Asphalt Surface Treatment Synthesis

Transcription

1 1 Asphalt Surface Treatment Synthesis Hesham Ali, PhD, PE, CPM Mojtaba M Afzali, Ph.D. Candidate

2 The 2

3 Outlines 3 Introduction Surface Treatment Techniques Fog Seal Chip Seal Slurry Seal Micro Surfacing Cape Seal Novachip Summary Brief Description Recent Studies Survey Results

4 Introduction Surface Treatments 4 Surface Treatments: Pavement preservation techniques which are applied on the entire surface of the road Why? It cost less to maintain roads in good condition than in poor condition Limited budget to maintain 3 million miles of paved roads in the US

5 Introduction Sustainability Crisis: Back to The Stone Age! 5 In Michigan, at least 38 of the 83 counties have converted some asphalt roads to gravel in recent years. In 2001, South Dakota turned at least 100 miles of asphalt road surfaces to gravel. Counties in Alabama and Pennsylvania have begun downgrading asphalt roads to cheaper chip-seal road.

6 Introduction Pavement Deterioration Curve 6 Effect of Preventive Maintenance at Life Cycle Cost (Galehouse, Moulthrop, & Hicks, 2003)

7 Effective Pavement Management: Right Road, Right Treatment, Right Time $ per CL mile ($22 per gal) $2.50 per SY $3.50 per SY $2.50 per SY $6.25 per SY 1 $5.25, 1.5 $8.25 per SY 1 $7.75, 1.5 $10.75 per SY $22.00 per SY w/ 1.5 HMA $25.00 per SY w/ 1.5 HMA 7

8 Quick Assessment Approach 8 How much work does the City need to do to stay at same condition? Let s Assume that a city has 300 lane miles of roads. They have a life expectancy of 25 years... We can say that: We now have 7500 (300 lane miles * Remaining life) lane mile years. Each Year, the roads grow 1 year older and we loose 300 lane mile years Next year 7200 The following 6900, and so on.

9 9 Example City with 300 Lane Miles of Roads WORK MIX I Work Lane Miles Design Life Lane Mile Years Lane Mile Cost Total Cost Re-Construction $250,000 $2,000,000 Rehabilitation $100,000 $1,600,000 Preservation $30,000 $ 480,000 TOTAL $ 4,080,000 WORK MIX II Work Lane Miles Design Life Lane Mile Years Lane Mile Cost Total Cost Re-Construction $250,000 $1,500,000 Rehabilitation $100,000 $1,000,000 Preservation $30,000 $ 1,500,000 TOTAL $ 4,000,000

10 Purpose of This Synthesis 10 Asphalt Surface Treatment Synthesis Brief introduction to surface treatment techniques Summarize previous surface treatment research Assess surface treatment implementation in agencies Focus on state of practice in Southeast U.S. A useful reference for practitioners;

11 Research Methodology 11 Literature Review Survey Preparation & Distribution Response Analysis Final Report Comprehensive review of the literature References: LTRC Transportation Research Record NCHRP reports Asphalt Institute Manuals Text books SHA guidance Industry publications Three Questionnaires: Q1: General Q2: Technical Q3: Research Status Statistical Analysis Evaluation of commonalities and contrasts in methodology and application of techniques Summarize Literature Explain objectives and methodology Report survey analysis results Plain Language Graphical representation

12 Surveys 12 The survey consists of three questionnaires: Questionnaire 1: Administrative General questions regarding Implementation status, specification, performance, cost, problems, Does not delve into technical details Questionnaire 1: Technical Technical detailed questions regarding pavement condition, material, design, construction, performance and cost For respondents with technical information Questionnaire 1: Research Status Questioning completed, ongoing and planned research projects relate d to surface treatment techniques. For respondents who are involved in research and development Qualtrics survey development software

13 Survey Participants participants from 7 states responded to Questionnaire 1 Florida DOT(5),Georgia DOT, West Virginia DOT, North Carolina DOT, Arkansas AHDR Louisiana LTRC, Virginia VCTR City of Orlando, City of Kissimmee, City of Clermont, Okaloosa county(2), Lee County 8 participants responded to Questionnaire 2 and 3

14 General Survey Results 14 Number of Participants Reported Implementation of each Surface Treatment Technique

15 Surface Treatment Techniques 15 Surface Treatment Techniques Fog Seal Rejuvenation Chip Seal Sandwich Seal Sand Seal Scrub Seal Slurry Seal Micro Surfacing Cape Seal Novachip

16 Fog Seal 16 light sprayed application of diluted asphalt emulsion to an asphalt pavement surface. Main functions: To seal cracks and voids and decrease permeability To renew old HMA pavements which have aged and become dry and brittle Hold chip seal aggregate in their place Material: Diluted asphalt emulsion Diluted asphalt has lower viscosity and penetrates to deeper layers Dilution water to emulsion Ratio :(1:1) to (1:5) Some common emulsions: SS-1, RS-a, SS-1h, CSS-1h, CRS-1 Typical application rate of for (1:1) diluted emulsion 0.03 to 0.22 gal/yd

17 17 Fog Seal Rejuvenation Fog seal with rejuvenator Main purpose: Rejuvenation of the aged asphalt binder Asphalt is consisted of a solid fraction, Asphaltenes and liquid Maltenes As the asphalt ages, the Maltene oxidize and so its ratio to Asphaltenes reduces Asphalt mix gets brittle and dry and pavement performance drops Rejuvenators or recycling agents are special chemicals which can soften asphalt and restore its original properties

18 18 Fog Seal Recent Studies Effect of fog seal on surface friction Shuo Li et al. (2012) ; Indiana Department of Transportation and Purdue University Friction measurement decrease dramatically after application of fog seal It normally takes the pavement surface friction about 18 months after a fog seal application to return to the original level Friction numbers before and after fog seal Fog Seal Treatment Effectiveness Analysis of Pavement Binders N.Prapaitrakul, T.Freeman, C.Glover. (2010) Texas A&M Binders recovered from 1/4-in. slices from the top inch of the cores Ductility evaluated using DSR The upper quarter inch of pavement is most affected by fog seal. There was almost no penetration below 1/4 below the pavement surface.

19 19 Fog Seal Rejuvenation Recent Studies The Role of an Asphalt Rejuvenator in Pavement Preservation: Use and Need for Asphalt Rejuvenation Jim Brownridge (2010) Binghamton University Effective rejuvenation in the top 1 4 to 3 8 inch of asphalt surface Durability is improved in the top portion by changing chemical composition The rejuvenator can seal pavement against intrusion of air and water Rejuvenating is green: No cutback solvents, less truck, less use of aggregate Laboratory investigation of rejuvenator seal materials on performances of asphalt mixtures Juntao Lin, Peida Guo, Li Wan1, Shaopeng Wu (2012) Rejuvenator Seal Materials (RSM) can soften the aged asphalt binder RSM effectively decrease the raveling of asphalt mixture RSM decrease the rutting resistance of asphalt mixture RSM decrease the skidding resistance of asphalt mixture

20 20 Fog Seal Survey Results Reported in North Carolina, West Virginia, Arkansas and 3 Florida counties. Okaloosa county: 20 ongoing and 50 completed fog seal projects No well-stablished and widely accepted specification is out there Common emulsions: CSS-1h, CRS-2p Quantity: 0.08 to 0.22 gal/yd2 Expected life extension: 1 to 5 years Cost: $ $0.5 per sq. yd Major problems: Lack and specifications and skilled local contractors, sudden rain showers Curing sometimes takes more time than expected, the road is open to traffic when still wet, tire mark on driveway

21 21 Fog Seal Survey Results Pavement Condition Before Fog Seal

22 Chip Seal 22 sprayed application of asphalt emulsion which is followed by spreading a single layer of uniform size aggregate Protects pavement from deterioration due to traffic and environmental condition improves skid resistance of the pavement surface Multiple chip seal : Two or more courses of chip seal which are placed one on each other Material- Asphalt Fluid enough to can be easily sprayed and viscous enough to retain consistency to aggregates Rapid Curing Some Common material : RS-1, RS-2, CRS-1, CRS-2, MS1, HFMS1, PG 46-34, PG 52-28, PG 64-22, PG 58-28, PG Aggregate: Uniform

23 Chip Seal 23 Quantities of asphalt and aggregate for single layer chip seals Asphalt in Pavement Preservation and maintenance (Asphalt Institute)

24 24 Chip Seal Recent Studies Significant Research Work By NCDOT and NCSU (Dr.Richard Kim) Improved Rolling Pattern and Process (2008, 2009 & 2010) Performance Based Uniformity Coefficient for Aggregates (2009) Improved Performance by Polymer Modified Emulsions for Using in High Volume Roads(2009 & 2010) New Performance-based Mix Design Method (2012) Performance Evaluation (2013) Dr.Jordan with Mississippi DOT(2010): Rejuvenation effect of chip seal Banerjee and Prozzi (2012): Modeling Evaporative Water Loss of Emulsions

25 25 Chip Seal Recent Studies Improved Rolling Pattern: The optimal rolling pattern is strongly related to the delayed rolling time between spreading and rolling The optimum delayed rolling time depends on aggregates water content Optimum number of coverages: THREE Begin with Pneumatic roller and finish with combination roller

26 26 Chip Seal Recent Studies Performance Evaluation of Chip Seals (2013) The uniform gradation of aggregate is one of the most important factors for good chip seal performance The rolling pattern that yields the least aggregate loss: Three passes of a pneumatic tire roller immediately after the aggregate is spread, followed by three passes of two combination rollers side by side For a double seal compact first layer and for triple seal compact second layer (one coverage) Polymer modifies emulsions improve the performance of chip seals in terms of aggregate gradation, bleeding, and rutting. A performance evaluation model is proposed

27 27 o o o o Variations of Chip Seal Sandwich Seal and Sand Seal Sandwich Seal A layer of large aggregate (15-20 mm) is applied Asphalt is sprayed A layer of smaller aggregate is spread Is used to cure excessive asphalt on pavement surface o Sand Seal : Chip seal using fine uniform aggregate Excellent surface texture

28 28 Variations of Chip Seal Scrub Seal A specified scrub broom which is towed behind the distributor forces the emulsion into the old pavement. seals minor cracks in pavement and makes it more waterproof Scrub seal emulsion application Hwy 35 Chip and Scrub Seal Field Test Results for Hwy 17 and Hwy 35 Isaac L. Howard (2009), Missisipi DOT Report Aggregate retention performance of scrub seal sections was higher than chip seal Aggregate loss values in the lane center were generally higher than in the wheel path. No significant differences in popouts between chip and scrub seals was observed

29 29 Chip Seal Survey Results Nine agencies reported application of Chip Seal Sandwich seal in Florida and Scrub seal in Arkansas and Virginia In average 20 ongoing chip seal projects and 100 in last 5 years were reported NCDOT self performs lane miles of chip seal Agencies are well familiar with chip seal Chip seal is often performed on pavement in fair to good condition (60<PCI<84) Most of state DOTs have well-established specifications Cost : 1.87 to 2.7 $/yd2 The purpose of doing Chip Seal

30 30 Gaps in Specifications: Chip Seal Survey Results Specifications for higher traffic (more than 2000 ADT) and higher trucks (more than 200 TPD) roads Need for expanding or modifying types of emulsions allowed Lack of specifications for scrub seal Maximum and Minimum Size of Aggregate Agency Aggregate Maximum Size Aggregate Minimum Size GDOT 1/2" 3/8" NCDOT 5/16" 1.5% passing 200 sieve KCI Technologies Inc (Florida) 3/8" FDOT #89 stone 1/4" FDOT #89 stone

31 Slurry Seal 31 Application of a mixture of emulsified asphalt, fine aggregate, mineral filler and water on the surface of the pavement Both preventive and corrective - correction of minor irregularities and non working cracks Advantages: Excellent texture, Fast application, Minimum curb height loss (for its small thickness) Material: Aggregate: uniform, clean, angular, durable ASTM D 2419 Sand Equivalent Value not less than 45 ASTM C 131 Los Angeles Abrasion Loss not greater than 35 Emulsion: SS-1h, CSS-1h and CQS-1h Small amount of mineral fillers like Portland cement and limestone dust to stabilize the slurry Survey: Only two slurry convectional seal was reported. Micro surfacing is obviously being preferred by agencies Schematic Slurry machine

32 Slurry Seal 32 Optimum Time for Application of Slurry Seal to Asphalt Concrete Pavements ElieY. Hajj et. al. (2011), Transportation Research Board of the National Academies The long-term pavement performance data collected by MicroPAVER system for the past 15 years was evaluated Cost-effectiveness of slurry seals applied to new and existing flexible pavements at recent years Allow at least 3 years between initial pavement construction and first slurry seal Early application of slurry seal is not effective for either the benefit to users or the benefit cost ratio for the agency A timely applied slurry seal protects the asphalt mix from excessive aging and improve its resistance to fatigue, thermal, and block cracking.

33 Micro-Surfacing 33 Micro-Surfacing is a mixture of polymer-modified asphalt emulsion, mineral aggregate, mineral filler, water, and other additives, properly proportioned, mixed and spread on a paved surface (International Slurry seal Association) Advantages: Variable thickness Provide desired wet friction Accept traffic after a short time after application Emulsion Quick setting polymer modified emulsion quality test requirements

34 Micro-Surfacing 34 Aggregate: 100% crushed stone Quality test requirements: Gradation: Mineral Filler: Any recognized brand of non-air entrained Portland cement or hydrated lime that is free from lumps

35 Micro-Surfacing Machine 35

36 36 Micro-Surfacing Survey Results Reported by 10 agencies Slurry seal is being substituted by Micro Surfacing Is often used when pavement in Fair condition (60<PCI<69). But is sometime applied on those with better or worse condition (40<PCI<84) Florida, North Carolina and West Virginia have their own specifications for Micro-Surfacing Performance is often reported to be good but not excellent Five to seven years of life extension is expected Micro Surfacing is not favored by FDOT. Reason: A microsurfacing project that deteriorates after five years can be perceived by the public as a road that failed after only five years. Cost: $1.90 to $3 per sq. yd. for single course (ave. $2.6 / sq. yd.) ; $3.75-$4.00 per sq. yd for double course

37 Cape Seal 37 Cape seal is application of single layer chip seal followed by slurry seal or Micro surfacing The name of the technique is driven from Cape Administration of South Africa The rich slurry mix over the chip seal eliminates the problem of loose aggregate, holds stones of the seal coat firmly in place, and reduces traffic noise Very effective to correct medium severity fatigue cracks Also addresses other types of crack, raveling, water infiltration and friction loss Specifications used for chip seal and micro surfacing should be followed Slurry is laid 3 to 12 days after the chip seal

38 38 Cape Seal Previous Studies Solaimanian & Kennedy (1998) Two Strategies: I. High rate of slurry seal; A thin layer over chip seal II. Low rate of slurry seal to fill the voids; the top of the chips are exposed

39 39 Cape Seal Previous Studies

40 40 Cape Seal Survey Results Three agencies reported using Cape Seal; Not very popular NCDOT has done 20 Cape Seals during last 5 years Often is done on pavement with fair condition (60<PCI<69) Expected life extension: 6-7 years Cost: $ $3.6 per sq. yd. Problems: Lack of skilled contractors, knowledgeable personnel and proper material

41 NOVACHIP TM 41 Also known as Ultra Thin Bonded Wearing Course (UTBWC) Thin layer (½inch ¾ inch) of gap-graded HMA over a layer of polymer modified emulsion membrane Developed by SCREG Routes STP in France in 1986 The whole process is done by a specified piece of equipment Used in high-speed, high- volume auto routes and the national route systems Typical application rate of membrane: 0.23 ± 0.07 Gal/yrd 2 The first NOVACHIPTM projects in the US: Alabama, 1992 The heat from the HMA causes the emulsion to break quickly and wick upward into the bottom portion of the HMA lift

42 42 NOVACHIP TM Machine (Spray Paver)

43 NOVACHIP TM 43 Advantages: Excellent adhesion to old surface Rapid construction and placement in one pass Quick opening to traffic and lower user delay costs Lower rolling noise (urban use) Excellent macrotexture matrix resulting in good skid resistance as well as reduced tire noise and back spray of road surface water

44 44 NOVACHIP Survey Results Reported by six agencies Very popular in North Carolina :10 ongoing and 50 completed projects Applied on road with 60 < PCI < 84 (Fair to Good) Very good performance reported by all respondents Expected life extension: 8-15 years Average cost: $5.2 per sq. yd.

45 Summary 45 Conventional thin overlay is much more common than other surface treatment techniques

46 Summary 46 Treatment PCI before treatment Expected life extension (years) 1 Cost per sq. yd Fog Seal 79 3 $0.5 Chip Seal $2.3 Microsurfacing $2.6 Thin Overlays $5 UBWC $5.2 The most common problems: Lack of skilled contractors ; Social, legal and political considerations