Technical Advisory T 5040.36 - Surface = Texture for Asphalt and Concrete Pavements

From: Subject: Technical Advisory T 5040.36 - Surface Texture for Asphalt and Concrete Pavements Date: Mon, 22 Oct 2007 11:50:14 -0400 MIME-Version: 1.0 Content-Type: multipart/related; type="text/html"; boundary="----=_NextPart_000_0000_01C814A1.B58F80B0" X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 This is a multi-part message in MIME format. ------=_NextPart_000_0000_01C814A1.B58F80B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.fhwa.dot.gov/legsregs/directives/techadvs/t504036.htm Technical Advisory T 5040.36 - Surface = Texture for Asphalt and Concrete Pavements

U.S. Department of = Transportation Federal=20 Highway Administration	Technical = Advisory Subject Surface Texture for = Asphalt and=20 Concrete Pavements

Classification Code	Date	Office of Primary Interest
T 5040.36	June 17, 2005	HIPT-20

Par.

What=20 is the purpose of this Technical Advisory?=20
Does=20 this Technical Advisory supersede another Technical Advisory?=20
What=20 are the surface texture components that influence wet-weather = friction?=20
What=20 is the background on pavement surface texture/friction?=20
How=20 is tire/pavement noise impacted by surface texture?=20
What=20 is the recommended level of surface texture on high-speed (50 miles = per hour=20 (mph) or greater) facilities?=20
What=20 techniques will provide surface texture for concrete and asphalt=20 pavements?=20
How=20 is adequate texture provided on concrete pavements over the = performance life=20 of the pavement?=20
What=20 techniques will restore desired surface texture to in-service pavement = surfaces?=20
What=20 factors should be considered when selecting pavement surface = techniques or=20 thresholds?=20
What=20 factors should be considered when evaluating new or innovative = texturing=20 methods for concrete pavement?=20
Are=20 there any reference materials on pavement surface = texture/friction?=20

What is the purpose of this Technical = Advisory? This Technical Advisory (1) issues information on=20 state-of-the-practice for providing surface texture/friction on = pavements and=20 (2) issues guidance for selecting techniques that will provide = adequate wet=20 pavement friction and low-tire/surface noise characteristics.
Does this Technical Advisory = supersede=20 another Technical Advisory? Yes. This Technical Advisory = supersedes=20 Federal=20 Highway Administration (FHWA) Technical Advisory 5140.10, "Texturing = and Skid=20 Resistance of Concrete Pavements and Bridge Decks," dated = September 18,=20 1979.
What are the surface texture = components that=20 influence wet-weather friction? Two types of surface texture = affect=20 wet pavement friction: microtexture (wavelengths of 1=B5m to 0.5mm) = and=20 macrotexture (wavelengths of 0.5mm to 50mm). Microtexture is generally = provided in asphalt pavements by the relative roughness of the = aggregate=20 particles and in concrete surfaces by the fine aggregate. Macrotexture = is=20 generally provided in asphalt pavement by proper aggregate gradation = and in=20 concrete surfaces by a supplemental treatment such as those listed in=20 paragraph 7(a).
What is the background on pavement = surface=20 texture/friction? The FHWA pavement policy is contained in 23 = Code of=20 Federal Regulations (CFR) 626.3, and it states: "Pavement shall be = designed to=20 accommodate current and predicted traffic needs in a safe, durable, = and cost=20 effective manner." To provide a safe pavement, wet pavement friction = should be=20 provided. The characteristics of pavement texture that provide wet = weather=20 friction are microtexture and macrotexture. Both microtexture and = macrotexture=20 are necessary to provide wet pavement friction at low and high speed=20 conditions. While safety considerations are paramount, tire/surface = noise=20 should be considered when specifying pavement and bridge surfaces. = Both=20 asphalt and concrete pavements can provide safe, durable, and = low-noise=20 surfaces when properly designed and constructed.
How is tire/pavement noise impacted by = surface=20 texture? Texture content of a pavement surface influences=20 tire/pavement noise. Increased macrotexture with wavelengths of 2mm to = 10mm=20 has been shown to decrease exterior noise caused by tire/pavement = interaction,=20 while increased megatexture (wavelengths of 50mm to 500mm) content has = been=20 shown to increase interior noise in vehicles. It may be possible to = reduce=20 tire/pavement noise, while providing adequate wet pavement friction, = by=20 providing an optimized pavement texture that provides adequate = microtexture=20 and macrotexture, while minimizing megatexture (particularly = wavelengths of=20 50mm to 100mm), to provide a safe, durable, and quiet pavement = surface.=20 Methods used to provide macrotexture for concrete surfaces, such as = transverse=20 tining and others, also tend to impart some megatexture content. It is = important to consider the impact on megatexture of methods to provide=20 macrotexture.
What is the recommended level of surface texture on = high-speed (50=20 miles per hour (mph) or greater) facilities? Providing = adequate=20 texture depth has been shown to improve pavement friction test results = at high=20 speeds and reduce crash rates on high speed facilities. Texture depth = targets=20 for new and in-service pavement surfaces should be established by=20 owner-agencies based upon project-specific factors as described in = paragraph=20 10. Findings in the references under paragraph 12 should be evaluated = for=20 relevancy when establishing texture threshold targets.
What techniques will provide surface texture for concrete = and=20 asphalt pavements?
1. Concrete surfaces. A supplemental treatment is = typically=20 required to provide adequate macrotexture on concrete pavements. = Paragraph 8=20 provides a summary of important research findings and = recommendations=20 relative to successful application of these texturing techniques.=20 Cost-effectiveness should be assessed prior to specifying a specific = texturing technique.
  1. (1) Tining, preceded by a burlap drag, has been shown to be a = low-cost=20 method for providing macrotexture to new concrete pavements. = Spacing,=20 depth, width, and orientation of the tine pattern have a = significant=20 influence on the friction and tire/surface noise characteristics = of the=20 completed surface.
  2. (2) Exposed aggregate surface has been shown to provide a lower = noise=20 surface for Portland Cement concrete (PCC) pavements. Texture = depth,=20 aggregate size, and durability of aggregate have a significant = influence=20 on the friction and tire/pavement noise characteristics of the = completed=20 exposed aggregate surface.
  3. (3) Broom or artificial turf drag finish for concrete surfaces = is=20 recommended for surfaces where the design speed is 50 mph or = greater,=20 provided adequate safety performance is demonstrated (see = paragraph=20 11(b))
  4. (4) Diamond grooving has been shown to be an effective method = for=20 providing macrotexture to new concrete pavements. Spacing, depth, = width,=20 and orientation of the grooves have a significant influence on the = friction and tire/surface noise characteristics of the completed=20 surface.
  5. (5) Diamond grinding of new concrete pavements for the purpose = of=20 imparting macrotexture is recommended, provided adequate safety=20 performance is demonstrated (see paragraph 11(b)) or non-polishing = large=20 aggregates are used.
  6. (6) Burlap drag surface texture should only be considered for = surfaces=20 where the design speed is less than 50 mph.
  7. (7) Other techniques may be utilized if research indicates = long-term=20 safety performance is achieved (see paragraph 11(b)).
  8. (8) The fine aggregate fraction of the aggregate concrete = matrix=20 provides microtexture. As such, the fine aggregate should be wear = and=20 polish resistant. A minimum 25% of the fine aggregate for concrete = should=20 be siliceous material. More information on concrete mix design is=20 contained in FHWA Technical Advisory T 5080.17, dated July 14, = 1994.
  9. (9) Thin asphalt overlays may be used to provide a surface on = PCC=20 pavement. Typically, asphalt surfaces include dense graded mixes,=20 gap-graded mixes, and open graded asphalt friction courses. = Paragraph 7(b)=20 provides guidance on design of asphalt surfaces.
2. Asphalt surfaces. Hot-mixed asphalt pavements = designed=20 in conformance with Superpave mix design will generally provide = adequate=20 macrotexture and microtexture without supplemental treatments. In = areas=20 where supplies of durable non-polishing aggregates are limited, an = agency=20 may choose to construct an asphalt pavement using high durability = aggregates=20 optimized for friction properties only in the top layer.
  1. (1) Asphalt surface course
    1. (a) Dense graded asphalt mixtures designed using appropriate = material=20 and design techniques as discussed below will typically provide = adequate=20 surface texture.
    2. (b) Open Graded Friction Courses should be designed and = constructed=20 in conformance with FHWA=20 Technical Advisory T 5040.31, dated December 26, 1990.
    3. (c) Stone Matrix Asphalt Courses should be designed and = constructed=20 in conformance with American Association of State Highway and=20 Transportation Officials (AASHTO) specifications MP8 and=20 PP41.
  2. (2) Surface treatments and other=20 methods
    1. (a) Asphalt-based surface treatments such as = microsurfacing.
    2. (b) Thin epoxy-bonded laminates.
  3. (3) Mix-related=20 characteristics=20
    1. (a) Proper texture characteristics of asphalt surfaces are = very much=20 influenced by asphalt content, voids in the mineral aggregate, = dust to=20 binder ratio, and void content. Proper mix design, following = Superpave=20 procedures, should be performed to ensure the needed ratio of = these=20 elements. It is recommended that test procedures listed in = AASHTO=20 specifications PP28 and M323 be used in performing Superpave = volumetric=20 mix design.
    2. (b) Surface characteristics of asphalt surfaces are also = dependent on=20 aggregate characteristics. This is particularly important after = the=20 surface is exposed to wear from traffic and weather = conditions.
      1. Aggregate angularity. Frictional = resistance of the=20 wearing course is improved when angular aggregates are used in = the Hot=20 Mix Asphalt (HMA) mixture. Increasing fractured faces of the = coarse=20 aggregate (reducing or eliminating rounded gravels) will = improve=20 stability of the HMA mix. Coarse aggregate angularity is = defined as=20 the percent by weight of aggregates larger than 4.75 mm with = one or=20 more fractured faces. Similar to coarse aggregates, = performance is=20 also related to the angularity of fine aggregates. It is = recommended=20 that the aggregate meet the requirements specified in AASHTO=20 specification M323.
      2. Aggregate soundness. Soundness is an = indication of=20 an aggregate's resistance to weathering. It is recommended = that sodium=20 or magnesium sulfate tests use the limits described in the = AASHTO=20 specification M 29. The recommended range for sodium sulfate = soundness=20 is 12-15% maximum and for magnesium sulfate soundness is = 15-20%=20 maximum for 5 cycles. Other methods may be used to = characterize=20 aggregate soundness.
      3. Aggregate toughness. Toughness is an = indication of=20 an aggregate's resistance to abrasion and degradation during = handling,=20 construction, and in-service. It is recommended that = specifications=20 require toughness tests and tests should be performed in = accordance=20 with AASHTO specification T96. The recommended specification = value for=20 a Los Angeles abrasion loss ranges from 35 to 45 percent = maximum.=20 (Consideration should also be given to utilizing the = Micro-Deval=20 Abrasion Test (AASHTO specification TP58).)
      4. Polish resistance. The use of aggregates = that=20 polish easily should be avoided. It is recommended that = polishing=20 resistance of aggregates be measured in the laboratory, prior = to use.=20 An appropriate test and value for the specific pavement should = be=20 established. A set of tests for evaluating aggregate polish = value is=20 Accelerated Polishing of Aggregates Using the British Wheel = (AASHTO=20 specification T-279) and Surface Frictional Properties Using = the=20 British Pendulum Tester (AASHTO specification T-278). AASHTO=20 specification T-278 may also be used to evaluate the polishing = condition (BPN) of pavement surfaces. Other methods may be = used to=20 characterize polish-resistance of=20 aggregates.
How is adequate texture provided on = concrete=20 pavements over the performance life of the pavement? In order = to=20 provide the desired texture over the performance life of the pavement = and=20 minimize objectionable level of tire-pavement noise, the following = techniques=20 are recommended.
1. Transverse tining=20
  1. (1) A width of 3mm (+/- 0.5mm) and a depth of 3mm maximum are=20 recommended. Narrower, deeper grooves are better than wider, = shallower=20 grooves, within the limits indicated, for minimizing noise.
  2. (2) Random spacing of either 13mm or 26mm average tine spacing = is=20 recommended. The 13mm random tine spacing shall have the following = tine=20 pattern (in millimeters): 10/14/16/11/10/13/15/16/11/10/21/13/10. = The 26mm=20 random tine spacing shall have the following tine pattern (in=20 millimeters): 24/27/23/31/21/34.
2. Longitudinal tining=20
  1. (1) A width of 3mm (+/- 0.5mm) and a depth of 3mm maximum are=20 recommended. Narrower, deeper grooves are better than wider, = shallower=20 grooves, within the limits indicated, for minimizing noise.
  2. (2) Straight, uniformly spaced grooves spaced at 19mm have been = shown=20 to provide adequate handling characteristics for small vehicles = and=20 motorcycles.
3. Exposed aggregate=20
  1. (1) Exposed aggregate is normally constructed in two layers
  2. (2) The top layer consists of 30% siliceous sand of 0-1mm, and = 70%=20 high-quality chips of 4-8mm
  3. (3) A water-cement ratio of 0.38 maximum is recommended.
  4. (4) A mean texture depth of 0.7mm is recommended.
4. Diamond grinding. Diamond grinding typically = provides=20 grooves of approximately 3mm width, spaced at 5-6 mm intervals. = Specific=20 groove depth and spacing is dependent on hardness of the aggregate. =
5. Diamond grooving. Diamond grooving, transverse = and=20 longitudinal, can provide adequate friction characteristics. Groove = geometry=20 should be consistent with recommendations for tining in paragraphs = 8(a) and=20 8(b).
6. Burlap drag. This is typically produced by = trailing a=20 moistened, course burlap from a construction bridge that spans the = pavement.=20 Striations of 1.5 - 3mm depth are typical.
7. Artificial turf drag. This is typically produced = by=20 trailing an inverted section of artificial turf from a construction = bridge=20 that spans the pavement. Striations of 1.5 - 3mm depth are typical = when=20 using turf with 77,500 blades per m².
8. Transverse broom. This is typically obtained = using a=20 hand broom or mechanical broom device that lightly drags stiff = bristles=20 across the surface. Striations of 1.5 - 3mm depth are typical
9. Other methods
  
  (1) Thin,=20 epoxy-bonded laminates. Aggregates are typically 4-6mm.
  
  (2)=20 Asphalt-based surface treatments such as = micro-surfacing.
What techniques will restore desired surface texture to = in-service=20 pavement surfaces? To restore adequate texture to an = in-service=20 pavement, the following techniques can be utilized in addition to=20 overlays.
1. Restoration of concrete surfaces. Restoration = techniques=20 have been shown to provide adequate friction characteristics. The = rate of=20 decrease in friction properties after treatment is typically = dependent on=20 the polish-resistance of the course aggregate.
  1. (1) Diamond grinding has been shown to restore = frictional=20 characteristics of concrete pavement for 8-10 years.
  2. (2) Transverse or longitudinal diamond grooving = can=20 provide adequate friction. However, random spacing is recommended = to=20 provide adequate noise performance.
  3. (3) Other methods
    1. (a) Thin overlays of asphalt such as dense graded asphalt and = open=20 graded friction courses or thin concrete overlays can be used to = restore=20 friction to concrete pavements.
    2. (b)Asphalt-based surface treatments such as = micro-surfacing.
    3. (c)Thin, epoxy-bonded laminates.
2. Restoration of asphalt surface. The most common=20 techniques for restoration of adequate surface texture on hot mix = asphalt=20 pavement are surface treatments or thin asphalt overlays. See = paragraph 7(b)=20 for mixture and aggregate recommendations. Concrete overlays may = also be=20 considered to restore adequate surface texture on asphalt=20 pavements.
What factors should be considered when selecting pavement = surface=20 techniques or thresholds? The selection of the surface = texture type=20 to be provided at a specific location should be based upon existing = conditions=20 at that site. When selecting a texturing method or establishing a = threshold=20 value for a friction-related parameter, an agency should consider many = factors=20 including splash and spray, climate, traffic, speed, geometry, = conflicting=20 movements, materials and costs, and presence of noise sensitive = receptors. Due=20 to widely varying conditions at individual project locations, it is = unlikely=20 that one surface type or texturing method will always be the best = choice for=20 all projects within a State or jurisdiction. References in paragraph = 12 should=20 be evaluated for current reported US and international texture or=20 friction-test targets.
1. Splash and spray. Reduced visibility caused by = splash=20 and spray may increase the probability of wet-weather crashes. = Adequate=20 pavement cross-slope or use of porous surfaces will provide surface = drainage=20 and has been shown to reduce splash and spray.
2. Climate. An increased probability of wet-weather = conditions would justify a higher level of texture or higher = threshold value=20 for a friction-related parameter. Research in Sweden concluded that, = for=20 worn pavements, crash rates increase on days with rainfall of 10mm = or=20 greater.
3. Traffic volume and composition. Pavements with = higher=20 traffic volumes would justify a higher level of texture or higher = threshold=20 value for a friction-related parameter. Increased traffic would = decrease the=20 reaction/recovery time in the event of loss of control of a vehicle. = Facilities with higher volumes of passenger cars will realize = greater=20 benefits of low-noise pavement characteristics than facilities with = higher=20 truck volumes.
4. Speed limit. Higher speed facilities may justify = a=20 higher level of texture or higher threshold value for a = friction-related=20 parameter. Friction test results will decrease with increasing = speed,=20 reaching a minimum at approximately 60 mph. Friction on surfaces = with low=20 texture falls more rapidly with speed than on high textured = surfaces.
5. Roadway geometry. Curves may justify a higher = level of=20 texture or higher threshold value for a friction-related parameter. = Research=20 in France and Great Britain has shown that curves with a radius of = curvature=20 less than 500 m have significantly higher crash rates.
6. Potential conflicting movements or maneuvers (frictional=20 demand). Intersections and presence of pedestrians will = justify a=20 higher level of texture or higher threshold value for a = friction-related=20 parameter. Intersections and pedestrians will increase the = likelihood of=20 sudden braking movements.
7. Materials quality and cost. The availability and = cost of=20 high-quality durable, non-polishing materials will influence the = choice of=20 materials and techniques to provide friction.
8. Presence of noise-sensitive receptors. A = pavement=20 located near a school, hospital, or other noise-sensitive receptor = may=20 justify a higher consideration of noise effects when selecting the=20 appropriate surface treatment for a pavement.
What factors should be considered = when=20 evaluating new or innovative texturing methods for concrete=20 pavement?
1. The primary purpose of adequate surface texture is to reduce = wet-weather=20 and total vehicle crashes. Where a State Highway Agency (SHA) has=20 time-history data to show a specific surface treatment or texturing = method=20 results in similar or improved safety performance compared to = transverse=20 tining texture, the proposed method should be allowed.
2. Safety performance. Safety performance shall be = based=20 upon long-term performance monitoring of either wet-weather crash=20 performance or friction test results. In the absence of long-term = safety=20 performance data for alternate texturing methods or treatments, = alternative=20 methods may be used on an experimental basis provided safety = performance is=20 monitored and reported. This approach may also be utilized to = evaluate the=20 impact of changes to asphalt pavement surfaces on pavement safety=20 performance.
  1. (1) Wet weather crash performance. = Reduced=20 wet-weather and/or total vehicle crash rates at the same or = similar=20 locations.
  2. (2) Friction test results. = Similar or=20 improved friction test results and speed gradient when tested in=20 conformance with American Society for Testing and Materials (ASTM) = E-274=20 (skid trailer) using the smooth tire (ASTM E-524), or = International=20 Friction Index (IFI) ASTM E-1960.
Are there any reference materials on pavement surface=20 texture/friction? Yes. The following references apply to = pavement=20 texture and friction.
1. P.G. Poe, A.R. Parry, and H.E. Viner, "High and Low Speed = Skidding=20 Resistance: The Influence of Texture Depth," TRL367, Transport = Research=20 Laboratory, Wokingham, UK, 1998
2. P.G. Poe, D.C. Webster, and G. West, "The Relation Between = Surface=20 Texture of Roads and Accidents," Research Report RR296, Transport = Research=20 Laboratory, Wokingham, UK, 1991.
3. J. Nichols and D. Dash, "Australian Developments to Reduce Road = Traffic=20 Noise on Concrete Pavement," 5th International Conference on = Concrete=20 Pavement Design and Rehabilitation, Purdue University, April 1993, = Volume 2,=20 pages 99-106.
4. A.P. Hewitt, P.G. Abbott, and P.M. Nelson, "Alternative Textures = for=20 Concrete Roads: Results of M18 and A50 Trials," TRL291, Transport = Research=20 Laboratory, Wokingham, UK, 1997.
5. B. Hibbs and R. Larson, "Tire Pavement Noise and Safety = Performance: PCC=20 Surface Texture Technical Working Group," FHWA-SA-96-068, Federal = Highway=20 Administration, Washington, DC, 1996.
6. P. Wetling, "Relationship Between the Functional Properties of = Road=20 Surface and Traffic Safety: A State-of-the-Art Report," Swedish = National=20 Road and Transport Research Institute, Linkoping, Sweden, April, = 1996.
7. World Road Association (PIARC), "Report of the Committee on = Surface=20 Characteristics," XVIII World Road Congress, Brussels, Belgium, = 1987.
8. J.J. Henry, "Evaluation of Pavement Friction Characteristics," = NCHRP=20 Synthesis 291, Transportation Research Board, Washington, DC, = 2000.
9. S. Rao, H.T. Yu, L. Khazanovich, M. Darter, and J. Mack, = "Longevity of=20 Diamond-Ground Concrete Pavements," Transportation Research Board,=20 Washington DC, 1999.
10. D.A. Kuemmel, R.C. Sonntag, J.A. Crovetti, Y. Becker, J.R. = Jaekel, A.=20 Satanovsky, "Noise and Texture on PCC Pavements - Results from a = Multi-State=20 Study," SPR 0092-45-91, Wisconsin DOT, Madison, WI,=20 2000.

3D"King

King W. Gee
Associate Administrator for=20 Infrastructure

FHWA = Home |=20 Directives = | Technic= al=20 Advisories | Feedback=20

=20

United States Department of = Transportation -=20 Federal Highway Administration

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