Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/358505
Better Roads August 2014 11 WHERE PRODUCTIVITY MEETS PROFITABILITY Easy maintenance. Low operating costs. Long service intervals. Maximize your productivity and profits with Atlas Copco breakers. Call today. Get more done tomorrow. 800-732-6762 | www.atlascopco.us 7H[W,1)2WRRUYLVLWZZZEHWWHUURDGVFRPLQIR Evaluation of High Performance Fiber-Reinforced Concrete for Bridge Deck Connections, Closure Pours and Joints. "Connections, closure pours and joints in bridges are often a source of distress due to cracks and openings in them," say Hoomes, Ozyildirim and Brown. "Wide separation facilitates the penetration of harmful solutions which can lead to costly repairs." Cracks are caused by volumetric changes due to moisture and temperature and the application of service loads after the concrete has hardened, they write. "The addition of a small amount of discontinuous fibers to a conventional concrete matrix minimizes cracking, but the size of these cracks still permits the intrusion of harmful so- lutions," say Hoomes, Ozyildirim and Brown. "High volumes of suitable fibers used in high performance fiber reinforced concrete produce multiple very tight cracks (< 0.1-mm wide), which do not allow for the ingress of water and other harmful solutions." The authors evaluated plastic and hardened mixture properties, with emphasis on deflection hardening, flexural toughness, and bond strength. Different systems were tested: engineered cementitious composite (ECC); hybrid fiber- reinforced concrete (HyFRC) systems, including both steel and synthetic discontinuous fibers; HyFRC including only synthetic fibers; and ultra-high performance concrete with steel fibers. The authors conclude the following: • ECC and HyFRC mixes achieve deflection hardening with high fiber content of steel or synthetic fibers. ECC achieved the highest deflection hardening capacity of all systems tested. • Although UHPC attained the highest stress capacity, the material did not deflection-harden; results are partly at- tributed to the settling of the fibers to the bottom. High shrinkage values do not necessarily indicate wide cracks. ECC exhibited the highest shrinkage values, yet showed deflection hardening and uniformly distributed, tight cracks instead of few wide cracks. • Workability of mixtures with steel fibers was higher than those with synthetic fibers. • All mixtures achieved adequate bond strength for use in closure pours.