User:Kosmashang

Produced by dragging an inverted section of artificial turf from a device that allows control time and rate of texturing. Usually a construction bridge that spans the pavement typically produces 1/16 to 1/8 inch deep striations.............................................................................................................................................................................................Artificial turf drag textures have shown sufficient friction characteristics for many roadways, as well as reduced noise relative to many transversely tined pavements. Minnesota has used this type of texturing to reduce noise on high-speed roads................................................................................................................................................................................................. Produced by dragging moistened coarse burlap from a device that allows control of the time and rate of texturing, usually a construction bridge that spans the pavement; typically produces 1/16 to 1/8 inch deep striations............................................................................................................ Burlap drag textures provide sufficient friction characteristics for many roadways, especially those with speeds less than 45 mph, and reduced noise relative to many transversely tined pavements. This texture is used on Germany’s high-speed Autobahn system............................................................................................................................................................................................. Produced by moving a mechanical device equipped with a tining head across the width of the paving surface laterally or on a skew. Consistent concrete mixture and constant forward movement of the paving train at a uniform speed is required for a consistent tining depth............................................................................................................................................................................................ For tined pavements, texture depth and groove width are important parameters in tire-pavement noise generation. Pavements with uniformly spaced transverse tining generally, but not always, exhibit undesirable “wheel whine” noise. Artificial turf or burlap drag texture precedes many projects.................................................................................................................................. Achieved by a mechanical device equipped with a tining head (metal rake) pulled in a line parallel to the pavement centerline. For consistent tining depth, maintain a consistent concrete mixture and move the paving train forward constantly at a uniform rate of speed. Most projects precede with an artificial turf or burlap drag texture..............................................................................................................................Tined texture depth and groove width are important parameters in tire-pavement noise generation. Longitudinal tining is often quieter than transverse tining. Narrower time spacings might be used to reduce vehicle tracking and possibly reduce noise even further. Lateral stability of narrow-tired vehicles may also benefit from this..................................................................................................................................... Longitudinal, corduroy-like texture made by equipment using diamond saw blades gang-mounted on a cutting head. About 50 to 60 grooves/ft. are produced by the cutting head 1/8 to ¾ inch is removed from the pavement surface................................................................................................................................ Diamond grinding has traditionally been used to restore pavement smoothness, but has also been shown to reduce tirepavement noise and improve friction in the short term. Diamond ground pavements do not affect vehicle tracking as much as widely spaced longitudinally tined pavements.......................................................................................................................................................................................... European practice includes applying a set retarder to the new concrete pavement and then brushing or washing away mortar to expose durable aggregates. Other techniques involve the uniform application of aggregates to the fresh concrete................................................................................................................................... Regarded as an effective method for reducing tire-pavement noise while providing adequate friction. Smaller aggregate sizes have been reported to provide larger noise reductions, while aggregates with a high polished stone value increase durability. Only one large-scale EAC pavement project has been completed in U.S...................................................................................................................................................... When used in highway applications, pervious concrete is typically used as a top layer (wearing course), providing both low noise emission and good drainage capacity. The pervious concrete typically overlays a conventional (dense) concrete pavement using a “wet-on-wet” process...................................................................................... ................................................ Sound absorption increases with higher porosity levels for pervious concrete, and also results from smaller aggregate sizes. Use of pervious pavements for high-volume, high-speed facilities is still in its infancy and will require more testing. Regular maintenance and cleaning may be needed to prevent clogged pores and to preserve the pavement’s acoustical performance. Research on durability is ongoing in wet, hardfreeze areas......................................................................................................................... 2.3.2 Other Innovative Pavement Solutions.......................................... Traditionally, two-layer porous asphalt is laid in two passes – one pass per porous layer. As a part of a Noise Innovation Program, equipment will be tested in the Netherlands to construct two-layer porous asphalt in one pass – both layers being laid at the same time.26 This technique is already in use in Germany with thin top layers. The objective of the research is to determine if the “one-pass placement” will increase the performance of the two-layer pavement materials................................................................. As a part of its Road to the Future program,22 transportation researchers in the Netherlands are focusing on long-term effects and the placement of pavement materials using innovative and/or fast construction techniques. Six experimental test sections have been constructed:....................................................................................................................................... a. The Very Silent Sound Module – this design has a functionally and physically modular system. The sound-reducing functional modules contain Helmholtz resonators. The road surface on top of the sound-reducing resonators is made of a thin porous top layer. This single layer of asphalt has optimized surface properties, such as low sound generation and a high skid resistance. ........................................................................................................................ b. The Way of No Resound – this road design has three layers. Two top layers with a combined thickness of 30 mm (1.2 in), are assembled in the factory as one roll-up layer. The bottom layer is made up of concrete elements with a high supporting power in which cavities that function as Helmholtz resonators are included. The prefabrication of the top layer promotes a pavement surface without irregularities in the macro-texture. This results in reduced vibration of a vehicle’s tires..................................................................................................... c. The Bonding Road – this design has a prefabricated asphalt mat on a roll that can be bonded to or removed from the substrate very quickly by utilizing an “on-off switching” bonding system. Prefabrication of the paving materials ensures a consistent high quality end product. The bonding between the asphalt mat and the substrate can be switched on or off by electromagnetic waves without any physical contact.................................................................................................. d. ModieSlab – the top layer of this road design consists of a 15 mm (0.6 in) open concrete layer, followed by another open concrete layer with coarsely broken gravel that is 35 to 55 mm (1.4 to 2.2 in) thick. The thickness of the lower layer decreases from the right to left lanes. Sound absorption is expected to match the type of lane traffic.................................................................................................. e. Quiet Transport – this road surface has porous asphalt with a very silent top layer. During construction a special layer is installed to absorb engine noise. The pavement design objective is to absorb both truck engine and tire noise........................................................................................................................................ f. Tapis Tolerance – the road construction for this pavement design includes a soft top layer, a perforated compression layer, and an absorption layer of honeycomb profiles in mineral wool. Due to the number of noise reducing elements, the expected noise reduction potential is high, and more than likely the cost of road construction will increase.......................................................................................................................... Initial results for the pavement types tested under the Road to the Futures program are shown in Table 6. These results reflect light vehicle traffic at 100 km/h (62 mph). The initial noise reduction levels reported for all pavement techniques vary between 5 and 7 dBA. The claimed reductions for some of the pavement techniques exceeded 10 dBA. However, optimization of new pavement techniques may produce higher reduction levels...................................................................................................... Table 6: Initial Noise Reduction Levels for Light Vehicles Road to the Future Project22..................................................... The 2005 FHWA Scanning Team noted the use of a single two-lift paver by Wirtgen during their visit to Belgium. The Wirtgen paver allows for the use of lower-quality aggregates in the base while using higher quality aggregates on the top surface.13, 16,23 The two-lift process is not new to the U.S. and has been around almost as long as concrete pavement. The two-lift paving technique was implemented extensively from 1950 to 1990 in many states to facilitate the placement of mesh in concrete during interstate pavement construction. This pavement consisted of two layers placed wet on wet, with the top layer consisting of a special surface mix. Beginning in the 1970’s the concrete paving industry moved away from a mesh dowelled design to a plain pavement design, and shortening panels eliminated the need to pave with a two-lift process. Today there are still some rare instances where the two-lift process is used in airport construction to facilitate the placement of mesh between dowel baskets................................................................................................... The two-lift process is used in Europe to develop a strong base pavement and a superior, but thin, wearing surface. In France, continuous reinforced concrete pavement was placed on two traffic lanes of highway A71 using the two-lift paving method.23 The top layer of this pavement, approximately 2 inches in depth, was made up of harder aggregates. These aggregates provided low noise and high friction for the pavement surface........................................................................................................................................................................ In Austria, the aggregate is secured with cement and then a two-inch layer of asphalt is placed on top. The recycled aggregate is then mixed into the bottom 8.5 in deep concrete layer, while the top 1.6 in deep layer was composed of a harder, higher quality aggregate. The purpose of using a higher quality concrete for the top layer was to reduce noise and increase friction, while keeping cost low by using a lower quality concrete for the bottom layer. The case is very similar in Germany. Two-lift paving is often used to reduce noise and increase friction. Germany also uses this method to reduce cost and achieve a smoother profile. In addition, Germany has somewhat drastic climate changes, which require the use of higher quality aggregate in the top layer to resist freezing and thawing effects.23