Presentation on theme: "Sub-Grade Preparation-Equipment Caterpillar Paving Products"— Presentation transcript:
1 Sub-Grade Preparation-Equipment Caterpillar Paving Products Asphalt 105: EquipmentSub-Grade Preparation-EquipmentCompaction & GradingSpeaker: Steve McCownMarket ProfessionalCaterpillar Paving ProductsPeoria, 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 WorldOur 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/PerceptionLoss of RevenuesAbility to draw new business and developmentMedia attention
5 Evolution of a Road Dirt road light traffic light loads. Improved Dirt road with layer of gravelWidened Dirt road for 2-way trafficImproved with asphalt for increased traffic/loadsEntered maintenance mode….
6 Typical Fix - OverlayRe-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 ProcessCold planing removes a portion of the asphalt layer (profiling)Process suitable when base is in good condition and will support axle loadsProcess suitable when cracks do not extend full depth of asphalt layerAsphalt LayerAggregate Base
9 Cold Planing Process Cold planing does not remedy base problems Process does not remove cracks that penetrate to baseNew asphalt layer will show reflective crack quicklyPoor economics (future maintenance)Asphalt LayercrackAggregate Basevoid
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 economicallyFast-growing maintenance alternativeEasily adapts to current highway maintenance design criteria
15 Full Depth Reclamation Process is different from cold planing or cold-in-place recyclingRotor always penetrates through the asphalt into the baseRotor depth can be set to blend desired portion of the existing base/sub-base with the asphalt layerAsphaltAggregate BaseReclaimed Material
16 Full Depth Reclamation Process Eliminates full depth crackingOpens base for stabilizationProvides better support for new asphalt layerCost savings by re-using existing pavement material and done in-placeAsphalt LayerAggregate Base
17 Major Indicators for Full Depth Reclamation Deep crackingReflective crackingPothole patchingRutting/shovingFrost heavesParabolic shapeInsufficient base strength
18 Reclaimed MaterialMaterial leaving mixing chamber well-graded & homogenousPulverized material will not be smaller than the original aggregatesNormal max. particle size of 50 mm (2")Eliminates cracks, ruts, bumps & potholes in asphalt layer
20 Benefits of Full Depth Reclamation Aggregate can be added to basePerfect use for RAP!Work is done in-place, saving expensive removal & replacement of deteriorated layersVersatility in the process as well as the types of structures
21 Secondary Road Reclamation Roads not designed to support today’s higher traffic volume & loadsHigh opportunity for reclamation on secondary roadsIdeal candidates for both strengthening & widening
22 City Street Reclamation Where frequent cracking & patching are presentCan be substituted for overlay or cold planingWith adequate traffic control, street can remain openBusinesses and home owners benefit from open road
23 State Road Reclamation Higher quality structures rehabilitated with corresponding gains in base strength0,8 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 baseFull asphalt layer is recycled or reclaimedThinner wear course maybe possible
25 Airport ReclamationReclamation rather than overlay eliminates reflective crackingNew surface on top of upgraded, uniformly compacted baseLife of the new asphalt structure is increased
27 Granular Materials & Soils – Lab Tests Attenberg Limits – ASTM D 4318Sand Equivalent Value – ASTM D 2419Sieve Analysis – ASTM C 136Materials finer than No. 200 sieve – ASTM C 177
28 75 mm (3") Asphalt or Less – Lab Tests Extraction of Bitumen – ASTM D 2172Sieve Analysis – ASTM C 136Materials finer than No. 200 sieve – ASTM C 177
29 75 mm (3") Asphalt or More – Lab Tests Recovery of Asphalt – ASTM D 1856Penetration of Bituminous Materials – ASTM D 5Viscosity 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 baseSizing is controlled by operator who balances machine speed & rear door openingTypical sizing specs – 100% 50 mm (2") – 95% 38 mm (1.5") – 25% max. fines
32 Additive ApplicationAdditives applied after pulverization or after rough gradingSprayed through on- board emulsion spray system or tanker truckPulverization & mixing passes are usually separate for better consistency
33 Additive ApplicationAdditives are often applied directly to the pulverized materialAmounts 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 PassesMultiple passes may be needed to achieve adequate homogeneitySequence of mixing passes depends on the additive characteristicsMixing depth needs to match the pulverization depth to ensure consistent material
35 Compaction of Reclaimed Material Normally after the mixing pass if additives are usedDelayed if asphalt emulsion is usedTypical compaction sequence – initial or breakdown – intermediate – finish
36 Shaping Reclaimed Material Performed after breakdown compactionFinal shaping occurs after crown & grade are established & all compaction is completeLoose 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 ashIn asphalt emulsion – water loss is required for base to set & hardenHeavy traffic not allowed during curing – may cause base failure
39 Placing the Pavement Layer May follow pulverization, shaping & compaction, if no stabilizing agents were utilizedMay be possible to apply a thinner asphalt layer or economical chip sealPurpose of reclamation – creation of a higher value, stronger base
40 Typical Asphalt Pavement Structure Hot Mix AsphaltCrushed Stone BaseSand & Gravel Sub-baseSub-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 + a3D3Example: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 conditionsSub-grade soil support valueEquivalent wheel load repetitionsExpected 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")& GravelSN = 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")& GravelPresent Serviceability = Terminal Serviceability = 2.00
46 Rehabilitation Techniques 75 mm (3") HMA overlayReconstruction – mill full depth asphalt removal – re-shape and compact existing crushed stone base – 125 mm (5") HMA overlayFull 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")& GravelSN = 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")& GravelSN = 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")& GravelSN = 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")GravelSN = 4.01
51 Structural Number Comparison Technique SNOverlay 2.853” Mill & Fill 2.22Reconstruction 3.50Full Depth Reclamation 4.01
52 Estimated Service Life Technique SN LifeReclamation yearsReconstruction yearsOverlay 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 MileLeveling Course, 1" (25 mm) avg. hot mix $4.40* $77,440.00Wearing Course, 3" (76 mm) (hot mix) $13.20* $232,320.00Total 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 MileLeveling Course, 1" (25 mm) avg. hot mix $4.40* $77,440.00Wearing Course, 2" (50 mm) (hot mix) $8.80* $154,880.00Total 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 MilePulverizing $ $13,904.00Grade Preparation $ $ 4,576.00Water $ $ 1,936.00Mixing $ $ 9,328.00Emulsion $ $47,168.00Grading and Compaction $ $ 7,392.00Fog Seal $ $ 2,992.003-inch Hot Mix $ $232,320.00Total 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 MileService Life Before Major MaintenanceCost/Year Per MileReclaimed Road $331, years $18,421.00Overlaid Road 3” $309, years? $25,813.00Overlaid Road 2” $232, years? $29,040.00Even 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 0.07Crushed Stone 0.14Cement 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 0.15Bituminous Treated (ATB) – course-graded 0.20 – 0.30– sand asphalt 0.30Lime Treated 0.15 – 0.30
60 Other Benefits Less Fuel Consumed Fewer Emissions Less Traffic DisruptionLess Business InterruptionPreserve Natural Resources