Road Science: Top 5 Trends of 2010
The generators are placed at a depth of 1.9 inch beneath the upper asphalt layer of a road. Piezoelectric materials convert mechanical energy generated from a vehicle’s weight into electricity. Drivers feel no change in the road. Regular vehicle traffic can generate 2,000 watts per hour. The electricity is accumulated in batteries placed along the side of the road.
4. Precast concrete paving slabs: attainable benefits
A change in contract proposed by a road contractor is causing the Utah DOT to look at the use of precast concrete pavement on a heavily traveled Interstate route.
“Precast concrete pavement systems have been shown to accelerate construction time and be economically feasible, while still maintaining the quality of conventional repair methods,” said Ken Berg of the Utah DOT Research Division.
Utah DOT in spring of 2009 advertised a concrete pavement rehabilitation project for I-15 near Clearfield, between Ogden and Salt Lake City. The successful bidder, B. Jackson Construction & Engineering, Inc., proposed use of precast concrete paving slabs, as they now are called. The proprietary system used was the Fort-Miller Super-Slab system, supplied by Mountain West Precast. Utah DOT approved the selection and construction began in March 2009.
The application unfolded against the backdrop of the AASHTO Technical Implementation Group Lead States Team for Precast Concrete Paving Slabs.
“Precast concrete panels for pavement applications is one such technology that should be added as a supplement to the pavement designer’s toolbox of treatment alternatives,” according to the TIG.
The TIG states that new products, emerging technologies and innovative construction practices should not sacrifice quality, durability and long-term performance; provide a means of accelerating the construction scheduling and sequencing; reduce congestion delays caused by excessive construction work zone time frames; and be economically feasible. “It is our belief that when precast paving elements are properly selected as a pavement or repair treatment, all of these beneficial characteristics are attainable,” the TIG. Its work will have ramifications for road builders and owners as 2010 unfolds.
5. Polymer rebar could supplant steel in concrete pavement
Use of polymer rebar could supplant reinforcing steel in continuously reinforced concrete pavements, if research now underway affirms its use. The 2009 research circular, Evaluating the Use of Fiber-Reinforced Polymer Bars in Continuously Reinforced Concrete Pavement, a product of the FHWA’S Concrete Pavement Technology Program (CPTP), reviewed their status.
Continuously reinforced concrete pavement designs (CRCP) are premium pavement designs that are often used on heavily-trafficked roadways and urban corridors. CRCP designs have no regularly spaced transverse joints, but contain a significant amount of longitudinal steel reinforcement (typically 0.6 to 0.8 percent of the cross-sectional area). The high steel content both influences the development of transverse cracks within an acceptable spacing (about 3 to 6 feet) and serves to hold them tightly together (see The ABCs of Continuously Reinforced Concrete, Road Science, May 2007).
The prevalence of wide cracks in CRCP has frequently been associated with ruptured steel and significant levels of corrosion, and fiber-reinforced polymer (FRP) composite materials are one product being investigated for use in CRCP in place of traditional steel bars. FRP composites consist of a matrix of polymeric material (polyester, vinyl ester, or epoxy) that is reinforced by fibers of other reinforcing materials, typically glass, carbon, or graphite.
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