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5Background It has long been recognized that the texture of portland cement concrete (PCC) pavement surfaces directly influences friction and safety characteristics (American Concrete Insti- tute [ACI], 1988). Prior to 1967, most PCC surface textures were constructed using a burlap drag process. However, at that time, this texturing method did not provide a minimum frictional coefficient of 0.30, as was required by at least one stateâCalifornia (Neal, 1985). Consequently, other textur- ing methods were developed to improve frictional/safety characteristics, the most common of which is transverse tining (grooving the PCC surface perpendicular to the traffic direction prior to curing). The uniform narrow grooves provide water drainage and increase the macro-texture of the surface, result- ing in good wet-weather pavementâtire friction and report- edly a good safety record. As the volume of urban traffic increased steadily, vehicle noise emission became a concern (ACI, 1988). In 1973, the Federal Highway Administration issued Policy and Procedure Memorandum 90-2, Noise Standards and Procedures that estab- lished noise criteria for federally funded highway projects (FHWA, 1973). From this time through 2004, over 2,205 mi (3,550 km) of noise barriers or combination berms and barri- ers were built at a cost of over $2.7 billion (FHWA, 2006). The criteria have since been updated and are currently outlined in the Code of Federal Regulation (CFR) Title 23, Part 772, Proce- dures for Abatement of Highway Traffic Noise and Construction Noise (U.S. Federal Government, 2008). While significant reductions in vehicle engine and drive- train noises were achieved in recent years, the noise associated with pavementâtire interaction has not been significantly reduced (Sandberg and Ejsmont, 2002). Public concern (espe- cially in urban areas) over the issue of high traffic noise and the substantial costs associated with noise emissions barriers have led to renewed interest in pavements that exhibit low- noise properties under traffic. Because pavementâtire noise is controlled primarily by (1) the tire design and materials and (2) roadway surface tex- ture and material properties, the highway community has been actively engaged in evaluating the methods used to texture pavements. Spurred on by the significantly lower noise of asphalt concrete (AC) pavement surfaces when compared with transversely tined PCC surfaces, particular effort has been devoted to developing improved alternatives to the transverse tine texture. Among the earlier alternatives were (1) the longi- tudinal tine that California specified starting in 1978 in spite of the requirement of FHWA guidelines for transverse tining (Neal et al., 1978; Hibbs & Larson, 1996); (2) the random (i.e., variable) transverse tine that was found to reduce or eliminate the âwhineâ associated with uniform transverse tining; and (3) the random (i.e., variable) skewed transverse tine that was shown to eliminate whine and reduce overall noise (Kuemmel et al., 2000). Other methods of noise reduction for PCC pavements have been evaluated internationally and more recently in the United States. These include longitudinal diamond grinding, longitu- dinal grooving, exposed aggregate concrete (EAC), porous PCC, shot-abraded PCC (e.g., Skidabrader), and ultra-thin proprietary surfacings (e.g., NovaChip® and Italgrip® System). Various strengths and weakness have been reported for all of the methods with regard to initial and long-term noise, friction, and other surface characteristics, as well as constructability and economics. Identifying optimal textures for various highway conditions and environments has been the goal in many of the past and ongoing investigations, and it is the goal in this study. Description of the Problem Tining generally is performed to enhance pavement-surface frictional characteristics and reduce potential for hydroplan- ing, skidding, and wet-weather crashes. However, there is a concern that the use of tining has evolved without adequate consideration of the effects on noise generation, long-term C H A P T E R 1 Introduction
6durability, smoothness, constructability, pavement service- ability, and cost-effectiveness. In addition, there are other options for texturing concrete pavements that might provide better performance and yield environmental and economic benefits. There are no widely accepted guidelines or procedures for identifying and selecting methods of texturing concrete pavements that consider relevant technical, environmental, economic, and safety issues. Research was needed to develop a rational procedure for use by highway agency personnel in identifying and selecting appropriate texturing methods for concrete pavements. NCHRP Project 10-67 was initiated to address this need. Project Objectives and Scope The objective of this research was to recommend appropri- ate methods for texturing concrete pavements for specific applications and ranges of climatic, site, and traffic condi- tions. These methods were to include tining and other means of texturing fresh and hardened concrete for the purpose of enhancing surface frictional characteristics. The research included a review of relevant literature, con- ducting surveys and interviews of state and industry profes- sionals, identifying and assessing the factors that influence texture level, and identifying test methods and criteria for assessing surface texturing. The research also included a field evaluation of in-place test sections and specially constructed full-scale test sections. Based on the analysis of acquired data, a process for texture selection and sample construction spec- ifications were prepared. Work Approach In this study, a large amount of information was collected, reviewed, and analyzed to establish the state of the practice in concrete pavement texturing and to identify promising and/or innovative texturing methods. A large field investigation involving texture, friction, and noise testing of 57 in-place pavement surfaces was conducted. Results from this investigation were used to identify con- crete surface textures for a more detailed evaluation through the construction of a formal texture test site. This test site, located and installed on a new stretch of the I-355 North-South Tollway near Joliet, Illinois, included nine different âformedâ textures (tining or drag finishes created in fresh concrete) and three different âcutâ textures (ground or grooved finishes cre- ated in hardened concrete), all of which were tested for texture, friction, and noise shortly after construction. The results of data analyses on both the in-place and new texture test sections together with the state of the practice infor- mation were used to develop a process (and related guidance) for selecting textures for a range of applications and for prepar- ing sample specifications for texturing concrete pavements. Overview of Report This report has seven chapters. Chapter 1 is this introduc- tion. Chapter 2 briefly describes the state of the practice of con- crete pavement surface texturing based on a review of literature and interviews with knowledgeable individuals. Chapter 3 describes the selection of 57 pavement sections located in 13 states and the conduct of texture, friction, and noise tests. Chapter 4 discusses the development and execution of a plan to build and test different surface textures (most of them iden- tified as having good friction and noise qualities) as part of a paving project in northern Illinois. Chapter 5 presents the results of analyses performed on texture, friction, noise and other pavement data collected on both existing and newly constructed test sections. The results together with the state-of-the-practice information were used to develop the texture selection process presented in Chapter 6. The final chapter summarizes the key findings of this research and presents the studyâs conclusions and recommendations. The report includes six appendices. Appendix A describes the state of the practice in concrete pavement texturing. Appendix B summarizes the interviews conducted with high- way agency, industry, and academia representatives. Appen- dix C gives detailed information on the locations, layout, and history of the 57 existing test sections. Appendixes D and E provide summary charts of the texture, friction, and noise test- ing results obtained for existing and newly constructed texture test sections, respectively. Appendix F presents guide/sample specifications for some of the PCC textures evaluated in this study. Appendixes A through F are not published herein, but are available on the TRB website.