Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85911
RoadScience location owned by the department may reduce construction costs and can minimize the impact of load restrictions, say At- tanayake, Abudayyeh, Aktan and Cooper. However, setting up a certified plant at or near the site for a small bridge can be costly. "Casting of large components such as abutment stems, pier columns and pier caps can be an option due to their weight and less-complicated details," they add. "Fabrication of circular columns requires vertical formwork while pouring concrete and curing. Columns with rectangular sections can make the fabrication process easier, hence allowing onsite production. Language should be considered in the special provisions to complete prefabrication of components before demolition of the existing structure." PRECAST SLABS ON I-66 A Virgina Interstate test and comparison to CIP Both standard precast and precast/prestressed pavement slabs are performing in a high-level Interstate highway installation, say M. Shabbir Hossain, Ph.D., P.E., and Celik Ozyildirim, Ph.D., P.E., Virginia Center for Transportation Innovation & Research, Charlottesville, Va., in their paper, Precast Concrete Pavement on I-66 in Virginia. "To expedite construction and reduce the associated traffic delay and provide longevity, precast concrete slabs have been used for more than 10 years with successive improvements in processes and systems," the authors write. "The Virginia DOT has recently tried two precast systems along with conventional cast-in-place repairs on I-66 near Washington, D.C." There, the existing pavement was jointed, reinforced-concrete pavement. One precast system used reinforced slabs with doweled joints and is called Precast Concrete Pavement (PCP). The other system used transversely prestressed slabs, post- tensioned in the longitudinal direction, and is called Prestressed Precast Concrete Pavement (PPCP). Three different mixtures were used for the cast-in-place (CIP) patches, PCP panels and PPCP panels, with varying cement contents of 846, 518 and 602 lb./cu. yd., respectively, and water/ cement ratios of 0.32, 0.34 and 0.36, respectively, they report. PCP panel mixtures used 172 lb./cu. yd. of slag, and PPCP panel mixtures had 150 lb./cu. yd. of Class F fly ash. Cast-in-place cyl- inders were cured using a standard wet cure, but the cylinders for both precast systems were cured using radiant heat. Concrete placed in both precast systems exhibited satisfacto- ry workability, air content and strength, Hossain and Ozyildirim say. All 15 batches of cast-in-place concrete achieved required 2,000-psi compressive strength in four hours, except one batch that reached 1,990 psi. Write on Reader Service Card Better Roads March 2012 25