) 45 Not reported 0.17-0.22MN project (18) 47 83 0.13-0.18

TABLE 9 Summaries of FAA, SE and MPD Results

A larger SE favorable to surface friction

CONCLUSIONS

A fresh 4.75-mm mix may produce good surface friction. However, the friction will decrease dramatically over time. A reduction >35% can be anticipated after 12 months of service.

The greater the traffic volume the greater the friction reduction, which is sensitive to truck traffic.It takes 12-18 months for a fresh 4.75-mm mix to produce It takes 12-18 months for a fresh 4.75-mm mix to produce true surface characteristics, the true FN is around 20 and the true MPD is around 0.20-0.25mm.

Typical gradations for 4.75-mm mixes are ARZ or CRZ gradations, it becomes important for the gradation to pass below the PCS control point, particularly when the restricted zone is removed.

CA ratios for 4.75-mm mixes are commonly out of the desired range. A greater CA ratio may produce larger macrotexture, but also unbalanced coarse aggregate structure. A CA ratio approaching but less than 1.0 sounds reasonable. Increasing the % Half Sieve and providing a non continuous gradation between 0.6-mm and 2.36-mm sieves may improve surface macrotexture properties.

Larger FAA or SE leads to better friction performance For 4.75-mm mixes, realistic and effective approaches to

enhance surface friction includeUse of polishing resistant aggregatesUse of a gradation passing below PCS control pointsUse of polymer modified asphalt binders

References1) Stacy G. Williams, Nathan L. Becknell, and Kevin D. Hall (2009). “Comparison of the

Frictional Properties of 4.75 and 12.5 mm HMA Surface Mixes,” Proceedings of the Fifty-Fourth Annual Conference of Canadian Technical Asphalt Association (CTAA), Moncton, NB, November, 2009, 191-211.

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Questions and Comments

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