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1 SUMMARY Texturing of Concrete Pavement The objective of the research performed under NCHRP Project 10-67 was to recommend appropriate methods for texturing concrete pavements for specific applications and ranges of climatic, site, and traffic conditions. To accomplish this objective, several sequential tasks were performed. First, information was collected, reviewed, and analyzed to establish the state of the practice in concrete pavement texturing and to identify innovative technologies. Next, a field investi- gation of pavement surfaces was conducted to identify concrete surface textures appropriate for construction and evaluation in a test site. The test site featured nine sections with "formed" textures (i.e., drag or tine finishes created in fresh concrete) and three sections with "cut" textures (i.e., ground or grooved finishes created in hardened concrete) that were tested for texture, friction, and noise shortly after construction. Analysis of data obtained from both the in-place and newly constructed texture test sections was combined with information on the state of the practice to develop a process and guide- lines for selecting textures for a range of applications and to prepare sample specifications for texturing concrete pavements. Evaluation of Existing Test Sections Several factors were considered in selecting texture test sections for evaluation in this re- search. The most important factors were (1) the availability of pavement sections with the de- sired textures, (2) the interest and willingness of state highway agencies (SHAs) to assist in evaluating the test sections, (3) the age of or amount of traffic experienced by the texture sec- tions, and (4) the geographical locations and site conditions of test sections. Fifteen states were identified initially as having desirable test sections, and a testing matrix was developed-- 57 test sections in 13 states were selected for data collection and analysis. Design, construc- tion, and site information for each of these test sections were obtained from state records. Also, various forms of texture, friction, and noise data for each section were available from field tests performed in 2005. Construction and Evaluation of New Test Sections Using a systematic procedure to rank the friction, texture, and noise characteristics of the existing test sections, the researchers identified several textures as having the potential to provide adequate friction and reduced noise characteristics. These textures were selected for additional evaluation through the construction of test sections as part of a paving project. The Illinois State Toll Highway Authority (now the Illinois Tollway) provided an oppor- tunity for constructing the texture test sections as part of a new alignment construction
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2 project in the southwest suburbs of Chicago--the South Extension of the I-355 North- South Tollway located between I-55 and I-80 near Joliet. A total of 13 different textures, in- cluding 10 of the selected textures, were constructed in 2007 as part of the 6-lane, 12.5-mi (20.1-km) long project. Portland cement concrete (PCC) paving and formed texturing ac- tivities were closely monitored and documented, including measurements of groove di- mensions (i.e., spacing and depth) at time of paving and at certain times after curing of the concrete. Also, the activities of three cut textures were closely monitored and documented. Test segments for each texture were subsequently identified and marked in the field, with each segment chosen on the basis of best representation of the specified texture and avoid- ance of roadway features that could affect test results (e.g., overpasses, areas ground to sat- isfy smoothness requirements). These sections were tested for texture, friction, and noise in the same manner as was performed on the existing texture test sections. Data Analysis Different types of analyses were used to provide a basis for developing a practical, compre- hensive process and guide specifications for texture type selection. The analyses recognized the limitations of the data and the role of micro- and macro-texture wavelengths on pavement friction and noise. Noise spectral analyses of existing test sections showed prominent tonal spikes for three transverse tine textures with uniform spacing (one with 0.5-in. [12.7-mm] spacing and two with 0.75-in. [19-mm] spacing) and one longitudinal tine texture (0.75 in. [19 mm]). Two uni- formly spaced (0.5 and 1 in. [12.7 and 25.4 mm]) transverse tine textures built on the Illinois Tollway exhibited similar tonal issues. Power spectral density (PSD) analysis of texture profile data collected on the sections yielded additional texture properties (besides micro- and macro-texture and texture di- rection) for possible linkage to near-field sound intensity (SI) noise (i.e., noise at the pavementtire source). These PSD parameters included two distinct ratios of high-frequency texture content to low-frequency texture content, and the peak texture wavelength. Plots of SI versus each of these PSD parameters generally confirmed that reducing the higher wavelength texture and increasing the lower wavelength texture results in lower noise. Comparative/qualitative analyses of textures within a specific test site/location, followed by statistical analyses (analysis of variance [ANOVA] and statistical performance groupings), resulted in many observations regarding texture, friction, and noise performance. With re- spect to general texture types, it was concluded that longitudinal tining and longitudinal di- amond grinding and grooving offer the greatest potential for reducing noise while maintain- ing adequate friction. Skewed variable transverse tine can eliminate objectionable tones and provide noise reduction benefits. Turf drag textures can be low noise, but significant tex- ture depth is needed to ensure adequate friction at high speeds. With respect to the effect of texture orientation (TO) on noise, it was generally found that positive textures (i.e., aggres- sive, protruding surfaces) are noisier than negative textures (i.e., flat, pocketed surfaces). A key exception to this was diamond ground textures, which were categorized as positive tex- tures, but exhibited low noise.
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3 Texture durability analyses were performed to evaluate the effects of aggregate quality on micro-texture loss over time/traffic and macro-texture loss experienced by general tex- ture types. This analysis showed that concrete mixtures with tougher, more durable aggre- gates retain higher friction values and that macro-texture loss over time/traffic is greatest for diamond-ground textures and lowest for dragged and grooved textures. Time-/traffic-series noise comparisons of all concrete surface textures evaluated in the study showed diamond ground and grooved textures provided the lowest overall initial noise levels, followed by longitudinal drag, transverse tine, and longitudinal tine textures. Long-term overall noise was lowest for diamond-ground and grooved textures and longi- tudinal tining. Various statistical analyses of the texture, friction, and noise data were conducted to dis- tinguish the performance of the various textures and to identify the key factors affecting tex- ture performance. These included SAS ANOVA and Tukey analyses of textures compris- ing individual sites/locations, SAS ANOVA and regression analyses of 70 test sections (57 existing sections and 13 newly constructed sections), and SAS multiple regression analyses/ modeling of texture and noise from the newly constructed sections. Results of these analy- ses provided a basis for distinguishing and ranking different textures and for observing the ef- fect of traffic on texture performance. These analyses also evaluated the influences of traffic, climate, and texture depth on friction/micro-texture performance and the influences of traf- fic, texture depth and direction, and joint frequency/spacing on pavementtire noise. Other texture characteristics, such as texture orientation (TO) and certain texture power spec- tral density (PSD) parameters, and joint frequency/spacing on pavementtire noise also were determined. Texture Selection Process Selecting a texture for a concrete pavement requires an understanding of the particular needs and requirements of the facility, and matching the friction and noise qualities of the available textures to those needs. A rational process is needed for determining the type of tex- ture to be used on a particular highway project. Such a process involves gathering and review- ing all available critical information about the project, identifying potential constraints/ limitations (both internally and externally) in terms of available resources/technologies and performance/cost expectations, developing alternative feasible solutions, and determining the most economical and practical alternative. Figure S-1 illustrates the process for identifying pavement surface texturing options at the project level. In this process, key information about the project is obtained and used to establish tar- get levels for friction, noise, and other surface characteristics. The target levels are then combined with information on available aggregate types and contractor experience to generate feasible texturing options for the project. Once the options are identified, the cost of each texturing option (both initially and over the lifecycle of the pavement) is esti- mated, and the results are evaluated with consideration given to the overall functional and structural requirements and performance of the pavement.
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4 Step 1---Project Information Input Step 2---Friction Analysis Available Aggregates (incl. Perf Characteristics) Highway Features/Environment (vehicle maneuvers) Highway Alignment (vertical, horizontal) Design Traffic Characteristics (amount, composition) Friction/Texture Matrix Target Friction (Identification of Levels Climatic Conditions Candidate Textures) Design Speed Highway Setting & Adjacent Land Use Contractor Experience Feasible Texture Options Agency Experience & Policies Step 4---Selection of Preferred Texture Step 3---Noise Analysis Consideration of Economic Feasible Texture Noise Regulations & Other Surface Considerations Options Preferences Characteristics Noise/Texture Matrix Preferred Texture Target Noise (Identification of Alternative Levels Candidate Textures) Figure S-1. Process for identifying pavement surface texturing options.