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Sub-Grade Preparation-Equipment Caterpillar Paving Products

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1 Sub-Grade Preparation-Equipment Caterpillar Paving Products
Asphalt 105: Equipment Sub-Grade Preparation-Equipment Compaction & Grading Speaker: Steve McCown Market Professional Caterpillar Paving Products Peoria, IL

2 Growth Happens! The Real World
Todays Reality for most contracting agencies is….. Growth Happens! The majority of our budget dollars are spent on maintenance and rehabilitation of existing roads. WHY?

3 The Real World Our challenge is not the proper construction of new roads but how to better manage the dollars we have to improve & maintain our existing streets and highways. Public Pressure/Perception Loss of Revenues Ability to draw new business and development Media attention

4 Evolution of a Road

5 Evolution of a Road Dirt road light traffic light loads.
Improved Dirt road with layer of gravel Widened Dirt road for 2-way traffic Improved with asphalt for increased traffic/loads Entered maintenance mode….

6 Typical Fix - Overlay Re-paving on top of a weak base is a short term fix

7 Typical Fix - Mill & Fill
Alternative for mildly distressed roads where re-profiling is needed.

8 Cold Planing Process Cold planing removes a portion of the asphalt layer (profiling) Process suitable when base is in good condition and will support axle loads Process suitable when cracks do not extend full depth of asphalt layer Asphalt Layer Aggregate Base

9 Cold Planing Process Cold planing does not remedy base problems
Process does not remove cracks that penetrate to base New asphalt layer will show reflective crack quickly Poor economics (future maintenance) Asphalt Layer crack Aggregate Base void

10 Typical Fix - Reconstruction Process
Scarification of existing pavement

11 Typical Reconstruction Process
Removal of the scarified material

12 Typical Reconstruction Process
Material hauled to dump site for later processing as RAP.

13 The Full Depth Reclamation alternative
It is a Process, Performed in Cold, which pulverizes and mixes Existing pavement structure In Place with a certain amount of Underlying Base Material to form an Improved and Upgraded Road Base

14 Full Depth Reclamation
Proven process that provides quality results economically Fast-growing maintenance alternative Easily adapts to current highway maintenance design criteria

15 Full Depth Reclamation
Process is different from cold planing or cold-in-place recycling Rotor always penetrates through the asphalt into the base Rotor depth can be set to blend desired portion of the existing base/sub-base with the asphalt layer Asphalt Aggregate Base Reclaimed Material

16 Full Depth Reclamation Process
Eliminates full depth cracking Opens base for stabilization Provides better support for new asphalt layer Cost savings by re-using existing pavement material and done in-place Asphalt Layer Aggregate Base

17 Major Indicators for Full Depth Reclamation
Deep cracking Reflective cracking Pothole patching Rutting/shoving Frost heaves Parabolic shape Insufficient base strength

18 Reclaimed Material Material leaving mixing chamber well-graded & homogenous Pulverized material will not be smaller than the original aggregates Normal max. particle size of 50 mm (2") Eliminates cracks, ruts, bumps & potholes in asphalt layer

19 Common Stabilizing Agents
Asphalt emulsion Foamed asphalt Portland cement Fly ash Dry lime Lime slurry Calcium chloride

20 Benefits of Full Depth Reclamation
Aggregate can be added to base Perfect use for RAP! Work is done in-place, saving expensive removal & replacement of deteriorated layers Versatility in the process as well as the types of structures

21 Secondary Road Reclamation
Roads not designed to support today’s higher traffic volume & loads High opportunity for reclamation on secondary roads Ideal candidates for both strengthening & widening

22 City Street Reclamation
Where frequent cracking & patching are present Can be substituted for overlay or cold planing With adequate traffic control, street can remain open Businesses and home owners benefit from open road

23 State Road Reclamation
Higher quality structures rehabilitated with corresponding gains in base strength 0,8 to 1,6 km (1/2 to 1 mile) of two-lane road processed per day

24 Interstate Highway Reclamation
Portion of asphalt layer milled & remaining asphalt is pulverized & blended with the base Full asphalt layer is recycled or reclaimed Thinner wear course maybe possible

25 Airport Reclamation Reclamation rather than overlay eliminates reflective cracking New surface on top of upgraded, uniformly compacted base Life of the new asphalt structure is increased

26 Pre-Project Evaluation
Core Sampling – asphalt layer – base/sub-base – sub-grade Pavement Condition Survey – buried obstacles – cracking – rutting/shoving – settlement – heaving – potholes

27 Granular Materials & Soils – Lab Tests
Attenberg Limits – ASTM D 4318 Sand Equivalent Value – ASTM D 2419 Sieve Analysis – ASTM C 136 Materials finer than No. 200 sieve – ASTM C 177

28 75 mm (3") Asphalt or Less – Lab Tests
Extraction of Bitumen – ASTM D 2172 Sieve Analysis – ASTM C 136 Materials finer than No. 200 sieve – ASTM C 177

29 75 mm (3") Asphalt or More – Lab Tests
Recovery of Asphalt – ASTM D 1856 Penetration of Bituminous Materials – ASTM D 5 Viscosity of Asphalt – ASTM D 2171

30 Equipment Requirements
Full Depth Reclamation Process – reclaiming machine (with additive system) – motor grader(s) – compactor(s) Auxiliary Equipment (all may not be required) – tanker truck (water, emulsion) – end or bottom dump trucks – water distributor truck – wheel loader – oil distributor truck (fog/curing seal)

31 Full Depth Reclamation Process
First step is to pulverize existing asphalt layer with portion of the base Sizing is controlled by operator who balances machine speed & rear door opening Typical sizing specs – 100% 50 mm (2") – 95% 38 mm (1.5") – 25% max. fines

32 Additive Application Additives applied after pulverization or after rough grading Sprayed through on- board emulsion spray system or tanker truck Pulverization & mixing passes are usually separate for better consistency

33 Additive Application Additives are often applied directly to the pulverized material Amounts are specified in liters sq/m gal (sq/yd) Additional aggregate can also be added after pulverization if required. Perfect use for RAP!

34 Mixing Passes Multiple passes may be needed to achieve adequate homogeneity Sequence of mixing passes depends on the additive characteristics Mixing depth needs to match the pulverization depth to ensure consistent material

35 Compaction of Reclaimed Material
Normally after the mixing pass if additives are used Delayed if asphalt emulsion is used Typical compaction sequence – initial or breakdown – intermediate – finish

36 Shaping Reclaimed Material
Performed after breakdown compaction Final shaping occurs after crown & grade are established & all compaction is complete Loose material should be removed for proper bonding of the asphalt prime coat or curing seal

37 Curing of Stabilized Base
Required for development of strength & minimization of shrinkage cracks in portland cement or fly ash In asphalt emulsion – water loss is required for base to set & harden Heavy traffic not allowed during curing – may cause base failure

38 Quality Control Gradation Additive content Moisture content
Mix uniformity Compaction Layer thickness Finished surface

39 Placing the Pavement Layer
May follow pulverization, shaping & compaction, if no stabilizing agents were utilized May be possible to apply a thinner asphalt layer or economical chip seal Purpose of reclamation – creation of a higher value, stronger base

40 Typical Asphalt Pavement Structure
Hot Mix Asphalt Crushed Stone Base Sand & Gravel Sub-base Sub-grade

41 Construction Materials Coefficients
HMA a1 = 0.42 D1 = 125 mm (5") CSB a2 = 0.14 D2 = 150 mm (6") Sand a3 = 0.11 D3 = 200 mm (8") & Gravel

42 Structural Number (SN) Formula
SN = a1D1 + a2D2 + a3D3 Example: SN = (0.42)(5) + (0.14)(6) + (0.11)(8) SN = SN = 3.82

43 Determining the Structural Number
Class of road – (terminal serviceability typical ) Climatic conditions Sub-grade soil support value Equivalent wheel load repetitions Expected life before major maintenance

44 New Pavement Structure
HMA a1 = 0.42 D1 = 125 mm (5") CSB a2 = 0.14 D2 = 150 mm (6") Sand a3 = 0.11 D3 = 200 mm (8") & Gravel SN = Life Expectancy = 15 Years Terminal Serviceability = 2.00

45 Pavement Structure after 15 Years
Deteriorated HMA a1 = 0.42 D1 = 125 mm (5") Decompacted CSB a2 = 0.14 D2 = 150 mm (6") Decompacted Sand a3 = 0.11 D3 = 200 mm (8") & Gravel Present Serviceability = Terminal Serviceability = 2.00

46 Rehabilitation Techniques
75 mm (3") HMA overlay Reconstruction – mill full depth asphalt removal – re-shape and compact existing crushed stone base – 125 mm (5") HMA overlay Full depth reclamation – 200 mm (8") asphalt and base pulverization – stabilize with 7,57 L (2 gal/sq yd) asphalt emulsion – 75 mm (3") HMA overlay

47 Overlay Alternative HMA Overlay a1 = 0.42 D1 = 75 mm (3")
Deteriorated HMA a2 = 0.15 D2 = 125 mm (5") Decompacted CSB a3 = 0.06 D3 = 150 mm (6") Decompacted Sand a4 = 0.06 D4 = 200 mm (8") & Gravel SN = 2.85

48 Mill & Fill Alternative
HMA Overlay a1 = 0.42 D1 = 75 mm (3") Deteriorated HMA a2 = 0.06 D2 = 125 mm (2") Decompacted CSB a3 = 0.06 D3 = 150 mm (6") Decompacted Sand a4 = 0.06 D4 = 200 mm (8") & Gravel SN = 2.22

49 Reconstruction Alternative
HMA Overlay a1 = 0.42 D1 = 125 mm (5") Reconstructed CSB a2 = 0.14 D2 = 150 mm (6") Decompacted Sand a3 = 0.07 D3 = 200 mm (8") & Gravel SN = 3.50

50 Reclamation Alternative
HMA overlay a1 = 0.42 D1 = 75 mm (3") Reclaimed ATB a2 = 0.25 D2 = 200 mm (8") Decompacted CSB a3 = 0.09 D3 = 75 mm (3") Decompacted Sand a4 = 0.06 D4 = 200 mm (8") Gravel SN = 4.01

51 Structural Number Comparison
Technique SN Overlay 2.85 3” Mill & Fill 2.22 Reconstruction 3.50 Full Depth Reclamation 4.01

52 Estimated Service Life
Technique SN Life Reclamation years Reconstruction years Overlay years

53 Typical Overlay Project
Overlay. The process: Place and compact leveling course with average 1 inch (25 mm) hot mix asphalt concrete. Place and compact 3 inch (76 mm) wearing course of hot mix asphalt concrete. Example Only: Cost per Square Yard Cost per Mile Leveling Course, 1" (25 mm) avg. hot mix $4.40* $77,440.00 Wearing Course, 3" (76 mm) (hot mix) $13.20* $232,320.00 Total estimated cost for one mile $17.60* $309,760.00 * Based on asphalt price of $80/ton

54 Typical Overlay Project
Overlay. The process: Place and compact leveling course with average 1 inch (25 mm) hot mix asphalt. Place and compact 2 inch (50 mm) wearing course of hot mix asphalt concrete. Example Only: Cost per Square Yard Cost per Mile Leveling Course, 1" (25 mm) avg. hot mix $4.40* $77,440.00 Wearing Course, 2" (50 mm) (hot mix) $8.80* $154,880.00 Total estimated cost for one mile $13.20* $232,320.00 * Based on asphalt price of $80/ton

55 Typical Reclamation Project
Full Depth Reclamation. The process: Pulverize the existing roadway structure and shoulder material to a width of 30 feet (9.1 m) and a depth of 6 inches (152 mm), reshape and mix asphalt emulsion at a rate of 2.0 gallons (7.6 liters) per square yard (square meter) to a depth of 6 inches (152 mm). Shape and compact the emulsion treated base, apply fog seal and allow to cure. Finish with a hot mix asphalt wearing course after proper curing period.

56 Typical Reclamation Project
Example Only: Cost per Square Yard Cost per Mile Pulverizing $ $13,904.00 Grade Preparation $ $ 4,576.00 Water $ $ 1,936.00 Mixing $ $ 9,328.00 Emulsion $ $47,168.00 Grading and Compaction $ $ 7,392.00 Fog Seal $ $ 2,992.00 3-inch Hot Mix $ $232,320.00 Total Estimated Cost for One Mile $ $331,584.00

57 Expected Service Life/Cost Comparison
Expected Service Life/Cost Comparison. While many factors influence the useful life of any road or street, there has been sufficient experience with full-depth reclamation to predict service life (assuming minimal maintenance). In the above example, using asphalt emulsion for added binder in the new base and a 3“ (76 mm) wearing course, an 18-year life for the reclaimed structure is expected. The same street or road corrected with leveling course and a 3“ (76 mm) wearing course, has a projected life of 12 years. The potential for reflective cracking and accelerated deterioration is much greater on overlaid surface than on reclaimed and paved structures. Therefore, the reclaimed road will last longer and provide better long-term value.

58 Expected Service Life/Cost Comparison
Initial Cost per Mile Service Life Before Major Maintenance Cost/Year Per Mile Reclaimed Road $331, years $18,421.00 Overlaid Road 3” $309, years? $25,813.00 Overlaid Road 2” $232, years? $29,040.00 Even though the initial cost to reclaim and pave with hot mix asphalt is usually about 15-30% higher than the overlay method, in the long term, full depth reclamation is about 20-40% more economical because reclaimed roads last longer!

59 Structural Layer Coefficients (AASHTO)
Sandy Gravel 0.07 Crushed Stone 0.14 Cement Treated (not soil cement) compressive strength at 7 days – 650 psi or more 0.23 – 400 psi to 650 psi 0.20 – 400 psi or less 0.15 Bituminous Treated (ATB) – course-graded 0.20 – 0.30 – sand asphalt 0.30 Lime Treated 0.15 – 0.30

60 Other Benefits Less Fuel Consumed Fewer Emissions
Less Traffic Disruption Less Business Interruption Preserve Natural Resources

61 Thank You! QUESTIONS?

62 © Caterpillar 2009

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