Better Roads

February 2014

Better Roads Digital Magazine

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RoadScience 6 February 2014 Better Roads The GlasGrid system has a significant modulus advantage over asphalt at warm temperatures, but more importantly, it also installs at low temperatures without becoming too brittle to perform across all temperature ranges, the maker says. Eliminating tack coats Tack coats provide a never-ending challenge for asphalt pav- ing contractors and government agencies. According to the Asphalt Emulsion Manufacturers Associa- tion (AEMA), a tack coat – also known as bond coat – is a light application of asphalt emulsion between hot mix asphalt layers designed to create a strong adhesive bond without slip- page. Without tack coat, the asphalt layers in a road way may separate, which reduces the structural integrity of the road and may also allow water to penetrate the structure, AEMA notes. However, on overlay projects, a tack coat can be tracked by tires and shoe soles into parking lots, businesses, vehicles and homes. Contractors and owning government agencies receive complaints as people aren't aware that there is fresh oil on the pavement, and they drive through a section getting black spots all over their white cars. But now innovative producers of sophisticated, polymer- modified asphalt emulsions are making tack coats more friendly. While a tanker truck with spray assembly still is required, instead of staying "tacky" and subject to spreading, the temperature-sensitive products cure in seconds to a solid coat, then activate in the presence of heat and bond with the hot mix asphalt when placed. One such manufacturer is Blacklidge Emulsions, Inc., whose Trackless Tack is a proprietary engineered asphalt emul- sion tack formulated to cure extremely fast into a hard and drivable coating, often in less than 10 minutes. A different engineered tack coat that has the potential to eliminate a spray paver on bonded thin overlays is UltraFuse bond coat from Blacklidge. It's a hot-applied, polymer-mod- ified tack coat that cools in seconds to form a non-tracking surface, and was specifically developed to provide user agen- cies and contractors with an option to the "spray paver" or Novachip system for bonded thin overlays. UltraFuse is applied with conventional distributors, as it fills cracks and seals the existing surface. Within seconds, the tack coat stabilizes and becomes non-tracking. But when paved over with a conventional paver after placement, heat from the fresh hot-mix asphalt or warm-mix asphalt (HMA or WMA) layer liquefies the polymer-modified tack coat to form a strong bond as is achieved with hot-applied spray paving. Ul- traFuse uses proprietary polymer modification for improved flexibility and bond strength. Its application rate equals the residual asphalt associated with emulsion applications, typically 0.08 to 0.18 gal/yd 2 in open-graded friction courses (OGFCs) and 0.04 to 0.08 gal/ yd 2 in dense-graded mixes. See these products at Blacklidge's booth No. 90630 in the Platinum Hall in the Platinum Lot. New waves in drainage pipe The assault of high-density polypropylene (HDPE) against reinforced concrete pipe (RCP) and corrugated metal pipe (CMP) has been ongoing for decades, and road and highway drains have been ground zero for this battle. English chemists Reginald Gibson and Eric Fawcett created a solid form of polyethylene in 1935. This discovery was first used commercially was an insulating material for radar cables during World War II. In 1953, Karl Ziegler of the Kaiser Wil- helm institute invented high-density polyethylene, and two years later HDPE was first used as a pipe. For his invention of HDPE, Ziegler won the Nobel Prize for Chemistry in 1963. Pipe behavior can be broadly classified as flexible or rigid, depending on how it performs when installed. Flexible pipe – like HDPE – has to move, or deflect, to transfer the overbur- den load to the surrounding fill, according to ConExpo-Con/ Agg 2014 exhibitor, Advanced Drainage Systems, Inc. (ADS), at booth No. 65716 in the Technology & Construction Solu- tions section of South Hall 2. HDPE combines mechanical and chemical properties for Correct backfill placement is critical for long-lived installation of easy-to-handle HDPE pipe. Photo courtesy of Advanced Drainage Systems, Inc

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