December 2001 Table of Contents

Features Work Crews Working in Rhythm

The sport called crew is an Olympic event. If you have ever witnessed a live crew event, you are immediately impressed with the coordination, leadership, positioning, and skill needed to bring a group of individuals together into a single rhythm. One member of the team who is just a split second early or late can take the entire boat off course. Read more

Features 2001 ACPA Award Winners

For almost 4 decades, the American Concrete Pavement Association's Excellence in Concrete Pavements awards have been presented to agencies, contractors, and engineers whose work represents the best highways, streets, roads, and airports in the United States. The competition for these highly coveted awards is steep, the judging criteria rigorous, and the awards ceremony is arguably the most spectacular show in the industry. Read more

Features Post-Tensioned Concrete: Five Decades of American Building Construction

Beginning in the 1950s as a European import, post-tensioned concrete has changed the face of American building construction. Starting from lift slabs with button-headed wires and evolving into flying forms and cast-in-place slabs post-tensioned with strand tendons, post-tensioning has become a common technique in American construction. Read more

Features How Much Fly Ash

Are we ready to accept high-volume fly-ash concrete in cold-weather climates? A number of practitioners in Canada's largest city, Toronto, think so. They are betting that a 50/50 fly-ash-to-portland-cement mix for a four-story 120,000-square-foot computer sciences building on the campus of York University will prove their point. Read more

Features Paving Repair Finds a Four-Hour Champion

The California Department of Transportation (Caltrans) needed a concrete pavement that would deliver a surface ready for traffic in 4 hours. Different admixture manufacturers experimented with various combinations to try to achieve this. Finally, Master Builders came up with what they call "4x4 Concrete," an innovative mixture that develops 400-psi flexural strength in just 4 hours after placement. This material costs about half as much as current fast-setting hydraulic cement concrete and can be produced with standard locally available materials. Chumo Construction recently placed over 500 cubic yards of this new mix on a remove-and-replace job for the California Department of Transportation with great success. We asked Tom Pyle, chief, Office of Rigid Pavements & Structural Concrete with Caltrans, and James Anderson, engineering service western manager for Master Builders, to discuss this new development in high-early-strength concrete for paving repair. Read more

Features Do Hand-Held Vibrating Screeds Affect Surface Air Entrainment?

Across the Midwestern states last December, there was a much greater accumulation of snowfall than usual. Ground temperatures, as a result, tended to remain around freezing. With little snow in January and temperatures frequently fluctuating above and below freezing, exterior concrete slabs experienced more freeze/thaw cycles than usual. By spring of this year, the number of reports of spalled and scaled concrete, especially for residential driveways, was skyrocketing. Concrete installed during the 2000 construction season had the most damage. Read more

Decorative Concrete Release Agents for Stamping Concrete

In 1956 Bill Stegmeier, president of the Stegmeier Corp., Arlington, Texas, developed a powdered release agent which not only provided the release between texturing tools and plastic concrete but also imparted colored highlights and antique effects to decorative finishes. Now 80 years old, Stegmeier says he originally developed the product for use with their "Cool Deck" process. He added, "I hold 102 patents for things we've invented over the years, but I didn't patent this process." He also developed a wood-texturing stamp, which simulated wood plank patterns 12 inches wide and of varying lengths. In 1976 he granted the Bomanite Corporation a license to use his invention and several years later sold them the rights. Read more

Problem Clinic Stain Won't Stay

We have a problem with a concrete stain product. It appears that the stain did not truly penetrate. We are told that the use of liquid curing compounds created a barrier to the stain even though the contractor applied a paint stripper first. These areas n Read more

Problem Clinic New Slab on Top of Old

I recently poured a 30x50-foot pad that has cracked very badly. The pad had no rebar and no expansion joints. Read more

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