March 1993 Table of Contents

Features Beware the Iceberg

An accident's economic costs are far greater than most contractors realize. The reason is that many accident costs are hard to recognize or given little thought. However, like the underwater part of an iceberg, they loom large and dangerous. Read more

Features Form Reuse

Costs of forming account for about half the value of typical cast-in-place concrete construction. Planning for maximum form reuse can reduce forming costs and provide an opportunity to win bids in competitive markets. Read more

Features Repairing Architectural Precast Concrete

Because appearance is important, patching and repair of architectural concrete needs to be done carefully. Attempts to patch some minor defects may make the flaws more noticeable. Since experts recommend that repairs be inconspicuous from about 20 feet away, flaws visible only at very close distances usually can be left alone unless there are functional or structural reasons for the repair. Read more

Features Certifying Plants and People in the Concrete Industry

Certification programs fit into two main categories: plant certification and personal certification. Prestressed, precast, and ready mixed concrete producer associations have established programs requiring thorough inspections of production facilities. The inspections are conducted by impartial, professional engineers who are qualified to certify that the plants have properly calibrated and maintained equipment that can produce and deliver concrete and concrete products that meet industry standards and project specifications. Read more

Features Cast-in-Place Details Enhance Short-Span Bridge

The Dunks Ferry Road Bridge over Poquessing Creek at the boundary between Philadelphia and Bucks counties in Pennsylvania demonstrates that small bridges need not be mundane. This single 60-foot-span bridge, a combination of cast-in-place and precast concrete, was deigned and is owned by the City of Philadelphia, Department of Streets, Bridge Section. Contractor Tony DePaul & Son built the approaches and cast abutments, wing-walls, and parapets in place, using adjacent concrete box beams as the principal superstructure members. Read more

Problem Clinic Patching Materials for Frozen Deck Slabs

We're doing some remodeling of a hospital building that includes installing new floor coverings. The floor slab is a lightweight concrete placed over metal deck forms. Evidently when the concrete was placed, the top surface froze and was patched. Then it Read more

Problem Clinic Is Entrained Air Required for Wet-Mix Shotcrete?

Does an air-entraining agent serve any purpose in wet-process shotcrete? I believe shotcrete is placed with such force that any air-entraining effect is negated. Should we use air-entraining agents in concrete that will be placed by wet-mix shotcreting? Read more

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