Presentation on theme: "2009 RMAC Annual Meeting Asphalt 105: Equipment Sub-Grade Preparation-Equipment Compaction & Grading Speaker: Steve McCown Market Professional Caterpillar."— Presentation transcript:
2009 RMAC Annual Meeting Asphalt 105: Equipment Sub-Grade Preparation-Equipment Compaction & Grading Speaker: Steve McCown Market Professional Caterpillar Paving Products Peoria, IL
2009 RMAC Annual Meeting The Real World Todays Reality for most contracting agencies is….. The majority of our budget dollars are spent on maintenance and rehabilitation of existing roads. WHY? Growth Happens!
2009 RMAC Annual Meeting 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 Media attention Loss of Revenues Ability to draw new business and development
2009 RMAC Annual Meeting Evolution of a Road
2009 RMAC Annual Meeting 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….
2009 RMAC Annual Meeting Typical Fix - Overlay Re-paving on top of a weak base is a short term fix
2009 RMAC Annual Meeting Typical Fix - Mill & Fill Alternative for mildly distressed roads where re-profiling is needed.
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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 Aggregate Base crack void
2009 RMAC Annual Meeting Typical Fix - Reconstruction Process Scarification of existing pavement
2009 RMAC Annual Meeting Typical Reconstruction Process Removal of the scarified material
2009 RMAC Annual Meeting Typical Reconstruction Process Material hauled to dump site for later processing as RAP.
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting Full Depth Reclamation Proven process that provides quality results economically Fast-growing maintenance alternative Easily adapts to current highway maintenance design criteria
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting Major Indicators for Full Depth Reclamation Deep cracking Reflective cracking Pothole patching Rutting/shoving Frost heaves Parabolic shape Insufficient base strength
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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)
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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!
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting Typical Asphalt Pavement Structure Hot Mix Asphalt Crushed Stone Base Sand & Gravel Sub-base Sub-grade
2009 RMAC Annual Meeting Construction Materials Coefficients HMA a 1 = 0.42D 1 = 125 mm (5") CSB a 2 = 0.14D 2 = 150 mm (6") Sand a 3 = 0.11D 3 = 200 mm (8") & Gravel
2009 RMAC Annual Meeting Structural Number (SN) Formula Example: SN = (0.42)(5) + (0.14)(6) + (0.11)(8) SN = SN = 3.82 SN = a1D1 + a2D2 + a3D3
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting HMA a 1 = 0.42D 1 = 125 mm (5") CSB a 2 = 0.14D 2 = 150 mm (6") Sand a 3 = 0.11D 3 = 200 mm (8") & Gravel New Pavement Structure SN = 3.88 Life Expectancy = 15 Years Terminal Serviceability = 2.00
2009 RMAC Annual Meeting Pavement Structure after 15 Years Present Serviceability = 1.44 Terminal Serviceability = 2.00 Deteriorated HMAa 1 = 0.42D 1 = 125 mm (5") Decompacted CSBa 2 = 0.14D 2 = 150 mm (6") Decompacted Sand a 3 = 0.11D 3 = 200 mm (8") & Gravel
2009 RMAC Annual Meeting 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
2009 RMAC Annual Meeting Overlay Alternative SN = 2.85 HMA Overlaya 1 = 0.42D 1 = 75 mm (3") Deteriorated HMAa 2 = 0.15D 2 = 125 mm (5") Decompacted CSBa 3 = 0.06D 3 = 150 mm (6") Decompacted Sand a 4 = 0.06D 4 = 200 mm (8") & Gravel
2009 RMAC Annual Meeting Mill & Fill Alternative SN = 2.22 HMA Overlaya 1 = 0.42D 1 = 75 mm (3") Deteriorated HMAa 2 = 0.06D 2 = 125 mm (2") Decompacted CSBa 3 = 0.06D 3 = 150 mm (6") Decompacted Sand a 4 = 0.06D 4 = 200 mm (8") & Gravel
2009 RMAC Annual Meeting Reconstruction Alternative SN = 3.50 HMA Overlaya 1 = 0.42D 1 = 125 mm (5") Reconstructed CSBa 2 = 0.14D 2 = 150 mm (6") Decompacted Sand a 3 = 0.07D 3 = 200 mm (8") & Gravel
2009 RMAC Annual Meeting Reclamation Alternative SN = 4.01 HMA overlaya 1 = 0.42D 1 = 75 mm (3") Reclaimed ATBa 2 = 0.25D 2 = 200 mm (8") Decompacted CSBa 3 = 0.09D 3 = 75 mm (3") Decompacted Sanda 4 = 0.06D 4 = 200 mm (8") Gravel
2009 RMAC Annual Meeting Structural Number Comparison TechniqueSN Overlay2.85 3” Mill & Fill2.22 Reconstruction3.50 Full Depth Reclamation4.01
2009 RMAC Annual Meeting Estimated Service Life TechniqueSNLife Reclamation years Reconstruction years Overlay years
2009 RMAC Annual Meeting Example Only: Cost per Square YardCost per Mile Leveling Course, 1" (25 mm) avg. hot mix $4.40* $77, Wearing Course, 3" (76 mm) (hot mix) $13.20* $232, Total estimated cost for one mile $17.60* $309, 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. Typical Overlay Project * Based on asphalt price of $80/ton
2009 RMAC Annual Meeting Example Only: Cost per Square YardCost per Mile Leveling Course, 1" (25 mm) avg. hot mix $4.40* $77, Wearing Course, 2" (50 mm) (hot mix) $8.80* $154, Total estimated cost for one mile $13.20* $232, 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. Typical Overlay Project * Based on asphalt price of $80/ton
2009 RMAC Annual Meeting 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.
2009 RMAC Annual Meeting Typical Reclamation Project Example Only: Cost per Square YardCost per Mile Pulverizing $0.79 $13, Grade Preparation $0.26 $ 4, Water $0.11 $ 1, Mixing $0.53 $ 9, Emulsion $3.36 $47, Grading and Compaction $0.42 $ 7, Fog Seal $0.17 $ 2, inch Hot Mix $13.20 $232, Total Estimated Cost for One Mile $ $331,584.00
2009 RMAC Annual Meeting 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.
2009 RMAC Annual Meeting Expected Service Life/Cost Comparison Initial Cost per Mile Service Life Before Major Maintenance Cost/Year Per Mile Reclaimed Road $331, years $18, Overlaid Road 3”$309, years? $25, Overlaid Road 2”$232, years? $29, 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!