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ULTRA HIGH PERFORMANCE CONCRETE GUIDE

UHPC has been commercially available for more than a decade. A contributor to NPCA’s UHPC White Paper, Lafarge Group has promoted its branded mix, Ductal, for precast and cast-in-place applications around the world.The National Precast Concrete Association recently published an overview of ultra high performance concrete (UHPC), a material on the leading edge of innovation with potential to expand producers’ architectural and structural offerings. UHPC mix designs vary. Reinforced with high-carbon metallic fibers, structural product formulation can achieve compressive strengths up to 29,000 psi and flexural strengths up to 2,900 psi. UHPC for architectural elements typically incorporates polyvinyl alcohol (PVA) fibers, and can achieve compressive strengths up to 17,000 psi and flexural strengths up to 2,900 psi. Due to the material’s superior compressive and flexural properties, the need for passive reinforcing can be eliminated or greatly reduced, depending on the application. UHPC is also highly moldable and replicates form materials with extreme precision.

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CREATIVE TENSION

Full-scale prototypes in the Topocast Lab netted the finished Cast Thicket, shown here in the UT Arlington School of Architecture Gallery.St. Louis design studio yo_cy took first place in the APPLIED: Research through Fabrication competition with Cast Thicket, a precast piece that artists Kenneth Tracy and Christine Yogiaman dub “an exploration in tensile concrete.”

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MICROSTRUCTURE-BASED KINETICS MODEL

MICROSTRUCTURE-BASED KINETICS MODELA November 2013 CSHub research profile letter, “Early hydration: A local business,” charts calorimetry (heat measurement) curves from tricalcium silicate paste experiments—with specimens of three particle size distributions (PSD)—to support a proposed model of microstructure-based kinetics. It suggests a “reaction zone” extending a few micrometers in from the cement particle surface, and can reconcile longtime observations on PSD and water/cement ratio.

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PAVEMENT-VEHICLE INTERACTION II

PAVEMENT-VEHICLE INTERACTION IIIn its “PVI Mechanistic Model Gen II” research brief (December 2013) CSHub extends earlier observation of pavement-vehicle interaction, which impacts truck fuel consumption and, in turn, concrete and asphalt life cycle assessment. The new model can account for the impact of temperature and vehicle speed, plus other pavement structural and material properties, on fuel consumption, and is thereby applicable to viscoelastic (e.g. asphalt concrete) pavements. Model Gen II provides what CSHub staff affirms is “a rigorous tool for comparative studies and LCA of the roadway network.”

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Lehigh Valley venue artfully balances basic building materials

PHOTOS: Barry Halkin Photography for Spillman Farmer ArchitectsCombining a restored concrete slab and existing timber construction, with new steel and clay masonry, the $1.7-million, 7,000-sq.-ft. Arts Plaza is a raw, open-air space for the arts at Lafayette College in Easton, Pa. The project transformed a former auto-repair facility into a dynamic outdoor teaching space that responds to its natural environment and built context. Designed as an outdoor black box theater, the plaza hosts a wide variety of planned and spontaneous artistic endeavors, including performance art, visual art exhibits, and small group musical performances.

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