MnDOT Reclamation Inspector s Guide Full Depth Reclamation and Stabilized Full Depth Reclamation 2/2/2016

Transcription

1 MnDOT Reclamatin Inspectr s Guide Full Depth Reclamatin and Stabilized Full Depth Reclamatin 2/2/2016

2 Frward Reclamatin utilizes large quantities f in-place materials. The quality and placement f these materials invlves the applicatin f varius test prcedures and inspectin techniques t ensure that they are placed within the specificatin requirements. This manual helps t ensure that unifrmity f prcess is fllwed. Pavement Preservatin, Reclamatin & Grading & Base Engineer Minnesta Department f Transprtatin Index This Inspectr s guide is brken dwn int five sectins: Reclamatin Basics Preliminary Respnsibilities Prject Inspectin Respnsibilities Cmmn Prblems and Slutins Summary: The nine mst imprtant aspects t have a successful reclamatin prject. A) Reclamatin Basics The reclamatin prcess reuse existing rad materials and significantly reduces the use f fssil fuels and virgin resurces such as aggregate and asphalt. Reclamatin cnsists f pulverizing and mixing in-place asphalt materials with r withut underlying base and with r withut the additin f stabilizing agents such as asphalt, additinal aggregate, cement r cmpactin aids. The material is then typically verlaid with a new asphalt pavement. The tw types f reclamatin currently emplyed by MnDOT are: Full Depth Reclamatin (FDR): where in-place bituminus is grund with in-place base, with r withut the placement f additinal aggregate n tp f the bituminus pavement befre reclaiming. Stabilized Full Depth Reclamatin (SFDR): where n the first pass in-place bituminus is grund with in-place base, with r withut the placement f additinal aggregate n tp f the bituminus pavement befre reclaiming. Then there is a secnd pass where liquid asphalt and smetimes cement is incrprated. Inspectin guidelines fr Cld In-Place Recycling (CIR) are included in a separate dcument. CIR is a prcess where in-place bituminus pavement is reclaimed and new asphalt binder r emulsin is added in a single pass. B) Preliminary Respnsibilities 1) Dcument Review Prject Specificatins Mix Design Structural Pavement Design

3 Cnstructin Manual Traffic Cntrl Plan Owner/Agency Requirements Stabilizing Agent Manufacturers Instructins Safety Data Sheets (SDSs) Health and Safety Plan and Jb Hazard Analysis Schedule f Materials Cntrl 2) Nte In-Place Pavement Distresses that may indicate weak subgrade that needs t be repaired Much f the fllwing shuld be perfrmed in the scping stage f design, and may already be identified in the plan fr remediatin. Hwever the inspectr shuld als examine the prject area, as they may find additinal deficient areas that need t be addressed. Nte the types and causes f existing pavement distresses. See MnDOT Distress Identificatin Manual. Identify areas f excessive surface defrmatin which may indicate sft subgrade cnditins r drainage deficiencies. T crrect subgrade prblems the reclaimed material typically is mved t ne side r cmpletely remved, then the subgrade is either: dried and re-cmpacted, stabilized with cement r a getextile fabric is placed as a separatin layer. Pr drainage cnditins can be addressed by eliminating the surce f water by installing surface and/r subsurface drains t direct the water away frm the radway. The reclaimed material is then placed back n the prepared subgrade and cmpacted. Review cre and Grund Penetrating Radar (GPR) data frm bth the center and edge f the pavement, t cnfirm the thickness f materials t be reclaimed fr bth the bituminus and base. Verify that existing structures, e.g. guardrails, curbs and bridge clearances, d nt impse limitatins n FDR peratins r final pavement gemetry. Determine whether paving fabric r ther getextile materials r cal tar are present within any f the layers t be reclaimed, because fabric and getextiles will nt get prcessed well during reclamatin. Fr SFDR, ld cal tar bituminus des nt mix well with new emulsins r new bituminus famed materials, and yu will end up with lwer anticipated SFDR strength. Nte the presence f utility cvers (manhles and valves), their lcatin, frequency and elevatin and crdinate with utility wners and the Cntractr a plan t address affected areas withut disturbing utilities. Cnsider the impact f ther issues such as patched areas and reclaiming shulders, as they will usually have a different depth f bituminus and aggregate, and different bituminus cmpsitin.

4 Cntact maintenance persnnel t get their input regarding rutine and extrardinary maintenance fr the prject site, and als review rad histry reprts. 3) Materials Checks Obtain a sufficient number f cres/samples (minimum ne every half mile) fr mix design develpment and t ascertain cnsistency f in-place bituminus thickness and cnditin. Samples are evaluated fr cnsistency ver the length f the prject. The stabilizing agents may include: Aggregate fr mechanical stabilizatin Emulsified asphalt r famed asphalt fr stabilizatin Cement fr Chemical Stabilizatin 4) Precnstructin Meeting Ensure that all necessary cntractr and agency persnnel attend the precnstructin meeting. 5) Surface Evaluatin Identify areas in the Plan where the subgrade is t be repaired. Identify additinal areas nt in the Plan where the subgrade may need t be repaired. Review required pre-milling depths t ensure that there is adequate bituminus, aggregate and crushing in the final prduct. If yu are cnsidering milling t a prescribed depth t meet a prfile, but milling wuld remve t much f the aggregate and crushed fines, cnsider instead remving material after pulverizatin. This excess material may then be used fr ther shulders r gravel surfaced rads within yur system. Ensure that pre-milling is perfrmed satisfactrily. 6) Equipment Inspectins - Review and special prvisins fr equipment requirements. a) Reclaimer Verify that the cutting drum is the crrect width. Verify that the reclaimer has sufficient weight and hrsepwer t cut t the depth and tlerances specified within the cntract dcuments. Verify that the carbide cutting teeth are all in place and in adequate cnditin. SFDR: Verify that the spray bar and nzzles are wrking prperly and nt clgged. SFDR: Verify that the n-bard stabilizing agent system is equipped with a meter capable f recrding the rate f flw and ttal amunt f each liquid being added t the reclaimed material. SFDR: Verify that the reclaimer is equipped with an n-bard fam generating system including a famed asphalt sampling valve when famed asphalt is being used as the stabilizing agent. SFDR: Verify that the n-bard stabilizing agent system has a psitive interlck system linked t the frward speed f the reclaimer s that the amunt f liquid stabilizing agent

5 being added will change accrding t the peratinal speed f the reclaimer. Verify that the crrect amunt f water is being added t achieve a hmgenus mixture and achieve specified percent cmpactin. SFDR: The ttal in-place misture, plus any additinal misture plus the bitumen added shuld be at r belw the ptimum misture cntent f the mix design. b) Spreader SFDR: If required, verify that the spreader is prperly calibrated and is capable f accurately dispensing the required quantity f stabilizing agent and/r additive. c) Mtr Graders Verify that the mtr graders used are in accrdance with thse specified in the cntract dcuments. d) Rllers and Scrapers Verify that wrking scrapers are in place n all rllers as required by the cntract dcuments. e) Other Equipment Haul trucks Frnt End Lader Water Truck 7) SFDR: Weather Requirements Verify that the ambient air temperature (in the shade) meets cntract specificatin requirements, typically a minimum f 50 F and rising when using bituminus prducts and nt fggy. Cnsider that variatins in temperature, humidity, and wind cnditins will all affect breaking and curing times. There can be n anticipated freezing temperatures within 48 hurs after stabilizatin, see C. Verify that n significant precipitatin (r fg fr bituminus stabilizatin) is predicted during cnstructin peratins, in accrdance with cntract specificatins. 8) Mix Design Review the mix design requirements. 9) Traffic Cntrl Verify that the traffic cntrl plan cmplies with the cntract dcuments and the Manual n Unifrm Traffic Cntrl Devices. Verify that the signs and devices erected n the radway match the traffic cntrl plan cntained in the cntract dcuments. SFDR: Ensure that flaggers d nt hld stpped traffic n freshly treated material. Ensure that signs are remved r cvered when they n lnger apply. Ensure that an apprpriate actin plan is develped and implemented fr emergency vehicles passing thrugh the prject.

6 Ensure that any unsafe cnditins are reprted t a supervisr. C) Prject Inspectin Respnsibilities 1) Testing required during the prject (See Schedule f Materials Cntrl) The testing required fr FDR includes: Gradatin Cmpactin (DCP) Misture Cntent during Cmpactin Depth Check Test Rlling The testing required fr SFDR includes: Gradatin: tp size and full gradatin Cmpactin (DCP) fr unstabilized prtin Misture Cntent during cmpactin f unstabilized prtin Depth Check Misture cntent befre injectin with bituminus Yield checks n asphalt Cntrl strip, fr cmpactin Cmpactin cmpliance using nuclear density gauge Bituminus samples Calibratin f cement applicatin rate, if applicable Faming checks, if applicable 2) Pulverizatin Verify that the depth f pulverizatin and during the injectin stage meets the Cntract; hwever beware f pulverizatin that is t deep, especially fr sectins with n granular subbase. If pulverizatin ges thrugh the base and int a plastic subgrade, it will cntaminate the material with subgrade fines. Als, the prcess requires a strng platfrm t cmpact against; therefre t minimize risk, it is best t leave at least three t fur inches f base, unless there is a granular subbase. Verify that the pulverized material meets the tp size gradatin per the specificatin. Direct the Cntractr t remediate areas where the tp size is t large. Pay clse attentin t areas which are highly alligatr cracked as these areas will nt tend t meet gradatin. Oversize material tends t get buried, therefre bserve when the mtr grader makes its initial pass t see if ver-size material is expsed. The Cntractr can mdify his prcess t lwer the ccurrence f versize material by using several methds including:

7 Slwing the speed f reclaiming Adjusting the breaker bar within the reclaimer (check gap between drum and breaker bar) Making a secnd reclaiming pass Manually picking ut ver-sized material SFDR: Review the full gradatin and cmpare it t the gradatin used in the mix design t see if it is finer r carser. Finer grund material may need mre bitumen and carser less. Cnfer with the Cntractr fr pssible applicatin rate mdificatins. Additinal, small areas within a prject may need variatins in the mix design, again cnfer with the Cntractr fr pssible applicatin rate mdificatins. 3) SFDR: Mixing and Placement SFDR: Verify the misture cntent f the pulverized material befre injectin t determine if an adjustment is needed t reach r maintain ptimum misture. Verify that the blending/mixing f water (if needed) and stabilizing agent is adequate t ensure a hmgenus, cnsistent blend thrughut the treatment sectin. Mnitr the amunt f water intrduced t maintain the specified range f ptimum misture cntent. 4) SFDR: Field Observatins & Tests t Evaluate Cnsistency & Design Applicatin Rate The cnsistency in the clr f the material immediately behind the recycler will usually indicate whether r nt the machine is set up prperly. A gradual change in clr acrss the width nrmally indicates that ne end f the drum is lwer than the ther. A lighter appearance indicates dilutin (under-applicatin f water and bitumen stabilizing agent) caused by the drum nt penetrating t deep int the pavement. A darker clr indicates an ver-applicatin due t the drum nt penetrating t the required depth. A lighter appearance f material thrughut the full applicatin width may als indicate a finer gradatin, which may need additinal asphalt. 5) SFDR: Tire Test Bitumen treated material shuld nt adhere t the rear wheels f the recycler. The left picture shws what shuld be seen behind the recycler. The right picture shws material sticking t the rear wheels may indicate that the treated material is prly mixed. This peratin shuld be stpped immediately t determine the cause. Prly mixed material will als stick t the drum f the rller, causing material build-up and further prblems. Sticking material may als be cause by t high an applicatin f bitumen because f a carser gradatin. Additinally, in very ht weather sticking may als ccur, and a slight increase in water may alleviate the sticking.

8 Observe Tires Behind the Reclaimer (TG 2 Bitumen Stabilized Materials) 6) SFDR: Ball Test This test requires a rund specimen the size f a fist t be made frm a sample f material picked up frm behind the recycler and firmly squeezed between bth hands. Balls made with Famed AC can be tested right away, but balls made with emulsin shuld be left in the sun and allwed t dry fr at least 30 minutes s that the bitumen emulsin can break (clr change frm brwn t black). Once a ball has been frmed, the fllwing visual bservatins can be made: The test cnsists f hlding the ball between the thumb and index finger and gently applying pressure n ppsite sides f the ball t gauge the chesiveness f the material. The ball shuld defrm befre falling apart. Inspect the face f the brken ball t see hw well the bitumen has dispersed. If n bitumen can be seen, the mix is perfect. The mre bitumen blbs r stringers there are that can be bserved, the wrse the quality f the mix. Clean all lse material frm the palms f the hands and bserve the bitumen spts. The warmth f the hands and pressure applied will permit the bitumen t stick. Lts f tiny spts indicate gd dispersin whilst larger blbs are the stringers resulting frm pr dispersin. If a ball cannt be frmed r des nt defrm befre breaking, then the mix may be t lean. 7) Stabilizing Agent and Stabilizing Additive Spreading SFDR: Verify that applicatin rates f stabilizing agents and additives are meeting the applicatin rates specified in the mix design and remain cnsistent thrughut the treatment area. SFDR: Check that applicatin rates n the reclaimer's flw meter (bituminus binder) are accurate. SFDR: Check that the calibratin n the spreader equipment fr cement is crrect. Check that the calibratin n the spreader equipment fr additinal rck is crrect. 8) SFDR: Stabilizing Agent Mixing and Depth If cement is used, ensure that the mixing begins within 30 minutes f cement placement, as hydratin f cement may ccur and strng wind can disperse the cement. During injectin, check the depth f injectin and visually bserve that the new asphalt is being unifrmly blended int stabilized material. If the material is nt unifrmly blended, r the depth is nt as per the Plan, require the Cntractr t remix the nn-cmpliant areas. Check the first 200 feet each day t insure that the reclaimer is perfrming crrectly. 9) SFDR: Cmpactin, see C.7, C.8 and C.8.a Verify that an adequate rlling pattern has been established and that the cmpactin rller is

9 immediately fllwing the reclaimer. Breakdwn rlling shuld be with a padft rller. Rlling shuld cntinue until the rller walks ut f the material. Mnitr that density/cmpactin f the mat meets specificatin/cntract dcument requirements. Fr the injectin pass a cntrl strip is required. 10) SFDR: Grading Mnitr t ensure the mtr grader is clsely ( feet maximum) fllwing the cmpactin rllers. Be careful t nt verwrk the treated mat as t cmprmise its structural integrity during the curing prcess. Ensure that the material is kept within the radway width. Mnitr surface misture cntent and apply water as necessary t maintain ptimum misture. Check prfile. Check crss-slpe. Make sure the centerline is frmed. 11) SFDR: Finish Rlling It is preferred t rll the mat in static mde t reduce the pprtunity fr micr-cracking f the FDR surface. 12) SFDR: Initial Opening t Traffic Ensure that the material in the recently cmpleted mat meets the cntract requirements fr cmpactin density. Prf rll the surface prir t pening t initial traffic t verify material can supprt light traffic. Ensure that temprary pavement markings, if required by the cntract dcuments are in place prir t pening the surface t traffic. Ensure initial traffic des nt impair material curing. 13) Seal Apply a fg seal t the tp surface, using the rate and type and at the time as required f the Cntract. 14) SFDR: Bituminus Placement Place and cmpact new asphalt pavement n sner than three calendar days after injectin and cmpacted at any lcatin, and when the surface des nt deflect under cnstructin equipment and meets quality cmpactin per F.2. The SFDR will cntinue t gain strength as it cures ut. D) Cmmn Prblems and Slutins

10 Pulverized material is nt cnsistent with the material samples used in mix design: Determine if the current mix design is still applicable. Cnsider adding additinal rck fr FDR, if cmpactin targets are nt being met. SFDR: Determine if a new stabilizing agent applicatin rates will be better suited based n the gradatin f material n the prject. SFDR: The pulverized material is nt at target misture cntent: Add water t reach target misture cntent befre r during treatment. Dry the pulverized material by aeratin befre treatment. Final target misture is the ptimum misture frm the mix design and equals the inplace misture plus any additinal misture added during stabilizatin plus the added bituminus emulsin r fam. The material is sft r defrms excessively Aerate, reshape and cmpact if instability is due t excessive misture. Replace with suitable materials. The subgrade is failing belw the prpsed sectin: Remve the pre-pulverized material and repair the subgrade. Pre-milling depth Mill and remve enugh material t accunt fr the vlume gain acquired by the pulverizatin prcess and additin f a stabilizing agent (typically 10% f the riginal vlume); this is particularly imprtant n prjects that are lcked in by grade. E) Summary: The nine mst imprtant aspects t have a successful reclamatin prject are: 1) Use the required equipment fr cmpactin, and d nt allw the Cntractr t start reclaiming until all required equipment and peratrs are mbilized n the prject. 2) Assess if a field change is required either by requiring additinal crushed rck, a mdificatin f the mix design rates fr SFDR, r repairing the subgrade. 3) Mnitr the reclaim depth and mdify if necessary. If yu d nt have a granular subbase r subgrade, leave a minimum f 3-4 inches f base fr FDR. Fr SFDR reclaim nly an inch r tw int the base as the deeper yu g the amunt f il demand increases. Als fr bth FDR and SFDR the deeper yu reclaim the less slid substrate yu will have t cmpact against. Use depth checks t mnitr this. Additinally, if Pit Run material is under the bituminus and cntains rcks larger than 3, raise the reclaimer s cutting head. 4) Review cre and GPR (grund penetrating radar) data fr depth changes f the bituminus and base. Mark rad sectins where depth f bituminus changes. Take extra depth checks in transitin areas. As an illustratin the tw cres belw were sampled frm the same prject in the design stage.

11 If the design called fr milling the tp fur inches and reclaiming the next six inches, then in the area f the cre n the left there wuld still be a gd amunt f rck in the final prduct and mst likely (yu shuld als check the in-place base gradatin and depth) there wuld be base t cmpact against. Fr the cre n the right, this wuld nt be the case. Therefre, fr that area, cnsider nly milling tw inches and reclaim t a depth leaving 3-4 inches f base in-place. If yu d decide t mill shallwer in this area, yu will either have t plan fr a slight grade raise, r have the Cntractr remve the excess material. 5) Use the crrect amunt fr water t cmpact FDR (3-7%) and SFDR (final ttal misture shuld be at the ptimum misture cntent frm the mix design (includes the in-place misture plus any additinal misture added during stabilizatin plus the added bituminus emulsin r fam). 6) Mnitr the tp size gradatin 7) SFDR: Mnitr the entire gradatin, and cmpare t the mix design, cnsult with the Cntractr if a change in the mix design is warranted. 8) Check fr cmpactin cmpliance 9) SFDR: When the faming asphalt methd is used fr SFDR, keep away frm the supply truck, as the il is in excess f F. Mnitr the cntractr fr the required faming checks. Surces MnDOT Specificatins 2215 & 3135, special Prvisins & MnDOT Grading & Base Manual Basic Asphalt Recycling Manual, Secnd Editin, Annaplis, MD: ARRA. Full Depth Reclamatin Cnstructin Checklist. Publicatin N. FHWA-HIF , Washingtn, D.C FHWA. Available at Technical Guideline: Bitumen Stabilized Materials. A Guideline fr the Design and Cnstructin f Bitumen Emulsin and Famed Bitumen Stabilized Materials. Published by the Asphalt Academy Pretria, Suth Africa MnDOT Distress Identificatin Manual. February 2011