September 2002 Table of Contents

Features Project of the Month

The Milwaukee Art Museum represents an exceptional and unprecedented use of concrete, steel, and glass. These unusual forms that draw the eye are primarily exposed structural elements, spectacular in form. Read more

Features Reducing Curling of Concrete Floor Slabs

One of the most litigious issues for the U.S. concrete industry is floor slab curling. Though all parties involved in a project, including the owner of the project, share responsibility for a problem floor when it becomes a lawsuit, the contractor who constructed the floor often bears the brunt of the financial liability. Unfortunately, curling is present in nearly all finished concrete floors. Read more

Features Fibers for Tomorrow

From humble beginnings more than 30 years ago as scrap byproducts of the carpet and steel wool industries, fibers today offer many advantages for reinforcing concrete. Today's market offers great variety, from short, hair-thin strands (micro- or monofilament) to macro-fibers up to about 2 inches long. Fibers are made of glass, carbon, steel, nylon, polypropylene, and other materials. They can be fibrillated (frayed) or smooth, crimped or flat, colored or transparent. Read more

Features 3-D Laser Screeding

In 1985, David Somero built a prototype laser-controlled screed that could strike off freshly placed concrete. A short time later, he and his brother started Somero Enterprises to manufacture and market their idea, and in 1987 they were awarded a patent for their invention. Their machines can screed floors to high FF requirements, making construction easier and more productive. Read more

Features Fall Brings Changes in Concrete Work as Well as Yardwork

As late summer is turning into fall, many of us are spending less time cutting the grass. In fact, as the weather turns cooler up North, we start thinking about raking leaves and putting lawn mowers and weed trimmers away for the season. It's no coincidence that the same change in seasons cools down concrete temperatures in the field, slowing down the rate of slump loss, extending the time of setting, and complicating the relationship between the strength of the concrete in the structure and the strength indicated by standard lab-cured cylinders. By taking a closer look at how temperature affects natural growth processes of plants like turf grass, we can gain some interesting insight about how temperature affects concrete. Read more

Features Beyond the Call of Duty

A few years ago, a subcontractor's employee was hurt on a Clayco jobsite while working on a tower crane boom arm 230 feet above the ground. With a storm coming and his leg injured, the immobilized ironworker needed immediate assistance (a high-angle rope rescue) from the Clayton fire department's special emergency response team. Thus began the unique and remarkable relationship between Clayco Construction Co. and the Clayton (a suburb of St. Louis) Fire Department (CFD). Read more

Safety Matters Safety Report: It Won't Happen to Me

A 20-year-old finisher and six journeymen and apprentices were working from two levels of a 24-foot-high, tubular-steel, welded frame scaffold. The crew was applying a decorative finish to a concrete wall. The scaffold was erected just 21 inches horizontally from an elevated electrical power line rated at 7620 volts. Read more

Decorative Concrete Using Color Hardeners

Concrete can be colored integrally or with color hardeners. Integral colors are added to concrete before placement. Color hardeners (also referred to as "dust-ons" and "dry-shakes") are broadcast as powders over the top of freshly struck concrete and are finished into the surface. Read more

Problem Clinic Slump Test Outdated?

I seem to remember reading that testing for slump was very outdated and that there is really no difference between a 5-inch slump and 61/2-inch slump. Is this true? Read more

Problem Clinic Lower Strength With Fibers?

Over the years I have observed a trend of lower compressive strength results when fibers are used in concrete mixes. Read more

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