Better Roads

September 2013

Better Roads Digital Magazine

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HighwayContractor Improved Technology Many years ago, when we talked about evolving concrete overlays to what we're seeing now, we talked about the need to create better bonds and shorter joint spacing. That made a big difference as we engineered shorter joint spacing to facilitate thinner slabs. This removed one of the key failure criteria, so the science has led us to doing shorter panels in the range of 5 to 7 feet, depending on the configuration. Even panels as short as 2 feet were evaluated but found not to be effective. Therefore, with 5- to 7-foot panels, you have only one load per slab and an effective pavement. The original design equations for concrete overlays came from the U.S. Army Corps of Engineers' research. Before that, most overlays were placed using engineering judgment and experience. The ACPA has added concrete overlay designs to its newest generation of pavement design software, StreetPave 12. The software can be used for all six types (bonded on asphalt, unbonded on asphalt, bonded on concrete, unbonded on concrete, bonded on composite and unbonded on composite). It accounts for the benefits of fibers, as well, which is another technological advancement that plays an important role in "thinning up" overlays. ACPA's Bonded Concrete Over Asphalt (BCOA) calculator is also a great resource that designers and others can use for thickness design. This web-based tool ( is based primarily on the results of FHWA-ICT-08-016, "Design and Concrete Material Requirements for Ultra-Thin Whitetopping," a research project conducted in cooperation with the Illinois Center for Transportation (ICT) at the University of Illinois, the Illinois Department of Transportation (IDOT) and the FHWA. Also, HIPERPAV (high-performance concrete paving) software is a key to the successful design and construction of bonded concrete overlays. The software tool is used to determine the early age behavior of bonded concrete overlays, as well as jointed – and continuously reinforced concrete pavements. Fibers, and particularly the blend of microfibers and structural fibers, also have a profound effect on the construction of concrete overlays, especially as they get thinner. They provide toughness, help reduce plastic shrinkage cracking potential and offer greater latitude with curing. They extend the fatigue factor of the concrete because the fibers hold cracks, and they contribute to the preservation benefit we are looking for with thinner and pavements. Many other factors will continue to contribute to thinner concrete overlays, but it's safe to say the needs of the marketplace will drive innovation as we strive for thinner concrete overlays to meet performance and cost expectations. Keep your crews out of harm's way Make the SAFE choice for work zone traffic control. We are North America's leader in automated flagger assistance devices (AFADs) and portable traffic lights. • High-intensity signals more visible than human flaggers • MUTCD compliant • Control traffic from a safe location • Solar powered • Fast delivery; 24/7 support • Buy or rent direct Call or visit us online TM SINCE 1994 1.877.352.4626 Text INFO to 205-289-3789 or visit 12 NorthAmerica_BR0413pg27.indd 1 September 2013 Better Roads Job 145-015 Filename 3/28/13 1:00 PM 145-015 Better Roads 7x4.5 4C.indd Last Modified Fonts & Placed Graphics etup Client North America Traffic Bleed None HighwayCon_BR0913.indd 12 Trim 7" x 4.5" 9-11-2012 11:25 AM Family Style AvantGardeMdITCTT (Bold), AvantGarde Bk BT (Demi, Book, Demi Oblique) Name Color Space Eff. Res. Prev. Users Adam Savage/MSS1 Inks Cyan Magenta 8/29/13 1:10 PM Yellow

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