texturing concrete pavements

ACI 325.6R-88 (Reapproved 1997) Texturing Concrete Pavements Reported by ACI Committee 325 Ralph L. Duncan* Chairman Richard O. Albright Walid Abu-Onk Glen Bollin Robert J. Fluhr Wilbur C. Greer, Jr. Starr D. Kohn Jerry A. Breite Torbjorn J. Larsen Benjamin Colucci Richard A. McComb, Sr. Michael 1. Darter B. Frank McCullough The importance of the need for skid-resistant pavement has been known for many years. Increased traffic volumes and speeds have increased the need for an improved skid-resistant surface. The empha- sis has been to improve skid resistance by creating new surface textures that increase the “macrotexture” of the concrete pavement. These textures are created by forming the deeper textures in the plastic concrete during the finishing operations. Skid resistance has also been improved in existing concrete pavements by sawing grooves in the hardened concrete with cutting heads composed of a number of circular diamond saw blades. The traveling public may better under- stand this as a process of placing a“tread” in the pavement surface, which complements the tread on the car tires, and stops the vehicle without skidding or loss of control by permitting the rapid escape of water. Keywords: concrete finishes (hardened concrete); concrete finishing (fresh concrete); concrete pavements; maintenance; measurement; skid resistance; texture. CONTENTS Chapter 1-Need for texture, p. 325.6R-1 1.l-Development of textures 1.2-Benefits of texturing 1.3-Factors affecting skid resistance Chapter 2-Texture types, p. 325.6R-3 2.l-Texturing plastic concrete 2.2-Texturing hardened concrete Chapter 3-Testing, p. 325.6R-8 3.1-Measuring skid resistance 3.2-Measuring texture ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in designing, plan- ning, executing, or inspecting construction and in preparing specifications. Reference to these documents shall not be made in the Project Documents. If items found in these documents are desired to be part of the Project Documents they should be phrased in mandatory language and incorporated into the Project Documents. Shiraz D. Tayabji Secretary Carl P. Meglan Jon I. Mullarky Thomas J. Pasko, Jr. Robert W. Piggott Steven A. Ragan John L. Rice* Raymond S. Rollings Michel Amin Sargious Terry W. Sherman Douglas C. Staab William V. Wagner, Jr. C. Philip Weisz* Gerald E. Wixson William A. Yrianson* Chapter 4-Maintenance, p. 325.6R-9 4.1-Snow and ice removal 4.2-Retexturing Chapter 5-Standards related to this report, p. 325.6R-9 Chapter 6-References, p. 325.6R-10 6. l-Cited references 6.2-Related references CHAPTER 1 -NEED FOR TEXTURE 1.1- Development of textures The importance of the need for a uniform surface texture to increase skid resistance of both highways and airport pavements has been recognized for many years. ‘s2 The problem of skidding vehicles is not considered to be critical when low volumes of traffic and low speeds are prevalent .3 During the late 1940s and early 1950s, civil engineers raised serious concerns about pavement safety on the highway system. Increasing traffic volumes and speeds, which were contributing to a con- stantly increasing number of accidents and fatalities in the United States, were the two main factors that led engineers to believe that pavement skid resistance needed to be improved if skidding accidents were to be reduced. Copyright @I 1988, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. *Texturing Concrete Pavement Task Group. The committee would like to recognize the contribution made by Martin L. Cawley for background information and editorial help in preparing this report. 325.6R-1 325.6R-2 ACI COMMITTEE REPORT During the same period, aircraft runways were being more critically examined in terms of pavement slipperiness. The advent of jet-powered aircraft quickly estab- lished that high-performance airplanes, with accompa- nying higher takeoff and landing speeds, were much more difficult to control on wet runways than were pis- ton-type aircraft .4 Published reports on the adverse effect of pavement slipperiness on vehicle control go back to the late nine- teenth century. The first concrete street in the United States, built in Belfontaine, Ohio, had 4 x 4 in. (102 x 102 mm) squares formed in the plastic concrete to provide traction for horses’ hooves. Grooving hardened concrete pavement appears to have been a British innovation that was used in 1956 on a number of airfield pavements in England. In the United States in the early 1960s the California State Division of Highways started sawing grooves in pavements to reduce hydroplaning on curves. 4 Textures have also been constructed on bridges and parking-deck ramps by building up a multicomponent epoxy coating system, as indicated in ACI 503.3-79. For many years, pavement texturing in plastic concrete had been accomplished with a burlap drag or a belt drawn longitudinally along the pavement surface. Dur- ing the late 1960s, deeper texturing efforts were initi- ated. Textures on pavements have been made with both longitudinal and transverse patterns using brooms, tining combs or rakes, roller imprints, and a longitudinally drawn, coarse polyethylene artificial-turf drag in- verted to provide texture. The concerns of engineers in developing new deeper textures in concrete whether in the plastic state or in the hardened state were: 1. The possibility of objectionable pavement noise. 2. The possibility of increased roughness, which would cause objectionable vehicle handling characteristics. 3. Problems associated with vehicles, particularly motorcycles, experiencing sensations of “tracking” or loss of handling control of the vehicle on longitudinal grooves. 4. Increased aircraft-tire wear associated with high- speed landings on deeper textured pavements. 5. Increased pavement wear and rutting. Highway and airport designers have no control over vehicle speed and tire characteristics, and therefore must pay attention to the skid resistance of the pavement surfaces in their designs. Specifications should be adopted for constructing new portland cement concrete pavements with satisfactory surface textures and crowns for existing older pavements that have lost their skid resistance. Cross slopes (or crowns) built into concrete pavements, airport runways, and high-speed turnoffs provide for draining the water from the surface rapidly. Generally, a minimum cross slope on highways of 1 percent is recommended. Slopes greater than this can be used provided they are consistent with road safety and driveability of the vehicles using them. Cross slopes on airport runways and taxiways vary from 1 percent to a maximum of 1.5 percent. The cross slopes enhance the skid resistance of textures by proving a good drainage characteristic. 1.2 - Benefits of texturing The results of testing with a standard skid trailer (ASTM E 274) indicate that transverse textures produce higher friction numbers than longitudinal textures (higher friction numbers indicate greater skid resistance). However, it does not necessarily follow that transverse textures should be used throughout the highway system, since friction numbers, as measured with the locked-wheel device, are not sensitive to cornering friction. It is apparent from studies of grooved pavement that longitudinal grooving increases cornering friction significantly, whereas transverse grooving increases mainly longitudinal braking friction. 5 Trans- verse grooves provide a path perpendicular to the direction of travel for the escape of water under the tire, which is an important factor in reducing hydroplaning. The Edens Expressway in Cook County, Ill., was constructed as a jointed portland cement concrete pavement in the early 1950s. The pavement was resur- faced with a bituminous concrete mix in the late 1960s. Between 1979 and 1980, it was reconstructed as a con- tinuously reinforced concrete pavement. The texturing technique used in the reconstructed pavement was a longitudinally drawn artificial turf drag followed by a transverse tine device. The positive benefits of surface tining are reflected in a comparison of the accident statistics compiled for the four years before and after its reconstruction, as shown in Table 1.2. The northbound lanes were installed in 1979 with tining combs that had tines spaced at 1 /2 in. (13 mm). In 1980, the south- bound lanes were constructed; however, the tine spac- Table 1.2 - Statistics compiled by Illinois De- partment of Transportation, District 1 Bureau of Traffic Safety impact of Edens Expressway reconstruction - Four years before-after comparison of Edens Expressway versus System* Accidents before reconstruction: Accident type 1 1974 to 1977 I Accidents after econstruction: Change, 1981 to 1984 percent 59,869 - 3.9 3249 - 22.9 181 - 7.7 11 - 8.3 13,677 - 8.9 1001 - 22.8 16,470 + 8.9 851 - 40.8 7769 + 2.4 510 - 40.8 *Chicago Metropolitan Expressway System accident experience excluding Edens Expressway. Note: Edens Expressway under construction 1978 to 1980. TEXTURING CONCRETE PAVEMENTS 325.6R-3 ing was changed to 3 /4 in. (19 mm) to reduce tearing of the concrete surface. Although a slight increase in noise level was anticipated, it was negligible when measured and actually screened out by other noises. The 3 /4 in. (19 mm) tine spa cing is now standard in Illinois.” The reduction of the “wet, snow/ice road surface conditions” accidents in Table 1.2 shows a very im- pressive safety impact has been achieved by reducing accidents. This improvement has been attributed to the improved surface texture. Additional benefits observed on pavements with the deeper textures are: 1) a reduction in water spray from traffic due to improved surface drainage, by providing channels for the expulsion of water at the tire-pavement interface into the grooves or deeper striations; 2) a reduction in headlight glare due to the rougher surface of the pavement; and 3) a slower buildup of rubber on runways due to airplane touchdowns on grooved airport pavements. 1.3 - Factors affecting skid resistance Skid resistance of pavements is affected by both the “microtexture” of the pavement as related to the sand in the mortar portion of the concrete mixture; and by the “macrotexture,” which is defined as the measur- able deeper striations or grooves formed in the plastic concrete during the finishing operations, or the shallow grooves cut in the hardened pavement with cutting heads composed of uniformly spaced circular diamond saw blades. This report will not discuss microtexture. The term “hydroplaning” refers to the separation of tire contact from the pavement surface by a layer of water. This separation causes a loss of steering and braking control of the vehicle. Hydroplaning is a complex phenomenon that is affected by 1) water depth; 2) pavement texture; 3) tire-tread depth; 4) tire-inflation pressure; 5) tire-contact area; and 6) vehicle speed. An approximate relationship exists between the speed at which hydroplaning will occur and the tire inflation pressure \/ ___________ Hydroplane speed = 10.35 tire pressure when speed is in mph and pressure is in psi. Some of the earliest investigations and technical reports on loss of vehicle control, which came from the National Aeronautics Space Administration (NASA), were primarily concerned with hydroplaning of aircraft during wet weather operations. The U.S. Army Air Corps, and its successor the U.S. Air Force, also did valuable work on this subject. Later, the Road Re- search Laboratory in Great Britain began investigations related to hydroplaning of automobiles. Concur- rent with this research, the Americans and Germans studied tires and road surfaces to seek their own theo- ries of the factors contributing to skidding. 5 CHAPTER 2 - TEXTURE TYPES 2.1 - Texturing plastic concrete 2.1.1 Artificial turf texture - This finish (Fig. 2.1.1) 2.1.1) may be accomplished by using artificial turf in- verted and suitably attached to a device that will permit control of the time and rate of texturing. A transverse artificial turf with approximately 2 ft. in contact with the pavement surface and operated longitudinally in the direction that the pavement is being placed should be required. The artificial turf may be weighted to produce a deeper and more uniform texture. One artificial turf that provides a satisfactory texture is made of molded polyethylene with turf blades approximately 0.85 in. (21.6 mm) long, and containing 7200 individual blades per ft 2 (930 cm 2 ). 2.1.2 Transverse tine texture - This finish (Fig. 2.1.2) may be obtained by using a single pass of an artificial turf or burlap followed by a mechanically operated transverse-texturing device. The texturing device consists of a single line of flat, slightly flexible, tem- pered spring steel tines, spaced at not less than 1 /2 in. (12.7 mm) nor more than 1 in. (25 mm) centers. Closer centering of the tines will lead to early raveling while larger spacing may lead to objectionable road noise. Random spacings have been used on some projects due to the concern for noise developing from a uniform spacing. The tine width should be 1 /8 in. (3.2 mm). Texturing is applied while the concrete is still plastic Fig. 2.1.1-Artificial turf texture 325.6R-4 ACI COMMITTEE REPORT enough to obtain a depth of at least 1 /8 in. (3.2 mm) but not more than 1 /4 in. (6.4 mm). The texture is obtained by one continuous pass of the width of pavement being textured. Additional passes or overlapping are not desirable because they create weak narrow ridges of mortar that will break easily under traffic. 2.1.3 Longitudinal tine texture - The longitudinal tine texture (Fig. 2.1.3) is accomplished with the same basic materials, equipment, and care as the transverse tine texture, except that the tines are pulled in a line parallel with the centerline of pavement. 2.1.4 Transverse broom texture - This finish (Fig. 2.1.4) may be obtained by using a mechanically operated transverse broom finishing device. The broom consists of multiple rows of stiff bristles capable of producing striations 1 /16 to 1 /8 in. (1.6 to 3.2 mm) deep in the plastic concrete. The striations are uniform in appearance with a spacing approximately equal to their depth and are transverse to the pavement centerline. 2.1.5 Longitudinal broom texture - The longitudinal broom texture (Fig. 2.1.5) is accomplished with the same basic materials, equipment, and care as the trans- Fig. 2. 1 .2- Transverse tine texture Fig. 2.1.3-Longitudinal tine texture Fig. 2. 1. 4- Transverse broom texture TEXTURING CONCRETE PAVEMENTS 325.6R-5 verse broom finish except that the brooms are operated in a direction parallel to the pavement centerline. 2.1.6 Transverse tine with longitudinal artificial turf texture - The transverse tine texture preceded by the longitudinal artificial turf finish (Fig. 2.1.6) is recommended for high-speed highways or where sudden ac- celeration or deceleration (panic stops) may occur. The transverse texture provides 1) a better drainage pattern; 2) improved initial skid resistance in a longitudinal direction; 3) a longer lasting texture due to deeper valleys as compared to the broom; and 4) a slight improvement in cornering control provided by the initial pass of longitudinal artificial turf. A longitudinal tine texture could be used on areas such as curves where cornering forces are required. Other textures may be appropriate on low-speed roads or city streets and highways; they provide satisfactory initial skid resistance, but they will wear smooth at an earlier age. 2.1.7 Friction numbers of textures - Table 2.1.7, for friction numbers at 30, 40, and 50 mph, indicates that the best results were obtained by the various textures as follows. 7 The results are listed from highest (best) to lowest: 1. Longitudinal artificial turf and transverse tine 2. Transverse tine 3. Transverse broom 4. Longitudinal artificial turf 5. Longitudinal tine 6. Longitudinal broom The values were obtained when the various surface textures were tested in accordance with ASTM E 274 for a locked-wheel skid trailer. The following graphs illustrate the changes in friction numbers obtained in October, 1976 (when constructed) and for three succeeding years for each of the textures constructed in plastic concrete. Fig. 2.1.7(a) and 2.1.7(b) are plotted for regular (treaded) tires at 40 mph from data listed in Table 2.1.7. 2.1.8 Factors affecting pavement texture - The depths obtained with the various types of texturing in plastic concrete depend upon the timing of the texturing operation. Therefore, field-inspection personnel should work with the contractor to achieve the desired depth of texture. Because timing is critical, it is recommended that the texturing machine be a separate piece of equipment. Combining this operation with another one, such as a membrane-curing machine, may delay the texturing until less than desirable depths of texturing are obtained. The benefit of the deeper texture is longer service life, assuming studded tires are not per- Fig. 2.1.5-Longitudinal broom texture Fig. 2.1.6 -Transverse tine texture with longitudinal artificial turf texture 325.6R-6 ACI COMMITTEE REPORT Table 2.1.7 - Friction number at 30,40 and 50 mph (Reference 7) Texture FN 30 Range Transverse tine and artificial turf (longitudinal) 10-05-76 07-18-77 10-24-77 04-24/25-78 Reg.* 04-24/25-78 Slic 10-10-78 Reg. 10-10-78 Slicks 07-06-79 Reg. 07-06-79 Slicks 10-19-79 Reg. 10-19-79 Slicks 67 63 61 57 56 61 60 55 52 68 71 75 71 62 58 62 61 65 62 Transverse tine 10-05-76 07-18-77 10-24-77 04-24/25-78 Reg. 04-24/25-78 Slicks 10-10-78 Reg. 10-10-78 Slicks 07-06-79 Reg. 07-06-79 Slicks 10-19-79 Reg. 10-19-79 Slicks 79 __ 62 67 61 54 57 47 58 54 57 47 65 68 72 61 61 50 61 56 61 56 Transverse broom 10-05-76 07-18-77 10-24-77 04-24/25-78 Reg. 04-24/35-78 Slicks 10-10-78 Reg. 10-10-78 Slicks 07-06-79 Reg. 07-06-79 Slicks 10-19-79 Reg. 10-19-79 Slicks 69 __ 61 62 61 29 53 25 55 33 53 29 66 70 73 40 61 37 65 37 62 39 Artificial turf (longitudinal) 10-05-76 07-18-77 10-24-77 04-24/25-78 Reg. 04-24/25-78 Slicks 10-10-78 Reg. 10-10-78 Slicks 07-06-79 Reg. 07-06-79 Slicks 10-19-79 Reg. 10-19-79 Slicks 68 __ 57 63 60 33 54 31 58 39 54 29 64 65 73 48 61 45 62 46 64 39 Longitudinal tine 10-05-76 07-18-77 10-24-77 04-24/25-78 Reg. 04-24/25-78 Slicks 10-10-78 Reg. 10-10-78 Slicks 07-06-79 Reg. 07-06-79 Slicks 10-19-79 Reg. 10-19-79 Slicks 66 __ 61 64 61 56 56 54 61 53 58 48 62 64 70 64 58 47 62 59 60 50 Longitudinal broom 10-05-76 07-18-77 10-24-77 04-24/25-78 Reg. 04-24/25-78 Slicks 10-10-78 Reg. 10-10-78 Slicks 07-06-79 Reg. 07-06-79 Slicks *“Reg. ,, denotes treaded tires ; “slicks” are smooth or nontreaded tires. Lane 2 Lane 1 Lane 2 Lane 1 __ 69-87 __ 62-69 65-69 61-67 56-65 55-61 52-61 60-64 54-65 52-58 48-53 65-72 68-74 73-78 66-76 61-65 55-61 58-65 57-66 63-68 59-65 71 __ 62 64 56 51 54 48 57 54 53 46 72-86 __ 61-64 64-69 59-64 40-61 55-60 42-55 54-64 38-61 53-61 39-53 62-70 64-73 68-75 45-72 59-64 36-54 59-64 44-64 58-64 43-63 65 __ 56 61 56 45 54 39 56 43 53 41 60-74 __ 56-67 59-66 59-62 25-31 48-55 23-27 53-57 29-37 51-55 24-31 53-71 68-73 71-77 33-46 56-64 34-39 63-67 32-40 60-64 32-42 61 __ 53 59 52 21 51 19 52 27 49 21 61-78 __ 47-63 62-66 54-63 27-39 50-59 24-40 56-59 28-51 51-57 25-37 60-67 61-68 66-78 34-61 59-64 35-50 60-65 38-52 62-65 29-44 55 __ 48 52 51 23 49 21 50 27 49 21 60-72 - 53 __ 56-67 55-66 54 61-68 62-68 58 58-66 66-72 53 45-61 51-74 36 54-59 56-59 52 49-57 39-55 40 58-64 60-63 59 45-58 53-62 49 54-60 59-62 55 37-54 42-56 41 65 __ 52-76 __ 56 60 52-61 62 63 58-64 61 71 55-63 31 42 29-33 55 59 53-58 35 39 31-38 60 63 58-61 36 38 34-39 57-64 60-66 68-73 36-47 58-60 35-44 61-65 35-44 52 __ 49 57 49 23 53 21 53 28 67 68 71 66 60 54 63 60 64 57 58 63 66 60 56 44 59 53 59 50 57 64 65 42 56 26 60 30 60 32 55 58 65 38 56 31 60 35 57 26 54 59 65 48 54 39 59 50 56 40 51 56 62 28 53 26 61 26 Range FN 60 Range ____ ___ Lane 1 Lane 2 Lane 1 62-77 __ 61-64 62-67 54-58 46-57 52-55 46-49 55-58 48-57 51-57 43-49 63-71 66-70 69-74 61-73 58-62 45-57 61-64 58-62 60-68 50-60 62 __ 57 59 53 47 50 46 53 50 50 41 59-73 __ 53-59 57-63 52-58 29-55 52-55 23-45 54-58 28-52 50-55 27-47 54-60 60-65 63-68 46-66 53-58 31-50 56-62 45-58 57-62 34-55 56 __ 51 55 50 35 51 35 52 43 47 36 56-66 __ 48-57 56-62 51-54 17-25 48-53 18-22 49-54 22-30 46-53 18-23 50-62 60-67 59-69 36-48 55-57 23-30 58-61 22-39 57-62 28-38 50 __ 45 53 45 14 46 15 48 22 44 16 42-65 - 42 __ 40- 50 48-60 40 48-58 54-64 49 46-57 60-68 43 15-33 29-48 16 44-54 53-58 44 18-27 23-34 16 50-51 57-61 47 21-34 23-41 24 47-54 53-60 44 17-26 22-34 16 46-60 __ 47-60 52-63 49-59 22-50 48-55 33-47 57-61 41-55 52-57 30-48 46-60 55-62 62-67 28-58 50-57 31-46 58-61 42-55 53-58 28-48 45 __ 47 54 48 38 49 35 52 39 49 34 43-65 __ 46-52 55-59 45-52 19-40 52-54 18-23 49-56 26-31 45-56 54-59 61-64 23-30 49-56 22-33 59-64 22-29 37 __ 43 50 44 14 45 20 48 20 Lane 2 63 64 68 57 58 51 61 58 60 52 56 59 62 49 53 40 56 43 54 44 50 56 61 21 51 22 54 25 54 24 46 51 54 24 49 25 54 26 50 23 48 52 58 41 49 31 57 43 50 31 46 49 55 17 48 21 56 21 Lane 1 Lane 2 53-74 __ 54-59 56-61 52-55 45-50 48-54 39-50 50-55 48-51 48-54 38-44 60-68 61-69 66-69 48-64 56-59 44-57 58-65 44-62 57-61 49-55 52-61 __ 45-53 53-58 47-53 26-42 48-54 18-40 50-54 29-49 45-49 25-43 53-62 54-62 58-64 36-59 50-55 31-47 54-58 30-53 49-57 29-49 45-55 - 39-53 42-52 51-55 54-59 40-47 57-63 12-18 14-28 45-47 50-53 13-18 18-26 44-50 51-57 19-26 21-33 42-46 53-56 14-20 16-27 38-48 __ 31-47 42-57 39-46 10-25 38-48 13-22 43-52 18-30 41-47 9-19 41-50 49-53 51-59 15-34 46-52 18-32 49-57 21-34 47-55 17-28 39-57 __ 36-53 49-58 46-51 25-45 45-52 24-41 49-56 30-45 46-52 24-41 41-56 46-57 54-61 22-59 45-51 23-45 53-60 34-59 46-53 21-41 35-41 __ 38-49 46-52 42-45 12-16 42-47 15-32 45-50 18-23 41-48 47-51 53-57 14-21 46-50 18-30 54-58 17-23 TEXTURING CONCRETE PAVEMENTS 325.6R-7 65 64 63 62 61 60 59 56 57 56 55 54 53 52 51 50 49 1976 1977 1976 1979 __ CALENDAR YEARS __ Fig. 2.1.7(a)-Friction number changes: Various textures ( ^ = transverse tine; X = longitudinal tine; \/ = transverse broom) 70 66 66 56 54 52 50 46 1976 1977 1976 1979 CALENDAR YEARS Fig. 2.1.7(b)-Friction number changes: Various textures (0 = longitudinal broom; T = transverse tine and longitudinal turf; 0 = artificial turf [longitudinal]) mitted on vehicles using the road. There is no known texture that can survive wear in the tire paths caused by normal volumes of traffic using studded tires. Rain on a pavement surface during construction may obliterate the texture if the concrete has not hardened sufficiently. 8 This can be corrected by grinding the pavement and grooving the concrete in the hardened state by the use of diamond-blade saws. Leaving a rain- damaged texture uncorrected will create an area of pavement with a surface of a different texture. This will cause different vehicle-handling characteristics, especially during rain, snow, or icing conditions, which may cause an operator to lose control of his or her vehicle. 2.2 - Texturing hardened concrete Skid resistance on worn, polished, contaminated, or slippery hardened concrete may be improved by several methods, including diamond grinding and/or grooving, sandblasting, waterblasting, or chemically treating of the pavement surface. Sandblasting, chemical treat- ment, or grinding can produce an improved skid resistance; however, sawed transverse grooves will result in 325.6R-8 ACI COMMITTEE REPORT Fig. 2.2.2-Diamond saw-blade texture improved texture, better drainage, greater skid numbers and a longer life with improved skid resistance. 2.2.1 Groove patterns - Sawed groove patterns for highways should be not less than 1 /8 in. (3.2 mm) wide or more than 1 /4 in. (6.4 mm) deep and centered at not less than 1 /2 in. (13 mm) nor more than 1 in. (25 mm). Highway grooving may be transverse or longitudinal. The transverse grooves are cut at 90 deg to the centerline of the pavement while the longitudinal grooves are cut parallel to the centerline of the pavement. Generally, transverse grooving is recommended for highways, particularly where frequent braking action is required. The exception might be on curves or heavily traveled highways. However, the interference to traffic caused by closing more than one lane at a time, along with the greatly increased time to groove the pavement and increased cost, has resulted in longitudinal grooving being used in lieu of transverse grooving. Trans- verse textured surfaces tend to be noisier than longitudinally textured surfaces when the textures are new. As the surfaces experience traffic wear, the variations between the noise levels decrease and are insufficient to rule out their use as a final finish. 7 For airports, the Federal Aviation Administration of the U.S. Department of Transportation recommends that the sawed-groove pattern on runways should be transverse (perpendicular to the direction of aircraft motion). The grooves should be 1 /4 in. (6.4 mm) wide by 1 /4 in. (6.4 mm) deep with center-to-center groove spacing not less than 1 1 /8 in. (28.6 mm) nor more than 2 in. (50.8 mm). 9 2.2.2 Reprofiling pavements - Before texturing hardened concrete, particularly in areas where studded tires are permitted, field checks should be made to de- termine whether ruts have been worn in the pavement surface, creating water channels and making hydroplaning very probable. A suggested method of reprofiling pavements is the use of a multiple diamond saw- blade grinding machine. These machines have been de- veloped specifically to restore the cross slope or crown in the pavement, and will leave a texture of shallow fins of concrete, as shown in Fig. 2.2.2. CHAPTER 3 - TESTING 3.1 - Measuring skid resistance 3.1.1 Airport pavements - The skid resistance of airport pavements is measured by the British “Mu-Me- ter” (ASTM E 670), which is used throughout the world. It is a simple device and consistent when used on level, tangent sections of pavement and has the mobil- ity needed to take measurements with a minimum amount of runway downtime. 9 3.1.2 Highway pavements 3.1.2.1 Skid trailer - Surface friction-number measurements of highway pavements in the United States are typically made using a locked-wheel skid trailer that meets the requirements of ASTM E 274. This procedure measures the frictional force on a locked test wheel as it is dragged over a wet pavement surface under constant load and a constant speed, with its major plane parallel to the direction of motion and perpendicular to the pavement. The standard reference speed is usually 40 mph, and the results are expressed as a friction number (FN). Well-textured new pavements will have friction numbers above 60 when tested at a speed of 40 mph. 3.1.2.2 British pendulum - The British pendulum device (ASTM E 303) has also been used to measure surface friction properties. A number of other devices have been used, including the diagonal brake vehicle, Swedish skiddometer, James brake decelerometer, and the Miles friction trailer. 3.2 - Measuring texture Pavement textures are complex, and therefore efforts at correlating skid resistance with texture measurements have had marginal success. There are many different proposed methods for measuring pavement texture. All attempt to set some minimum value that would produce an acceptable macrotexture. 10 They all give a measurement of the average texture depth. The sand-patch test, the NASA grease smear technique, the silicone-putty test, static drainage (outflow meter), and stereo photo interpretation are methods that have been used. TEXTURING CONCRETE PAVEMENTS 325.6R-9 3.2.1 Sand patch test - A measured amount of sand is poured on the pavement and the pile is carefully spread over the surface to form a circle. The texture depth of the surface is then determined from the diameter of the circle of sand.” 3.2.2 NASA grease smear technique - A measured amount of grease is placed on the pavement and spread on the pavement between two lines of masking tape 4 in. (102 mm) apart. The grease is then worked into the voids of the pavement with a rubber squeegee, with care taken that no grease is left on the tape or squeegee. The distance along the taped lines is measured and the area is then computed. 9 3.2.3 Silicone putty test - A known volume of silicone putty is formed into an approximate sphere and placed on the pavement surface. A recess in a plate is centered over the putty, and the plate is pressed down in firm contact with the surface. The average diameter of the deformed putty is recorded.” 3.2.4 Static drainage (outflow meter) test - A spec- ified-size cylinder with a rubber ring glued to its bot- tom face is placed on the pavement surface and loaded so that the rubber ring will drape over the aggregate particles, similar to that expected of tire tread ele- ments. Water is poured into the cylinder, and the time required for a known volume of water to escape through the pavement and between the rubber ring and surface is measured. 10 3.2.5 Stereophotograph test (E 770-80) - The ster- eophotographs of the pavement surface are viewed through a transparent grid with a 10 x 10 mm grid. The six texture parameter numbers for each of ten random centimeter-squares are noted. The texture parameter number of the pavement photograph is the average of the parameter number of the ten squares. CHAPTER 4 - MAINTENANCE 4.1 - Snow and ice removal Pavements that are located in areas with snow or icing conditions, and which require deeper textures to obtain higher skid resistance, may require an increased maintenance effort to remove the snow and ice. Snow- plows may experience more rapid wear of the plow blades. Windblown snow tends to accumulate more on deeper textures, especially when the wind is blowing in a direction which is at right angles to the striations of the texture. In some cases, increased quantities of snow-removal chemicals will correct the condition. Al- though concern has been expressed by some observers that the increased use of deicing chemicals on pavements with the deeper textures may cause earlier deterioration (especially in areas adjacent to curb and gut- ter sections and on bridge decks adjacent to the curb sections where brine accumulations may occur), this has not been verified by field observation. Salt-exposure laboratory tests on properly air-entrained concrete indicate that increasing amounts of deicing salts do not contribute to increased texture deterioration. 4.2 - Retexturing Large areas of smoother textures, such as those caused by rain damage in plastic concrete surfaces, have been reported to ice up faster than areas with deeper textures, thereby lowering the friction number. Drivers traveling from a new section of pavement with the deeper textures onto a rain-damaged pavement, or to an older pavement surface where the surface texture has been worn smooth, may experience inferior vehicle-handling characteristics. This is particularly true in rainy, snowy, or icing conditions. These areas can be corrected by grooving the older pavement with multiple diamond saw-blade grinding or grooving machines. CHAPTER 5 - STANDARDS RELATED TO THIS REPORT The documents of the various standards-producing organizations referred to in this document are listed below with their serial designation, including year of adoption or revision. The documents listed were the latest effort at the time this document was written. Since some of these documents are revised frequently, generally in minor detail only, the user of this document should check directly with the sponsoring group if it is desired to refer to the latest revision. American Concrete Institute 503.3-79 (Reapproved 1986) Standard Specification for Pro- ducing a Skid-Resistant Surface on Concrete by the Use of a Multi-Component Epoxy System ASTM E 274-85 E 303-83 E 501-82 E 524-82 E 556-82 E 660-83 E 670-85 Standard Test Method for Skid Resistance of Paved Surfaces Us- ing a Full-Scale Tire Standard Method for Measuring Surface Frictional Properties using the British Pendulum Tester Standard Specification for Stan- dard Tire for Pavement Skid-Re- sistance Tests Standard Specification for Smooth-Tread Standard Tire for Special-Purpose Pavement Skid- Resistance Tests Standard Method for Calibrating a Wheel Force on Torque Trans- ducer Using a Calibration Plat- form (User Level) Standard Practice for Acceler- ated Polishing of Aggregates or Pavement Surfaces Using a Small-Wheel, Circular Track Polishing Machine Standard Test Method for Side Friction on Paved Surfaces Using the Mu-Meter 325.6R-10 ACI COMMITTEE REPORT E 707-79 Standard Test Method for Skid (Reapproved 1984) Resistance of Paved Surfaces Us- ing the North Carolina State Uni- versity Variable-Speed Friction Tester E 770-80 Standard Test Method for Clas- (Reapproved 1985) sifying Pavement Surface Tex- tures E 965-83 Standard Test Method for Mea- suring Surface Macrotexture Depth Using a Sand Volumetric Technique These publications may be obtained from the following organizations: American Concrete Institute P.O. Box 19150 Detroit, MI 48219-0150 ASTM 1916 Race St. Philadelphia, PA 19103 CHAPTER 6 - REFERENCES 6.1 - Cited references 1. Murphy, William E.,“The Skidding Resistance of Concrete Pavements: A Review of Research, Development and Practice in the United Kingdom,” Roadways and Airport Pavements, SP-51 , Amer- ican Concrete Institute, Detroit, 1975, pp. 231-256. 2. “Guidelines for Texturing of Portland Cement Concrete Pave- ments,”Technical Bulletin No. 19, American Concrete Pavement Association, Arlington Heights, 1975, 13 pp. 3. Davis, J. L.; Ledbetter, W. B.; and Meyer, A. H., “Final Re- port on Concrete Experimental Test Sections in Brazos County, Texas,” Research Report No. 141-4F, Texas Transportation Insti- tute, College Station, 1974. 4. “A Guide to Highway Grooving,” General Electric, Worthing- ton, Ohio. 5. Gallaway, B.M.; Ivey, D. L.; Ross, H. E., Jr.; Ledbetter, W. B.; Woods, D. L.; and Schiller, R. E., Jr., “Tentative Pavement and Geometric Design Criteria for Minimizing Hydroplaning,” Report No. FHWA-RD-79-3 1, Federal Highway Administration, Washing- ton, D.C., 1979. 6. “Standard Specifications for Road and Bridge Construction,” Illinois Department of Transportation, Springfield, Oct. 1983, 238 pp. 7. Dierstein, Phil G., “A Study of P.C.C. Pavement Texturing Characteristics in Illinois,” IDOT Physical Research Report No. 95, Illinois Department of Transportation, Springfield, 1982, 54 pp. 8. “Interim Guidelines for Protection and Acceptance of Concrete Pavements Exposed to Rain During Construction,” Technical Bulle- tin No. 17, American Concrete Pavement Association, Arlington Heights, 1974, 11 pp. 9. “Methods for the Design, Construction, and Maintenance of Skid Resistant Airport Pavement Surfaces,” Advisory Circular No. 150/5320-12, Federal Aviation Administration, Washington, D.C., 1975, 73 pp. 10. Rose, J. G.; Hutchinson, J. W.; and Gallaway, B. M., “Sum- mary and Analysis of the Attributes of Methods of Surface Texture Measurement ,"” Skid Resistance of Highway Pavements, STP-530, ASTM, Philadelphia, 1973, pp. 60-77. 11. Chamberlin, William P., and Amsler, Duane E., “Measuring Surface Texture of Concrete Pavements by the Sand-Patch Method,” Report No. FHWA-NY-78-RR62, New York State Department of Transportation, Albany, 1978, 18 pp. 6.2 - Related references 12. “Skid Resistance,”NCHRP Synthesis No. 14, Highway Re- search Board, Washington, D.C., 1972, 66 pp. 13. “Guidelines for Skid Resistant Pavement Design,” American Association of State Highway and Transportation Officials, Wash- ington, D.C., 1976, 20 pp. 14. Ryell, J.; Hajek, J. J.; and Musgrove, G. R., “Concrete Pave- ment Surface Textures in Ontario - Development, Testing and Per- formance,” paper presented at Transportation Research Board, Washington, D.C., Jan. 1976. 15. “Skidding Accidents-Pavement Characteristics,” Transpor- tation Research Record No. 622, Transportation Research Board, 1977, 110 pp. 16. Balmer, G. G.,“The Significance of Pavement Texture,” Re- port No. FHWA-RD-75-12, Federal Highway Administration, Washington, D.C., 1975, 44 pp. 17. “Interim Report for Runway Rubber Removal Specification Development: Field Evaluation Results and Data Analysis,” Report No. DOT/FAA/PM-85/32, Federal Aviation Administration, Wash- ington, D.C., July 1984-July 1985, 106 pp. 18. “Rubber Removal Specification Development-Final Re- port,”Report No. DOT/FAA/PM-85/33, Federal Aviation Admin- istration, Washington, D.C., May 1983-Sept. 1985, 51 pp. This report was submitted to letter ballot of the committee and was approved in accordance with ACI balloting procedures. . by permitting the rapid escape of water. Keywords: concrete finishes (hardened concrete) ; concrete finishing (fresh concrete); concrete pavements; maintenance; measurement; skid resistance;. of textures 1.2-Benefits of texturing 1.3-Factors affecting skid resistance Chapter 2-Texture types, p. 325.6R-3 2.l -Texturing plastic concrete 2.2 -Texturing hardened concrete Chapter 3-Testing,. portland cement concrete pavements with satisfactory surface textures and crowns for existing older pavements that have lost their skid resistance. Cross slopes (or crowns) built into concrete pavements,